Complete Dentures

Complete Dentures
241
Complete dentures for the maxilla and mandible comprise denture bodies and arti cial
teeth that are inserted into the oral cavity to replace natural teeth and missing alveolar
ridges. The denture bodies and teeth resemble the natural tissue parts in shape and size
because they are meant to take on their functions. Use of complete dentures involves
not only replacing the missing teeth and resorbed parts of the alveolar ridges but also
making a radical intervention into the existing massively damaged masticatory system.
For a partial denture, it is important to  nd the most favorable anchorage to the resid-
ual dentition—from a technical and functional standpoint—to ensure that the prosthesis
is  rmly seated and masticatory forces are largely transferred to the periodontal tissues
of the residual dentition. By contrast, complete dentures lie mechanically loosely on the
edentulous dental arches without additional anchorage.
For tooth setup in the case of complete dentures, the anatomical and functional condi-
tions of the variable jaw movements as well as the physical and mechanical conditions
of a denture body resting on the mucosa in unstable equilibrium have to be taken into
consideration. The real problem of complete dentures lies in shaping the dentures so
they lie  rmly on the dental arch during chewing without moving and so that masticatory
forces are transferred to the underlying mucosal support over a large area.
The problems of complete dentures have been studied by many dentists since the
early days of dental research, with special emphasis being placed on the relationship
between scienti c research and practical testing. In particular, it is a matter of interpret-
ing the existing anatomical circumstances of edentulous jaws in light of the physical
and mechanical conditions of the dynamic masticatory system so that usable models for
practical fabrication of complete dentures can be developed.
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242
Complete Dentures
Fig 8-1 Work ow for complete dentures.
10. Insertion and  nal check
• Selective grindi ng
• Remove pressure points
TechnicalClinical
1. Analysis of denture-bearing area
• Surgical measures:
Lower the vestibular fornices
Shorten the ligaments
Smooth the alveolar ridges
2. Anatomical impression
Preliminary impression for the
preliminary model
• Margins marked for the custom tray
• Extension impression
3. Custom trays
• On the preliminary model
• Edge length marked
4. Functional impression of edentulous
arches
• Use the mucodynamic method
Record the variable states of mucosal
shape
5. Functional casts and bite blocks
6. Interocclusal registration
Determine the vertical dimension of
occlusion
Determine centric relation with the
tracing stylus
• Mark static lines on the occlusion rims
7. Tooth setup
• Mount the casts
Perform cast analysis and tooth
selection
• Set up the teeth
• Wax up the denture body
8. Try-in of the setup
Check tooth position, shade, and
occlusal position
• Shape the margins
9. Completing the dentures
• Final wax-up and investment
• Working of the acrylic resin
Selective grinding in the articulator
243
Anatomical Changes After Total Tooth Loss
What is striking is that most of these explana
tory models accentuate one anatomical or physi
comechanical feature and prioritize individual
measures for successful fabrication of a complete
denture. For instance, the view might be put for
ward that the denture should be kept stable dur
ing masticatory function by means of statically
favorable posterior tooth shapes. On the other
hand, the premise might be that only a precise
impression of the edentulous jaws will guarantee
successful treatment. Techniques for interocclusal
registration are available, with the appropriate ar
ticulators, facebows, and instrument kits, as well
as special tooth molds for static setup of poste
rior teeth with detailed instructions.
The success of a complete denture, however,
cannot be guaranteed by prioritizing individual
measures but only by the most accurate imple
mentation of all the individual measures. The fol
lowing individual measures are involved in the
fabrication of complete dentures (Fig 8-1):
1. Clinical and surgical preparation and analysis
of the denture-bearing area in the maxilla and
mandible
2. Functional impression as the basis for anatomi
cally functional shaping of the denture margins
and the denture base
3. Interocclusal registration with approximate de
termination of joint values
4. Tooth setup based on the principles of denture
statics in relation to mandibular movement
and taking into account esthetic and phonetic
concerns
5. Contouring of the denture bodies to support
the lip and cheek muscles and to increase den
ture retention
6. Final check of the denture while it is function
ing to eliminate slip interferences in the oc
clusal area and pressure points on the denture
base
Fundamental knowledge about the fabrication
of complete dentures needs to be acquired in
the aforementioned sequence of measures. This
chapter therefore works through the following in
detail:
Morphologic and physiologic changes after tooth
loss
• Impression-taking of edentulous jaws
• Interocclusal registration of edentulous jaws
• Tooth setup for complete dentures
• Retention of complete dentures
Various working methods for fabricating complete
dentures are also presented.
Anatomical Changes After
Total Tooth Loss
Normal dentition is described as functional occlu
sion, on the basis of which the shapes of teeth,
tooth positions, jaw shapes, and inclinations in
their morphology are the result of the differen
tiated functions that have to be fullled. In ad
vanced age, the capacity for cellular regenera
tion declines, and physiologic wear is only poorly
replaced; age-related physiologic degeneration
of the tissue (senile involution) occurs. This in
volves continuous tooth loss with advancing age,
which happens faster in the maxilla than in the
mandible. Owing to their large periodontium, the
canines—especially in the mandible—are the last
to be lost.
As a consequence of senile osteoporosis, there
is a decrease in the weight of the cranium. In
edentulousness, the alveolar areas of the maxilla
and mandible are almost fully resorbed because
these bony parts are no longer being loaded in
their original form. In principle, atrophy of disuse
ensues.
Atrophy of disuse (or inactivity) means ac
tive shrinking of tissue due to impaired function
or nonuse of that tissue. For example, muscles
shrink when a plaster cast is used to immobilize
a limb for a lengthy period after a bone fracture.
This process is reversible; after healing, the tissue
is built up again, provided that functional loading
and proper nutrition are ensured.
Resorptive atrophy refers to shrinkage of the
alveolar process after tooth loss when the stim
ulus provided by the tooth roots is missing and
the bony sockets lose their physiologic function.
This process can be delayed by suitable shaping
of the denture base for extensive loading of the
denture-bearing area, but it cannot be reversed.
In the maxilla, the maxillary body forms the ba
sic framework from which the functionally orient
244
Complete Dentures
ed processes originate. The alveolar process will
shrink noticeably after tooth loss; the three other
processes will continue to provide static support
to the upper face and will only shrink slightly.
Weakening of the bone substance will take place
at the muscle attachments (eg, zygomatic pro
cess).
The substance of the palatine processes of the
maxilla is retained because essentially functional
loading of this bony part persists because of the
suction effect in the mouth. Nevertheless, in the
case of the palatal bone, the posterior third of the
bony palate can be paper-thin and even perforate
so that the oral and nasal cavities are only sepa
rated from each other by a fold of mucosa.
In the mandible, the parts oriented by loading
during masticatory function resorb after total
tooth loss (eg, the coronoid process, angle of the
mandible, and alveolar part). The senile mandible
is hook-shaped and attened at the angle of the
jaw. If there has been severe atrophy, the men
tal foramen lies at the upper edge of the alveolar
ridge.
As a result of atrophy, the distance between the
mandibular canal and the upper edge of the al
veolar ridge shortens; in rare cases, the inferior
alveolar nerve may lie directly below the mucosa.
The distance from the mandibular canal to the
lingual and buccal wall of the mandible remains
roughly constant. Jaw relations will also change;
that is, the position of the mandible relative to the
maxilla will shift. Initially the mandible gets closer
to the maxilla due to chewing with the bony al
veolar ridges (Fig 8-2).
After prolonged edentulousness, the condyles
and condylar path become attened; the condy
loid process of the mandible as a muscle attach
ment (lateral pterygoid muscle) also loses sub
stance and is displaced dorsally. The mandible is
displaced forward. This results in structural adap
tation of the temporomandibular joints (TMJs)
and the neuromuscular system. Joint cartilage
and the articular disc do not carry any blood ves
sels, so no repair process occurs, but defects (in
cluding atrophy) happen in the cartilage and the
disc.
Fig 8-2 After total tooth loss, the jaw relations shift because
the mandible is closer to the maxilla. If the vertical dimension
of occlusion is normal, the midline of the mandibular anterior
alveolar ridge lies behind that of the maxilla; the more the man
dible approaches the maxilla, the more the chin shifts forward.
Fig 8-3 Side view of a senile skull. The outline of the fully
dentate jaw shows the extent of resorptive atrophy after total
tooth loss: (1) Alveolar processes in the mandible and maxilla
shrink almost completely down to the basal bone. (2) The TMJ
is deformed by abnormal loading. There are also changes in
muscle attachments and (3) the angle of the mandible, (4) the
zygomatic arch, and (5) the temporal fossa.
2
5
4
1
3
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Forms of Shrinkage of Alveolar Ridges
The appearance of a senile skull illustrates the
shrinkage that affects not only the alveolar pro
cesses of the jaws but also the muscle tissue and
muscle attachments to the bone (Fig 8-3). When
the alveolar process in the maxilla is subject to
atrophy, the tip of the nose falls downward so
that eventually the tip of the chin and the tip of
the nose move close together in the senile skull.
Atrophy of muscle mass of the masseter may
make the cheeks appear hollow and the cheek
bones stand out prominently. This impression is
further intensied by the sunken temporal fossae
in which the temporal muscle is shrunken.
Forms of Shrinkage of
Alveolar Ridges
The anatomical changes in the mouth mainly re
late to shrinkage of the alveolar processes or alve
olar parts of the maxilla and mandible. After tooth
loss, the roots leave sockets (alveoli) in which
secondary bone is formed. In the maxilla, the
vestibular bone lamellae of the alveolar process
are thinner, while the palatal parts are relatively
compact; in the mandible, the thin bone walls lie
lingually and the more compact bone walls lie
vestibularly. The thin bone lamellae shrink more
markedly than compact ones. As a result, the
alveolar ridges appear to shrink toward the pal
ate in the maxilla and toward the vestibule in the
mandible (that is, in their direction of inclination).
Hence, narrowing arises due to the vestibular in
clination of the maxillary ridge, and widening of
the ridge lines occurs given the lingual inclination
of the mandibular ridge (Fig 8-4).
In fully dentate arches, the midlines of the al
veolar ridges lie vertically on top of each other.
As the alveolar ridges are inclined toward each
other, the mandibular central incisors are inclined
lingually and the maxillary central incisors in the
vestibular direction. This gives rise to a peculiar
feature after tooth loss, namely that the maxilla
apparently becomes smaller and the mandible
larger (Figs 8-5 and 8-6). The rate of resorption
of the alveolar part in the mandible can be three
times greater than the shrinkage of the alveolar
process in the maxilla. This means the mandibu
lar ridge line widens considerably more than the
maxillary ridge line narrows.
The interalveolar connecting line (interalveolar
line) joins the centers of the shrunken alveolar
ridges together (Fig 8-7). Depending on the pro
gression of the ridge shrinkage, the interalveolar
connecting line inclines toward the occlusal plane
to a variable degree. The greater the incline of the
interalveolar line, the more difcult it is to set up
the posterior teeth. According to Gysi, the setup
is in crossbite if the angle of inclination is less
than 80 degrees.
In the anterior region, the widening or narrow
ing of the alveolar ridge lines must be viewed in
a more differentiated way. In the maxilla, all the
teeth show a more or less pronounced vestibu
lar inclination so that the shape of the ridge line
is preserved as a semi-ellipse. In the mandible,
Fig 8-4 The alveolar ridges have
a vestibular inclination in the max
illa and are lingually inclined in the
mandible. Shrinkage happens in the
direction of inclination so that the
mandibular ridge line widens and
the maxillary ridge line narrows. This
shrinking process is further intensi
ed by the fact that the thin walls
(lingually in the mandible, vestibularly
in the maxilla) shrink more than the
compact walls. This results in differ
ent ridge proles: (a) normal alveolar
ridge; (b) high, wide ridge shortly af
ter extraction; (c) narrow and pointed
ridge; and (d) at alveolar ridge with
out mechanical retentions.
a b c d
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Complete Dentures
however, only the posterior teeth are clearly in
clined lingually; the canine stands vertically, and
the incisors have a labial inclination. This means
the ridge line changes from a parabola to a rather
trapezoidal basic shape (Fig 8-8). The relationship
of the parts of the alveolar ridge is maintained
in the canine area; they are vertically shrunken.
The anterior areas are sunken lingually, and be
cause the central incisors are inclined more labi
ally than the lateral incisors, the symphysis area
shrinks more markedly lingually than laterally. As
a result, an almost straight ridge line is formed
between the canine points in the mandibular an
terior region.
The ridges of the posterior teeth have a vari
ably pronounced lingual inclination in the man
dible (the tooth inclination decreases dorsally;
the ridge inclination increases), which is why
the ridge line widens more in the dorsal direc
tion. Following shrinkage of the alveolar parts,
Fig 8-5 As the alveolar processes of the maxilla shrink in the
direction of inclination, the maxillary ridge line narrows in the
lingual direction; the maxilla becomes smaller, which has reper
cussions for the statics of the complete denture.
Fig 8-6 To achieve better positional stability of the denture,
the vertical dimension of occlusion is reduced in complete
dentures. As a result, the height of the denture body also de
creases, and the mandible moves closer to the maxilla. Conse
quently, the midline of the mandibular anterior alveolar ridge is
displaced forward.
Fig 8-7 The interalveolar line is the connecting line between
the centers of the ridges of the shrunken dental arches; to
gether with the occlusal plane, it forms the interalveolar angle.
The interalveolar angle changes depending on the progress of
shrinkage. The more the jaws shrink, the smaller the interal
veolar angle becomes.
Fig 8-8 In the mandible, the posterior parts of the alveolar
ridge are displaced vestibularly due to resorption, and the an
terior parts are displaced lingually; the result is a roughly trap
ezoidal ridge-line contour.
Occlusal plane
Interalveolar angle
Interalveolar line
247
Impression-Taking of the Edentulous Jaw
the retromolar triangle appears to be displaced
lingually. As this bony part does not shrink after
tooth loss, it will retain its real position, relative to
which the alveolar ridge is then displaced.
The conditions are similar for the maxillary
tuberosity and the incisive papilla. The tuberosi
ties appear to be displaced vestibularly, while the
incisive papilla is shifted onto the center of the
alveolar ridge contour; the tip of the papilla may
lie on the anterior contour of the alveolar ridge.
Depending on how much shrinkage has occurred
due to the duration of edentulousness and the
damage caused by faulty denture bases, different
forms of jaw shrinkage will arise.
In the edentulous maxilla, the alveolar process
forms the brous marginal zone, and the median
raphe of the hard palate forms the brous median
zone in the form of immovable mucosa. Between
the brous median and marginal zones lie the
plicae palatinae in the fatty zone, which merge dor
sally into the glandular zone with serous-mucous
salivary glands. Fatty and glandular zones are more
resilient than the brous zones. The soft palate
borders the hard palate dorsally.
The edentulous alveolar ridge in the mandible
also develops a brous zone, which ends dorsally
in the alveolar tubercle of the mandible, a ridge
of connective tissue covered by mucosa. The im
mobile, brous ridge mucosa is bordered vestib
ularly by the mucosa of the vestibular fornix and
lingually by the mobile oor of the mouth.
Impression-Taking of the
Edentulous Jaw
Taking impressions of edentulous jaws falls with
in the dental practitioners area of responsibility.
The aim is to take a precise, extensive impression
of the denture-bearing area, in which the transi
tions from the attached to the mobile mucosa are
recorded in particular.
The functional impression is used to reproduce
the border area individually during functional
move ments of the mucosa. The impression does
not record the functioning of the mucosa but
rather the space required by the mobile mucosa
or muscles and ligaments as they function (Fig
8-9). In practical terms, a custom impression tray
is used, which is rst prepared from an anatomi
cal cast or preliminary model. For this purpose,
an overextended anatomical impression is taken
based on the principle of mucostatic impression
taking (Fig 8-10).
1
2
3
4
5
A
B
C
Fig 8-9 The contours of the periphery of functional trays allow for reduction needs and extension possibilities for edentulous jaws,
such as all vestibularly attached ligaments, the labial frenum (A), and the buccal frenum (B). Note the pterygomandibular raphes
in the maxilla and mandible (C), the path of the vibrating line in the maxilla, and the muscle attachments in the mandible, such as
the mylohyoid line (1) lingually and the oblique line (2) vestibularly. Extension areas in the mandible are the sublingual areas (3),
paralingual areas (4), and buccinator pockets (5).
248
Complete Dentures
The mucostatic impression is taken with the
mouth relatively wide open and the mucosa in
the rest position. The impression negative depicts
the equilibrium position between the resting ten
sion of the tissue and the consistency of the im
pression material, usually an alginate mixed to a
viscous consistency. Slight movements of cheeks,
lips, and tongue cause the attachments of the lig
aments to stand out. This results in an extension
impression in which the vestibule is widened in
order to record the limits of the dental arch, in
cluding into the undercuts.
The custom tray is prepared on a preliminary
model, which is derived from this impression. A
felt-tip pen may be used to mark the edge of the
tray on the alginate impression. This mark then
appears on the preliminary model and provides a
guide to the contour of the tray edge. The tray is
made from a rigid plastic and has an easy-to-grip
handle in the middle.
Fabrication of a custom tray varies depending
on the tray material—whether thermoformed
sheet or chemoplastics. What is crucial to both
techniques, however, is the shaping of the tray
edges. If the tray is kept slightly longer than the
depth of the vestibular fornix, the edge can be in
dividually reworked in the mouth. To do this, the
edge is shortened until it does not lift off during
check movements and does not create any pres
sure points. The edges can be reinforced with wax
after correction in order to mold lip shields and
buccal rests as well as the length of the sublin
gual roll and the paralingual wings.
Possible impression materials are heavy- and
light-body silicones; thermoplastic materials allow
long-term impression-taking in which the edges
A
B
B
C
D
Fig 8-10 An impression of edentulous jaws is usually taken in two working steps: The mucostatic impression deliv
ers a preliminary model (A) on which the custom functional trays are made (B). They show the path of the periphery
of the eventual denture. Undercuts are blocked out on the models (C). The vibrating line area and the paralingual and
sublingual areas are individually reinforced on the functional tray before impression-taking in order to exploit these
important parts of the jaw for special prosthetic purposes. The nished functional impressions are given a horizontal
wax rim above the impression of the valve margin (D). This produces the model rim thickness with functional margin.
249
Interocclusal Registration
are harmoniously rounded in the border area.
Various methods can be used to take a practical
functional impression in order to record the vari
able contours of the mucosa.
A chewing impression is an impression of the
surface of the dental arches during the muscle ac
tivity involved in chewing. This is taken to record
the mucosal loading that would be caused under
denture functioning conditions. A custom tray
with bite planes in the correct vertical dimension
of occlusion is coated with thermoplastic impres
sion material and placed in the mouth. Chewing
movements are then performed for about 30
minutes.
A swallowing impression takes an impression
of the jaw’s border to the oor of the mouth,
which is important in recording the sublingual
spaces for the sublingual roll and the paralingual
wings.
An impression taken when the patient is pro
nouncing certain groups of vowels and conso
nants records the variable range of movement of
the lips, cheeks, tongue, muscles of mastication,
vestibule, and soft palate.
A closed-mouth impression involves taking a
simultaneous impression of the maxilla and the
mandible with preliminary registration of occlu
sal position. Prefabricated stock trays are used
for the anatomical impression; they can be xed
in their position relative to each other. For this
purpose, bite plate trays are prepared, which are
used when determining the occlusal position for
the functional impression (Fig 8-11). The function
al movements can be performed actively by the
patient or passively by the operator.
The functional model made from dental stone
shows the functional periphery to the dimensions
required for fabricating a valve margin with an
adequate outer valve. To do this, the edge of the
model is raised about 3 to 4 mm outward on the
impression. A broad wax pad can be stuck onto
the impression at that distance from the valve
margin so that the base plaster can be raised up
to this stop.
The vestibular fornix, the border of the oor of
the mouth, and the vibrating line can be clearly
identied and must not be damaged. On these
functional models, the bite plates are now pre
pared in the dimensions of the eventual denture
base and used for interocclusal registration.
Interocclusal Registration
Interocclusal registration is intended to establish
the positional relationship of the jaws to each
other and their position relative to the joints. The
aim is to regain the former centric occlusion or
habitual intercuspation position in which the con
dyles lie pressure free and tension free deep in
the mandibular fossae. In an edentulous mastica
tory system, the equivalent of the former centric
occlusion will have to be determined in the verti
cal and horizontal relationships.
The vertical dimension of occlusion is mea
sured in various ways. It can be assumed to be
a statistical average, namely a 38- to 42-mm dis
tance from the mandibular to the maxillary for
nix. It can be assumed to be the position of the
smallest speaking distance when pronouncing
test words (eg, counting from one to ten). It can
be deduced from the facial proportions as a har
monious length, whereby the facial prole lines
yield three facial sections of equal length: the
upper, mid-, and lower face. The distances from
the root of the nose to the lower nasal point and
from the lower nasal point to the tip of the chin
are equal.
20–22 mm
18–20 mm
Fig 8-11 The occlusion rims are placed on rm bite plates
following the course of the center of the alveolar ridge. The
vertical dimension of occlusion is measured from the lowest
point in the fornix to the occlusal plane. The occlusal plane
runs roughly parallel to the contour of the maxillary ridge; in
the mandible, it runs dorsally through the upper third of the
retromolar triangle; anteriorly, the occlusion rims may be pad
ded by the dentist to match full lip volume or in the course of
the vertical anterior arch.
250
Complete Dentures
The horizontal relationship encompasses the
transverse and sagittal positional relationship of
the jaws. This relationship can be registered us
ing various methods. One possibility is to get the
patient to adopt the most retruded mandibular
position, for example by guiding the mandible
back by hand or getting the patient to swallow.
However, the most retruded position of the man
dible, in which the condyles are in contact with
the dorsal joint limit about 1 mm behind the nor
mal position, is a forced position in most patients.
Gothic arch tracing offers another means of de
termining the horizontal relationship. A tracing
stylus mounted centrally on the maxillary (or
mandibular) bite plate marks what is known as
the Gothic arch on the tracing plate of the man
dibular (or maxillary) bite plate. The intersection
of the marked lines derived from the horizontal
mandibular excursions indicates the centric hori
zontal relationship (Figs 8-12 and 8-13). The point
of intersection lies about 1 mm in front of the
arrowhead. Using the facebow and Gothic arch
tracing technique, the precise position of the man-
dible relative to the joint points can be established
and thus transferred to the articulator. The bite
plate has a rm base that matches the dimen
sions of the denture base. The occlusion rims are
placed exactly on the center of the alveolar ridge
and are roughly 10 mm wide by 10 mm high.
The exact height depends on the position of the
occlusal plane. For instance, the mandibular oc
clusion rim—measured from the deepest point
in the fornix (next to the labial frenum)—will be
between 18 and 20 mm high, follow the occlusal
plane, and pass through the upper third of the
alveolar tubercle of the mandible. The maxillary
occlusion rim extends from the deepest point of
the fornix (next to the labial frenum) 20 to 22 mm
up to the occlusal plane.
Interocclusal registration is intended to deter
mine the relationship of the mandible to the
maxilla and the joints and to provide guidance
for eventual tooth setup. For this purpose, the
maxillary occlusion rim to beyond the canine
position is padded up to about 7 mm before the
midline of the papilla, corresponding to the con
tour of the vertical anterior arch, until normal lip
volume is achieved with wrinkles smoothed out.
The markings on the occlusion rims are also
intended to provide pointers for tooth setup and
tooth proportions (Fig 8-14):
The midline is based on the middle of the face
and indicates the middle of the dental arch.
The occlusal plane runs parallel to the pupil line
and Camper plane, or it is marked as the lip clo-
sure line.
The mandibular incisal point arises as the inter
section point between the midline and lip clo
sure line and provides xation for the incisal pin
on articulators.
The smile line is marked as the position of the
upper lip when smiling or maximum raising of
the upper lip. The length of the teeth is deduced
from the lip closure line and smile line.
Fig 8-12 Intraoral occlusal registration involves marking the
centric occlusion position by using a centrally placed tracing
point to trace mandibular movement on a tracing plate in the
form of a Gothic arch. The point where the arch intersects indi
cates the position of centric occlusion.
Fig 8-13 To get the mandible into centric relation, in which
both condyles lie in the most retruded position, a wax bead
can be placed at the dorsal edge of the plate, where it will be
touched with the tip of the tongue. This means the mandible is
pulled evenly into the most posterior position.
251
Tooth Setup for Complete Dentures
The canine points or labial angle points for de
termining tooth width are obtained by transfer
ring the extension line of the width of the wings
of the nose to the occlusion rims or by indicat
ing the position of the angle of the mouth.
The lower lip line is obtained with the mouth re
laxed and open. This line may indicate the path
of the maxillary incisal edges. The base of the
nose line is often traced as well for this purpose.
Tooth Setup for Complete
Dentures
A number of orientation guides and measures are
available for reconstructing the positions of the
teeth (Fig 8-15), which dental technicians must
be familiar with and able to use. The descriptive
models of the dental arches in a normal denti
tion are generally valid pointers to the position of
teeth. They provide guidance for reconstructing
the inclinations of axis and dental arch forms. The
dental arch forms are parabolic in the mandible
and ellipsoid in the maxilla. The occlusion follows
the antagonist rule, an overjet being formed from
overlap and overbite of the anterior teeth, and the
anterior teeth forming the vertical anterior den
tal arch. The Bonwill circle, Bonwill tangent, and
Pound lines can be used when shaping the dental
arch of the mandible. The maxillary arch shows
the premolar tangent.
Dentists’ instructions on tooth positions are the
markings on the occlusion rims that are placed
during interocclusal registration. In addition, ana
tomical casts of the original position of the teeth
or photographs of the patient may be used. Notes
on the patient’s physiognomy, from which indi
vidual tooth positions may be deduced, may also
be provided.
Measures are taken to ensure that the static po
sitional stability of complete dentures takes into
account the position of the teeth relative to the
center of the alveolar ridge, denture body height,
tooth position within the compensating curves
for all-round sliding contact, and balance of the
tone of tongue and cheek.
Findings of model analysis are the link between
anatomical xed points and the position of teeth.
They provide a symmetric grid of static lines by
which the tooth positions are aligned. Tooth posi
tion instructions to take account of phonetics and
esthetics can also be used.
The setup for a complete denture is done in an
average-value articulator, in which the basic man
dibular movements are possible. Setup in a fully
adjustable simulator of masticatory movements
requires individual surveying of condylar paths
and cranium-related interocclusal registration for
adjusting the models.
Setup in an average-value articulator after average-
value adjustment of the models in the articulator
can be conclusively legitimized: In most clinical
cases for which a complete denture is to be pre
pared, there is extensive pathologic deformation
1
2
3
4
5
Fig 8-14 After occlusal registration, the operator can make
the following markings to indicate tooth shape, tooth size, and
position: (1) Smile line: The upper lip raised when laughing, the
smile line, and the occlusal plane establish the tooth length. (2)
Position of the occlusal plane (lip closure line). (3) The canine
points, labial angle points, and midline points determine the
tooth width. (4) Midline: The midline of the face is not neces
sarily the same as the midline of the jaw. (5) The lower smile
line or nasal base line indicates the position of the central to
the lateral incisors and establishes the length of the mandibular
teeth.
252
Complete Dentures
Descriptive models of
dental arches
Dentition pattern
OverjetPremolar tangent Bonwill circle
Antagonist rule Dental arch forms
Dentist’s positional
instructions
Findings of model
analysis
Measures to ensure static
positional stability
Static position Compensating curve
Fixed points
Static lines
Esthetics
Occlusal registration
Fig 8-15 Range of orientation possibilities.
253
Statics of Denture Design
of the TMJs, which can be treated by a standard
ized complete denture (ie, fabricated according to
average values).
Setup aid is provided by templates (calottes) in
which the radii of curvature are laid out according
to average condylar paths. These average-value
templates can be adjusted in an average-value
articulator to the height of the occlusal plane to
enable the mandibular teeth to be set up within
compensating curves.
For template setup, the mandibular posterior
teeth are placed with their cusp tips on the tem
plate so that the occlusal surfaces lie within the
sagittal and transverse compensating curves.
The exception is the mandibular rst premolar,
which only contacts the buccal cusp of the calotte.
When the maxillary dentition is opposed accord
ing to the antagonist rule, an occlusal eld may
arise that exhibits all-round sliding contact during
translative movements.
Template systems are available with templates
showing different curves that represent different
condylar path inclinations. Matching sets of pos
terior teeth are supplied in which slopes of cusp
surfaces are referenced to different joint values.
Statics of Denture Design
A complete denture lies on the jaw without me
chanical anchorage so it can be moved on the
tissue foundation while functioning. Denture stat
ics involve constructing the denture so that it lies
evenly on the whole alveolar ridge under loading
as well as during chewing and speaking. It would
be statically unsatisfactory if the denture moved
to and fro on the alveolar ridge and were tipped
off during functioning. The static relationships af
fecting a denture are inuenced by the following
factors:
• The denture-bearing area of the jaws
• The height of the denture body
Tooth position relative to the alveolar ridge (see
Fig 8-17)
• Tooth position relative to the occlusal plane
The denture-bearing area inuences denture
statics in the described way: A minimally atro
phied, rm alveolar ridge with adequate mechan
ical retentions is favorable; a severely atrophied
jaw whose connective tissue support forms a
mobile, abby ridge without undercut retention
areas is unfavorable. The form of shrinkage and
progression of that shrinkage also inuence the
size of the denture body.
A denture body acts like a lever arm: The more
the alveolar ridges have been resorbed, the taller
the denture body will be. Hence, the denture body
as a lever arm for occlusally acting forces be
comes longer, and the resulting torque becomes
greater (Fig 8-16). The conclusion is to keep the
denture body at, which can only be achieved by
shortening the vertical dimension of occlusion.
The tooth position relative to the center of the
alveolar ridge has a signicant inuence on den
ture statics (Fig 8-17). On one-sided masticatory
loading, as a result of the tooth being positioned
on the ridge center, the denture can be either
pressed down on the opposite side or levered off.
Three static states are identied: neutral, unsta
ble, and stable tooth position.
a
t
L
L
b c
Fig 8-16 The statics of a complete denture are determined
by the state of shrinkage of the alveolar ridges: (a) Where the
ridges are well developed, even loading occurs in centric occlu
sion. (b) On transverse loading (t), the denture body acts as a
lever arm (L) so that torque (T) tips the denture. (c) If the ridges
are severely atrophied, the lever arm is longer because of the
height of the denture body, and the torque is correspondingly
greater. The vertical dimension of occlusion has a direct inu
ence on denture stability.
T = t ·
L
t
254
Complete Dentures
Neutral tooth position (neutral state) shows the
arrangement of the articial teeth on the center
of the alveolar ridge. On functioning, the den
ture is initially pressed only onto the side of the
loading.
Unstable tooth position (unstable state) exists if
the teeth are located outside the middle of the
alveolar ridge. On masticatory pressure, the
denture is levered off on the opposite side.
Stable tooth position (stable state) arises when
the articial teeth are positioned lingually rela
tive to the ridge midline. A torque then acts on
the denture body around a pivot on the middle
of the alveolar ridge. The denture is pressed onto
the opposite side by the masticatory forces. The
stable tooth position guarantees secure reten
tion of the complete denture and produces even
pressure distribution to the underlying tissue.
The stable tooth position has two serious draw
backs. First, the normal processes of shrinkage
widen the ridge line in the mandible while nar
rowing it in the maxilla. As a result, the ridge lines
no longer lie one on top of each other (Fig 8-18).
If the maxillary posterior teeth are now set up
slightly inside the ridge line, the mandibular pos
terior teeth will lie well inside the ridge line if they
are arranged in normal occlusion. They stand far
more lingually than the natural teeth did previ
ously. This means unacceptably severe crowding
of the tongue; the patient would be constantly bit
ing his or her tongue and having pronunciation
problems.
Second, if the maxillary anterior teeth are set
up in the stable position inside the ridge line, lip
support is lost and the patient’s facial expression
is greatly altered—as in an edentulous senile face.
Fig 8-17 The position of the articial teeth relative to the ridge midline has a decisive inuence on the statics of a complete den
ture: (a) The stable state denotes the position of the articial tooth inside the ridge line; here loading causes downward pressure on
the opposite side because of the eccentric tooth position. (b) In the unstable state, the tooth is positioned outside the ridge line,
which leads to the denture being lifted off on the opposite side. (c) The neutral state refers to the tooth position over the middle of
the alveolar ridge; here only the loaded side is pressed on.
α
α
Fig 8-18 Arranging the teeth in a statically
favorable position is difcult because the fol-
lowing anatomical features have to be taken
into account: (a) In a fully dentate dentition,
the ridge lines lie almost on top of each oth
er. (b) After the jaws have shrunk, the ridge
lines are displaced relative to each other, de
pending on how advanced the shrinkage is.
The interalveolar line is inclined toward the
occlusal plane at an angle α. (c) The inclina
tion of the interalveolar line increases if the
vertical dimension of occlusion is altered.
If the teeth are arranged inside the interal
veolar line, they will be displaced toward the
middle of the ridge.
a b c
a b c
255
Statics of Denture Design
Therefore, the maxillary anterior teeth are placed
labially in front of the middle of the alveolar ridge
for esthetic reasons.
The posterior teeth in the maxilla are positioned
in the neutral position for functional reasons, there-
by placing the mandibular posterior teeth in nor
mal occlusion in a minimally stable tooth position
(Fig 8-19). If atrophy is very advanced, however,
the neutral tooth position in the maxilla can give
rise to an extremely stable tooth position in the
area of the mandibular posterior teeth, with the
aforementioned drawback of crowding of the
tongue.
Crossbite position becomes necessary in shrunk
en dental arches if the maxillary ridge is extreme
ly narrowed and the mandibular ridge is widened
vestibularly (Figs 8-20 and 8-21). This arrangement
is used when the angle between the interalveolar
line (the vertical line connecting the ridge mid
lines) and the occlusal plane is smaller than 80
Fig 8-19 The interalveolar line can be
used as a reference line for setting up teeth
in the posterior region. If the teeth are ar
ranged in normal occlusion, the mandibu
lar central incisors are in a stable position
and the maxillary central incisors are in an
unstable position. If the mandibular teeth
are moved closer to the middle of the al
veolar ridge, taking into account the space
required for the tongue, the change to the
static relationships is extremely disadvan
tageous for the maxillary teeth.
Fig 8-20 Static relationships in severely atrophied alveolar
ridges can be improved by setting up the posterior teeth in a
crossbite position, moving the mandibular teeth upward and
the maxillary teeth downward in a crosswise fashion so that
the left teeth are on the right side and the right teeth on the left
side. The space for the tongue is enlarged, and the teeth are
moved toward the middle of the alveolar ridge.
Fig 8-21 If the alveolar ridges shrink in the direction of inclina
tion because the teeth are missing, this also has repercussions
for lip volume. In the normal physiologic rest position of the
mandible, the lips attain their natural fullness in a fully dentate
jaw because of support from the maxillary incisors. If the man
dible is brought into this position in an edentulous situation, the
mouth will cave in. Thus, the anterior teeth must be brought
into the original position. To do this, the maxillary anterior teeth
are positioned anterior to the shrunken alveolar ridge.
256
Complete Dentures
degrees. Practically speaking, the maxillary left
incisors beyond the second premolars are moved
down and to the right and reversed, and the max
illary right incisors are similarly placed down and
to the left and reversed. The posterior teeth are
swapped crosswise.
Position of teeth relative to the
occlusal plane
The position of teeth relative to the occlusal plane
also inuences the statics of a complete denture,
which can be depicted in relation to the Chris
tensen phenomenon (Fig 8-22) and Bennett side
shift.
On lateral movements of the mandible, the idling
condyle on the nonworking side drifts down and
forward on its condylar path, while the working-
side condyle rotates around its vertical axis and
slips outward and often backward in the direction
of the lateral movement. This lateral movement of
the condyle is the Bennett side shift (or laterotru
sion). In a normal dentition, the posterior teeth on
the working side are rmly pressed together
while the posterior teeth on the nonworking side
gape. This is the transverse Christensen phenom-
enon (Fig 8-23).
On protrusive excursions, there is a gap be
tween the two rows of teeth while the anterior
teeth are in incisal contact. This sagittal Chris
tensen phenomenon arises because, during pro
trusive movements, the condyles on both sides
slide downward and forward on the condylar
paths and the mandible is dorsally lowered. In
normal occlusion, the separation into working
and nonworking sides is an expression of the
functional orientation of the rows of teeth in the
form of sagittal and transverse occlusal curves,
whereby faulty contacts in dynamic occlusion are
avoided.
Preparing plano-parallel occlusion rims for in
terocclusal registration at the level of the occlu
sal plane will give rise to an extreme Christensen
phenomenon. If the teeth are set up parallel to
the occlusal plane, the rows of teeth will gape on
functional chewing movements; this results in the
denture tilting and lifting off.
All-round sliding contact of all the teeth dur
ing lateral and protrusive movements would be
advantageous because the denture would be re
peatedly stabilized against possible tipping off
(Fig 8-24). How can such all-round sliding contact
be achieved?
In the normal dentition, complete and rm oc
clusal contact between posterior teeth occurs
during a lateral movement on the working side,
while anterior teeth and the opposite side remain
without contact. This rm and complete occlu
sal contact of the posterior teeth on the working
side comes about because the occlusal surfaces
are inclined inside a gently arched sagittal and
transverse occlusal curve (Fig 8-25); on the oppo
site side, however, these occlusal curves prevent
tooth contact. It is worth checking whether or not
the shape of the occlusal curves might be exploit
ed to gain all-round sliding contact with complete
dentures because full occlusal contact or selec
tive tooth contact arises at least on the working
side because of the occlusal curves.
With strongly arched curves, all-round sliding
contact can be achieved, and the Christensen phe
Fig 8-22 The Christensen phenom
enon occurs when two occlusion rims
arranged in parallel in the occlusal plane
(a) are meant to be kept in contact dur
ing protrusive movement, but instead a
large gap is created in the posterior re
gion while the anterior teeth remain in
contact (b).
a b
257
Statics of Denture Design
nomenon and the positional defect of the Bennett
side shift can be compensated for. This is why
these curves are called compensating curves.
They have basically the same shape as the famil
iar occlusal curves but are more strongly arched.
Disturbances in the occlusal plane move the
denture against the mucosal base, which may ac
celerate resorption of the bony foundation. For
instance, a one-sided increase in the vertical di
mension of occlusion—if it is not remedied—will
cause that side to be particularly stressed via re
ex movements, which may lead to deformation
of the TMJ.
In this context, a similar aspect applies to guid
ance from groups of teeth, for example canine
guidance in the case of complete dentures. The
maxillary canine—including those in complete
dentures—can guide the mandibular denture into
centric occlusion but only in interaction with the
cusps of the posterior teeth (Fig 8-26). If neces
sary, the canine must be ground back to allow for
the individual movement pattern.
Fig 8-23 During lateral movements and
the transverse Christensen phenom
enon, the Bennett movement also inu
ences the curvature of the compensating
curve. The teeth should be positioned so
that tooth contact exists in the balancing
position (a) and the working position (b).
a b
Fig 8-24 All-round sliding contact can
be ensured in the transverse plane by
means of a compensating curve arched
caudally. From the central articulator po
sition (a), the maxilla is moved relative to
the mandible to the side (b) so that the
calotte-shaped, curved occlusion rims
move against each other in sliding con
tact.
a b
Fig 8-25 The occlusal plane can take on
a curved shape (a), which favors sliding
contact on mandibular excursions (b).
The arrangement of the occlusal curves
in space may result in a calotte shape.
a b
258
Complete Dentures
In summary, the following may be concluded
regarding denture statics: The articial teeth
should be set up over the middle of the alveo
lar ridge, the mandibular posterior teeth may be
placed slightly inside the ridge line, and the max
illary anterior teeth must be placed in the origi
nal tooth position (hence anterior to the alveolar
ridge) for esthetic reasons and to aid pronuncia
tion. To secure denture statics, the posterior teeth
should be set up inside the sagittal and transverse
compensating curves (Fig 8-27). In the process,
the denture body should be kept as at as pos
sible. The articial teeth should exhibit a statically
stable form to avoid transferring horizontal shear
ing forces to the denture.
Articial Teeth for
Complete Dentures
Modern articial teeth are precisely matched to
their natural counterparts in terms of shape and
color. This acknowledges the fact that the natural
tooth represents the optimum functional form
with which the functions of the masticatory sys
tem can be best performed. These tooth shapes,
reproduced according to the natural model, are in
themselves stable and more functionally reliable
(Fig 8-28). For the anterior region, a vast array of
different tooth shapes are available, enabling in
dividual restoration of any possible case.
Posterior teeth are supplied in a few selected
shapes and sizes. The occlusal surfaces are ana
tomically precisely shaped, which makes it easy
to locate their position in centric occlusion and
produces a favorable esthetic impression. Some
manufacturers include a certain theory of occlu
sion; for example, the Physiodens from Vita has
simultaneous and uniform point contacts with oc
clusal clearances.
Abrasion surfaces on the occlusal surfaces are
re-created in a few forms. These surfaces are re
lated to condylar paths based on variable values.
This makes setting up the teeth easier, based part
ly on average values but also on individual joint
values. Using these teeth, problem-free setup is
Fig 8-26 If teeth whose occlusal surfac
es have slanting cusps (a) are mounted,
these slanting cusp surfaces will nd
sliding contact on protrusion (b) while the
mandible can be moved without tilting.
Fig 8-27 Increasing the curvature of the compensating curves in the sagittal plane
so that the condyles and teeth move on a shared arc of a circle is in line with Ferdi
nand Graf von Spee‘s diagrams. The curve of Spee (or anteroposterior curve), which
is named for him, is often used as a synonym for the occlusal and compensating
curves. The curve of Spee is a special type of sagittal occlusal curve in that occlu
sal curves typically follow a atter course. The compensating curves are also not so
sharply arched that extension of the curves touches the condyles. More importantly,
the condylar path—as a guide variable for the condyle—is not arched in the path of
the curve of Spee.
a b
259
Articial Teeth for Complete Dentures
possible in multipoint contact during functional
chewing movements.
Variations from the natural tooth shape can be
found in the ranges of posterior teeth supplied by
certain manufacturers (Fig 8-29). These are usu
ally modications of the original shape down to
statically more favorable reduced forms. Dur
ing the development of articial tooth forms, at
tempts have been made to diverge from the natu
ral functional form and develop greatly reduced
forms that are intended to support the statics of
the denture.
Hiltebrandt’s mortar-and-pestle tooth is the
most successful modication of the natural tooth
shape, which was further developed into a differ
entiated form such as the Condyloform teeth de
veloped by Gerber. According to this principle of
form, the punctiform occlusal contacts of natural
teeth are simplied into a at mortar-and-pestle
contact in which the contact surfaces are displaced
lingually and the vestibular contacts are designed
merely as supporting and balancing contacts to
position each individual posterior tooth so that it
is statically stable (Fig 8-30); no balancing contact
is required on the opposite side.
Fig 8-28 Articial posterior teeth differ from natural teeth, especially in terms of static suitability. Manufacturers usually offer a
smaller form that meets the special static demands placed on a complete denture. The process starts with replication of puncti
form occlusal contacts of natural tooth shapes (a) and moves on to pronounced abrasion of occlusal surfaces with variably inclined
cusps, which are derived from average condylar paths (b). Modication into a trough-shaped tooth in which a pestle-like occlusal
surface engages (c) then leads to a different form in which the condylar path–related parts of the abrasion surface are combined
with mortar-and-pestle sections (d).
a b c d
Fig 8-29 Modern posterior
teeth have cusp slopes that re
late to different types of occlu
sion, as is the case here with
the posterior tooth from Ivo
clar Vivadent. The cusp groove
angles relate to the condylar
forward glide path; there is a
difference between deep bite
(approximately 29 degrees),
normal occlusion (26 degrees),
and crossbite (25 degrees). The
cusp surfaces have punctiform
contacts.
Fig 8-30 In the case of Gerber
Condyloform molars and pre
molars, the maxillary posterior
teeth have a palatal occluding
cusp in the form of a pestle,
which engages in the mortar
like occlusal surface of the
mandibular teeth; these cusps
involved in chewing are posi
tioned inside the middle of the
alveolar ridge. The vestibular
cusps have a stabilizing effect
on chewing; the bulbous buc
cal tooth surfaces have cheek
contact.
260
Complete Dentures
Fig 8-31 Bilabial sounds (B and P) are
impeded if the lip position is altered by
incorrect tooth positioning. If the anterior
teeth are placed too far lingually, the lips
will cave in and the consonants will be
poorly formed.
Fig 8-32 Apart from the position of the teeth, the shape of the denture base also
inuences pronunciation. In the case of large faults, malpositioning of teeth, and incor
rect denture shape, the patient may never get used to the denture and may always
retain a speech impediment. The tongue’s position relative to the anterior teeth when
pronouncing various consonants shows the area in which the most common problems
occur due to denture design: (a) The voiced consonants C and Z are formed when the
tip of the tongue is pressed against the maxillary anterior teeth and lies close to the
mandibular incisal edges. (b) S also arises as a fricative when air is squeezed through
the narrow gap formed by the tip of the tongue and the palatal surfaces of the maxil
lary incisors. Incorrect tooth positions often result in lisping.
B; P
C; Z
S
a b
Fig 8-33 A forward rolled R is formed
when the tongue is moved behind the
anterior teeth in a powerful tremolo and
produces a vibrating plosive sound. Er
rors in tooth position and incorrect den
ture base shapes impede the formation
of this consonant.
R
Fig 8-34 The tongue lies on the palatal
plate directly behind the anterior teeth
when pronouncing T and D. If the base
is too thick or angular in this area, the
tongue will shift and T or D will become
a G.
Fig 8-35 The same applies to the con
sonant L, which is formed in the same
place, with the tongue also lying against
the premolar region. Replication of the
plicae palatinae will make it easier to ori
ent the tongue.
LT; D
261
Position of Teeth and Phonetics
Position of Teeth and
Phonetics
The unstable tooth position must always be cho
sen for the maxillary anterior teeth for esthetic
reasons. Restoring the natural lip volume is the
primary aim so that the patient is not identiable
as a denture wearer. However, the functional im
portance of the natural position of the maxillary
anterior teeth is also closely linked to the patient’s
speech. The formation of sounds is a complex
interplay between tongue, lips, and teeth. Most
consonants are inuenced by the teeth and their
position during the sound. It is not uncommon for
patients to complain of having difculty forming
certain sounds with their new teeth.
Bilabial sounds, such as B, P, and M, become
possible on normal lip closure (Fig 8-31). The cor
rect position of the anterior teeth and hence the
correct lip position have functional signicance
for pronunciation. If the vertical dimension of oc
clusion is too big, lip closure is prevented; if the
maxillary anterior teeth are placed too far palatal,
the lips will cave inward. In both cases, this leads
to weak formation of bilabial sounds.
Sibilants (dentoalveolar sounds), such as C, S,
and Z, are formed when the tongue is pressed
against the palatal surfaces of the maxillary ante-
rior teeth and the anterior palate. Gaps between
the teeth lead to spluttering; if the teeth are tipped
in the oral direction or if the transition from den
ture base to the teeth is too thick or worked too
smoothly, the patient will lisp (Fig 8-32). Repro
duced plicae palatinae provide orientation for the
tongue (Fig 8-33).
Glottal stops (palatoalveolar sounds), such as
D, T, or L, arise when the tongue is pressed onto
the palate behind the teeth. If the teeth are tipped
orally or placed too far lingual, a glottal stop is not
possible (G instead of D); a thick base will press
the tongue downward and prevent pronunciation
of these sounds (Figs 8-34 and 8-35).
Fricatives (labiodental sounds), such as V and
F, arise when the lower lip contacts the maxillary
incisal edges. If the maxillary anterior teeth are
too short, the sounds V and F will be distorted into
B (Fig 8-36).
Postpalatal sounds, such as J, K, and G, arise
when the tongue is supported on the posterior
teeth. If the dental arch is too narrow, this will
impede tongue movements (Fig 8-37). If the tran
sition from the denture base to the teeth is too
rough, too angular, or worked too thickly, the
space for the tongue will be impeded and nar
rowed.
Fig 8-36 If the maxillary anterior teeth
are too short or the occlusal plane is dis
placed, the weak fricatives (V and F) are
distorted into a blurred glottal stop.
Fig 8-37 The “ck” consonant group is
palatally formed. This fricative is impeded
if the dental arch is too narrow.
V; F
“ck”
262
Complete Dentures
Model Analysis of
Edentulous Jaws
Points and lines can be xed on the dental arches,
allowing individual tooth positions relative to an-
atomical landmarks to be located later. The pur
pose of model analysis is to locate and trace points
on the edentulous jaws that remain unaffected by
the normal atrophy that occurs after tooth loss.
From these, a symmetric grid is created from static
lines, and this grid is used when setting up the
teeth and shaping the dental arches.
Statics analyses have shown the relationship
between these points and normal tooth position.
Based on these lines and xed points, the original
tooth position can be reconstructed. The setup for
complete dentures can then be claried with the
aid of topographic features from the description
of the normal dentition. The position and form
of the model analysis xed points are presented
here; their references to natural tooth position are
explained, and other prosthetic references are
identied.
Model analysis of the maxilla
Figure 8-38 shows the xed points in model anal
ysis of the maxilla. The median palatine suture
xes the middle of the jaw or the model midline.
The symmetry axis of the maxillary dental arch
along the median palatine raphe is generally the
rst to be traced on the model. On this midline,
the labial frenum is located in the anterior ves
tibular area, while the dorsal end is formed by the
posterior nasal spine of the palatine bone.
The incisive papilla appears to be labially dis
placed in an edentulous jaw because the alveolar
ridge is resorbed in the palatal direction. The raphe-
papillary cross-line runs transversally through the
middle of the incisive papilla (about 2 mm from
the tip backward) through the canine tips and in
the fully dentate jaw touches the lingual edges of
the maxillary central incisors. The labial contours
of the incisors are located approximately 7 mm
labially.
The rst pair of large plicae palatinae end about
2 mm anterior to the palatal edges of the maxillary
canines. In an edentulous jaw, the canine points
can therefore be xed on the alveolar ridges (ie,
approximately 5 mm from the plicae palatinae
toward the raphe-papillary cross-line) (Fig 8-39).
This value is variable, depending on the extent of
ridge atrophy.
The maxillary tuberosity marks the dorsal end of
the alveolar ridge, which is not resorbed after tooth
loss. The middle of the tuberosity is indicated by
the attachment of the pterygomandibular raphe.
The centers of alveolar ridges in the posterior
region are identied by the canine points and the
midpoints of the maxillary cusps. The middle of
the ridge in the anterior region can be drawn from
the canine point to the tip of the incisive papilla.
Model analysis of the maxilla therefore encom
passes the following steps:
1. Mark all the xed points (incisive papilla, rst
large pair of plicae palatinae, median palatine
suture, and midline of the maxillary tuberosity).
Fig 8-38 The reference points of model analy
sis must be present on each dental arch, must
always be located at the same place and be un
affected by resorptive atrophy of the jaws, and
must be clearly visible and clearly related to
tooth position. The gure shows the xed points
in model analysis.
Anterior vestibular fornix
Incisive papilla
First pair of large plicae
palatinae
Median palatine raphe
Maxillary tuberosity
263
Model Analysis of Edentulous Jaws
2. Mark the middle of the model and extend the
tracing onto the edge of the model.
3. The canine point must be constructed: Draw a
diagonal from the midline of the maxillary tu
berosity through the tip of the opposing rst
large plica palatinae. To do this, select the xed
points that are clearly visible. To obtain a sym
metric grid, reect the clear xed points and
the found canine point over the axis of sym
metry.
4. Trace the centers of the alveolar ridges in the
posterior and anterior region and extend the
tracing onto the model edges.
5. Draw the raphe-papillary cross-line and extend
it to the model edges. On the model edges, this
produces a typical image of model analysis
markings.
Application of model analysis ndings
The static reference lines (model midlines, cen
ters of ridges) as well as the position points for the
canines and maxillary central incisors are found
by means of model analysis (Figs 8-40 and 8-41);
this also establishes the position of the maxillary
lateral incisors. The position of the posterior teeth
is located via the center of the alveolar ridge. The
lines of the central developmental grooves of the
posterior teeth lie over the middle of the ridge. To
ensure that the mouth does not look overfull and
that the buccal corridor is created, the premolars
are placed inside the premolar tangent (ie, the
connecting line between the labial marginal ridge
of the canine and the mesiobuccal cusp ridge of
the rst molar).
Fig 8-39 The canine point is constructed with the aid of model
analysis xed points. The model midline is rst drawn through
the median palatine raphe; then the maxillary tuberosity and
the rst pair of large plicae palatinae (which can clearly be
seen) are selected. A diagonal line is drawn from the center
of the maxillary tuberosity over the tip of the opposing rst
large plica. The canine point lies on this line approximately 5
mm vestibularly. The found canine point is reected over the
axis of symmetry.
Fig 8-40 The static lines through the model analysis xed
points are the model midline over the median palatine raphe,
the raphe-papillary cross-line through the middle of the papilla,
the midlines of the anterior alveolar ridges through the canine
points and to the tip of the papilla, and the midlines of the
posterior alveolar ridges through the center of the maxillary
tuberosities and the canine points.
Fig 8-41 The static lines are carried over to the model edges
so they can still provide orientation during setup on a nontrans
parent base. Twelve markings must appear on the edge of the
maxillary model, and these produce a symmetric grid.
264
Complete Dentures
Model analysis of the mandible
Figure 8-42 shows the xed points in model anal
ysis of the mandible. The retromolar triangle or
pad can be used for constructing various static
lines. It is not resorbed after tooth loss, so half
the height (or the upper third) of the triangle con
tinues to indicate the dorsal position of the occlu
sal plane. Half the height of the triangle serves in
many template setup devices and average-value
articulators as a xed point for the appropriate
calibration keys, which are adjusted to the trian
gles and the mandibular symphysis point.
The symphysis point is located directly on the
center of the alveolar ridge and is the equiva
lent of the mandibular incisal point. (Assuming
that the anterior apex of the Bonwill triangle tips
downward at the mandibular incisal point after
tooth loss, this apex will describe a section of an
arc and, after shrinkage of the alveolar ridge, will
lie on the middle of the ridge, namely on the sym
physis point, without the length of the sides of the
Bonwill triangle having changed.) The symphysis
point is found on the middle of the alveolar ridge
contour where labial and lingual frena attach
ments can be joined.
The axis of symmetry of the mandibular dental
arch or the jaw midline runs through the symphy
sis point and half the distance of the triangle (Fig
8-43). To put it another way, a triangle is spanned
through the centers of the retromolar pads and
the symphysis point; its midline drawn through
the symphysis point indicates the middle of the
model or midline of the jaw.
Canine points on the mandible lie clearly on the
corner of the edentulous alveolar ridge, which is
resorbed into a trapezoidal basic shape because
of its direction of inclination.
The alveolar ridge centers in the posterior re
gion run through the centers of the triangle and
the canine points (Fig 8-44). In the anterior region,
the center of the ridge runs through the canine
points.
Vestibular fornices in the anterior region of the
maxilla and mandible are xed points for the ver
tical anterior arch, which touches the labial sur
faces of the maxillary central incisors; this arc of
a circle runs 7 mm away from the middle of the
papilla. The labial surfaces of the incisors thus
give the upper lip its necessary volume, while the
cutting edges of these maxillary teeth support the
lower lip.
The inferior vestibular fornix is a reference
point for the position of the occlusal plane, which
lies about 18 to 20 mm above the deepest point
of the vestibular fornix directly next to the labial
frenum. In addition, this lowest point of the fornix
is used as the approach for some calibration keys.
Molar points can be seen in the posterior re
gion as a clear depression in the region of the
mandibular rst molar, from where the ridge pro
le increases very steeply dorsally and relatively
gently ventrally. This depression arises because
of the natural shape of the dental arch inside the
sagittal occlusal curve and is further accentuated
by severe resorption of the bone material after
loss of the largest posterior tooth.
Retromolar triangle
Molar point
Symphysis point
Canine point
Anterior vestibular fornix
Fig 8-42 The model analysis xed
points on the mandible must have the
same quality as those in the maxilla.
They must always be present in the
same place on each jaw, remain unaf
fected by resorptive atrophy, be clearly
visible, and be clearly related to tooth
position. The gure shows the xed
points in a model analysis.
265
Model Analysis of Edentulous Jaws
This deep point in the prole of the alveolar
ridge serves as a reference point for calibration
keys by the average-value technique in order to
align mandibular jaw models in an average-value
articulator (Fig 8-45). This also provides a direct
reference for reconstructing original tooth posi
tions: the mandibular rst molar is set up above
this lowest point.
Model analysis of the mandible therefore en
compasses the following steps:
1. Trace all the model analysis xed points again
(symphysis point, retromolar triangle, and ca
nine points).
2. Construct the model midline and continue to
the model edge. To do this, halve the distance
of the triangles and draw a connecting line to
the symphysis point. The halved distance be
tween the molar points can also be used for
locating the midline.
3. Mark the ridge centers in the posterior and
anterior region and extend them to the model
edges. On the model edges, this again pro
duces the typical picture of the model analysis
markings.
Application of model analysis ndings
Once again, the static reference lines (model mid
lines, centers of ridges) as well as the position
points for the canines and the rst molars are
found (Fig 8-46). The posterior teeth lie with their
central developmental grooves exactly over the
middle of the ridge.
Fig 8-43 The midline of the model has
to be constructed in the mandible: The
xed points are rst traced, then the
distances between the molar points and
the retromolar triangles are halved. The
midline runs from the symphysis point
between these arithmetically averaged
points.
Fig 8-44 The centers of the alveolar
ridges run anteriorly between the canine
points and posteriorly between the ca
nine points and the middles of the retro
molar triangles. The actual ridge contour
deviates in a vestibular direction at the
molar points. The midlines of the alveolar
ridges form a trapezium.
Fig 8-45 The mandibular alveolar ridge
shrinks most around the position of the
rst molar so that the prole of the ridge
dips most here from the vestibular view.
This point, known as the molar point,
serves as a reference point for calibration
keys in average-value articulators and
helps to reconstruct the original tooth
position as the mandibular rst molar is
set up directly above this lowest point.
Fig 8-46 In the mandible, the static
lines have to be carried over to the model
edges so that they can be used for ori
entation during setup. Ten markings are
made, including the position of the rst
molar, which identies the deepest point
of the alveolar ridge contour.
266
Complete Dentures
The mandibular parabolic dental arch can be
described by the Bonwill circle and its premolar
tangents. The size of the Bonwill circle is xed by
the canine points; the buccal boundary of the tri
angles establishes the path of the tangents (Figs
8-47 and 8-48).
General Setup Rules
Comparison of different descriptions and illustra
tions of complete dentures shows that there are
a few fundamental rules governing the setup of
articial teeth. These fundamentals, drawn from
the various interpretations, are applied here. No
particular method is given priority, but essential
advice is taken from all the depictions of tooth
setups. As most setup compendia relate to spe
cic tooth shapes, no single method can claim to
be universally valid.
An average-value articulator is the minimum
requirement for setting up two complete den
tures in order to perform check movements and
arrange the teeth inside the compensating curves.
A setup in a fully adjustable articulator would re
quire the condylar path to be surveyed in the pa
tient. Whether it is appropriate to carry out time-
consuming condylar path surveying for complete
dentures is a matter for the dentist to decide, es
pecially because determination of an average-
value occlusal eld can also be used therapeuti
cally for the TMJs.
The ndings of model analysis are the primary
orientation guides and the static lines that the
dentist draws in place. On the other hand, the
familiar descriptive models of normal occlusion
can also provide orientation.
Static positional stability of the denture is
achieved if the articial teeth are positioned on
the center of the alveolar ridge. If they are placed
outside the ridge middle, that is called vestibular
placement, and adverse lever effects will arise in
response to eccentric mandibular movements.
Instead, the mandibular posterior teeth can be
placed slightly lingually, provided that they do
not crowd the tongue. The maxillary anterior
teeth are the exception to this principle; these
teeth are placed anterior to the alveolar ridge to
provide support to the lips (Figs 8-49 to 8-54).
The compensating curves have to be created.
The teeth should be set up inside sagittal and
transverse compensating curves. The term three-
point contact claries this point: On lateral and
protrusive movements, the denture may be le
vered off on the nonworking side if tipping is not
avoided by means of antagonist contacts on the
nonworking (balancing) side.
Fig 8-47 The mandibular dental arch can be described by the
Bonwill circle (yellow), where the mandibular anterior teeth
and the rst premolar lie on an arc of the circle. Tangents (teal)
placed at the rst premolars intersect the buccal cusps and
buccal border of the triangle. The central incisors are positioned
slightly lingually inside the arc of the circle if the alveolar ridge
is severely atrophied.
Fig 8-48 The Pound line touches the lingual border of the tri
angle and runs over the lingual cusps of the posterior teeth
up to the mesial edge of the canine. The simplest and most
reliable method of setting up the posterior teeth is to align the
central developmental grooves with the middle of the alveolar
ridge.
267
General Setup Rules
7 mm
2 mm
5 mm
Fig 8-49 The maxillary anterior teeth can be reconstructed
in their original arrangement with the aid of model analysis
to improve the esthetic impression. The central incisors are
placed with the labial contour about 7 mm in front of the
raphe-papillary cross-line. The canines can be brought into their
original position with relative accuracy by reference to the rst
pair of large plicae palatinae; in the process, the canine tips
touch the raphe-papillary cross-line.
7 mm
Fig 8-50 The labial contours
of the maxillary incisors should
be about 7 mm in front of the
middle of the papilla so that a
natural lip volume is created.
Fig 8-51 The lips will cave
in if the maxillary incisors are
placed on the center of the
ridge. The impression of an
aging face is accentuated if
the vertical dimension of oc
clusion is reduced.
Fig 8-52 If the denture body
is reinforced to tighten the
wrinkles around the mouth,
the vermilion of the lips is
pulled inward and the lips ap
pear very thin.
Fig 8-53 The natural lip vol
ume with adequate vermilion
is restored if the maxillary an
terior teeth are arranged in
side the vertical anterior arch
approximately 7 mm in front
of the middle of the incisive
papilla and the denture body
only compensates for the at
rophy of the alveolar ridge.
The vestibule is a capillary gap
in a fully dentate dentition, but
this is widened by the denture
base so that this part of the
mouth is altered.
Fig 8-54 The incisive papilla in conjunction with the raphe-
papillary cross-line is used as a xed point in model analysis. In
a fully dentate dentition, it is clearly located behind the alveolar
ridge. It apparently drifts as far as the center of the alveolar
ridge, depending on how advanced the atrophy is (A and B).
A
B
268
Complete Dentures
When chewing food, there is no guarantee that
the balancing side will have contact. The highest
masticatory pressure and hence the risk that the
denture will be levered off occurs immediately
before gliding into terminal occlusion, or directly
before tooth contact on the balancing side; stabi
lization is then instantly possible.
The direction of movement when sliding into
terminal occlusion can also help stabilize the
denture (Fig 8-55). During chewing, the move
ment stroke is always guided into centric occlu
sion coming from the vestibular toward the lin
gual; the direction of movement is then toward
the palate (Fig 8-56). Hence the maxillary denture
presses on the dental arch on the opposite side
(Fig 8-57). If the mandibular teeth lie slightly in
side the alveolar ridge line, the force vector pass
es inside the center of rotation and the denture
presses onto the jaw.
During speaking and normal play movements,
the teeth are also moved against each other un
der contact, and the denture might be levered off
if teeth have not been set up inside the compen
sating curves. If the teeth are placed inside these
curves, however, the patient can readily be guar
anteed stabilization. The embarrassment of inse
cure denture retention is particularly highlighted
when the wearer is speaking, which is why a den
ture should have balancing contacts for this pur
pose.
Canine guidance (or guidance from a group of
teeth), which lifts the posterior teeth out of occlu
sal contact when protrusive or lateral movements
are performed, is inappropriate for complete
prosthodontics because even the best functional
impression and positional stability provided by
the mechanical retentions of undercuts can never
offer the type of secure retention a xed restora
tion can provide. Even if canine guidance would
not lever off the denture, the dentures will still
be moved transversally against the underlying
mucosa. Over the long term, these usually trans
verse, forced movements will damage the tissue
base and accuracy of t will be lost, which in turn
means dynamic loading increases on the mucosa
(Figs 8-58 and 8-59). Relining becomes necessary,
but it is often not done promptly enough, result
ing in remarkably fast breakdown of the bony
foundation; the necessary denture-bearing area
is lost.
Fig 8-55 In terminal occlusion, it does
not matter what path is followed because
the opposite side is also in tooth contact.
Patients adapt their movement habit when
chewing so masticatory forces stabilize
the denture. Biting-off movements and
reex-checking movements are critical.
Fig 8-56 The chewing cycle in the nal
phase is directed toward the palate. The
mandible presses the food in that direc
tion against the maxillary teeth. In the
maxillary denture, the resultant force
(Res) passes the center of rotation on the
middle of the alveolar ridge, and the den
ture is stabilized on the opposite side.
Fig 8-57 Shortly before terminal occlu
sion, when masticatory force is greatest
and is applied rather vertically, the resul
tant directed palatally goes past the cen
ter of rotation. As a result, the denture is
pressed onto the opposite side.
Res
Res
269
Ways to Check Tooth Positioning
Ways to Check Tooth
Positioning
The teeth are set up tooth by tooth while check
movements (lateral and protrusive excursions)
are constantly performed to ensure that all-round
antagonist contact exists. The incisal guide pin
must always maintain contact with the incisal
guide plate, especially when a certain plate slope
is specied.
On lateral movements, the buccal cusps of the
posterior teeth on the working side lie on top of
each other, while the cutting edges of the ante
rior teeth on this side have edge-to-edge contact.
The anterior teeth on the balancing side have no
antagonist contact, while the buccal cusps of the
mandibular posterior teeth on this side lie on the
palatal cusps.
On protrusive movements, the anterior teeth
have edge-to-edge contact, and in the posterior
region individual cusp tips on the molars touch
each other. In some circumstances, the incisal
guide pin may lose contact with the guide plate.
The position of the individual teeth is checked in
three spatial directions: from the occlusal, vestib
ular, and approximal directions. From the occlu
sal aspect, rotation inside the dental arch should
be checked and corrected. The reference point is
the central developmental groove for posterior
teeth and the incisal edge for anterior teeth. The
central developmental grooves form a straight
line that lies directly over the alveolar ridge. The
incisal edges form the dental arch.
From the vestibular aspect, the mesial or distal
inclination of the axis is checked and corrected.
This involves checking the height of the tooth rel
ative to the adjacent tooth; a correct interdental
embrasure must result, in which the antagonist
contacts are evenly distributed to both teeth. On
lateral movements, the antagonist cusps glide
along in these embrasures.
From the approximal aspect, the lingual inclina
tion of axis of the alveolar ridge is checked. In the
mandible, the teeth are inclined lingually in keep
ing with the tooth inclination; in the maxilla, the
teeth have a vestibular inclination, which gives
rise to the transverse curve.
The length of the maxillary anterior teeth is
denitely dependent on the length of the upper
lip. The safest way of establishing this length is
for the dentist to make markings on the occlusion
rims. If the lip closure line is marked, the anterior
teeth should project 1 to 2 mm beyond it.
Fig 8-58 Guidance for a group of teeth in the anterior region
can be constructed for complete dentures if adequate mechan
ical retentions are available; these are recorded by an accurate
functional impression. In the posterior region, occlusal contact
is broken on eccentric movements of the mandible. However,
transverse forced movements of the denture occur that non
physiologically load the denture-bearing area and damage it.
Fig 8-59 If the mechanical retentions are inadequate, the
dentures will be levered off their rest area by guidance from a
group of teeth. This positional instability lessens the dentures
functional value and leads to dynamic stresses on the underly
ing tissue. Progressive breakdown of the bony foundation oc
curs, which further reduces positional stability. For complete
dentures, bilaterally balanced occlusion should be attempted.
270
Complete Dentures
In principle, an overjet is formed; that is, the
anterior teeth, including the canines, have no
antagonist contact in centric occlusion (Figs 8-60
to 8-62). If this overjet is not formed, the denture
may lever off when biting off food or during pro
trusive movements.
Individual tooth positions are always positive
if they are prepared according to the dentist’s
instructions or based on an anatomical model
of the original tooth positions, with any extreme
positional anomalies obviously being alleviated.
An individual tooth position must not impede the
statics of the denture (Figs 8-63 to 8-68).
It is advisable to carry out individual variations
from normal tooth position after setup of all the
teeth has been fully completed; a better overview
is then possible because dynamic occlusion al
ready functions with all-round sliding contact.
Then interferences only need to be sought on the
repositioned teeth. The following variations from
normal tooth position may be selected:
Fig 8-60 The term overjet denes the overbite and is equiva
lent to the amount of protrusive occlusion; that is, the incisors
are placed in relation to each other so that the maxillary incisal
edges reach beyond the mandibular teeth by the amount to
which the maxillary teeth stand anterior to the mandibular in
cisal edges.
Fig 8-61 The degree of overjet should ensure that, on protru
sion, the anterior teeth glide past each other while the poste
rior teeth simultaneously remain in sliding contact. With this
balanced occlusion, the dentures are stabilized on the denture-
bearing area and are not levered off.
Fig 8-62 The position of the dental arch
es relative to each other inuences the
overjet: If the mandible lies in front, a small
amount of overjet is selected. As a result,
the anterior teeth achieve sliding contact
after only short movement deections.
Fig 8-63 Abrasion edges can be ground
into the anterior teeth, along which these
teeth glide during eccentric movements.
Many prefabricated teeth already have
abrasion edges; canines usually have to
be ground in.
Fig 8-64 The overbite may be extended
if the upper lip is long. As a result, the
mandibular teeth must be placed far back
or the maxillary teeth placed far forward
to achieve a balanced amount of overjet.
This jeopardizes positional stability.
271
Ways to Check Tooth Positioning
Fig 8-65 For checking purposes, the lateral movement is executed
until the approximal edges between the central and lateral incisors
of the maxilla and mandible lie above one another. Then the incisors
on the working side have edge-to-edge contact (A). On the working
side, the posterior teeth then have cusp-to-cusp contact (B), while
on the balancing side the palatal mandibular cusps have sliding con
tact with the buccal cusps of the mandibular teeth (C). The incisal
guide pin will not lift off the guide plate.
Fig 8-66 Rotation of the posterior teeth from the occlu
sal view. As a basic principle, the central developmental
grooves form a line. If this criterion is applied, it is no
ticeable when a tooth tips out or is twisted out of the
arch. This indicates that the interdental niche is disrupted
and the dental arch form is defective, which has esthetic
drawbacks, especially in the case of the premolars.
Fig 8-67 The position of the tooth axes can be checked when
viewed from the vestibular aspect. Although more esthetic as
pects come to the fore in the anterior region, in the posterior
region it is a matter of shaping the interdental embrasures be
cause this is where the contact areas of the antagonist cusps
lie. Otherwise, gliding interference may arise in the embrasure
area on lateral excursions.
Fig 8-68 (right) It is important to check the approximal incli
nation of the teeth because it determines the position of the
teeth relative to the occlusal curves. (a) If a mandibular tooth is
tipped in the vestibular direction, an inverted curve rather than
a transverse compensating curve will arise. (b) If a maxillary
tooth is tipped lingually, the palatally placed occlusal contacts
will be lost; however, if it is placed too far vestibularly, this will
lead to static and esthetic disadvantages.
a
b
A
C
B
272
Complete Dentures
The contour of the incisal edges of the ante
rior teeth follows the lower lip contour or the
nasal baseline. The dentist can mark both lines
on the occlusion rims. The shape and width of
the wings of the nose can be used to select the
width of the anterior teeth (Fig 8-69).
The anterior teeth can be rotated within the den
tal arch. For instance, the central incisors can be
twisted with their distal edges out of the den
tal arch or conversely with their mesial edges
twisted out of the dental arch. The anterior teeth
can also be moved with their vestibular axes so
that the teeth partly overlap at the incisal edges.
Spaces between individual teeth can also be set
up, although the central incisors are excluded
from this if the patient experiences vocalization
problems afterward.
The dentist chooses the tooth color, taking into
consideration the patient’s age, complexion, lip
color, and facial hair. The shape of the anterior
teeth should be established by the dental prac
titioner in order to select the basic shapes that
match the patient’s physical type (Fig 8-70).
Position of Mandibular
Anterior Teeth
There is no hard and fast rule about which teeth
to start with in a complete denture setup. If start
ing from the model analysis markings on the
maxilla, supplemented by the markings and pad
ding of the occlusion rims, it makes sense to be
gin by setting up the maxillary teeth. If this pad
ding is absent and an average-value template is
used for the setup, it is advisable to set up the
mandibular teeth rst, for which the static lines
from the model analysis of the mandible provide
reliable guides. In any case, the parabolic dental
a
b c d
Fig 8-69 The shape of the nose can be used to determine
the width of the anterior teeth: (a) The vertical tooth axes of
the canines line up with the outer edges of the wings of the
nose. (b) The incisors can be aligned with the baseline of the
nose; a long, pointed nose invites stepped positioning of the
anterior teeth. (c) A normally curved base of the nose allows
harmonious positioning of the anterior teeth. (d) A relatively
uniform line of incisal edges ts well in a patient whose nose
has a broad base.
Fig 8-70 The Kretschmer constitutional typology is reected
in the shape of the maxillary central incisors, as illustrated
here: (a) The athletic constitution is well balanced, powerful,
and represented by an angular, almost square tooth shape. (b)
The leptosomic or asthenic type, rather lanky, nervous, and
panicky, is characterized by a triangular tooth shape. (c) The
round and trusting pyknic type is best represented by an oval
basic tooth shape.
a b c
273
Position of Mandibular Anterior Teeth
arch shape is easier to reproduce than the semi-
ellipse in the maxilla.
The procedural approach to setup being adopt
ed here starts with the mandibular anterior teeth,
followed by the maxillary anterior teeth and
shaping of the overjet. The posterior teeth are set
up in xed pairs of antagonists (tooth to tooth):
mandibular premolars and maxillary rst premo
lars in order to determine possible tooth spacing
between canines and the rst premolars. This is
followed by the mandibular rst molar and the
opposing maxillary second premolar, then the
mandibular second molar and nally the maxil
lary molars.
The mandibular anterior teeth invariably stand
on the alveolar ridge. Seen from the incisal as
pect, they form the start of the Bonwill circle, the
arc of the circle whose tangents form the refer
ence lines for the posterior teeth (Figs 8-71 and
8-72). As the alveolar ridge of the mandible is
generally straight in the anterior region, the arc
must be created by the approximal inclination
of the anterior teeth and by rotation around the
tooth axis. It is inadvisable to use the tooth axis
for aligning in the approximal inclination; the la
bial contours of the anterior teeth provide better
orientation.
OP
Fig 8-71 The mandibular anterior teeth stand exactly on the occlusal plane (OP), and their incisal edges form a straight line. The
tooth axes display a mesial tendency when seen from the labial aspect. The dental arch, seen from the occlusal aspect, forms the
Bonwill circle with the canines positioned over the canine points.
Fig 8-72 The approximal inclinations are
varied to form the dental arch in keeping
with the Bonwill circle. All the anterior
teeth stand on the center of the alveolar
ridge. The approximal inclination can be
checked by looking at the path of the labi
al contour: The labial contour of the cen
tral incisor stands vertically, that of the
lateral incisor is inclined slightly lingual
ly, and that of the canine shows a pro
nounced lingual inclination. These match
the correct inclinations of the tooth axes.
274
Complete Dentures
The incisal edges of the mandibular anterior
teeth form a straight line congruent with the lip
closure line (occlusal plane), while the canine may
exceed this line slightly at its tip (Fig 8-73). From
the vestibular view, the central and lateral inci
sors stand perpendicular with a slight mesial ten
dency, while the canine is inclined mesially.
The mandibular central incisors stand with their
tooth axis inclined strongly toward the vestibular
aspect; the labial contour runs vertically, and its
extension points into the mandibular vestibular
fornix (Figs 8-74 and 8-75). The mandibular lateral
incisors stand with their tooth axis almost per
pendicular on the center of the ridge; the labial
contours are inclined slightly in the lingual di
rection. The mandibular canines stand with their
tooth axis vertical and slightly toward the lingual
aspect, while the labial contours show a marked
Fig 8-73 From the labial view, the incisal edges form a straight
line corresponding to the occlusal plane, beyond which the tips
of the canines protrude slightly. In a symmetric setup, the
mandibular anterior teeth appear to be inverted because of the
aforementioned approximal inclinations.
Fig 8-74 (left) The mandibular central incisor has a vestibular
inclination in a normal dentition; its labial contour, extended
vertically, points into the mandibular vestibular fornix. On total
tooth loss, the vertical dimension of occlusion is reduced so
that the middle of the anterior alveolar ridge of the mandible is
displaced forward. If the mandibular central incisor is brought
into its original position, it stands slightly in front of the center
of the ridge.
Fig 8-75 (right) When setting up the central incisor in the man
dible, the mandibular vestibular fornix may provide good orien
tation: The labial contour points vertically downward into the
depth of the vestibular fornix, and the incisor stands slightly in
front of the middle of the alveolar ridge and displays the neces
sary vestibular inclination. The maxillary vestibular fornix is not
suitable for orientation because the shift in the jaw relation will
also shift the relationship of the maxillary vestibular fornix to
the position of the mandibular teeth.
275
Position of Maxillary Anterior Teeth
lingual inclination. The position of the canines is
determined by the canine point, as dened by
model analysis.
An individual tooth position caused by rotation
and overlapping is permissible and should be
formed so that no interference in occlusion occurs
and sliding contact is always maintained during
lateral movements. The mandibular anterior teeth
can be set up irregularly to create a favorable es
thetic impression (Fig 8-76). If the teeth are twist
ed in their vertical tooth axes and pushed togeth
er, the anterior width from canine to canine may
also be reduced. The anterior width can be in
creased by leaving spaces between the mandibu
lar anterior teeth.
Error analysis
It is difcult to make proper use of the orienta
tion lines and positional guidance provided. The
requirement for tooth positioning on the center of
the alveolar ridge is difcult to carry out. When is
an inclined incisor actually on the ridge middle?
Must the cervical margin and the ridge contour
show, or should the incisal edge lie above the
ridge middle, or should the base overlap the ridge
contour? For static reasons, the incisal edges
should be placed over the middle of the ridge, but
then it is not possible to form the Bonwill circle.
By way of compromise, the cervical margins of
all the mandibular anterior teeth form a roughly
straight line parallel and approximately 2 mm
in front of the ridge middle; the dental arch is
shaped by the previously described vestibular
inclination of the teeth and their rotation around
the tooth axis. The advice to let the extension of
the labial contour of the mandibular rst incisor
point into the vestibular fornix is a good guide.
This advice also allows considerable leeway. The
labial contour can point into the depth of the for
nix at the outer or the inner edge; another varia
tion will arise if the contour does not lie vertically.
A ruler held against the contour can show this
variation clearly.
Position of Maxillary
Anterior Teeth
The maxillary anterior teeth should form the
overjet. Thus, the mandibular anterior teeth are
placed up to the lip closure line, while the maxil
lary anterior teeth overhang this line by about 2
mm. The maxillary anterior teeth lie in front of the
mandibular anterior teeth by the same amount.
If the mandibular anterior teeth have been set up
rst, the maxillary teeth can rst be placed with
the appropriate overbite to the mandibular ante
rior teeth, and provided the wax is still soft, a lat
eral movement can be performed until edge-to-
edge contact is achieved, which means pressing
the maxillary incisor in the vestibular direction. If
the maxillary anterior teeth are allowed to glide
back into centric occlusion, normal overjet to the
correct extent will emerge, and protrusive occlu
sion will be equivalent to overbite.
The maxillary central incisor stands in front of
the alveolar ridge, in keeping with the occlusion
rim padding or, based on the average from model
analysis, 7 mm from the center of the papilla as far
as the contour of the labial surface (Fig 8-77). The
vestibular inclination, checked from the approxi
mal aspect, shows the following: It is vestibularly
inclined with the neck of the tooth at the alveolar
ridge, and the labial contour follows the vertical
anterior arch. The incisal edge overhangs the lip
Fig 8-76 The mandibular anterior teeth can be set up irregularly to create a favorable esthetic impression. If the teeth are rotated in
their vertical tooth axes and pushed together so that they partly overlap, the anterior width from canine to canine may be reduced.
Spacing the mandibular anterior teeth can enlarge the anterior dental arch, which can also create a favorable esthetic impression.
276
Complete Dentures
Fig 8-77 The maxillary central incisor stands in front of the alveolar ridge so that the labial surface is about 7 mm in front of the
middle of the incisive papilla. It has a vestibular inclination. When seen from the labial aspect, the mesial inclination of axis can be
seen. The tooth projects about 1 to 2 mm beyond the occlusal plane or the lip closure line. Seen from the occlusal aspect, both
central incisors stand in the dental arch.
Fig 8-78 The lateral incisor has a more pronounced approximal inclination, is set up to be slightly shorter, and is tipped more mesi
ally. The lateral incisors stand anterior to the alveolar ridge and continue the dental arch.
277
Position of Maxillary Anterior Teeth
closure line by about 2 mm, and hence an over
bite over the mandibular anterior teeth is formed
that corresponds to the overjet. The mesial axis of
inclination is checked from the vestibular aspect,
although this inclination is very weak. From the
occlusal aspect, there must already be a sugges
tion of the dental arch when looking at the incisal
edges of both central incisors.
The maxillary lateral incisor also stands an
terior to the alveolar ridge, like the central inci
sor, and hence is in keeping with the vertical an
terior arch or follows the occlusion rim contour
(Fig 8-78). The inclinations of axes are more pro
nounced: seen from the labial aspect, there is a
stronger inclination, but from the approximal
aspect, the neck of the tooth shows more at the
alveolar ridge. The lateral incisor is shorter than
the central incisor but still projects beyond the lip
closure line. From the incisal aspect, the dental
arch is visible.
The maxillary canine also stands in front of the
alveolar ridge (Fig 8-79). The canine point has
been located by model analysis or xed by mark
ings on the occlusion rim. The canine is inclined
mesially. Its approximal inclination is in the ves
tibular direction, which means the tip of the canine
and the cervical margin lie roughly vertically on
top of each other; as a result, the bulbous canine
appears very dominant. The canine is not longer
than the central incisor, which is checked with a
at plate parallel to the occlusal line. Canine guid
ance is not attempted. At best, antagonist contact
exists with the mandibular rst premolar, hence
distally; the mandibular canine has no contact in
centric occlusion. It may become necessary to
prepare the maxillary canine for interference-free
lateral movement.
The incisal edges of the maxillary anterior teeth
can be ground in, as they are beveled labially to
palatally and abrasion surfaces are created. This
may even become necessary if the ash on fac
tory teeth is not adequately buffed. Usually, it
then becomes necessary to bevel these areas of
ash toward the labial aspect in the case of the
mandibular anterior teeth. This results in a regu
lar sliding contact.
Fig 8-79 The canine is also located in front of the alveolar ridge. The canine point is xed by the rst pair of large plicae palatinae.
The canine, like all the anterior teeth, displays a vestibular tendency and is inclined slightly mesially. Its length corresponds to that
of the central incisor. From the occlusal view, the canine must be given an exposed position. It is the corner in the dental arch, 2
mm in front of the rst pair of large plicae palatinae.
2 mm
278
Complete Dentures
Fig 8-80 Subtle, deliberate irregularities in tooth position en
hance the natural effect of the dentures. Based on this knowl
edge, it is possible to deviate from regular positioning (A) and
create a harmonious individuality seen from the labial aspect
by means of convergence and divergence of the tooth axes
(B and C).
Fig 8-81 Positional changes achieved by rotation around the
vertical tooth axis, so that some of the teeth may overlap, will
also increase the natural impression (B and C).
Individual tooth positions
Subtle, deliberate irregularities in tooth position
enhance the natural effect of dentures (Fig 8-80).
Based on this knowledge, it is possible to deviate
from regular positioning and create a harmoni
ous individuality seen labially by convergence and
divergence of the tooth axes. Positional changes
achieved by rotation around the vertical tooth
axis, so that some teeth may overlap, will also in
crease the natural impression (Fig 8-81).
Error analysis
The canine is often placed with the neck of the
tooth facing vestibularly for esthetic reasons.
However, inverted placement of a canine, where
the cutting edge is tipped inward, causes massive
interference in lateral movements; as a result,
the canine will be pressed out in the vestibular
direction by forced movements. The canine is de
formed by corrective preparation. Therefore, the
canine should be set up so that the neck and inci
sal edge overlie each other vertically. The degree
of overjet has esthetic aspects and functional val
ue. The sagittal distance of all the teeth must be
uniform. The distance often increases on the lat
eral incisor and canine. This error arises if the ar
ticial teeth have the wrong vestibular inclination
or are placed inverted; this error will also arise if
the maxillary teeth are placed too close together.
Position of Mandibular
Posterior Teeth
For static reasons, the mandibular posterior teeth
are placed on the middle of the alveolar ridges.
Provided that the tongue is not crowded, it is
possible to move the posterior teeth slightly lin
gually. The compensating curves are formed by
the position of the posterior teeth. The curves
are achieved in an average-value articulator with
a template (calotte) by placing the teeth against
the mounted template. If the posterior teeth are
set up without accessories—hence without tem
A
B
C
A
B
C
279
Position of Mandibular Posterior Teeth
plates—the following points should be kept in
mind.
Setup starts with the mandibular posterior
teeth, and the maxillary posterior teeth are set
against them. This is because the static lines in
the mandible are clearer when the anterior teeth
are in place, which makes setup easier. Setup is
done tooth by tooth in antagonist pairings; the
necessary corrections always relate to all the
teeth involved.
The mandibular second molar stands with its
distobuccal cusp at the same height as the tip of
the canine, which means level with the occlusal
plane. This occlusal plane runs from the mandib
ular incisal point to half the height of the retro
molar triangle (Figs 8-82 and 8-83). This occlusal
plane is marked in every average-value device so
that this plane can be readily identied by simple
placement of a ruler. Stretching a rubber band
is not accurate because it can be shifted by the
standing teeth or the occlusion rim.
The sagittal compensating curve must emerge
when viewed from the vestibular aspect: Only
the canine and the distobuccal cusp of the sec
ond molar touch the occlusal line. The premolars
stand below this line. The rst molar stands per
pendicular and is the lowest within the curve (Fig
8-84).
Fig 8-82 The second molar is set up with a mesial inclination
inside the compensating curve, and its distobuccal cusp tip
touches the occlusal plane.
Fig 8-83 The occlusal plane is xed by half the height of the
retromolar triangle and by the lip closure line, which in turn
is represented by the incisal indicator on the articulator. The
compensating curve intersects the occlusal plane at the canine
and at the distobuccal cusp of the second molar. The curve
arises because the rst premolar lies lower than the canine,
the second premolar lower than the rst premolar, and the rst
molar lower than the second premolar, while the second molar
is tipped so steeply that it touches the occlusal plane again.
Fig 8-84 The rst molar is placed at the lowest part of the sunken alveolar ridge, where the center of masticatory force is located.
280
Complete Dentures
The transverse compensating curve is formed
when the tooth inclination of the mandibular pos
terior teeth is reproduced; that is, all the posterior
teeth are inclined lingually (Fig 8-85). The central
developmental grooves of the mandibular poste
rior teeth form a straight line that aligns with the
middle of the alveolar ridge; as a result, the buc
cal cusps lie on the tangent of the Bonwill circle.
The lingual cusp tips lie on the Pound line. Check
movements show whether an antagonist contact
exists with the maxillary canine, without the inci
sal guide pin lifting off.
The mandibular rst premolar stands with its
buccal cusp tip slightly lower than the canine.
This cusp tip should point exactly to the interden
tal embrasure between the canine and rst pre
molar in the maxilla. Inclination of axis from the
vestibular view is slightly distal (Fig 8-86).
A space between the rst premolar and the ca
nine becomes necessary to compensate for the
differing widths of the anterior teeth. To do this,
the two mandibular premolars and the maxillary
rst premolars are xed in their approximate po
sition to determine where the space is needed. If
the maxillary set is too wide or the overjet is too
small, a space is needed in the mandible; if the
maxillary set is too narrow or the overjet is very
wide, the space will arise in the maxilla.
The mandibular second premolar stands with
its buccal cusp again slightly lower than the rst
premolar, approximately 0.75 mm below the oc
clusal plane; the sagittal curve is formed. From
the vestibular view, the tooth axis is perpendic
ular, which supports the shape of the curve. So
that a precise interdental embrasure is created,
the mesial edge of the second premolar lies at
the same height as the distal edge of the rst
premolar. The approximal inclination shows the
tooth inclination, whereby the transverse curve
arises. In the tooth-by-tooth setup, the maxillary
rst premolar is now set up to correct the sliding
contacts during check movements.
The mandibular rst molar in the vestibular
view stands vertically at a distance of about 1 mm
from the occlusal plane. It forms the lowest point
on the sagittal compensating curve. Its central
developmental groove forms a straight line with
the rst and second premolars, running parallel
to the ridge line. It stands with a slight tooth incli
nation lingually in order to shape the transverse
curve. In the tooth-by-tooth setup, the maxillary
second premolar must be set up to correct the
sliding contacts during check movements.
The mandibular second molar, seen from the
buccal aspect, stands inside the sagittal com
pensating curve and is tipped mesially so that it
forms a correct interdental embrasure with the
rst molar and touches the occlusal plane with
its distobuccal cusp. The transverse curve is very
weakly developed at the terminal molar. In the
tooth-by-tooth setup, the antagonists are now set
up, and complete sliding contact is corrected.
Fig 8-85 The approximal inclinations of the mandibular posterior teeth in the lingual
direction produce the transverse compensating curve. This inclination can be found
in a tooth-by-tooth setup by the check movements in which sliding contacts have to
exist. The transverse curve decreases distally; that is, the rst premolar is the most
strongly inclined lingually and the second molar the least inclined.
Fig 8-86 The premolars are tted inside
the compensating curve; their vestibular
contours display the same inclination as
the canine.
281
Position of Maxillary Posterior Teeth
Position of Maxillary
Posterior Teeth
For static reasons, placement of the maxillary
posterior teeth on the middle of the alveolar ridge
is compulsory. Slight deviations in the vestibular
direction may arise because of the inclination of
axis inside the transverse compensating curve
(Figs 8-87 and 8-88). Nevertheless, secure reten
tion of the complete denture can be ensured by
means of the functional impression and the me
chanical retentions.
The dental arch is shaped into a semi-ellipse;
the premolars stand inside the premolar tangent
in order to shape the buccal corridor, for which
the canine and rst molar serve as xed points
(Figs 8-89 and 8-90). It makes sense to set up the
mandibular pair of posterior teeth rst and then
to align the maxillary antagonists accordingly (Fig
8-91). It is important to ensure that the posterior
teeth are placed in normal occlusion according to
the antagonist rule, where the cusp tips always lie
in the interdental embrasures of the antagonists
(Figs 8-92 and 8-93).
If the mandibular teeth are set up, the maxil
lary antagonist can be xed with a little wax in
its correct intercuspation position on this row of
teeth (Figs 8-94 and 8-95). It is then pressed into
the maxillary softened wax rim by closing the ar
ticulator. The maxillary and mandibular occluding
cusps each engage in their antagonist contact ar
eas. The correct sliding contact is checked by lat
eral and protrusive movements.
The maxillary premolars stand perpendicular,
and their lingual cusps touch the antagonists in
the interdental embrasures. The correct position
should also be checked intraorally. The palatal
cusps appear longer than the buccal cusps and
form the transverse compensating curve. The pre-
molars have only a slight overbite buccally and
glide past each other in antagonist contact with
out interference and without losing the sliding
contact of the anterior teeth.
The maxillary rst molar is brought into the
correct intercuspation position by resting the me
siolingual occluding cusp in the central develop
Fig 8-87 (top) In a complete denture setup, the inclinations of
the tooth axes of the maxillary (and obviously the mandibular)
posterior teeth deviate from the natural inclinations of axis be
cause the sagittal compensating curve is more curved than the
natural occlusal curve. The rst and second molars are tipped
markedly in the distal direction. In addition, the posterior teeth
project beyond the occlusal plane because of the shape of the
curve.
Fig 8-88 (bottom) The axes of the mandibular posterior teeth
are inclined so that the sagittal compensating curve arises:
The rst molar stands perpendicular, and the second molar is
tipped mesially; the rst and second premolars have a slight
distal tendency to the alveolar ridge.
282
Complete Dentures
Fig 8-89 The maxillary dental arch forms a semi-ellipse. To
achieve this, the second molar is twisted distally into the den
tal arch. Ellipsoid shaping of the dental arch is necessary so
that the cheek is not pulled between the rows of teeth on mas
tication in the narrow buccal vestibular space.
Fig 8-90 Two principles apply to setting up the maxillary inci
sors: placement on the center of the alveolar ridge and follow
ing the premolar tangent. The vestibular edges of the rst mo
lar and the canine are touched by a straight line, behind which
the premolars stand; the buccal corridor should emerge.
Fig 8-91 The approximal inclinations of the maxil
lary posterior teeth should be selected so that the
palatal occluding cusps have occlusal contact in the
central areas of the mandibular teeth. The rst pre
molar stands over the ridge line so that its palatal
cusp is shorter than its buccal cusp; in the case of
the second premolar, both cusps are at the same
height; the occluding cusp of the rst molar is lon
ger than the buccal nonsupporting cusp (shear),
a relationship that is further accentuated on the
second molar. From the vestibular view, the buccal
cusps follow the compensating curve and project
beyond the occlusal plane caudally.
Fig 8-92 If the overjet
is small but the maxillary
anterior width is large, a
space between the man
dibular canines and rst
premolars will become
necessary on both sides.
If the anterior teeth are
set up rst, the mandibu
lar premolars and the max
illary rst premolar must
be placed in an antagonist
pairing to identify where
and how much of a space
needs to be left.
Fig 8-93 If the maxillary
anterior teeth are too nar
row and the overjet is very
wide, a space will form
between the maxillary ca
nine and the rst premolar.
This space is often referred
to as a primate space. In
any case, it is advisable to
leave a slight gap between
the posterior teeth during
setup so that the individual
antagonist pairings can be
placed in an interference-
free intercuspation position.
283
Position of Maxillary Posterior Teeth
A C D
A
B
Fig 8-95 The size of overjet can vary within the aforementioned excursion if the contact situations of the abraded incisal edges
are altered: (a) Setting the abraded incisal edges exactly to edge-to-edge contact will produce an average amount of overjet. (b)
If the maxillary central incisor is placed with the vestibular edge of its abrasion facet on the lingual edges of the abraded cutting
edges of the mandibular antagonists, a very small overjet will be created. (c) If, on the other hand, the maxillary central incisor is
placed with the lingual edge of its abrasion facet on the vestibular edges of the abraded cutting edges of the mandibular teeth, a
wide overjet will result.
a b c
Fig 8-94 The overjet is constructed by reference to a dened
excursion: Once the mandibular anterior teeth have been set
up, the maxillary central incisor is placed in the soft wax in
its position, precisely on the midline with an overbite (ap
proximately 2 mm) (A). A lateral movement guided by the in
cisal guide table is then performed until the distal approximal
edges of the maxillary and mandibular central incisors are in
alignment (B). In the process, the maxillary central incisor is
pressed in a vestibular direction; in this lateral position, it is
pressed to the edge-to-edge position in the soft wax (C). If the
excursion is reversed, the maxillary central incisor will lie in the
correct overjet (D).
284
Complete Dentures
mental groove of its antagonist. Its distolingual
occluding cusp lies in the interdental embrasure
between the mandibular rst and second molars.
The mesiobuccal facet with the labial contour of
the canine forms the premolar tangent on which
the premolars lie.
The second molar is tted into its correct in
tercuspation position. Keeping the second molar
inside the ellipsoid dental arch can pose prob
lems. If a buccal overbite is dispensed with and
an edge-to-edge position is chosen instead, the
correct position within the dental arch can be
achieved. The compensating curves are deter
mined by the position of the mandibular teeth.
If a complete antagonist contact is created, the
transverse compensating curve is clearly identi
able from the maxillary teeth.
The central developmental grooves of the max
illary posterior teeth—as in the mandibular denti
tion—form a roughly straight line that lies over
the middle of the alveolar ridge.
As a departure from tooth-to-tooth setup, the
mandibular dentition can be set up and ready,
and then the maxillary rst molar can be placed in
its position so that the premolars can be brought
into the space. This gives rise to a space between
the canine and rst premolar if the occlusion or
the different widths of the anterior teeth demand
it; if a space becomes necessary in the mandible,
the setup of the mandibular posterior teeth must
be repeated.
Error analysis
To check tooth position, lateral and protrusive
movements are executed, during which the de
scribed sliding contacts must arise without the
incisal guide pin lifting off the guide table. Each
antagonist pairing is checked and corrected until
sliding contact exists during all eccentric move
ments; only then is another antagonist pairing set
up. The interdental embrasures, the oral and ves
tibular intercuspation, and the curvature of the
compensating curves are checked and corrected.
If balancing contacts are missing, the oral in
tercuspation may be defective, or the transverse
compensating curve will have to be strengthened.
If working-side contacts are missing, the vestibu
lar intercuspation may be defective, or both com
pensating curves are too pronounced. The rst
antagonist pairing (mandibular premolars and
maxillary rst premolars) may already point to
this error. If the buccal cusp of the maxillary rst
premolar glides into the interdental embrasure, it
should retain contact with both antagonists. If the
sagittal curve is too pronounced, a gap with the
mandibular second premolar will occur, which
should be raised by exactly the width of the gap.
In this way, the sagittal compensating curve can
be corrected.
Retention of Complete
Dentures
The main problem when restoring edentulous
jaws lies in ensuring that the complete denture
has secure enough retention when in the rest po
sition and when functioning. Complete dentures
are supported on the dental arch without mechan
ical anchorage, whereby static relationships and
dynamic processes inuence functioning capabil
ity. Retention of the complete denture is affected
by anatomical and physical realities, including
the quality of the underlying tissue (Fig 8-96). Ad
equate retention must be provided against with
drawal forces.
These withdrawal forces may be lever forces
arising from masticatory function, traction forces
due to sticky foods, or the weight of the denture
itself. Denture retention onto the dental arch can
usually be achieved without additional aids, pure
ly by the effect of suction, forces of adhesion and
cohesion, and mechanical retentions from under
cut parts of the jaw.
The denture margins and body can be prepared
with such accuracy of t by means of a precise
functional impression that the denture is rmly
retained. The quality of the retention can be mea
sured by the way in which the denture rest area—
the tissue of the jaw—is protected and how effec
tively the denture is protected against withdrawal
forces.
The following physical factors inuence reten
tion of a complete denture:
• Adhesive and bonding effect
• Accuracy of t
• Stable support
• Mechanical retentions
285
Retention of Complete Dentures
• Effect of suction
• Statics of denture design
Adhesive and bonding effects due to forces of
adhesion and cohesion are crucial to retention of
a complete denture. There is saliva in the gap be
tween the mucosa and the denture base, which
creates adhesive forces to the denture acrylic on
the one hand and to the tissue on the other. This
form of retention can be illustrated by the exam
ple of two glass microscope slides.
Adhesion refers to the forces of attraction be
tween the molecules of two bodies. The closer
these two bodies are brought together, the great
er the force. The size of the gap between the bod
ies can usually be lled with the easy-to-move
molecules of a liquid substance, so that the ad
hesive effect happens via these molecules and,
as shown by two wet glass slides, can produce
enormous forces. The adhesive force of the den
ture base is consequently greater if the gap is
very small (that is, the accuracy of t of the den
ture is very great).
Cohesion refers to the force of attraction be
tween the molecules of a substance. Cohesive
force arises through the saliva. This cohesive
force is relatively strong with a thick viscous sa
liva but can be further increased by suitable ad
hesive agents (adhesive powder). Adhesive and
bonding effects always act together, namely ad
hesive force between saliva and the denture or
tissue and cohesive force in the saliva.
Accuracy of t increases the capillary action of
the aforementioned forces due to adhesion and
cohesion. The more tightly the denture base ts
to the mucosa, the more effective is the capillary
action and the effect of suction. Good accuracy of
t also prevents any adverse dynamic behavior
of the denture while functioning; that is, during
chewing function or when the wearer is speaking,
a very accurately tting denture will not slip to
and fro on the mucosal support as much as an
ill-tting denture, which will produce sore spots.
Stable support from a relatively rm denture-
bearing area is necessary for secure retention of
a complete denture. A bony alveolar ridge with
minimally resilient mucosal covering is best suit
ed as support for a denture. On a mobile support
(abby ridge) comprising tough connective tis
sue, a denture will be displaced and levered off.
Denture movements counter to jaw movements
produce areas of opposing pressure loading,
leading to substantial pressure sores.
Mechanical retentions are undercut areas of the
alveolar ridge on the jaws into which the denture
bases have to be extended. In the maxilla, these
Fig 8-96 Horizontal positional stability depends on the underlying tissue. In the case of abby ridges (a), where the ridges consist
of tough connective tissue only, the dentures can be displaced transversally and sagittally on very strong compression of the mu
cosa. High, well-preserved alveolar ridges are the prerequisite for good denture retention. This is because the denture can still be
shifted when the bony support with uniform mucosal covering is not high and its shape offers no mechanical retentions (b). Denture
movements and compression of the mucosa will accelerate bone resorption.
a b
286
Complete Dentures
areas include parts of the left and right tubercles,
between tubercle and anterior alveolar ridge, and
sometimes the entire vestibular area (Fig 8-97).
In the mandible, the undercuts include the ante
rior parts of the alveolar ridge and the retromolar
wings (Fig 8-98). These morphologic features of
the jaws can be described as extension options.
Suction Effect
A suction effect arises because a space lled with
rareed air gets smaller because of the effect of
normal atmospheric pressure. The effect can be
illustrated by a suction pad: If a rubber pad is
pressed onto a smooth surface, its edges offer a
tight marginal seal. The pressure difference arises
because the rubber pad that is deformed when
it is pressed will try to upright itself because of
its elasticity. Hence a small gap of rareed air is
formed between the pad and smooth surface. At
mospheric air pressure presses the edges of the
rubber pad onto the smooth surface. If the pad is
pulled perpendicular to the surface, the rareed
air space and hence the pressure difference will
get bigger and the pad will stick more.
The functional margin in a denture acts like the
edges of the suction pad, producing a space that
is closed on all sides (Fig 8-99). To achieve this
suction effect with a denture requires this closed
space on all sides, which can be made bigger by
withdrawal forces and gives rise to the rareed
air space. Atmospheric air pressure becomes
effective because of withdrawal force as it tries
to restore the original spatial dimensions. If the
denture is pulled off vertically, the space between
the jaw and the denture base will increase. In the
small amount of air found in the saliva within this
space, a pressure difference occurs in response
to higher outer pressure and creates a suction ef
fect. This suction effect is greatest when subject
to axial forces (withdrawal forces perpendicular
to the suction surface); in other words, at jaws
Fig 8-97 In the maxilla, the
mechanical retentions on well-
preserved alveolar ridges are
found in the undercut anterior
vestibular areas and the buccal
vestibular areas. These areas act
as mechanical retentions but only
interact when the width of the
vestibular fornix (Vf) is less than
the tuberosity width (Tw); there
fore, the anterior areas do not
become effective until the dorsal
retentions are also present.
Vf
Tw
Vf
Tw
Fig 8-98 In the mandible, well-preserved alveolar ridges in
the anterior vestibular area are undercut and offer mechanical
retentions. If the denture base is extended into the sublingual
areas, the downward pressure of the tongue may serve as me
chanical retention. The paralingual areas are always undercut
and can be used as mechanical retentions if appropriate im
pressions are taken.
287
Suction Effect
are not unfavorable but need to be better protect
ed against axial forces.
A valve-type margin is a specially shaped func
tional margin to a complete denture base. The
vestibular fornix in the rest position is a narrow
space in which the mucosal parts touch each oth
er (Fig 8-100). Therefore, a denture margin in the
transitional area from attached to mobile mucosa,
having been shaped, smoothed, and rounded ac
cording to a functional impression, may slightly
displace the mucosa that is pulling toward the
vestibule. The mucosa is slightly stretched and
remains at the denture margin during denture
movements. The denture margin forms the valve-
type seal throughout its course, with a distinction
being made between an outer valve and an inner
valve. The inner valve is the area of the immobile
mucosa from the depth of the vestibular fornix
up to the alveolar ridge. The outer valve is formed
when the mucosa is displaced out of the rest po
sition toward the vestibule by the broad denture
margin and is stretched around the functional
margin. The denture margins should not be so
wide that they cause pressure points to develop
on loading because of the space they occupy.
The more accurately and more extensively the
valve margin (especially the outer valve) is shaped
according to the functional impression, the more
effective the valve margin. The surface of the out
er valve can be enlarged by suitable shaping of
the outer surface of the denture so that the
pressure-equalizing air travels a longer distance.
The inner valve can be effectively created if the
mucosa in this vestibular fornix area is also dis
placed out of the rest position toward the bony
support and is thereby placed under tension.
Etched lines marking the vibrating line on the
dorsal edge of the baseplate of the maxillary den
ture complete the valve margin (Fig 8-101). The
vibrating line is etched in place so that the edge
of the plate presses into the mucosa. The etch
ing can be shaped in various ways. To prevent
retching by the patient, the contour of the etch
ing should ideally be adapted to the bony sup
port; that is, it should be at, should rise dorsally,
and then should be sunk into the transition from
hard to soft palate. The etching should be about
2 to 3 mm wide and about 1 to 1.5 mm deep. The
acrylic resin plate can be gently tapered so that
a smooth, dorsal transition is formed from den
Fig 8-99 In the same way as a normal suction cup, the suction
effect of a complete denture arises as the space between the
denture and tissue is enlarged when the denture is pulled off
its support. In the case of a suction cup, pre-tension caused by
the elasticity of the pressed-on rubber holds the cup onto the
smooth surface. In the case of a denture, the suction force only
ensues when external pulling forces increase the size of the
space. The denture margin in the vestibular fornix must provide
an airtight seal, as with a suction cup. It therefore becomes
necessary to shape the functional margins as valve margins.
O I
Fig 8-100 In the rest position, the vestibular fornix is a nar
row space in which the mucosal parts touch each other (a).
The entire functional margin of the denture (b) must be shaped
as a valve margin. A distinction is made between the outer
valve and the inner valve. The outer valve (O) arises when the
mucosa is displaced out of the rest position in the vestibular
direction by the wide denture margin and is stretched around
the functional margin. The inner valve (I) is the area of immo
bile mucosa from the depth of the vestibular fornix up to the
alveolar ridge.
a b
288
Complete Dentures
ture to mucosa. Etching of the vibrating line, as
well as the effect of the valve margin, should also
compensate for any inaccuracy of t of the dorsal
plate edge caused by shrinkage of the acrylic resin.
Even if shrinkage is largely offset by re-pressing
devices for acrylic polymerization and accuracy
of t is improved, it is still advisable to etch a vi
brating line to complement the valve margin.
Additional etchings on the surface of the palate
can increase retention of the maxillary denture
base. Etching additional ridges will divide the en
tire retentive surface into several compartments
with their own separate retentive effect. Tools
with different proles may be chosen for this pur
pose. Etched lines should be placed so that the
bony support is not damaged.
Extension Options
Extension options are the design principles in
volved in extending denture bases into mucosal
areas so that masticatory forces are distributed
according to the snowshoe principle and addi
tional retention is created for the denture base.
In the maxilla, it is mandatory to encompass
the entire vestibule with the denture base right
into the buccal vestibular spaces. This includes
the maxillary tubercle, which is not affected by at
rophy after tooth loss and can offer excellent sup
port. In individual cases, the denture body may
be extended buccally into the cheek area to ac
commodate the posterior teeth, so that the buc
cal mucosa creates additional retention for the
denture.
Shaping the outside of the denture to ensure
denture retention includes the sparing, smooth
reproduction of the alveolar eminences as well
as the creation of a circumferential channel di
rectly above the valve or functional margin. Al
lowing for reduction needs, the buccal and labial
mucosae, along with their muscle bundles, can
settle here and support the denture. The outer
surface of the denture body in the anterior re
gion is shaped to grip muscle; this is done by
constructing lip shields for the orbicular muscle
of the mouth. In the posterior region, buccinator
rests should be created, and the muscle tracts to
the buccal frena should be traced (Figs 8-102 and
8-103). Due regard should be given to reduction
needs (Fig 8-104).
A
B
Fig 8-101 The dorsal edge of the maxillary complete denture
is etched to complete a circumferential valve margin. As in the
vestibular area of the margin, the mucosa must be displaced
out of the rest position. For this purpose, a 3-mm-wide and
1.5-mm-deep groove falling continuously in the dorsal direction
is etched directly at the transition to the soft palate. The path of
the vibrating line becomes visible in the functional impression
if the soft palate is moved during impression-taking by the pa
tient’s swallowing or pronouncing “ah” or by the nose-blowing
effect. As a result, the position of the posterior nasal spine
of the palatal bone becomes visible; this should denitely be
taken into account because the palatine suture is thickened
here (A). This etching of the vibrating line (ah line) must follow
the dorsal edge of the bone precisely to avoid pressure points.
It is worth noting that the dorsal edge of the bone is beveled
cranially and ends in a sharp edge (B), which meets the etching
of the vibrating line.
289
Extension Options
In the mandible, the retromolar triangle or the
mandibular tubercle is enclosed on both sides to
support the denture and enlarge the base. These
dorsal ridge areas can be slightly restricted by a
well-developed pterygomandibular raphe, which
is tightened when the mouth is opened and le
vers off the denture. Therefore, the dorsal limit of
the margin must be suitably reduced here.
Sublingual pockets (in the anterior sublingual
space) can be covered with a so-called sublingual
roll (Figs 8-105 and 8-106). This is a horizontal ex
tension of the denture margin under the tongue
into the area of the premolars. Vertical extension
would have the opposite effect and would actu
ally cause the denture to lift off during tongue
movements. Horizontal extension of the margin
considerably increases the retentive effect of the
denture. The functional impression involves tak
ing an extension impression of the anterior sub
lingual space without impeding tongue move
ment and while sparing the lingual frenum.
Paralingual pockets (posterior sublingual spac
es) are located on both sides in the dorsal lingual
area under the retromolar triangle. These are usu
ally undercut areas behind the mylohyoid line
into which retromolar wings of the denture base
engage and, as mechanical retention in combina-
tion with the undercut ridge parts of the anterior
region, can secure retention of the mandibular
denture (Fig 8-107). The size and the shape of this
retromolar region are limited by the movement of
the root of the tongue.
Mo
A
B
D
E
G
G
G
F
C
Ma
1
2
Fig 8-102 The outer surfaces of the denture body are shaped
to grip the muscles; that is, lip shields are prepared for the or
bicular muscle of the mouth, in the posterior region buccinator
rests are created, and the muscle tracts to the buccal frena are
traced. Reduction needs should be taken into consideration.
Fig 8-103 The course of the muscle tracts originating from
the modiolus (Mo) allows shaping that grips the muscles: The
tract of the orbicular muscle of the mouth (A + B) engages in
the lip shields. The levator and depressor anguli oris (C + D) pull
toward the buccal frena. The major zygomatic muscle (E) pulls
with parts of the buccinator (G) toward the zygomatic crest.
The risorius muscle (F) also runs with parts of the buccinator
(G) backward and toward the oblique line. The masseter (Ma)
overlays the buccal vestibular space.
Fig 8-104 A normally shaped mandibular denture that makes
allowance for reduction needs ([1] mylohyoid line, [2] oblique
line) has a slim mucosal rest. If the denture base is enlarged
into the extension spaces, excellent mechanical retentions are
achieved in undercut areas of the jaw.
290
Complete Dentures
Buccinator pockets are the posterior buccal
spaces into which the denture margin can be ex
tended by buccinator supports. In the same way
as the sublingual roll, a horizontal extension can
be created above the plate edge that has been
trimmed in keeping with the oblique line; this ex
tension takes the form of a rest for the cheeks,
whereby the denture is pressed onto the dental
arch (Fig 8-108).
Balanced muscle tone between the tongue and
the cheek can aid retention of the mandibular
denture if the teeth are set up so that the den
ture cannot be moved by these muscles and so
that the patient does not bite his or her tongue
or cheek (Fig 8-109). Typically, the teeth stand fur
ther lingually than they did before tooth loss for
static reasons. Therefore, the space for the tongue
is always slightly restricted. This is why manufac
Fig 8-105 The sublingual space can be
lled by an extended denture margin so
that the tongue can stabilize the man
dibular denture by its own weight. It is
inadvisable to extend the denture margin
vertically because this will displace the
oor of the mouth and impede move
ment of the tongue.
Fig 8-106 Extending the denture mar
gin in the horizontal plane under the
tongue does not impede the oor of the
mouth and therefore fullls the function
of an additional retentive aid because
the weight of the tongue can press the
denture downward. A denture margin
extended in this way is known as a sub-
lingual roll.
Fig 8-107 An individual impression
must be taken of the paralingual areas
(A), which provide space for the retromo
lar wings on the denture. The vestibular
undercuts on the anterior ridges form us
able supports for the retromolar wings.
The sublingual spaces (B) can be used for
the sublingual roll.
A
A
B
Fig 8-108 In the posterior region, the denture
body can be extended into the buccal space so
that the cheek can lie on these convexities and
give the denture additional retention. The bucci
nator support starts above the vestibular fornix.
In the mandible, the buccinator support can be
extended vestibularly over the oblique line. A suit
able impression is always the foundation for shap
ing these accessory retentive aids.
Fig 8-109 The posterior teeth are placed so that
they do not impede the cheeks or tongue. Thus,
they are positioned over the middle of the alveolar
ridge and are accompanied by balanced tongue
and cheek tone. Balanced tone is the position of
equilibrium between the resting tension of the tis
sues of the tongue and cheek. When the posterior
teeth are accompanied by balanced tone, the pa
tient cannot bite the cheeks or tongue.
291
Extension Options
turers supply articial teeth that have a smaller
vestibular-lingual breadth than normal teeth.
Hollowing out the papilla, the palatine raphe,
and the torus can increase the suction effect of
a maxillary complete denture in the short term
(Fig 8-110). A kind of suction chamber is formed,
but this closes after a short wearing time due to
proliferation of the mucosa. If lines are etched
and hollowing out is done at the same time, the
foils are guided over the etched lines up to the
hollowed-out area.
The retentive force of the denture—due to the
suction effect, the force of adhesion, and cohe
sion—is between 70 and 100 N if the accuracy of
t is good and the valve margins are functioning
properly (Fig 8-111); on vertical withdrawal, this
force may be considerably higher.
Fig 8-110 In the brous median area (palatine raphe and palatine torus), a rocking movement around the median palatine suture
can occur when the denture is loaded on one side, and the denture margin may be lifted off on the unloaded side. Therefore, it
may be advisable to hollow out this area so that the denture sinks in evenly and can be more heavily loaded. If the denture base is
hollowed out in the area of the median palatine suture, an additional suction effect may arise because a vacuum chamber has been
created. This effect is lost after a short time because the mucosa proliferates into the chamber.
Fig 8-111 Retention of a maxillary complete denture can be improved by etching lines. The retentive surface is divided into areas
of different sizes, forming separate retentive compartments. If air gets under the denture at the valve margin, the denture will still
hold because the individual compartments can still have adequate negative pressure. The etching, in this case Frankfurt etching,
is preferably done in the glandular and fat pad area. Vertical band etching is another method in which the whole alveolar ridge is
encompassed by a circumferential ridge. The ridge is angular and about 1.5 mm deep. A vibrating line etching is also created. This
form of etching has been used for abby ridges and is not recommended for normal dental arches.
1 mm
0.5 mm
292
Complete Dentures
Gysi’s Working Method
The term articulation theory is closely linked to
the name of Professor Gysi because he presented
what he called the “articulation problem” in a
1908 publication. In that and subsequent publica-
tions, as well as through his teaching work, he
studied and was the rst to prove the functional
relationship between tooth shape and tooth po
sition, the TMJ, and mandibular movement. The
proof was provided by long-term studies, experi
mental research, and statistical analyses, all of
which laid down the principles of modern dental
research.
Based on his research ndings, Gysi developed
a comprehensive and, in the truest sense, com
plete theory, which was applied to create instruc
tions for the practical fabrication of dentures.
According to Gysi, the chewing cycle involves a
movement habit that depends on the consistency
of the food and varies between individuals but
follows a xed principle: Food is crushed as slid
ing occlusal surfaces grind against each other. To
do this, the mandible is brought into a slightly
lateral position from which a grinding, sliding
movement takes place into terminal occlusion.
According to Gysi, the four-phase round bite is
the movement sequence involved in masticating
food (Fig 8-112):
1. The rst phase is opening the mouth to take in
the food.
2. The second phase is a slight sideways gliding
of the mandible to the chewing side to grasp
the food.
3. The third phase involves closure of the mouth
into approximate cusp-to-cusp contact, where
by the food is crushed but not ground.
4. The fourth phase involves gliding out of the lat
eral position into terminal occlusion, when the
food is broken down into small pieces by the
constant increase in masticatory force.
The single phases ow seamlessly into each
other. Only the fourth phase is of interest, when
the teeth on the chewing side glide into centric
occlusion in full tooth contact and the mandible
is guided not only by the joints but also by the oc
clusal pattern of the teeth. This tooth guidance be
comes even clearer when looking at the process
of biting off food: The mouth is opened and the
mandible pushed forward to grip the food. If the
Opening the
mouth
Mandible
gliding sideways
Closing on
cusp contact
Gliding into
terminal occlusion
Phase 1 Phase 2
Phase 3 Phase 4
Fig 8-112 The movement sequence of the
chewing cycle is described by Gysi as a four
phase round bite. The sequence of move
ments follows a xed principle but is depen
dent on the consistency of the food and is
therefore variable. Four phases are identied.
The phases merge seamlessly. The fourth
phase is of interest: gliding into terminal oc
clusion under masticatory force, during which
balanced articulation is required for a com
plete denture according to Gysi.
293
Gysi’s Working Method
food now has to be sheared off, the incisors glide
into centric occlusion under contact. To glide into
terminal occlusion, the anterior teeth and canines
guide the mandible into the correct position.
Guiding elements in mandibular movement are
the TMJs and the occlusal patterns of the teeth
(Fig 8-113). The occlusal patterns of all the teeth
can be presented as a combined virtual guide
plane: the incisal guide (surface).
The mandibular movements can be understood
from the condyles and a xed point on the inci
sors. It is noticeable that the condyle moves on a
xed path both forward and to the side, namely
on the sagittal and lateral condylar paths. In the
process, the xed point on the mandibular inci
sors moves on the palatal surfaces of the maxil
lary incisors within what is known as the sagittal
and lateral symphysis path. (The symphysis point
and mandibular incisal point are considered syn
onyms for the anterior Bonwill triangle point.)
Gysi describes the sagittal and lateral symphy
sis path and condylar path as a functional unit
with the cusp slopes of the posterior teeth and the
inclinations and positions of the teeth inside the
occlusal curves. In this context, these curves con
tinued to be called curves of Spee, even though
there was already evidence that the ideal form of
the Spee curve, according to Spee’s description,
must be regarded as a special case.
Certain conclusions necessarily arise from
these connections. If the chewing cycle involves
xed, recurring movements and the mandible
is guided by the TMJs and the tooth shapes and
positions, fabricating a fully functioning denture
should follow these steps:
1. Initiate the mandibular movement.
2. Precisely reproduce the anatomical tooth shapes.
3. Position teeth relative to mandibular movement.
To put it simply, Gysi proved that precise repro
duction of specic parts of the functioning mas
ticatory system ensures the success of a denture.
Articulators according to Gysi
Gysi developed articulators for copying mandibu
lar movements, which made it possible to simu
late a close approximation of individual move
ments. The Simplex articulator is the best-known
average-value device developed by Gysi (Fig
8-114). It allowed the essential mandibular move
ments to be executed on condylar paths with a
sagittal inclination to the occlusal plane of about
33 degrees and a Bennett angle of roughly 15 to
17 degrees. Joint-related mounting of the models
was possible in the average-value articulator. A
key factor was that the incisal guide plate could
be variably inclined between 0 and 55 degrees to
handle patients’ asymmetric condylar path incli
nations.
Gysi’s Trubyte articulator enabled the sagittal
condylar path inclination to be set between 0 and
55 degrees, based on individual values, and an
individual Bennett angle to be chosen between 0
and 20 degrees. These individual joint values had
to be measured with a specially developed face
bow and special tracing plates.
The tooth shapes Gysi went on to develop em
ulated the anatomical pattern and had cusp sur
faces with a slope that was adapted to the condy
Fig 8-113 The guiding elements of mandibular movement, ac
cording to Gysi’s mechanical explanatory model, are the joints
and occlusal patterns of the teeth; the musculature is ignored.
The occlusal patterns are combined in incisal guidance. With
the joints, this forms a three-point support on which the upper
arm of the articulator can be moved relative to the mandible. If
the three guides are individually adjustable, each occlusal area
can be reconstructed.
294
Complete Dentures
lar path inclination. The Anatoform articial teeth
had a sagittal inclination of 32 degrees and a
buccal and lingual inclination between 10 and 20
degrees; the molars based on Gysi had a sagittal
inclination of 20 degrees and a lateral inclination
of 3 degrees.
Gysi described tooth positioning relative to
mandibular movement with the term balanced
articulation, dividing the rows of teeth into the
working side and the balancing side (nonworking
side) during chewing (Fig 8-115). During chewing,
the working side is the loaded side; Gysi described
the nonworking (idling) side as the balancing side
because the tooth contacts on that side were sup
posed to prevent the denture from being levered
off or tipping during the fourth phase of chewing.
On protrusive movements, tooth contact in the
anterior region is meant to be compensated for
by balancing contacts on the terminal molars. The
teeth must therefore have both a sagittal and a
transverse occlusal curve, thereby compensating
for the Christensen phenomenon. These dental
arch forms that Gysi called compensating curves
also had to be replicated when setting up the
teeth. The aim was to achieve three-point contact
during lateral and protrusive movements, which,
distributed over the entire dentition, had one con
tact in the posterior region on each side and one
contact in the anterior region.
The static conditions affecting the denture body
in relation to the shrunken alveolar ridges had to
be taken into account during setup of the teeth.
In the law of the ridge line, Gysi required the ar
ticial teeth to be set up over the center of the
alveolar ridges in a statically stable position to
prevent lever effects caused by the denture body
(Fig 8-116).
Crossbite setup in the posterior region be
comes necessary if the lines connecting the ridge
centers are at an angle less than 80 degrees to the
occlusal plane. This connecting line and angle are
known as the interalveolar line and the interalve-
Fig 8-114 The Simplex articulator is an average-value articula
tor in which the Bennett movement is produced by dorsally
positioned joints; the crosspiece located on the upper arm in
front of the joint surfaces serves as the marking of the hinge
axis (A).
Fig 8-115 The term balanced articulation in the fourth phase
of Gysi’s round bite denes the working side (A) and the bal
ancing side (B). The working side is the side into which the
mandible is pushed, while there are tooth contacts on the bal
ancing side that should prevent the unloaded parts of the den
tition from being levered off (a). When biting off food, sliding
contacts on the posterior teeth in the protrusive position must
prevent any tipping of the denture (b).
A
A
B
a b
α > 80°
α < 80°
Occlusal
plane
Interalveolar line
Fig 8-116 The varied shrinkage of alveolar ridges can
pose a problem when setting up the posterior teeth.
If the teeth have to be arranged on the ridge line ac
cording to the law of ridge lines, normal intercuspa
tion may be disrupted. According to Gysi, a normal
occlusion should be set up if the inclination of the in
teralveolar line to the occlusal plane is greater than 80
degrees, and a crossbite should be set up for inclina
tions less than 80 degrees.
295
Gysi’s Working Method
olar angle, respectively. In conclusion, Gysi gave
working instructions for fabricating complete
dentures. A functional impression with custom
trays is rst required, and then a precise interoc
clusal registration.
Gysi described and recommended extraoral oc
clusal registration (Fig 8-117). This involved mold
ing occlusion rims out of stent material (thermo
plastic impression material) and setting them
onto the bite plates over the center of the alveolar
ridge to the exact vertical dimension of occlusion
so that they contact in the occlusal plane. A trac
ing plate was then mounted on the mandibular
occlusion rim and the tracing pin onto the maxil
lary occlusion rim.
The tracing plate and tracing pin protruded out
of the mouth and enabled mandibular movements
to be checked, during which the Gothic arch was
traced into the registration wax. The tip of the
Gothic arch indicated the position of centric occlu
sion. The bite plates were xed in this position.
As positional indicators for the teeth, the occlu
sion rims had to be padded to reect natural lip
volume so that the middle of the face could then
be traced on the occlusion rims as well as the lip
closure line, the canine points, and the smile line
of the upper lip, thereby establishing tooth length
and width (Fig 8-118). These tracings then had to
be transferred to the models, and the tracing of
the sagittal inclination of the posterior mandibu
lar ridge had to be added.
1
2
3
4
5
6
Fig 8-117 Extraoral occlusal registration is an attempt to regain centric occlusion with suitable registration kits and, using a face
bow, to carry out joint-related mounting of the casts in the articulator as well as survey the condylar paths. (a) The tracing pin (1) is
mounted on the maxillary occlusion rim and the tracing plate (2) on the mandibular occlusion rim; the registration wax (3) for tracing
mandibular movement is located on the mandibular tracing plate with the facebow mounting pins (4). (b) The facebow is mounted
on the pins, and the exible condyle indicators (5) are aligned with the condylar points of the patient. Adjusting pins (6) are tted
onto the facebow; these are height adjustable so that the bite plates can be brought into the correct height when plastering up in
the articulator.
Fig 8-118 The maxillary anterior teeth are placed on the oc
clusal line and stand with their labial contours on the outer
contour of the wax occlusion rim, which has been padded to
reect lip volume. The inclinations of axis are located. The man
dibular central incisor should be in contact with its antagonist
without an overjet.
a b
296
Complete Dentures
Surveying the condylar path
It was possible to t a facebow onto the tracing
plate of the mandibular bite plate in order to al
low joint-related mounting of the models in the
articulator. The exible ends of the facebow were
aligned with the patient’s condylar points and
represented the spatial relationship between the
condyles and the occlusal plane. The facebow
could be adjusted in the articulator with the trac
ing plate, bite plate, and mandibular model in
such a way that the exible ends pointed to the
condyles of the device and the mandibular incisal
point on the bite plate coincided with that of the
articulator.
The facebow technique permitted individual
surveying of the condylar paths and occlusal reg
istration, the sagittal course of the condylar paths
actually being traced with the exible ends of the
facebow during Gothic arch tracing. To do this,
two tracing plates were placed on either side of
the patient’s head, and the black lead pencils on
the exible ends of the facebow traced the sagit
tal course of the condylar path onto the tracing
plates. The inclination of the condylar path to the
occlusal plane could then be determined by sim
ply measuring the angle.
This description of Gysi’s articulation theory
only provides a historical perspective but also il
lustrates his thoroughness, consistency, and sys
tematic working method, which remains exem
plary to the present day. After phases of hostility
and defamation, expert opinion now asserts the
importance of his theory. The methods commonly
used today for fabricating complete dentures—in
terms of their compendium-type setup rules and
their explanatory constructs—represent a rene
ment of Gysi’s ideas or partial concentration on
certain working methods based on this theory.
The criticisms of Gysi’s articulation theory arose
because certain anatomical facts allow for other
interpretations. For instance, Gysi considered the
balancing contacts to be the ideal form, including
in natural dentitions, and interpreted missing con
tacts as a degenerative deformation of the den
tition. Critics deduced from this that the theory
was incorrect. The high-cusp teeth were criticized
because they lacked the physiologic and func
tional abraded grinding surfaces. The position of
the maxillary anterior teeth and the lack of overjet
were also criticized because this supposedly gave
rise to unsatisfactory esthetics and statics of the
maxillary denture.
Setup instructions
Gysi developed precise instructions for fabricat
ing complete dentures, among which the setup
rules are of interest to dental technicians. They
establish the position of the teeth and the setup
sequence:
1. The maxillary anterior teeth are placed on the
occlusal line and stand with their labial con
tours on the outer contour of the wax occlu
sion rim, which has been padded to reect lip
volume. The inclinations of axis visible from
the vestibular aspect are identied.
2. The mandibular anterior teeth should stand in
contact with their antagonists without overjet.
Once again, the inclinations of axis visible ap
proximally and vestibularly are established.
3. The approximal inclination of the maxillary
anterior teeth is also established. Accordingly,
the labial contours of the canines stand verti
cally, and their tooth axes have a clearly ves
tibular inclination (Fig 8-119).
4. The rst premolar in the maxilla contacts the
occlusal line with its buccal cusp; this line is
simulated by a glass plate. A small space is
possible between the canine and the rst pre
molar (Fig 8-120).
5. The maxillary second premolar contacts the
occlusal line with both cusps (Fig 8-121).
6 The maxillary rst molar touches the occlusal
line with its mesiopalatal cusp (Fig 8-122).
7. The second molar has no contact with the oc
clusal line, in keeping with the compensating
curve (Fig 8-123).
8. The mandibular anterior teeth are placed on
the ridge midline with their incisal edges at
the same height. The labial inclination of axis
shows a mesial tendency, and the approximal
inclinations are established. The mandibular
dental arch is thus developed (Fig 8-124).
9. The mandibular rst molar is rst placed in its
correct position (Fig 8-125).
10. Only then are the remaining teeth set up (Fig
8-126).
297
Gysi’s Working Method
Fig 8-119 The approximal inclination of
the maxillary anterior teeth is also estab
lished, Gysi referring to the labial contour
in their inclination and not the tooth axis.
Accordingly, the canines stand with their
tooth axes showing a clear vestibular in
clination.
Fig 8-120 The maxillary rst premolar
touches the occlusal line with its buccal
cusp. A small space between the canine
and rst premolar is possible.
Fig 8-121 The maxillary second premo
lar contacts the occlusal line with both
cusps.
Fig 8-122 The maxillary rst molar
touches the occlusal line with its mesio
palatal cusp.
Fig 8-123 The second molar has no
contact with the occlusal line, in keeping
with the curve of Spee.
Fig 8-124 The mandibular anterior teeth
stand on the center of the ridge with
their incisal edges in a straight line. The
labial inclination of axis shows a mesial
tendency, and the approximal inclinations
are established. The mandibular dental
arch is thus developed.
Fig 8-125 The mandibular rst molar is
rst placed in its correct position.
Fig 8-126 The remaining teeth are then
set up.
298
Complete Dentures
Hiltebrandt’s Working
Method
The interpretations by Dr Carl Wilhelm Hiltebrandt
offer a cohesive theory with working instructions
for fabricating complete dentures. In this case,
the law of form and function is used to interpret
the relationship between functional mandibular
movements and the form of the masticatory sys
tem, thereby qualifying Gysi’s approach. Accord
ing to Hiltebrandt’s view, form and function make
up a harmonious unit in which the form can adapt
to functional disturbances. Mandibular move
ments are guided solely by the musculature,
which does not follow xed pathways. The TMJs
and occlusal patterns of the teeth have no signi
cance as elements that guide such movement.
The purpose of the condylar path inclinations
is to separate the rows of teeth during protru
sive and lateral movements in the area where no
chewing activity is performed. The separation into
working side and balancing side does not exist
in a healthy, complete dentition. Only the canine
guides the mandible into centric occlusion and is
therefore referred to as the anterior jaw joint.
Occlusal curves are interpreted according to
the law of the smallest unit of force. The stepped
positioning of the molars aids the stability of the
alveolar bone.
Mandibular movements are described as regu
latory control movements or as a crushing and
grinding movement in the occlusal eld. Regu
latory check movements are slight lateral move
ments under tooth contact, whereby slight ir
regularities on the cusps standing in the way of
articulation are ground off and the position of the
teeth and dentitions are kept in constant balance.
Crushing and grinding movement is the actual
chewing movement with which food is broken
down into small pieces. It is guided from the cen
tric to lingual aspect and takes place on one side
only. According to Hiltebrandt, this results in the
inclination of the teeth: vestibular at the top and
lingual at the bottom.
Physiologic abrasion arises because of the
crushing and grinding movement and the regu
latory check movements. As a result, the teeth
are ground down into trough-shaped and dome-
shaped functional forms.
The occlusal eld is the functional area of the
chewing surface that is formed and extended by
abrasion. The effective chewing movements take
place in the occlusal eld as crushing and grind
ing movements; it is the area of complete tooth
contact. All movements outside the occlusal eld
are termed articulation; all movements within the
eld are termed occlusion.
Molar roots are aligned so that the masticatory
forces are absorbed axially and transferred to the
jawbone. The mandibular rst molar stands in
side a line that runs as an axis through the palatal
root of the maxillary rst molar. The maxillary rst
molar stands perpendicular to the occlusal plane
(Fig 8-127). The ideal axis between the mandibu
lar and maxillary rst molars is the physiologic
connecting line, which is at an angle of about 160
degrees to the occlusal plane. The occlusal eld
lies within this axis.
The basic statics law states that the maxillary
rst molar stands perpendicular to the occlusal
plane on the ridge midline and that the mandibu
lar molar stands with its longitudinal axis along
the physiologic connecting line at an angle to the
occlusal plane.
Hiltebrandt’s conclusions include the following
(Fig 8-128):
Chewing movements abrade the teeth into at
functional forms; anatomically shaped, high-
cusp posterior teeth are unfavorable.
Compensating curves are not necessary be
cause:
The stability of the denture is ensured by static
tooth shapes
The chop bite is the effective chewing move
ment as a form of functional adaptation in den
ture wearers
The TMJs have no guiding functions; surveying
joint values and their transfer to articulators is
unnecessary, so:
–Occlusion is merely reproducible
Setup of the teeth is done in an occluder with
stable tooth positions and without support
contacts on the opposite side
Guidance of effective chewing movements takes
place in the occlusal eld; therefore, physiologi
cally domed and trough-shaped teeth are used.
For esthetic reasons, maxillary anterior teeth are
placed in front of the alveolar ridge with an in
299
Hiltebrandt’s Working Method
cisal gap from the mandibular anterior teeth for
effective chewing movements.
Posterior teeth are stable in themselves because
of the typical inclination to the occlusal plane.
Setup inside the physiologic connecting line
makes crossbite positioning unnecessary.
a
b
c
d
e
OF
90°
Tipping
zone
Support
zone
Fig 8-128 According to Hiltebrandt, the setup rules are simpler and easier to understand: (a) Based on esthetic considerations,
the anterior teeth are set up in the appropriate inclinations of axis. The canine stands perpendicular. (b) An overjet is left, and the
anterior teeth support the lips. (c) The mandibular rst molar is placed at the lowest point of the alveolar ridge to contribute to the
positional stability of the mandibular denture. The antagonist is precisely aligned with it. (d) The remaining teeth are accommodated
in the space from canine to rst molar. The row of teeth ends at the rst molar. According to Hiltebrandt, any dorsally placed tooth
could push the mandibular denture forward on the inclined plane of the sloping alveolar ridge.
a
b c d
Fig 8-127 According to Hiltebrandt, the maxillary rst molar stands perpendicular to the occlusal plane. The ideal axis of the man
dibular molar runs parallel to the palatal root axis of its antagonist. (a) The physiologic connecting line is derived from the ideal axes
of the two rst molars and is bent at an angle in the occlusal plane. (b) The basic law of statics requires the posterior teeth to be
placed on the alveolar ridge so that the ideal longitudinal axes intersect the ridge line. Tipping will occur outside the ridge line.
(c)
The occlusion rims already have a statically favorable position inside the physiologic connecting line. (d) The occlusal eld (OF) is a
limited area of the occlusal surface with a xed relationship to the root arrangement. (e) The physiologically shaped posterior teeth
have an enlarged occlusal eld into which the sagittally placed ridge of the antagonist engages. The mortar-and-pestle principle
becomes clear here.
300
Complete Dentures
Hallers Working Method
Ludwig Hallers working method is not a self-
contained theory of masticatory function but
deals with partial aspects of tooth positioning in
prosthodontics. Certain distinct, individual mea
sures are intended to enhance the functionality of
complete and partial dentures. The recommended
measures specically relate to a tooth positioning
that improves the statics and hence the retention
of a complete denture.
Haller calls his setup method a centripetal sys
tem for keying dentures. Retention of a complete
denture is improved by the fact that the posterior
teeth are notched within the occlusal line. The
very at and wide molars (Haller molars) of the
mandibular posterior regions are placed rooike
against each other so that they form a roof ridge
that ts into a notch inside the maxillary row of
teeth. The incorporated notch is intended to key
both dentures with each other and hold them in
the right position on the dental arches (Fig 8-129).
Functional performance is expected to increase
as the patient gains condence in bringing the
denture into the correct position by regulative
movements.
The TMJs are supported orthopedically by the
centripetal setup as favorable stimuli during
chewing function; this leads to regeneration of
atrophic processes in the joints as a result of the
securely xed centric occlusion. The keying en
sures retention of the denture to such an extent
that greater chewing efforts are possible, which
strengthen the muscles of mastication.
The principle of keying is preferred to a setup
inside compensating curves. This is because the
denture would be pushed dorsally against the
ascending ramus of the mandible as a result of
the curves. Furthermore, true three-point guid
ance over the excessively at cusps of anatomical
teeth is not considered possible.
Notching of the posterior teeth and a pro
nounced anterior overbite give rise to centripetal
force paths that are directed at one point and x
Fig 8-129 According to Haller, a denture can be stabilized on the edentulous jaw (and in a partially edentulous dentition) by special
positioning of the molars. (a) The four molars are set up in an exaggerated notch position to each other. In this positioning, the sec
ond molars are more inclined toward the occlusal plane than the rst molars. Angle α is smaller than angle β. (b) The force vectors
at the molars, premolars, and incisors run centripetally, hence toward the middle of the denture or the denture-bearing area. The
force diagram should yield a resultant that stands vertically on the jaw. (c) On biting off food, the notching of the molars prevents the
denture from being completely levered off. The patient can immediately stabilize the prosthetic appliance. (d) The specially molded
Haller molars are wider and longer than natural teeth and are entirely at on their occlusal surface. This produces a very large eld
of action. (e) The force paths on the mandibular dentition show that the notching presses the denture against the dental arch and
the ascending dorsal alveolar ridge. The mandibular denture should therefore sit stably.
a
b
c
d
e
α < β
α β
b
b
L
L
M
1
M
2
M
2
M
1
S
P
P
S
M
2
M
1
P
S
301
Fehr’s Working Method
the denture in a stable position. On the mandibu
lar denture, these force lines run directly to one
point; on the maxillary denture, by parallel trans
lation, a force diagram xed at one point can be
constructed.
For better retention of a complete denture,
Haller recommends reinforcing the labial edge of
the denture directly in the vestibular fornix with
ridges that are set against the denture body by a
pronounced notch. The mucosa of the lip area ts
into this notch or onto the ridge and protects the
denture. Furthermore, a peripheral denture an
chor can be created on the mandibular denture.
This roughly 5-mm-high, rounded ball anchor is
placed vestibularly level with the second molars
at the denture margin and is intended to wedge in
the cheek muscles.
Fehrs Working Method
Fehr’s working method is not a new approach to
clarifying the static relationships; here the views
about mandibular movements are stated in Gysi’s
terms. For the interocclusal registration, the oc
clusion rims are shaped to the correct vertical
dimension of occlusion in keeping with the com
pensating curves. The occlusion rims are then
modeled to such a length that all-round surface
contact exists during all translative movements
and the bite plates lie stably on the dental arches.
In other words, a smooth, curved, and individual
occlusal eld is modeled with the occlusion rims
that fully compensates for the Christensen phe
nomenon.
The Fehr method uses a template (calotte) for
interocclusal registration. A simple occluder and
at-cusped teeth are used for the setup. Canines
are trimmed at their tips, and the anterior teeth are
arranged at a sagittal distance of about 1 mm. The
working principle stipulates that the mandibular
teeth should rst be placed on one half of the jaw
precisely against the individually molded occlu
sion rim, then the antagonists should be placed
against them (Fig 8-130). Afterward the other
half of the jaw is set up in the same sequence.
This produces a tooth setup that in principle will
exhibit all-round sliding contact in the sense of
three-point support.
Other authors also offer concepts for setting up
teeth using calottes (eg, Eichner, Monson, Hall,
and Faber), and articulators with average-value
calottes or calotte-shaped setup templates are
available. All of these methods are based on the
realization that the positional stability of a den
ture is achieved by three-point support and not by
extreme keying of the dentures.
Fig 8-130 According to Fehr, if occlusion
rims have a calotte-like shape in the occlu
sal plane in maximal intercuspation and a
suitable instrument is used to rework man
dibular lateral and protrusive movements in
dividually until the bite plates can be moved
against each other without interference and
without tipping, the mandibular teeth can
be placed against the calotte-shaped oc
clusion rim. As a result, they are positioned
inside an individual occlusal curve. At try-in
in the mouth, lateral and protrusive move
ments can be performed without interfer
ence while maintaining complete denture
stability.
302
Complete Dentures
Schreinemakerss Working
Method
Another working technique for improving the re
tention of complete dentures is analysis of the
denture-bearing area to ensure functional ef
ciency by individual contouring of the denture
base. Analysis of the denture-bearing area, which
is set against articulation theory, involves draw
ing up an individual treatment plan. Based on
this plan, the shape of the denture body and the
marginal contouring in the vestibule, on the oor
of the mouth, and at the vibrating line are estab
lished. A form of denture is then produced that
secures the positional stability of the prosthetic
appliance. Tooth setup is performed based on
static aspects: in the posterior region on the ridge
midline and in the anterior region in front of the
ridge for esthetic reasons.
The working method of J. Schreinemakers is
based on a theoretical model demonstrating what
marginal contour, marginal length, and marginal
thickness the denture should have (Figs 8-131 to
8-136).
The action limit denes the transition from at
tached to mobile mucosa. No advice about the
resilience of the movable mucosa is given here,
but this is deemed to be noncompressible. The
denture margin should extend beyond the action
limit on all sides so that the tension of the close-
tting mucosa is bound to create a valve margin
that ensures negative pressure in the liquid layer
under the denture base. Accordingly, a denture
retained by suction is produced for each dental
arch.
By means of the functional impression, a den
ture margin is designed that creates a balanced
state between tissue tension at the valve margin
and levering muscle tension. The course of the
muscle attachments is accurately established un
derneath the vestibular fornices, on the oor of
the mouth, and in the soft palate. The direction of
force and pull is also described to indicate the di
mensions of margin thickness.
The marginal depth in the lingual area of the
mandible at the tongue and oor of the mouth
must be determined with the utmost accuracy.
The marginal depth of the labial vestibular fornix
area requires great accuracy as it must support
the lip parts in a tension-free way during func
tioning. The path of the fornices and the position
and extent of muscle attachments coincide with
the described denture-bearing area in the maxilla
and mandible.
The anterior sublingual area is analyzed in de
tail so that the lingual groove around the genio
glossus muscle, measuring about 2 mm long and
3 mm deep, can be used for the sublingual roll.
The seating for the tongue beyond this sublingual
roll can be enlarged by hollowing out the lingual
surface of the denture body from the teeth up to
the denture margin. The aim is to create function
al clearance for the tongue that improves denture
retention. In the buccal posterior region, how
ever, the denture body should bulge outward to
enable self-cleaning; a buccinator support is not
attempted.
The border of the denture margin with the soft
palate is placed at the vibrating line, where a
groove about 2.5 mm deep and 2.5 mm wide is
etched from the pterygomandibular raphe around
the palatine processes of the maxillary tuberos
ity to the transition from hard to soft palate. The
palatine foveae are indicated as reference points.
The etched line must be probed individually with
an instrument in the mouth.
The retromolar triangle (pad) is also nished at
its dorsal border by an etching that is 1 mm deep
by 1 cm long. This means the plate edge ends to
ward the pterygomandibular raphe.
In terms of the practical procedure, Schreine
makers offers a semi-individualized tray set for
the rst impression. Custom trays are prepared
on the anatomical casts from the rst impression.
Occlusion rims to the exact vertical dimension of
occlusion are simultaneously placed on the cus
tom trays. A functional impression is taken after
rigorous marginal checks at the action limit and
extremely accurate marginal correction of the bite
plate. The custom trays/bite plates should already
have a certain suction effect. An impression mate
rial is used that allows subsequent corrections to
be made. The functional impression is therefore
taken in various stages.
The anterior setup is based on esthetic consid
erations. The Pound line is used for aligning the
posterior teeth. If the mandibular posterior teeth
are aligned with their lingual surfaces on this line,
they will stand almost exactly over the ridge mid
line.
303
Schreinemakers’s Working Method
Fig 8-131 For Schreinemakers trays, the working instructions
relate to impressions of the dental arches. The rst impres
sion is taken with prefabricated Clan-Trays, which are closely
matched to the anatomical circumstances of edentulous arch
es.
Fig 8-132 The mandibular Clan-Tray extends deeply into the
oor of the mouth area to allow an impression to be taken of
the sublingual area and the mylohyoid line.
Fig 8-133 An initial impression with viscous-consistency al
ginate yields an extended representation of the mandibular
denture-bearing area.
Fig 8-134 The course of the lingual margin of the custom tray
is traced in the rst impression and will appear on the plaster
cast.
Fig 8-135 An impression is taken of the dorsal palatal area
into the soft palate. The denture margin should also pass in the
soft palate area.
Fig 8-136 The dorsal margin of the bony mass of the jaw is
probed and etched into the jaw model as a semicircular, 2-mm-
deep groove that extends into the tuberosity processes.
304
Complete Dentures
Uhlig’s Working Method
The working method of Professor Horst Uhlig
sets the analysis of denture-bearing areas against
Gysi’s articulation theory. Analysis of the denture-
bearing area is put forward as the only essential
requirement for fabricating a complete denture.
Denture retention on the dental arch is present
ed as the interaction of capillary forces (adhesion
and cohesion effect) and forces caused by pres
sure differences (suction effect), where the saliva
acts as an adhesion promoter. The marginal seal
comprises an inner and outer valve as well as the
mechanical locking between the edge of the den
ture and the undercut areas of the jaw. The func
tional margin displays an inner valve at the outer
surface of the jaw and an outer valve at the cheek;
it also exploits all of the mechanical retentions,
such as the maxillary tuberosity and anterior al
veolar ridge areas. Hollowing out of certain areas
of the palate, Frankfurt etching, and etching of the
vibrating line are recommended as accessory re
tentive aids.
In practical terms, a formalized procedure for
analyzing the denture-bearing area is proposed
in which the tissue condition; the position of liga-
ments, muscle attachments, and bony ridges; and
the shape of the alveolar ridges are described and
entered on a form. Based on this analysis, neces
sary surgical measures, such as tightening of a
abby ridge, lowering of vestibular fornices, sep
aration and movement of ligaments, or smooth
ing of sharp-edged ridges, are undertaken. The
resilient areas of the palate and the path of the
vibrating line are then traced.
For precise marginal locking of the denture
base, a custom tray is prepared and used to take
the functional impression. For tooth setup, tak
ing an impression of the “denture accommoda
tion” is recommended to establish the position
of the cheeks, lips, and tongue so that the teeth
can be set up while these tissues are in balance.
In a “technique of individual ne adjustment,” the
outer surfaces of the denture bodies should be
adjusted to the position, shape, and dimensions
of the cheeks and the tongue; that is, a circumfer
ential chamfer should be formed into which the
mucosa settles. The result can be described as a
dimensionally accurate dental prosthesis shaped
to grip the muscle.
In the maxillary labial area, the denture can be
thickly padded to tighten the upper lip and com
pensate for the shrinkage of the jaw. The maxil
lary anterior teeth are positioned in front of the
alveolar ridge to support the upper and lower
lips (Fig 8-137). In the posterior region, a cross
bite position is presented to stabilize the position
of the maxillary denture, together with a sagittal
occlusal curve that is not constructed relative to
the TMJ but emerges from the positioning of the
teeth inside the interalveolar line.
Jüdes Working Method
Professor Jüde established the course of the mar
gin of a mandibular prosthesis based on extreme
ly accurate studies. In particular, an extension
into the retromolar area is specied to provide
mechanical retention to the mandibular denture.
M depressor anguli oris
M orbicularis oris
M Ievator
anguli oris
M zygomaticus
major
M buccinator
M risorius
Fig 8-137 The anterior teeth, especially the canines, are posi
tioned in front of the alveolar ridge to support the lips. Padding
of the labial vestibule to tighten the upper lip must be rejected
as inadequate. The canine position anterior to the ridge deter
mines the position and shaping of the angle of the mouth as
the modiolus (insertion site for the illustrated muscles) is sup
ported. For this purpose, the mandibular canine must also be
precisely mounted to tighten this tissue area. If the canines are
placed too far lingually, the corner of the mouth will descend
(as it does if the vertical dimension of occlusion is too small),
saliva will leak, and the corner of the mouth may become in
amed.
305
Jüdes Working Method
The muscle movements of the retromolar re
gion are determined by the activity of the tongue
and can often give rise to an undercut mucosal
pocket into which the retromolar wings of a man
dibular denture can engage. These wings should
be dorsally guided caudally without impeding the
activity of the myloglossus muscle.
The genioglossus muscle described by Jüde
originates below the mandibular tubercle on the
inside of the mandible (Fig 8-138). The muscle
bundle runs from there to the root of the tongue
and thereby covers the posterior area of the my
lohyoid muscle. This limits the size of the retro
molar wings inferiorly.
The retromolar (paralingual) areas should be
individually determined by a functional impres
sion taken during tongue activity. The functional
movements of the tongue for taking an impres
sion of the sublingual area are usually the same
as those performed for dening the paralingual
area.
In practical terms, the length of the margin is
incorporated into the custom tray before the
functional impression is taken. In the process,
the lingual edge of the tray follows the border
of the oor of the mouth (Fig 8-139); trimming
along the mylohyoid line is carried out, followed
by extension into the paralingual area and sub
lingual lengthening for the sublingual roll. In the
oral vestibule, the tray edge is guided along the
vestibular fornix (Fig 8-140), trimmed in keeping
with the oblique line, and spared at the ligaments.
Fig 8-138 The position and shape of the mandibular tubercle
is described as a tough mucosal ridge located in front of, but
not above, the bony retromolar triangle. Therefore, the tubercle
and triangle are not in the same position, but the mandibular
tubercle on an edentulous jaw is located roughly at the position
of the third molar and should be contained.
Fig 8-139 The line of origin of the mylohyoid muscle indicates
the border of the mobile oor of the mouth. Jüde described
the limit of the oor of the mouth using a variety of shapes
for the areas of origin. The most commonly found line of origin
is depicted here. Any extension of the denture margin is sup
ported on the mylohyoid muscle in the paralingual region. It
therefore becomes necessary to avoid pressing the retromolar
wings against the mandible and instead to provide the mylohy
oid muscle with the space it needs to function.
Area of the
mandibular tubercle
Area of the retromolar
triangle
Mylohyoid line
Retromolar wing
Fig 8-140 The attachment of the mental nerve lies below the
vestibular fornix; in the case of severe atrophy, it may shift to
the middle of the anterior alveolar ridge in the denture-bearing
area and may impair the positional stability of the mandibular
denture.
306
Complete Dentures
Gerbers Working Method
In recent years, the working method of Profes
sor Gerber has gained in signicance because it
brings together the methods and theoretical prin
ciples outlined in the previous sections to create
a successful synthesis that also incorporates the
latest research ndings. Over the years, this has
led to an almost closed, mechanically based the
ory of masticatory function with practical instruc
tions on fabricating complete dentures.
The functional mandibular movements are
analyzed using varied analysis methods, includ
ing radiographic sequences of joint movements
and lm recordings of the chewing cycle in or
der to develop an articulator and static functional
shapes of articial teeth. First, the relationship of
the TMJs to tooth shapes and tooth positions is
established and dened. Maximum tooth contact
exists in centric occlusion in a normal dentition.
The two condyles are located in the depth (zenith)
of the mandibular fossae entirely pressure and
tension free. In this position, masticatory forces
are not transferred via the condylar heads.
According to Gerber, the chewing cycle follows
xed pathways (Fig 8-141). The loading phase is
the start of the chewing cycle, for which the man-
dible is guided to the chewing side to grasp the
food. In the process, the condyle on the chewing
side oats freely in the joint and can be pulled dor
sally and laterally by the musculature. A Bennett
movement is performed. In the loading phase,
the mandible is pushed out of the retruded lat
eral position forward and centrically to grind the
food. Then the mandible can be seen to change
position to the opposite side (balancing side) and
to the anterior teeth before gliding back into the
centric hinge position.
Analysis of the chewing cycle demonstrates the
basic movement sequence of the Bennett move
ment, but it also shows the position of the con
dyles during the movement sequence. In addi
tion, it becomes clear that the functional chewing
movement, in contrast to the four-phase round
bite, does not happen two-dimensionally in the
transverse plane but three-dimensionally to the
side and dorsally, after which it swerves over to
the balancing side.
Lip, cheek, and tongue activities during the
chewing process prevent food particles from slip
ping down into the vestibule, while the tongue
repeatedly presses the food between the rows
of teeth. This muscle activity is one of the factors
determining the excursions during mastication.
Based on observations regarding functional man
dibular movements, Gerber sets out the following
requirements:
The mandibular movement must be imitated in
suitable articulators in order to fabricate dentures.
Balancing side Working side
Fig 8-141 According to Gerber, the chewing cycle follows
xed pathways: (a) The mandible moves out of centric occlu
sion into the loading position. The condyle on the balancing
side slips forward and downward. The condyle on the working
side moves backward and outward in the Bennett movement
and remains unloaded. (b) Out of the loading area, the active
masticatory pressing and protrusive action occurs on the work
ing side. This involves the condyle slipping forward and inward
into the fossa. In this active chewing phase, the maxilla moves
in the direction of anterior contact and makes a contact-free
change of position to the balancing side in order to glide back
into centric occlusion. (c) During the active chewing phase,
sliding balancing contacts occur on the balancing side in the
molar region close to the joint.
a
c b
307
Gerbers Working Method
During occlusal registration, the centric, pressure-
free position of the condylar heads in the zenith
of the articular fossae must be relocated.
The condylar path must be surveyed so that in
dividual values can be transferred to the articu
lator.
The articial teeth must be referenced to the
man dibular movement and satisfy static require-
ments.
Tooth positioning on complete dentures must
secure the positional stability of the appliance.
The denture body must be shaped to enable the
muscles to support denture retention without
impeding muscle activity.
Gerber Condylator
The Condylator is a semiadjustable articulator in
which the condylar paths are adjustable from 0 to
60 degrees (Figs 8-142 and 8-143). The mandibu
lar fossa (Condylator aperture) and the condylar
heads (Condylator body) take on the functions of
guidance and limiting movement in all mandibu
lar excursions. They permit retral movement out
of centric occlusion. This backward movement is
not straight but curved in the Condylator aper
ture, in keeping with the natural hinge range. The
Condylator body has a double-cone shape; the
17-degree inward-facing cone and the 13-degree
Fig 8-142 The Gerber Condylator is an articulator in which the
inclination of the condylar path is adjustable between 0 and 60
degrees. The Condylator aperture (A) is curved in keeping with
the natural condylar path. The Condylator body (B) has a double-
cone shape and takes on guidance in all lateral-eccentric move
ments. On the joint plate (C), the articulation can be raised
from 0.3 to 1.0 mm using the Vario device (D). The xed table
(E) opens the joint movements in the raised state but other
wise blocks the Condylator body, so only hinge movement is
possible.
Fig 8-143 A facebow (3) is available for the Condylator, with which the inclinations of the condylar paths can be surveyed. (a) The
facebow is tted onto the tracing plate (1), and the tracing tips (2) trace the mandibular movements as condylar path tracings on
registration ags. (b) The facebow can be used for joint-related mounting of the casts in the articulator. To do this, the facebow
is xed onto the stand (4) and propelled around the articulator until the tracing tips point to the midpoint of the Condylator body.
A
B
C
D
E
1
3
4
2
1
3
4
2
a b
308
Complete Dentures
outward-facing cone undertake guidance of the
Bennett movement.
The incisal guide plate has an 18-degree incline
for complete prosthodontics, but dentate arches
can be modeled into an individual guide plate
with self-curing acrylic resin by means of the in
tact incisal guidance of the arches. An optimized
registration kit is recommended for the intraoral
occlusal registration (Fig 8-144).
Condyloform teeth
The Condylator articulator was developed on the
basis of observations of mandibular movements
as well as TMJ shapes and movements. Accord
ing to Gerber, this functional relationship also ex
ists between joint and tooth shapes. During de
velopment of the dentition, there is a progressive
adaptation between the sliding surfaces of the
TMJs and tooth surfaces. This wearing process
produces abraded surfaces on the molars, which
have a shape similar to that of the articular fos
sae.
The articular fossae and condyles t together
like a mortar and pestle. It was based on this
mortar-and-pestle principle that the maxillary pal
atal cusps and the mandibular occlusal surfaces
on Gerbers Condyloform posterior teeth were
created (Fig 8-145). The palatal cusps form micro
condyles, and the lingual chewing depressions on
the mandibular posterior teeth form microfossae.
The static principle of mortar-and-pestle teeth
according to Hiltebrandt is combined with the
anatomical cusp slopes according to Gysi’s in
terpretation. The chewing surfaces are shaped
as upside-down microjoints, in which one part of
the joint is xed and the other is mobile. The mi
crojoint chewing surfaces display guide surfaces
with the same slope and shape as real joint sur
faces (Fig 8-146).
The chewing surfaces on the mandibular poste
rior teeth have their mortar-shaped occlusal fos
sae shifted lingually, while the buccal cusps have
a noticeable abrasion surface that slopes down
toward the vestibule.
The palatal cusps of the maxillary teeth engage
pestle-like into the mandibular occlusal fossae,
while the maxillary buccal cusps engage with
their adapted abrasion surfaces over the mandib
ular teeth. In their eventual shape, the occluding
cusps resemble microcondyles that articulate in
the microfossae.
The condylar path inclinations and the move
ment patterns of the mandible are in the sloping
surfaces of the buccal cusps in the sagittal and
transverse direction, as reected in the curva
tures of the mortar-and-pestle cusps. Thus, pro
trusive movements on the long working facets
and retrusive movements on the short balancing
facets of the occlusal surfaces can be performed
under tooth contact.
The mortar-and-pestle teeth permit slight man
dibular movements under tooth contact in centric
occlusion but do not result in dynamic denture
movements or the need for slight changes to be
made to mouth opening. In the case of normally
shaped anatomical forms of abrasion, transla
tive movements are only possible if the mouth
is opened slightly and the teeth are lifted out of
centric occlusion.
Fig 8-144 The intraoral occlusal registration described by
Gerber follows the same principle as the Gysi extraoral regis
tration. In this case, however, the registration kit is mounted
centrically over the dental arches so that tilting is ruled out.
During mandibular movement, a Gothic arch also appears on
the tracing plate. A perforated plexiglass disk is xed over the
intersection point. The tracing stylus engages in the hole on
the disk, and the mandible is established in centric occlusion.
309
Gerbers Working Method
1
2
3
4
5
6
Fig 8-145 On the Condyloform posterior teeth, the maxillary occluding cusps engage like a mortar in the pestle-like occlusal sur
face of the mandibular teeth. (1) Occluding cusps resemble microcondyles that articulate in the microfossae. (2) Active masticatory
microcondyles and microfossae are located in the lingual part of the teeth: The bulbous buccal tooth surfaces have cheek contact
and stabilize the denture; positioning the active masticatory parts on the center of the alveolar ridge leaves adequate clearance
for the tongue; and functional elements lie markedly lingually, so the teeth can be positioned more vestibularly. (3) The abraded
buccal cusps aid statics and stability during mastication. (4) In crossbite, the molars are not swapped but the buccal cusps of the
maxillary molars become active masticatory cusps; the palatal cusp must not impede chewing movement. (5) The buccal cusps
can be ground back or placed out of contact. (6) To enlarge the space for the tongue, premolars can be used instead of molars in
the mandible.
Fig 8-146 The basic idea of interpreting the occlusal surfaces
of the posterior teeth as microfossae and microcondyles is il
lustrated in this diagram. The sliding movements of the real
joints are also possible on the posterior teeth. The occlusal sur
faces are interpreted as upside-down microjoints in which one
part of the joint is xed and the other is mobile. The microjoint
occlusal surfaces have the same guide surfaces as the real
joints; this is the desired relationship.
310
Complete Dentures
The lingually shifted occlusal fossae on the
mandibular teeth and the abraded buccal cusps
contribute to positional stability because these
functional elements (microcondyles and micro
fossae) are displaced from the middle of the teeth
in a pronounced lingual direction.
The balanced tone of the tongue and cheek
can be used because the teeth are kept wider in
the lingual/vestibular direction. The anatomically
shaped vestibular surfaces show a pronounced
curvature, which makes good cheek contact pos
sible. Denture wearers are able to guide and sta
bilize their dentures with their cheeks and tongue.
Condyloform teeth can be set up on the center
of the alveolar ridge, leaving their antagonists in
dependently stable on chewing (Fig 8-147). As the
functional elements are actually moved in a dis
tinctly lingual direction, the teeth can be placed
very vestibularly. Positioning the active masti
catory parts on the center of the alveolar ridge
leaves adequate clearance for the tongue. To
enlarge the space for the tongue, premolars can
even be used instead of molars in the mandible
without impairing chewing activity.
A crossbite, necessitated by advanced atrophy
of the jaws, is not created by swapping the mo
lars. Instead the buccal cusps of the maxillary
molars are turned into active masticatory cusps,
while the palatal cusps must not impede articula
tion movement. This is why the teeth are tipped
very buccally, whereby cheek contact is also re
stored. The buccal cusps can be ground back or
placed out of contact if they hamper denture sta
bility or articulation.
Stability during mastication
According to Gerber, positional stability depends
on tooth shape, the contouring of the denture
body, and the positioning of the articial teeth
relative to the alveolar ridges (Fig 8-148). The pos
terior teeth stand on the middle of the ridges. As
Fig 8-147 Gerber also addressed the principle of placing the posterior teeth on the center of the alveolar ridge. In the case of
Condyloform teeth, the active masticatory lingual parts of the surfaces must be positioned over the ridge line. In the mandible,
because of the buccally overhanging shape, the tooth can be moved slightly lingually, which benets the statics of the mandibular
denture but does not crowd the tongue. In the case of the rst premolar, the mortar-and-pestle principle is turned on its head.
This aids masticatory stability and tooth shape in this area. The buccal cusps of the subsequent teeth are placed far enough out of
contact that they do not interfere with denture statics but still provide balancing contact on lateral excursions. The maxillary second
molar can usually be omitted, while the mandibular second molar can be the shape of a premolar that serves merely as a second
ary antagonist to the maxillary rst molar.
First premolar
Second premolar
Second molar
First molar
3 11
Gerbers Working Method
stipulated by Gysi’s law of the ridge line and by
Hiltebrandt’s basic static law, this condition also
applies to Gerber. If tooth positions are outside
the ridge line, the denture may be levered off.
On Condyloform teeth, the functional elements,
such as the occlusal fossa and the lingual occlud
ing cusp, are moved markedly toward the lingual
aspect. If these functional mortar-and-pestle parts
are set up exactly over the ridge center, the buccal
cusps will extend far in the vestibular direction.
A crossbite position is only rarely necessary,
as the space for the tongue is almost normal and
not crowded and cheek contact can be used ex
tremely well for positional stability. All the teeth
stand with their independently stable antagonists
and permit slight movements under tooth con
tact. The requirement to position the teeth on the
center of the alveolar ridge does not become a
problem with Condyloform teeth, thereby satisfy
ing the rst criterion for positional stability of a
complete denture.
The instability of mandibular dentures on an al
veolar ridge rising dorsally can be contained by
special tooth positioning. Hiltebrandt thought the
solution was to shorten the dental arch up to the
rst molar, and Haller recommended an upward
notching of the posterior teeth. Gerbers solution
synthesizes these two views. The contour of the
alveolar ridge in the mandible is deected down
ward and is generally at its lowest at the rst
molar. This is where the masticatory center of a
complete denture must lie, which is why Gerber
describes this area as the stable center during
mastication. This lowest point is marked on the
edge of the cast, and the rst molar is arranged
there.
So that the masticatory center also remains on
this stable center during mastication, the maxil
lary row of teeth stops at the rst molar, and the
denture baseplates are kept a sufcient distance
from each other. One premolar is now placed
behind the mandibular rst molar, ending the
arched curve as a secondary antagonist for the
maxillary rst molar. The posterior teeth are set
up in a steep curve deected downward, which
produces a steep sagittal occlusal curve. The aim
of this notching, shortening of the dental arch,
and special tooth shape is to prevent the mandib
ular denture from slipping on the inclined plane
of the alveolar ridge during mastication.
To create balanced contacts on the nonworking
side, the posterior teeth should be inclined inside
the transverse curve. If no balancing contacts
are possible when crushing food, these contacts
will be achieved on functional mandibular move
ments during the swerve toward the balancing
side. Furthermore, these balancing contacts pro
tect the jaws and joints during normal functional
movements (eg, when speaking). According to
Gerber, the posterior teeth should be set up in
side the transverse and sagittal curves, and these
curves should create balancing contacts during
mandibular movements. Therefore, strictly speak
ing, these are compensating curves.
Another aspect of securing masticatory stabil
ity is supporting the denture in a particular way
in the canine region. Denture wearers often bite
food with the canines and premolars because the
Fig 8-148 According to Gerber, stability
during mastication (or masticatory stabil
ity) is linked to two facts: (a) The man
dibular rst molar must be placed at the
lowest point on the shrunken mandible.
The molar then stands between two in
clined planes whose contrary effect can
cels itself out. This stable position can
be compared with a saddle, which is se
curely seated in the dip of a horse’s back.
(b) The posterior teeth are set up inside a
steep occlusal curve. This is supposed to
compensate for positional defects due to
the Christensen phenomenon and Ben
nett movement, but it also reinforces the
contrary effect of the inclined plane.
a b
312
Complete Dentures
denture is usually more securely seated in this
area than in the region of the incisors. If broad
premolars are set up instead of maxillary canines,
the mandibular antagonists in the occlusal fossa
of the maxillary canine/rst premolar can produce
an excellent cutting effect without pressing the
maxillary denture outward and thereby levering
it off (Fig 8-149). This is because the mandibular
antagonists split up the food, like a knife between
two parallel cuts would do.
Finally, the positional stability of a complete
denture should be supported by the contour
ing of the denture body. Schreinemakers, Uhlig,
and Jüde recommend a thorough analysis of the
denture-bearing area, whereas Gerber suggests
molding lip shields on the maxillary and man
dibular dentures for mucosal support, based on a
muscle relief impression of the perioral muscles,
as well as modeling narrow channels in the di
rection of function of the ligaments for the buccal
frena.
Tooth setup according to Gerber
Gerber explains the special tooth positioning for
complete dentures by the special shape of the
Condyloform teeth (Fig 8-150). The antagonist
pairs of posterior teeth form harmonious mas
ticatory units that are meant to be independent
ly stable in their position in the dentition. This
means that the teeth have only occluding cusp
contact, and the abraded buccal cusps touch in
order to increase masticatory stability. The maxil
lary antagonists are centered in their antagonists
and do not have multiple cusp contact.
Setup calls for four phases:
1. Anterior teeth
2. Mandibular posterior teeth
3. Maxillary second premolar
4. Rest of the maxillary posterior teeth
The anterior teeth are set up by reference to
the model analysis markings, tracings on the oc
clusion rims, and static considerations. The inci
sors have a sagittal distance of 1.5 to 2 mm; the
cutting edges are abraded so they glide into an
unimpeded edge-to-edge occlusion on protrusive
movements.
The canines are never placed with a pronounced
overlap but permit free articulation move ments.
If necessary, the tips of the canines inhibiting
movement should be trimmed. The canines stand
slightly outside the dental arch, hence in a domi
nant position. The decisive canine stability is
achieved by placing a premolar instead of the
maxillary canine. The tip of the mandibular canine
engages in the mortarlike concavity of the maxil
lary canine/premolar, pressing the denture onto
the dental arch.
The broad posterior teeth are intended to gain
cheek contact with their bulging buccal surfaces.
The occlusal concavities and occluding cusps
stand over the center of the alveolar ridge.
The mandibular posterior teeth are rst set up,
a gap being left between canine and rst premo
lar. The curve of Spee is distinctively shaped by
imitating the occlusal line as a xed locator on
the articulator using a ruler or a rubber band.
Fig 8-149 The masticatory stability of the maxillary denture
is jeopardized primarily by the canine because anterior contact
is always sought in a chewing cycle. Gerber rst proposed set
ting up the incisors and canines so they could glide past one
another. If the maxillary canine is replaced by a broad premolar,
into whose chewing fossa the mandibular canine glides cen
trally, the effect of masticatory force could be used to stabilize
the denture. The “canine premolars” exhibit a particular posi
tional stability.
313
Biologic Prosthetics
The position of the maxillary posterior teeth is
referenced to the maxillary second premolar. This
tooth is the rst of the maxillary teeth to be set
up, then the two teeth still missing are inserted.
An oral check is done to see whether the pestle
cusps have full mortar contact and whether the
sloping abrasion surfaces permit unimpeded slid
ing movements.
The maxillary second premolars stand with
their lingual occluding cusps over the center of
the ridge, while the maxillary antagonists stand
with their markedly lingually displaced mastica
tory concavity in the middle. A comparable tooth
setup is also adopted for the rst molars. This po
sition also applies to the second molars, provided
that they can be arranged while maintaining fa
vorable ridge relationships.
For the mandibular rst premolar, it is impor
tant to position the buccal cusp tip over the ridge
midline, which means the maxillary rst premolar
then has to stand with its central developmental
groove over the ridge middle.
The mandibular rst molar should lie centrally
over the deepest point of the ridge prole. This
point is marked on the edge of the model, which
xes the position of the rst molar. This tooth
is also set up rst, and the other teeth are then
aligned with it.
Reoccluding the dentures is done so that er
rors in tooth position caused by wax stresses and
shrinkage during polymerization can be compen
sated for after completion. This involves selective
grinding of the nished dentures on the casts in
the articulator. Carbon paper is used to identify
gross interferences from a possible vertical in
crease of occlusion during functional lateral and
protrusive movements, and these interferences
are remedied with an abrasive stone. Correction
is only done on the mandibular teeth.
This is followed by selective grinding with a
paste made from carborundum powder and glyc
erin. Under gentle pressure, the teeth are moved
against each other with minute circular motions
alternately to the right and left, the movements
being guided by the joints and incisor guidance.
The palatal cusps of the maxillary posterior teeth
must not be ground off because the occlusion-
xing functions of these cusps need to be pre
served. Selective grinding on an average-value
articulator produces a chewing pathway that can
stabilize the denture but imposes a specic move
ment on the joint. Such movements are actually
adopted after a brief period of habituation so
that this relationship can be used for therapeutic
purposes.
Biologic Prosthetics
A biologic prosthetic is dened as a diagnostic
depiction of the occlusion and articulation of a
natural, intact, healthy, normal dentition that can
be applied equally to xed tooth replacements,
partial dentures, and complete dentures.
The eld of biologic prosthetics postulates
neuromuscular mandibular guidance, while the
classic concepts suggest mechanical tooth and
Fig 8-150 (a and b) According to Gerber,
the nished denture displays the follow
ing features:
The mandibular rst molar
has its occlusal concavity at the lowest
point of the trough-shaped alveolar ridge;
the posterior teeth stand inside the occlu
sal curves; the posterior teeth end at the
rst molar, and the mandibular premolar/
second molar is a secondary antagonist;
and the maxillary canine/premolar engag
es centrally over the mandibular canine.
The outer surface of the denture body is
shaped to grip muscle, with anterior lip
shields for the orbicular muscle of the
mouth. In the posterior region, buccinator
rests are created and the muscle tracts
at the buccal frena are traced. Reduction
needs are taken into consideration.
a b
314
Complete Dentures
condylar guidance. Dr E. End asserts that no ca
nine guidance, guidance from a group of teeth,
or bilateral balancing can be established in the
natural dentition for all physiologic movements.
In the masticatory system, there is no tooth guid
ance, only neuromuscular guidance (Fig 8-151).
Thus, biologic prosthetics presents an overarch
ing concept.
In a healthy dentition, the habitual intercuspa
tion coincides with a loose, relaxed centric occlu
sion adopted by neuromuscular methods. This
contact position is the physiologic centric occlu
sion, which can be adopted by the patient at any
time out of the mandibular rest position. Accord
ing to End, the physiologic centric occlusion of
the natural dentition displays the following char
acteristics (Fig 8-152):
Uniform and simultaneous point contacts are on
the occlusal surfaces in the posterior region in a
typical distribution.
Contact points mainly lie on the inner slopes of
the working cusps, on the lingual cusps in the
maxilla, and on the buccal cusps in the man
dible.
There are only a few marginal ridge contacts
(10% of contacts on posterior teeth).
There are only a few contacts on shears (non
working cusps).
Anterior teeth have full or only partial, slight
contact simultaneously with the posterior teeth.
The sagittal overbite has a vertical range of 1 to
8 mm and a horizontal range of 1 to 6 mm.
There is no point and surface support in the
sense of a long centric occlusion.
The terminal occlusion position is an unstable
balance of contacts with occlusal clearances.
Functional analysis of natural dentitions by
clinical and instrumentation methods shows that
unimpaired functioning maintains the physiol
ogy of the natural teeth. Physiology does not lead
to self-destruction but maintains the structure.
Physiologic, neuromuscularly guided mandibular
movements during chewing, swallowing, speak
ing, or reex probing movements do not produce
abraded surfaces on the teeth. Only nonphysio
logic movements of the mandible (parafunctions)
produce abraded states; tooth-guided movements
of the mandible are nonphysiologic.
In this respect, the axial loading of the teeth is
seen to be physiologic, while eccentric nonaxial
loading has atrophic and destructive effects. Only
when the feedback cycle of the masticatory sys
tem is disrupted will faulty movements and faulty
loading that have a pathologic impact occur.
Chewing movements are performed in a reex
ive, unconscious fashion. They are conditioned,
which means they have to be learned in childhood
and are sustained via feedback mechanisms. An
individual chewing style will develop. Only the
closing phase of chewing cycles is the same in all
Fig 8-151 The masticatory system works according to a
cybernetically controlled feedback cycle to maintain all of its
components. Physiologic centric and habitual intercuspation
come together in an interference-free masticatory system. The
chewing cycles are learned in childhood and are memorized
and maintained via feedback mechanisms. The eld of biologic
prosthetics postulates, as an overarching concept, neuromus
cular mandibular guidance in which no canine guidance, guid
ance from groups of teeth, or bilateral balancing can be estab
lished. No tooth guidance is seen in the masticatory system,
merely neuromuscular guidance.
315
Biologic Prosthetics
humans. Thus, when the mandible is moved back
into terminal occlusion, the movement is stopped
just before or on contact in centric occlusion.
The chewing cycles take place out of and end
in this physiologic centric occlusion. The typical
chewing movement starts with the movement
to open out of centric occlusion with immediate
separation of the rows of teeth. The closing move
ment again meets in physiologic centric occlusion
in the middle. In the process, the mandible moves
to the working side, where the food is meant to
be chewed between the teeth.
In conventional articulators, centric occlusion
is the only contact that can be physiologically
imitated. All other contact positions and contact
movements are nonphysiologic and are arbitrari
ly performed by dentists and dental technicians.
Chewing movements differ between individuals,
are dependent on the food being consumed, and
cannot actually be simulated in an articulator.
It may therefore be concluded that anterior
guidance or sequential lateral guidance by groups
of teeth cannot offer an articulation concept that
maintains the system. No standard dentition
guarantees intactness and physiologic function.
An individual physiologic dentition works with
out interference by means of neuromuscular
tooth guidance and physiologic centric occlusion.
Tooth setup in biologic prosthetics
Tooth setup for a complete denture according
to the concept of biologic prosthetics is outlined
here. Taking for granted the laws applicable to
natural dentitions, setup has to be done in physi
ologic centric occlusion without bilateral balanc
ing or tooth-group guidance. If a sufciently punc
tiform centric occlusion exists, without enforcing
posterior or anterior balances in the masticatory
system, parafunctions can largely be eliminated
or prevented.
Tooth contacts during the chewing cycles only
occur in centric occlusion where the grinding
work takes place. Canine guidance, one-sided
group guidance, or bilateral balancing are not
necessary in the natural dentition and hence are
not required in the complete denture.
Retention of complete dentures outside occlu
sion depends on the coordinated neuromuscu
lar interaction between intraoral and extraoral
structures and the denture. Therefore, the teeth
should also be placed so that there is neuromus
cular equilibrium of all the involved structures. In
physiologic centric occlusion, uniform loading of
the denture without tipping moments is achieved
by the punctiform occlusal contacts meeting si
multaneously.
The occlusal plane is aligned parallel to the
Camper and bipupillary planes on the midlines of
the retromolar triangles in the therapeutic verti
cal dimension of occlusion. The therapeutic verti
cal dimension of occlusion is measured from the
speech distance of 1 to 2 mm and from recon
struction of the patient’s prole.
The transverse and sagittal occlusal curves are
shaped. These are not compensating curves with
Fig 8-152 According to End, in a natural dentition there is no tripodization (three-point support) over the whole dentition and no
long centric occlusion with point-and-surface support. Only physiologic centric occlusion exists that has the following character
istics: even and simultaneous point contacts with occlusal clearances, contact points predominantly on the inner slopes of the
working cusps, few marginal ridge and shear contacts, anterior teeth with minimal touch contact, and sagittal overbite. (Illustration
from Vita.)
Gnathologic tripodization Long centric Physiologic centric
316
Complete Dentures
which balancing is to be achieved, but they op
timize the force vector of the muscles of mas
tication. The individual occlusal curves do not
balance or guide the dentures but facilitate the
stereotypically recurring chewing movements.
After the usual functional impression and mod
el fabrication, the physiologic centric occlusion
of the jaws is established using facebow regis
tration. The working models are mounted in an
average-value articulator.
The dentist shapes the mandibular anterior re
gion in the patient’s mouth, taking into account
esthetics and phonetics because the esthetics of
the face depend on the shape and positioning of
the anterior teeth. A plaster key that reproduces
the occlusion rim contour and length determines
the position of the maxillary teeth. The mandibu
lar anterior teeth are aligned after the maxillary
anterior teeth.
The overjet results from esthetic and phonetic
considerations. The maxillary anterior teeth are
clearly positioned in front of the ridge contour,
and the mandibular anterior teeth are placed
slightly in front of or on the alveolar ridge. The
labial contours of the mandibular anterior teeth
and rst premolars are usually located over the
vestibular fornix. After the anterior teeth, the
mandibular posterior teeth are fully set up.
The other mandibular posterior teeth should be
positioned centrally over a straight line from the
canine tips to the retromolar triangle, while the
maxillary posterior teeth should be placed on an
elliptical connecting line between canine tips and
tuberosities. The static positioning on the ridge
midlines would lead to a crossbite situation.
The setup limit is deemed to be the middle of
the retromolar triangle. If the second molars are
not set up, the ow of saliva to the pharynx is
interrupted. The tongue and cheeks press into the
free space and push the dentures forward, which
means atrophic stresses on the alveolar ridges. In
addition, pressure points may occur in the sublin
gual area and at the incisive papilla.
Physiodens teeth from Vita are designed for the
concept of biologic prosthetics and can be set up
in physiologic centric occlusion, which can be re
peatedly adopted as the neuromuscular contact
position (Fig 8-153). These teeth allow tooth setup
with the following (Figs 8-154 to 8-161):
• Uniform, simultaneous point contacts
• Freedom in occlusion
Contact points on the inner slopes of the work
ing cusps
• Few contacts of shears or marginal ridges
• Slight touch contacts on the anterior teeth
Positioning of anterior teeth optimized in func
tional, phonetic, and esthetic terms
Individual overbite without anterior guidance or
bilateral balancing
The naturally shaped occlusal surfaces and
their nonbalanced setup prevent parafunctions.
Excursions out of and into centric occlusion re
main neuromuscularly free of interference and
become possible due to the occlusal clearances.
Fig 8-153 Vita’s bodily, esthetic anterior tooth shapes that
function in mastication are based on the concept of biologic
prosthetics and can therefore be used equally for partial and
complete prosthodontics. The Vita 3D shade selection system
is shown in these sets of teeth. (Illustration from Vita.)
Fig 8-154 The classication of a patient’s physiognomy—oval
(O), triangular (T), rectangular (X), and square (Z)—forms the
basis of the systematization of types of tooth shape. (Illustra
tion from Vita.)
317
Biologic Prosthetics
Fig 8-155 The posterior teeth from Vita
Physiodens/Posteriores were developed by
End according to natural laws and by refer
ence to physiologic centric occlusion; they
have occlusal clearances with uniform oc
clusal point contacts. (Illustration from Vita.)
Fig 8-156 Setup of the maxillary posterior
teeth is done in the sagittal and transverse oc
clusal curve, which starts at the rst premolar
and continues with the subsequent teeth. (Il
lustration from Vita.)
Fig 8-157 The oral view of the maxillary
posterior teeth shows the sagittal and trans
verse incline of the occlusal surfaces for in
dividual shaping of a helicoid torsion curve.
(Illustration from Vita.)
Fig 8-158 The mandibular posterior teeth are also
set up in the sagittal and transverse occlusal curve,
but this is not intended to take on the function of
compensating curves. (Illustration from Vita.)
Fig 8-159 The occlusal plane, represented
here by a at mirror, provides the orientation
plane for tooth setup. The occlusal curves are
distinctly arched. (Illustration from Vita.)
Fig 8-160 The intercuspation visible from
the vestibular aspect follows the antago
nist rule in tooth–to–two-tooth occlusion.
(Illustration from Vita.)
Fig 8-161 Oral intercuspation follows the
antagonist rule. The anatomically shaped
Physiodens do not occlude very closely but
exhibit occlusal clearances for excursions out
of physiologic centric occlusion. (Illustration
from Vita.)
318
Complete Dentures
Ludwig Technique
Ludwig’s method is a technical approach to fabri
cating complete dentures that does not claim to
offer a self-contained articulation theory. In this
method, priority is given to a perfected impres
sion technique and physiologic shaping of the
denture base, especially in the case of severely
resorbed mandibular rest areas.
The technique starts with a preliminary func
tional impression, for which stable silicone is used
(Figs 8-162 to 8-164). This preliminary impression
records the function-related denture margin in a
dynamic process and is keyed by means of an im
pression of the vestibule to produce a provisional
interocclusal record. The vestibular impression
records the inner lip closure line, from which the
type of occlusion and path of the occlusal plane
can be deduced.
These keyed preliminary impressions are used
to prepare the individual bite plates based on jaw
relation in an adjusting and leveling device (Lu
temat), by means of an integrated kit for intraoral
occlusal registration. The integrated functional
tray/bite plates—used to take the impression and
register the occlusion—are functionally shaped
and leave freedom of movement for the tongue
and jaw muscles (Figs 8-165 to 8-167). The regis
tration kit is removed for the functional impres
sion.
Fig 8-162 A stabilizing splint is placed in
the silicone (Lutesil, Bisico) for the prelimi
nary functional impression; the impression
is taken in a nonperforated prefabricated
tray.
Fig 8-163 The limit dened by the ves
tibular fornix is marked in the nished
preliminary functional impression, and the
impression is removed from the tray.
Fig 8-164 A knife can be used to trim
the stable silicone into a temporary cus
tom tray.
Fig 8-165 The preliminary impression,
trimmed to form a custom tray, is coated
with light-body silicone (Perfekt), and an
impression is taken of the mandibular
denture-bearing area during functional
movements. This creates the foundation
for a custom tray.
Fig 8-166 The maxillary preliminary func-
tional impression is handled in the same
way: The limit of the margin is marked in
the vestibule and in the course of the vi
brating line.
Fig 8-167 The preliminary impression is
taken out of the tray and trimmed back
to the marked margin. This preliminary
impression, as a custom tray, is used to
perform a correction impression of the
maxillary denture-bearing area.
319
Ludwig Technique
The denitive functional impression is taken
again with a vestibular impression to depict the
inner shape of the lip. The aim is to establish the
lip closure line, correct lip volume, type of occlu
sion, overjet, and occlusal plane (Figs 8-168 and
8-169).
Gothic arch tracing is performed by the usual
method. The keying of the denitive functional
impressions to form a record and the vestibular
impression provide the necessary information for
correct positioning of the models in an average-
value articulator. The average-value position for
the articulator is ascertained and xed with the
Lutemat adjusting and leveling device.
The template designed for the Ludwig tech
nique is used for tooth setup; it can be integrated
into any type of articulator and adjusted to indi
vidual occlusal plane inclinations (Fig 8-170). A
matrix is prepared from the vestibular impres
sion, and this provides important orientation for
the subsequent anterior setup (Fig 8-171). The
maxillary anterior teeth are set up in the path of
Fig 8-168 The two preliminary functional impres
sions are aligned with each other by means of a
provisional interocclusal record, and a vestibular
impression is added. Based on these impressions,
casts are made, and all the information is available
for preparing custom bite-plate impression trays
onto which a registration kit for intraoral occlusal
registration is xed. Using these bite-plate impres
sion trays, the nal impression and nal interoc
clusal registration are performed, again with a ves
tibular impression.
Fig 8-169 The nal impression with
interocclusal registration and vestibular
impression reproduce the precise lip vol
ume; cuts are made to indicate the mid
line and canine points, and the inner lip
closure line stands out.
Fig 8-170 Casts are fabricated by the
split-cast method and prepared for
mounting in the articulator.
Fig 8-171 A matrix is prepared from the
vestibular impression; this is meant to
indicate the limit and extent of the ves
tibule.
320
Complete Dentures
the individual vertical anterior arch for the indi
vidual overjet to achieve natural lip volume (Fig
8-172). The posterior teeth are set up on the ridge
midlines based on static considerations. The aim
is to achieve a bilateral balanced occlusion upon
completion (Figs 8-173 to 8-175).
A nonhardening denture base, primarily for a
severely atrophied mandible, is another key as
pect of the Ludwig technique. The softly cush
ioned surface of the denture base is integrated
into the physiologic movement patterns of the
jaw and relieves potential pressure points. The
physiologic functional denture is fabricated in
three steps:
1. An individual steel reinforcement to receive
the nonhardening base material is rst pre
pared (Fig 8-176).
2. The nonhardening base material is partly vul
canized and nished. This base material (Lu
temoll 40, Bisico) has a hardness of 40 Shore
A; areas particularly susceptible to pressure
points can be worked with a softer material
(Lutemoll 25) with hardness of 25 Shore A.
3. The wax-up is done on the nished denture
base, and the denture is subsequently com
pleted in acrylic resin.
Durability of the special nonhardening base
materials is achieved after vulcanization at ap
proximately 150°C for 1 hour and subsequent
tempering at 200°C for 4 hours (Fig 8-177). It is
not possible to work the material directly joined
to the denture acrylic resin because this, as well
as the articial teeth, will depolymerize at the
high working temperatures. Therefore, an indi
vidualized steel reinforcement is rst prepared,
and the nonhardening base material is partly vul
canized, tempered, and nished. Then the wax-up
can be done on the denture base. It is advisable
Fig 8-172 The matrix on the mandibular
cast shows the dimensions of the vesti
bule. The matrix is lined with wax for set
ting up the maxillary anterior teeth; the
outer contour of the wax rim provides
orientation for the labial contours of the
maxillary anterior teeth.
Fig 8-173 The nished casts are set up
with the record in the Lutemat. This ad
ditional device is referenced to the geom
etry of the articulator.
Fig 8-174 The maxillary cast is xed to
the cast holder and transferred to the
compatible articulator, where the man
dibular cast is inserted next.
Fig 8-175 The template is adjusted to
the reference planes of the articulator
and plastered onto a cast holder. It is t
ted with one template tooth and a trans
parent template window.
321
Ludwig Technique
to perform nal completion of the denture by the
injection method, but the tamp-press technique
may also be used.
The fact that excellent fracture resistance is
achieved due to the steel reinforcement is an
other reported advantage of the physiologic func
tional denture. This method is also recommended
for implant-supported complete dentures.
Tooth setup according to the Ludwig technique
is presented in Figs 8-178 to 8-184.
Fig 8-176 A metal reinforcement is rst
produced by the model casting technique
to carry the elastic, nonhardening base
material.
Fig 8-177 The metal reinforcement is
lined with the nonhardening material,
which is vulcanized at approximately
200°C.
Fig 8-178 Tooth setup starts by placing
the sagittally movable template tooth
onto the middle of the mandibular alveo
lar ridge.
Fig 8-179 The rst mandibular central
incisor is then placed onto the nished
metal base next to the template tooth in
wax.
Fig 8-180 The rst maxillary central inci
sor is aligned with the articulator marking
and with the wax rim created from the
vestibular impression.
Fig 8-181 The anterior teeth are set up
according to the vestibular impression,
thereby satisfying esthetic requirements.
Fig 8-182 Starting from the mandibu
lar central incisor, the mandibular dental
arch is reconstructed; the marked lines
on the template provide orientation.
Fig 8-183 The try-in is done on the n
ished Lutemoll base.
Fig 8-184 In the nished denture, the
margins of the metal reinforcement ex
tend precisely into the vestibular fornix
and support the highly elastic, nonhard
ening base material.
322
Complete Dentures
APF
NT
System
The APF system ([A]esthetics, Phonetics, Func-
tion) has been supplied since 1975 by Dentsply
as a teaching, checkable setup guide. To enhance
the practical relevance of this system, the APF
NT
system (New Technology) was developed and in-
troduced in 2001. The new system is intended not
only to satisfy training requirements but also to
improve the standard of the fabrication of average-
value complete dentures.
The APF
NT
system describes four comprehen
sive measures for preparing a patient-related
tooth setup:
1. Mounting the model with the model positioner
for the Protar articulator from KaVo.
2. Determining the occlusal plane with the occlu
sion inclination indicator from the same KaVo
system.
3. Performing model analysis to determine the
setup areas on the bony base of the jaws.
4. Establishing tooth-to-tooth setup in lingualized
occlusion.
Average-value mounting of the maxillary cast
is done with the model positioner. The mandible
is matched to the maxillary cast with an intraoral
occlusal record. The maxillary model positioner
is a height-adjustable mounting device that has
a slider that rests in the starting points of the two
tuberosities and a movable fork for the deepest
points in the maxillary anterior vestibular forni
ces (Figs 8-185 and 8-186).
Fig 8-185 For systematic mounting of casts, a model posi
tioner is provided that is height adjustable and has a movable
fork for anterior xation and a slider for the tuberosity starting
points. This mounting device allows average-value positioning
of the maxillary cast.
Fig 8-186 The metal prongs of the fork are aligned with the
anterior support points in the depth of the anterior fornix and
the starting points of the tuberosities.
Fig 8-187 The occlusion inclination indicator is used as a set
up aid for the posterior teeth. The setup aid is xed in the Protar
articulator from KaVo with the mounting bracket.
Fig 8-188 Before aligning the occlusion inclination indicator
with the start of the tuberosities and the incisal edges, the
maxillary central incisors must be set up.
323
Fig 8-189 Model analysis is conned to tracing the alveolar ridge contours, the
depths of the fornices, and the mylohyoid line in order to limit the setup area within
which the antagonist contacts are supposed to lie.
Fig 8-190 Tooth-to-tooth setup in lin
gualized occlusion and with individual
overjet allows intermediate movements
at a maximum of 1 mm wide; these
movements are not excursion move
ments. The basic setup objective is cen
tric relation.
APF
NT
System
The occlusal plane as a reference line for pos
terior setup is referenced to the starting points of
the two tuberosities and the incisal edges of the
maxillary anterior teeth. The mandible is dened
as not belonging to the skull and thus does not
provide any orientation for the occlusal plane.
This is because the occlusal plane, which runs
from the mandibular incisal point to the upper
edges of the retromolar pads, slopes downward
and backward and destabilizes the mandibular
denture.
The occlusion inclination indicator (setup aid)
from KaVo is aligned with the starting points of
the two tuberosities and the maxillary incisal edg
es and shows how the occlusal plane is oriented
in the interalveolar space (Fig 8-187). The occlusal
plane rises backward so that the mandibular pos-
terior teeth project above the upper edge of the
retromolar pad. The occlusion inclination indica
tor set comprises the mounting bracket, setup aid
with anterior table, and operating tool.
To align the setup aid, tooth setup must start
with the maxillary anterior teeth, which are
placed in muscular equilibrium of the lips and
tongue to support the functional areas of speech
and the patient’s physiognomy (Fig 8-188). Opti
mized positioning of the anterior teeth is found
with a physiognomic check template that should
be individualized by the dentist. The overjet, as an
individual patient-specic measurement, is also
determined with the check template.
Marking of the ridge midlines is omitted in the
model analysis of edentulous jaws (Fig 8-189). In
stead the bony foundation of the jaw is dened as
the setup area for the posterior teeth. This setup
area lies inside the deepest points of the vestibu
lar fornix in the maxilla; in the mandible, it lies be
tween the inner border of the mylohyoid line and
the outer border of the oblique line. It is assumed
that the teeth positioned inside these lines safely
transfer all the forces to the denture-bearing area;
even though the teeth are not on the middle of
the alveolar ridge, the denture remains stable.
The posterior teeth are set up in a tooth-to-
tooth relationship (Fig 8-190); that is, only one
pair of teeth ever has contact with each other, and
324
Complete Dentures
each antagonist pairing of teeth stands alone. No
mesial or distal partners are needed for stability
in centric occlusion or during intermediate move
ments in dynamic occlusion. Corrective grinding
should be performed for intermediate move
ments. The intermediate guide paths are a maxi
mum of 1 mm wide and do not represent excur
sion movements.
The concept of lingualized occlusion, in which
the teeth are moved buccally, is stipulated to cre
ate more space for the tongue but without de
stabilizing the teeth. In lingualized occlusion, the
lingual occluding cusps of the maxillary denture
teeth engage in the central contact areas of the
mandibular denture teeth (central fossae). The
buccal cusp segments are markedly out of an
tagonist contact. However, they must be placed
inside the bony borderline. In centric occlusion,
there must be no anterior tooth contact.
Planning, Fabricating, and
Assessing Complete
Dentures
The working steps of creating a complete denture
are the following:
1. Create a normal interocclusal registration (Fig
8-191).
2. Perform model analysis of the maxilla (Fig
8-192).
3. Perform model analysis of the mandible (Fig
8-193).
4. Adjust the models in the articulator (Fig 8-194).
5. Set up the mandibular anterior teeth (Fig 8-195).
6. Set up the maxillary anterior teeth (Fig 8-196).
7. Set up the mandibular premolars and the max
illary rst premolar (Fig 8-197).
8. Set up the posterior teeth (Fig 8-198).
9. Wax up the denture body (Fig 8-199).
325
Planning, Fabricating, and Assessing Complete Dentures
Adapt the maxillary baseplate and establish the marginal
border of the maxillary baseplate:
Trace the marginal border.
Etch the vibrating line and hollow out the plicae
palatinae.
Isolate the model surface.
Adapt the baseplate material.
Cut out the baseplate margin and smooth.
Fill out the valve-type margin.
Adapt the mandibular baseplate and establish the
marginal border of the mandibular baseplate:
• Trace the marginal border.
• Isolate the model surface.
• Adapt the baseplate material.
• Cut out the baseplate margin and smooth.
• Create clearance around the mylohyoid line/oblique
line.
• Fill out the valve-type margin and enclose triangles.
Set up the occlusion rim in the maxilla and shape the
occlusion rim in wax or use occlusion rim bars:
Place on the middle of the alveolar ridge.
Raise to the occlusal plane.
Ensure that the distance from the vestibular fornix to
the occlusal plane is a minimum of 24 mm.
Make sure the maxillary alveolar ridge contour is
roughly level.
Set the occlusion rim parallel to the ridge contour.
Bevel the occlusion rim to the maxillary tuberosity.
Establish the occlusal plane and mark the occlusal plane
with a protractor:
Ensure that the distance from the vestibular fornix to
the occlusal plane is a minimum of 20 mm.
Fix the occlusal plane to the upper edge of the triangle.
Set the upper edge of the triangle on one side.
Reect the triangle and bring to a symmetric height.
Trace the occlusal plane markings on the base margins.
Set up the occlusion rim in the mandible and shape it in
wax:
• Use occlusion rim bars.
• Place on the middle of the alveolar ridge.
• Raise the occlusion rim to the occlusal plane.
(Note: The occlusion rim is dimensioned high enough to
provide sufcient space for the setup without having to
grind the teeth at the base.)
Fig 8-191 Step 1: Create a normal interocclusal registration.
326
Complete Dentures
Establish the model analysis xed points in the maxilla:
Anterior vestibular fornices
Incisive papilla
First large pair of plicae palatinae
Median palatine raphe
Maxillary tuberosities
Establish the axis of symmetry in the maxilla:
Construct it from the model analysis xed points.
Form a symmetric grid from static lines.
Include clear references to tooth position.
The middle of the model is the median palatine raphe,
which is the axis of symmetry.
Construct the canine point in the maxilla:
Canine points lie on the diagonal from the tuberosity,
over the rst large pair of plicae palatinae, and ap-
proximately 5 mm in front of that.
Reect the second canine point across the axis of
symmetry.
Trace the midlines of the alveolar ridges:
Mark the midline of the anterior alveolar ridge.
Mark the canine point to the tip of the papilla.
Mark the midline of the posterior alveolar ridge
(middle of the maxillary tuberosity to the canine point).
Mark the raphe-papillary cross-line at right angles to
the model midline through the middle of the papilla.
Mark the static lines:
Static lines must be transferred to the model margins.
These lines include 12 markings in the maxilla.
Fig 8-192 Step 2: Perform model analysis of the maxilla.
327
Planning, Fabricating, and Assessing Complete Dentures
Establish the model analysis xed points in the mandible:
Anterior vestibular fornices
Mandibular symphysis point
Canine points
First molar point
Molar triangle
Establish the axis of symmetry in the mandible:
Mark the middle of the mandibular model.
Mark from the symphysis point to the arithmetic mean
between half of the line connecting the triangles and
half of the line connecting the rst molar points.
Trace the ridge midlines:
Mark the midline of the posterior alveolar ridge from
the middle of the triangle to the canine point.
Mark the midline of the anterior alveolar ridge as a line
connecting the canine points, which usually lies behind
the ridge contour.
Transfer the static lines to the model margins:
Twelve markings in the maxilla and eight in the man-
dible are produced as a symmetric grid.
Adjust the models in centric relation:
Fix the models according to the model analysis grid.
Align the axes of symmetry.
Place the midlines of the anterior alveolar ridges so
that the maxilla protrudes 2 mm.
Place the midlines of the posterior alveolar ridges so
that the interalveolar lines are symmetrically inclined.
Fig 8-193 Step 3: Perform model analysis of the mandible.
328
Complete Dentures
Position the models with plasticine. The models are
inserted in two stages—rst the maxillary model and
then the mandibular model:
Set the mandibular model on plasticine.
Line up the occlusal plane marking on the articulator
with the occlusal plane of the interocclusal registration.
Check the occlusal plane from the front, behind, and
side.
String the occlusal plane markings with a rubber band.
Adjust the model midline/articulator midline, viewing
the models from the front and back:
Adjust the model midline to the articulator midline.
Pay attention to occlusal plane xation; do not tilt.
Open the upper articulator arm and line up the midline
of the model with the articulator midline (the model
midline must point to the oor of the maxillary base).
Line up the model midlines with the articulator midline.
Adjust the models/sagittal plane; view the models from
the lateral position:
Set the models to the incisal point based on the
Bonwill triangle.
Measure the intercondylar distance with dividers.
Project this distance onto the occlusal plane as the
incisal point.
Make sure the occlusal planes do not tilt.
Check the position of the models.
Fix the maxillary model with plaster, isolate the model
base, and t the base with a magnet capsule:
Mix plaster in the correct mixing ratio.
Apply plaster to the maxillary model base and
maxillary model holder.
Gently close the upper articulator arm.
Push plaster into the depressions in the base.
Let the plaster set before trimming.
Fix the mandibular model with plaster, isolate the model
base, and t the base with a magnet capsule:
Mix plaster in the correct mixing ratio.
Turn over the articulator and open the lower arm.
Apply plaster to the model base and model holder.
Gently close the lower articulator arm.
Push plaster into depressions in the base.
Let the plaster set before trimming.
Fig 8-194 Step 4: Adjust the models in the articulator.
329
Planning, Fabricating, and Assessing Complete Dentures
Check the reference and orientation planes and lines.
Setup starts with the mandibular anterior teeth and
reference lines for the mandibular anterior teeth:
Mark the midline of the alveolar ridge.
Create the Bonwill circle with the diameter referenced
to tooth widths.
Mark the mandibular vestibular fornix.
Mark the position of the occlusal plane.
Position the mandibular left central incisor:
It should stand with its base on the ridge midline and
its incisal edge exactly on the occlusal plane.
Position it approximally.
Tooth axes have a vestibular inclination.
The labial contour is perpendicular and shows in the
vestibular fornix.
The tooth axis viewed from the vestibular aspect is
perpendicular.
Its incisal edges form the start of the Bonwill circle.
Position the mandibular left lateral incisor:
It should stand with its base on the ridge midline and
its incisal edge exactly on the occlusal plane.
Position it approximally.
Tooth axes have only slight vestibular inclination.
The labial contour has a slight lingual inclination.
The tooth axis viewed from the vestibular aspect is
perpendicular.
Viewed occlusally, the incisal edge lies in the Bonwill
circle.
Position the mandibular canine:
• It should stand with its tooth axis vertical, its base on
the canine point, and its incisal edge exactly on the
occlusal plane.
• Tooth axes have a slight mesial inclination from the
vestibular aspect.
• The labial contour has a pronounced lingual inclination.
• Viewed occlusally, the incisal edge forms the Bonwill
circle.
Position the mandibular right anterior teeth:
• They should stand with their base on the ridge midline.
• The dental arch is formed by approximal inclinations.
• The labial contour of the central incisor is vertical, the
labial contour of the lateral incisor is slightly lingual,
and the labial contour of the canine shows pronounced
lingual inclination.
• The incisal edges rotate into the Bonwill circle, with
the incisors vertically positioned and the canine slightly
mesially inclined.
Fig 8-195 Step 5: Set up the mandibular anterior teeth.
330
Complete Dentures
Construct the overjet:
Place the central incisor with the necessary overbite without
protrusion and the correct mesial inclination exactly at the
midline of the dental arch.
Make lateral movements in soft wax until the approximal
edges of the maxillary and mandibular central incisors are
pressed out labially.
Maintain the lateral position and push the central incisor into
edge-to-edge position.
• In terminal occlusion, the central incisor is in exact overjet.
Position the maxillary left central incisor:
It should stand with its base in front of the ridge midline.
It forms the vertical anterior arch.
The labial contour stands vertically approximately 7 mm in
front of the papilla midline.
Viewed labially, there is a slight mesial inclination.
It protrudes approximately 2 mm beyond the occlusal plane.
Viewed occlusally, the dental arch is formed.
Position the maxillary left lateral incisor:
Viewed labially, it has a pronounced mesial inclination and
protrudes only about 1 mm beyond the occlusal plane, shorter
than the central incisor.
Viewed approximally, the labial contour has a slight vestibular
inclination, and the tooth axis has a pronounced vestibular
inclination.
Viewed occlusally, the dental arch is formed.
Position the maxillary left canine:
Viewed labially, it has a slight mesial inclination and pro-
trudes about 2 mm beyond the occlusal plane, as long as the
central incisor.
Viewed approximally, the labial contour stands perpendicular.
The tooth axis has a pronounced vestibular inclination.
If it stands vertically, it will interfere with lateral movements.
Viewed occlusally, the canine stands in front of the canine
point.
The raphe-papillary cross-line runs through the canine tips.
Construct the overjet. The size of the overjet depends on the
edge-to-edge position when the approximal edges of the
maxillary and mandibular central incisors are in alignment:
If the incisal edges touch labially, there is a small overjet (A).
If the incisal edges are in full edge-to-edge contact, there is
a medium overjet (B).
If the incisal edges touch lingually, there is a large overjet (C).
A B C
Fig 8-196 Step 6: Set up the maxillary anterior teeth.
331
Planning, Fabricating, and Assessing Complete Dentures
Temporarily position the premolars:
The gap between the canine and the premolar depends on
the size of the overjet and the tooth widths, so the position
of the premolars must be set up temporarily to see where
the gap arises.
With a small overjet or wide maxillary anterior teeth, there
is a gap between the mandibular canine and rst premolar.
With a large overjet and set of narrow maxillary teeth, there
is a gap between the maxillary canine and rst premolar.
Check the lateral movements:
For sliding contacts on the balancing side, a transverse
compensating curve must be formed.
For sliding contacts on the working side, a sagittal
compensating curve must be formed.
There will be no sliding contacts if the sagittal curve is
too pronounced, the lateral incisor is underdeveloped, the
occlusal plane has not been adhered to, or the canine is
too long or has too strong a mesial/inward inclination.
Position the mandibular left premolars:
Align the central developmental grooves with the ridge
midline.
The rst premolar should stand inside the compensating
curves, approximately 1 mm below occlusal plane, with a
slight mesial inclination.
The second premolar should have a pronounced tooth incli-
nation, with its central developmental groove over the ridge
line, approximately 1 mm lower than the rst premolar.
Position the maxillary left rst premolar:
Set the normal occlusion to the mandibular premolars.
Check the occlusion from the vestibular and oral direction.
It has a slight mesial and vestibular inclination.
Its lingual occluding cusp lies in the interdental embrasure
and extends onto the buccal cusps to the balancing side.
Its nonsupporting cusp lies approximally between the rst
and second premolars and extends through the interdental
embrasure to the working side on movement.
Set up the right pair of antagonists; for three-point or
multipoint contacts during lateral and protrusive move-
ments, the following are required:
Sagittal compensating curve
Transverse compensating curve
Overjet of the anterior teeth
Completely closed intercuspal position of the posterior
teeth vestibularly, lingually, and approximally
Fig 8-197 Step 7: Set up the mandibular premolars and the maxillary rst premolar.
332
Complete Dentures
Position the mandibular rst molar:
It forms the lowest point of the sagittal compensating curve.
It stands perpendicular, from the vestibular view.
It has its central developmental groove over the ridge
midline.
It shows a slight lingual inclination.
It forms a weak transverse compensating curve.
Position the mandibular second molar:
It shows a pronounced mesial inclination.
It touches the occlusal plane with its distobuccal cusp.
It has its central developmental groove over the ridge
midline.
It may be rotated slightly into the dental arch.
The mandibular dental arch is parabolic.
Viewed approximally, it stands perpendicular (no tooth
inclination).
Position the maxillary molars:
Ensure precise intercuspation on the ridge midline.
Place them in the sagittal and transverse compensating curve.
The rst molar with the canine forms the premolar tangent,
and its occluding cusp is placed in the central developmental
groove of the mandibular rst molar.
The second molar is rotated distally in the dental arch, which
forms a semi-ellipse, and its occluding cusp is placed in the
central development groove of the mandibular second molar.
The buccal overbite is reduced to edge-to-edge position.
Position the maxillary second premolar:
It should stand inside the premolar tangent on the ridge midline.
Its vestibular contour is roughly perpendicular.
Both cusps are the same height.
Its lingual occluding cusp lies in the interdental embrasure
and extends on the buccal cusp of the maxillary rst molar
to the balancing side.
Its nonsupporting cusp lies approximally between the second
premolar and rst molar and extends through the interdental
embrasure to the working side on movement.
Set up the posterior teeth:
Place them on the ridge midline.
Shape the dental arch to form a semi-ellipse.
The premolars should stand in the premolar tangent.
Perform check movements for balancing and working
contacts.
Make corrections to antagonists.
Sliding contacts arise due to precise shaping of the
compensating curves.
Fig 8-198 Step 8: Set up the posterior teeth.
333
Planning, Fabricating, and Assessing Complete Dentures
Apply alternating wax appropriately:
Apply wax without producing wax stresses.
Alternate application of wax so that the setup wax
is not heated through.
Smear wax layers with underlying wax and keep
bubble-free for a homogenous wax structure.
Prepare the models:
Prepare the maxillary model rst.
Etch a vibrating line in the double arch from tuberosity
to tuberosity and enclose the posterior nasal spine of
the palatine bone.
Hollow out the median palatine raphe and palatine
torus.
Isolate both models (possibly steep).
Plaster against wax.
Shape the denture margins:
Completely ll the denture margins in the vestibular
fornix area for a ridge-shaped valve-type margin.
Hollow out the denture body above the valve margin
as a lip shield for the musculature.
Allow for necessary reductions.
Create extension possibilities.
Wax up the anterior denture body:
Reproduce the gingival sulcus.
Reproduce alveolar eminences as far as the rst
premolar.
Close interdental spaces and hygienically shape the
interdental papillae.
Anatomically shape the gingival structure.
Smooth the wax-up.
Wax up the posterior denture body:
Extend the denture body toward the necks of teeth.
Close interdental spaces and hygienically shape the
interdental papillae.
Ensure that the denture body is smooth.
Do not reproduce any alveolar eminences.
Do not shape the gingival structure.
Shape a valve-type margin in the maxilla.
Avoid the oblique line and mylohyoid line.
Fig 8-199 Step 9: Wax up the denture body.

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Complete Dentures241Complete dentures for the maxilla and mandible comprise denture bodies and arti cial teeth that are inserted into the oral cavity to replace natural teeth and missing alveolar ridges. The denture bodies and teeth resemble the natural tissue parts in shape and size because they are meant to take on their functions. Use of complete dentures involves not only replacing the missing teeth and resorbed parts of the alveolar ridges but also making a radical intervention into the existing massively damaged masticatory system.For a partial denture, it is important to  nd the most favorable anchorage to the resid-ual dentition—from a technical and functional standpoint—to ensure that the prosthesis is  rmly seated and masticatory forces are largely transferred to the periodontal tissues of the residual dentition. By contrast, complete dentures lie mechanically loosely on the edentulous dental arches without additional anchorage. For tooth setup in the case of complete dentures, the anatomical and functional condi-tions of the variable jaw movements as well as the physical and mechanical conditions of a denture body resting on the mucosa in unstable equilibrium have to be taken into consideration. The real problem of complete dentures lies in shaping the dentures so they lie  rmly on the dental arch during chewing without moving and so that masticatory forces are transferred to the underlying mucosal support over a large area.The problems of complete dentures have been studied by many dentists since the early days of dental research, with special emphasis being placed on the relationship between scienti c research and practical testing. In particular, it is a matter of interpret-ing the existing anatomical circumstances of edentulous jaws in light of the physical and mechanical conditions of the dynamic masticatory system so that usable models for practical fabrication of complete dentures can be developed.http://dentalebooks.com 242Complete DenturesFig 8-1 Work ow for complete dentures.10. Insertion and  nal check• Selective grindi ng• Remove pressure pointsTechnicalClinical1. Analysis of denture-bearing area• Surgical measures:➞ Lower the vestibular fornices➞ Shorten the ligaments➞ Smooth the alveolar ridges2. Anatomical impression• Preliminary impression for the preliminary model• Margins marked for the custom tray• Extension impression3. Custom trays• On the preliminary model• Edge length marked4. Functional impression of edentulous arches • Use the mucodynamic method• Record the variable states of mucosal shape5. Functional casts and bite blocks6. Interocclusal registration• Determine the vertical dimension of occlusion• Determine centric relation with the tracing stylus• Mark static lines on the occlusion rims7. Tooth setup• Mount the casts• Perform cast analysis and tooth selection• Set up the teeth• Wax up the denture body8. Try-in of the setup• Check tooth position, shade, and occlusal position• Shape the margins9. Completing the dentures• Final wax-up and investment• Working of the acrylic resin• Selective grinding in the articulator 243Anatomical Changes After Total Tooth LossWhat is striking is that most of these explana-tory models accentuate one anatomical or physi-comechanical feature and prioritize individual measures for successful fabrication of a complete denture. For instance, the view might be put for-ward that the denture should be kept stable dur-ing masticatory function by means of statically favorable posterior tooth shapes. On the other hand, the premise might be that only a precise impression of the edentulous jaws will guarantee successful treatment. Techniques for interocclusal registration are available, with the appropriate ar-ticulators, facebows, and instrument kits, as well as special tooth molds for static setup of poste-rior teeth with detailed instructions.The success of a complete denture, however, cannot be guaranteed by prioritizing individual measures but only by the most accurate imple-mentation of all the individual measures. The fol-lowing individual measures are involved in the fabrication of complete dentures (Fig 8-1):1. Clinical and surgical preparation and analysis of the denture-bearing area in the maxilla and mandible2. Functional impression as the basis for anatomi-cally functional shaping of the denture margins and the denture base3. Interocclusal registration with approximate de-termination of joint values4. Tooth setup based on the principles of denture statics in relation to mandibular movement and taking into account esthetic and phonetic concerns5. Contouring of the denture bodies to support the lip and cheek muscles and to increase den-ture retention6. Final check of the denture while it is function-ing to eliminate slip interferences in the oc-clusal area and pressure points on the denture baseFundamental knowledge about the fabrication of complete dentures needs to be acquired in the aforementioned sequence of measures. This chapter therefore works through the following in detail:• Morphologic and physiologic changes after tooth loss• Impression-taking of edentulous jaws• Interocclusal registration of edentulous jaws• Tooth setup for complete dentures• Retention of complete denturesVarious working methods for fabricating complete dentures are also presented.Anatomical Changes After Total Tooth LossNormal dentition is described as functional occlu-sion, on the basis of which the shapes of teeth, tooth positions, jaw shapes, and inclinations in their morphology are the result of the differen-tiated functions that have to be fullled. In ad-vanced age, the capacity for cellular regenera-tion declines, and physiologic wear is only poorly replaced; age-related physiologic degeneration of the tissue (senile involution) occurs. This in-volves continuous tooth loss with advancing age, which happens faster in the maxilla than in the mandible. Owing to their large periodontium, the canines—especially in the mandible—are the last to be lost.As a consequence of senile osteoporosis, there is a decrease in the weight of the cranium. In edentulousness, the alveolar areas of the maxilla and mandible are almost fully resorbed because these bony parts are no longer being loaded in their original form. In principle, atrophy of disuse ensues.Atrophy of disuse (or inactivity) means ac-tive shrinking of tissue due to impaired function or nonuse of that tissue. For example, muscles shrink when a plaster cast is used to immobilize a limb for a lengthy period after a bone fracture. This process is reversible; after healing, the tissue is built up again, provided that functional loading and proper nutrition are ensured.Resorptive atrophy refers to shrinkage of the alveolar process after tooth loss when the stim-ulus provided by the tooth roots is missing and the bony sockets lose their physiologic function. This process can be delayed by suitable shaping of the denture base for extensive loading of the denture-bearing area, but it cannot be reversed.In the maxilla, the maxillary body forms the ba-sic framework from which the functionally orient- 244Complete Denturesed processes originate. The alveolar process will shrink noticeably after tooth loss; the three other processes will continue to provide static support to the upper face and will only shrink slightly. Weakening of the bone substance will take place at the muscle attachments (eg, zygomatic pro-cess).The substance of the palatine processes of the maxilla is retained because essentially functional loading of this bony part persists because of the suction effect in the mouth. Nevertheless, in the case of the palatal bone, the posterior third of the bony palate can be paper-thin and even perforate so that the oral and nasal cavities are only sepa-rated from each other by a fold of mucosa.In the mandible, the parts oriented by loading during masticatory function resorb after total tooth loss (eg, the coronoid process, angle of the mandible, and alveolar part). The senile mandible is hook-shaped and attened at the angle of the jaw. If there has been severe atrophy, the men-tal foramen lies at the upper edge of the alveolar ridge.As a result of atrophy, the distance between the mandibular canal and the upper edge of the al-veolar ridge shortens; in rare cases, the inferior alveolar nerve may lie directly below the mucosa. The distance from the mandibular canal to the lingual and buccal wall of the mandible remains roughly constant. Jaw relations will also change; that is, the position of the mandible relative to the maxilla will shift. Initially the mandible gets closer to the maxilla due to chewing with the bony al-veolar ridges (Fig 8-2).After prolonged edentulousness, the condyles and condylar path become attened; the condy-loid process of the mandible as a muscle attach-ment (lateral pterygoid muscle) also loses sub-stance and is displaced dorsally. The mandible is displaced forward. This results in structural adap-tation of the temporomandibular joints (TMJs) and the neuromuscular system. Joint cartilage and the articular disc do not carry any blood ves-sels, so no repair process occurs, but defects (in-cluding atrophy) happen in the cartilage and the disc.Fig 8-2 After total tooth loss, the jaw relations shift because the mandible is closer to the maxilla. If the vertical dimension of occlusion is normal, the midline of the mandibular anterior alveolar ridge lies behind that of the maxilla; the more the man-dible approaches the maxilla, the more the chin shifts forward.Fig 8-3 Side view of a senile skull. The outline of the fully dentate jaw shows the extent of resorptive atrophy after total tooth loss: (1) Alveolar processes in the mandible and maxilla shrink almost completely down to the basal bone. (2) The TMJ is deformed by abnormal loading. There are also changes in muscle attachments and (3) the angle of the mandible, (4) the zygomatic arch, and (5) the temporal fossa.25413 245Forms of Shrinkage of Alveolar RidgesThe appearance of a senile skull illustrates the shrinkage that affects not only the alveolar pro-cesses of the jaws but also the muscle tissue and muscle attachments to the bone (Fig 8-3). When the alveolar process in the maxilla is subject to atrophy, the tip of the nose falls downward so that eventually the tip of the chin and the tip of the nose move close together in the senile skull. Atrophy of muscle mass of the masseter may make the cheeks appear hollow and the cheek-bones stand out prominently. This impression is further intensied by the sunken temporal fossae in which the temporal muscle is shrunken.Forms of Shrinkage of Alveolar RidgesThe anatomical changes in the mouth mainly re-late to shrinkage of the alveolar processes or alve-olar parts of the maxilla and mandible. After tooth loss, the roots leave sockets (alveoli) in which secondary bone is formed. In the maxilla, the vestibular bone lamellae of the alveolar process are thinner, while the palatal parts are relatively compact; in the mandible, the thin bone walls lie lingually and the more compact bone walls lie vestibularly. The thin bone lamellae shrink more markedly than compact ones. As a result, the alveolar ridges appear to shrink toward the pal-ate in the maxilla and toward the vestibule in the mandible (that is, in their direction of inclination). Hence, narrowing arises due to the vestibular in-clination of the maxillary ridge, and widening of the ridge lines occurs given the lingual inclination of the mandibular ridge (Fig 8-4).In fully dentate arches, the midlines of the al-veolar ridges lie vertically on top of each other. As the alveolar ridges are inclined toward each other, the mandibular central incisors are inclined lingually and the maxillary central incisors in the vestibular direction. This gives rise to a peculiar feature after tooth loss, namely that the maxilla apparently becomes smaller and the mandible larger (Figs 8-5 and 8-6). The rate of resorption of the alveolar part in the mandible can be three times greater than the shrinkage of the alveolar process in the maxilla. This means the mandibu-lar ridge line widens considerably more than the maxillary ridge line narrows.The interalveolar connecting line (interalveolar line) joins the centers of the shrunken alveolar ridges together (Fig 8-7). Depending on the pro-gression of the ridge shrinkage, the interalveolar connecting line inclines toward the occlusal plane to a variable degree. The greater the incline of the interalveolar line, the more difcult it is to set up the posterior teeth. According to Gysi, the setup is in crossbite if the angle of inclination is less than 80 degrees.In the anterior region, the widening or narrow-ing of the alveolar ridge lines must be viewed in a more differentiated way. In the maxilla, all the teeth show a more or less pronounced vestibu-lar inclination so that the shape of the ridge line is preserved as a semi-ellipse. In the mandible, Fig 8-4 The alveolar ridges have a vestibular inclination in the max-illa and are lingually inclined in the mandible. Shrinkage happens in the direction of inclination so that the mandibular ridge line widens and the maxillary ridge line narrows. This shrinking process is further intensi-ed by the fact that the thin walls (lingually in the mandible, vestibularly in the maxilla) shrink more than the compact walls. This results in differ-ent ridge proles: (a) normal alveolar ridge; (b) high, wide ridge shortly af-ter extraction; (c) narrow and pointed ridge; and (d) at alveolar ridge with-out mechanical retentions.a b c d 246Complete Dentureshowever, only the posterior teeth are clearly in-clined lingually; the canine stands vertically, and the incisors have a labial inclination. This means the ridge line changes from a parabola to a rather trapezoidal basic shape (Fig 8-8). The relationship of the parts of the alveolar ridge is maintained in the canine area; they are vertically shrunken. The anterior areas are sunken lingually, and be-cause the central incisors are inclined more labi-ally than the lateral incisors, the symphysis area shrinks more markedly lingually than laterally. As a result, an almost straight ridge line is formed between the canine points in the mandibular an-terior region.The ridges of the posterior teeth have a vari-ably pronounced lingual inclination in the man-dible (the tooth inclination decreases dorsally; the ridge inclination increases), which is why the ridge line widens more in the dorsal direc-tion. Following shrinkage of the alveolar parts, Fig 8-5 As the alveolar processes of the maxilla shrink in the direction of inclination, the maxillary ridge line narrows in the lingual direction; the maxilla becomes smaller, which has reper-cussions for the statics of the complete denture.Fig 8-6 To achieve better positional stability of the denture, the vertical dimension of occlusion is reduced in complete dentures. As a result, the height of the denture body also de-creases, and the mandible moves closer to the maxilla. Conse-quently, the midline of the mandibular anterior alveolar ridge is displaced forward.Fig 8-7 The interalveolar line is the connecting line between the centers of the ridges of the shrunken dental arches; to-gether with the occlusal plane, it forms the interalveolar angle. The interalveolar angle changes depending on the progress of shrinkage. The more the jaws shrink, the smaller the interal-veolar angle becomes.Fig 8-8 In the mandible, the posterior parts of the alveolar ridge are displaced vestibularly due to resorption, and the an-terior parts are displaced lingually; the result is a roughly trap-ezoidal ridge-line contour.Occlusal planeInteralveolar angleInteralveolar line 247Impression-Taking of the Edentulous Jawthe retromolar triangle appears to be displaced lingually. As this bony part does not shrink after tooth loss, it will retain its real position, relative to which the alveolar ridge is then displaced.The conditions are similar for the maxillary tuberosity and the incisive papilla. The tuberosi-ties appear to be displaced vestibularly, while the incisive papilla is shifted onto the center of the alveolar ridge contour; the tip of the papilla may lie on the anterior contour of the alveolar ridge. Depending on how much shrinkage has occurred due to the duration of edentulousness and the damage caused by faulty denture bases, different forms of jaw shrinkage will arise. In the edentulous maxilla, the alveolar process forms the brous marginal zone, and the median raphe of the hard palate forms the brous median zone in the form of immovable mucosa. Between the brous median and marginal zones lie the plicae palatinae in the fatty zone, which merge dor-sally into the glandular zone with serous-mucous salivary glands. Fatty and glandular zones are more resilient than the brous zones. The soft palate borders the hard palate dorsally.The edentulous alveolar ridge in the mandible also develops a brous zone, which ends dorsally in the alveolar tubercle of the mandible, a ridge of connective tissue covered by mucosa. The im-mobile, brous ridge mucosa is bordered vestib-ularly by the mucosa of the vestibular fornix and lingually by the mobile oor of the mouth.Impression-Taking of the Edentulous Jaw Taking impressions of edentulous jaws falls with-in the dental practitioner’s area of responsibility. The aim is to take a precise, extensive impression of the denture-bearing area, in which the transi-tions from the attached to the mobile mucosa are recorded in particular.The functional impression is used to reproduce the border area individually during functional move ments of the mucosa. The impression does not record the functioning of the mucosa but rather the space required by the mobile mucosa or muscles and ligaments as they function (Fig 8-9). In practical terms, a custom impression tray is used, which is rst prepared from an anatomi-cal cast or preliminary model. For this purpose, an overextended anatomical impression is taken based on the principle of mucostatic impression-taking (Fig 8-10).12345ABCFig 8-9 The contours of the periphery of functional trays allow for reduction needs and extension possibilities for edentulous jaws, such as all vestibularly attached ligaments, the labial frenum (A), and the buccal frenum (B). Note the pterygomandibular raphes in the maxilla and mandible (C), the path of the vibrating line in the maxilla, and the muscle attachments in the mandible, such as the mylohyoid line (1) lingually and the oblique line (2) vestibularly. Extension areas in the mandible are the sublingual areas (3), paralingual areas (4), and buccinator pockets (5). 248Complete DenturesThe mucostatic impression is taken with the mouth relatively wide open and the mucosa in the rest position. The impression negative depicts the equilibrium position between the resting ten-sion of the tissue and the consistency of the im-pression material, usually an alginate mixed to a viscous consistency. Slight movements of cheeks, lips, and tongue cause the attachments of the lig-aments to stand out. This results in an extension impression in which the vestibule is widened in order to record the limits of the dental arch, in-cluding into the undercuts.The custom tray is prepared on a preliminary model, which is derived from this impression. A felt-tip pen may be used to mark the edge of the tray on the alginate impression. This mark then appears on the preliminary model and provides a guide to the contour of the tray edge. The tray is made from a rigid plastic and has an easy-to-grip handle in the middle.Fabrication of a custom tray varies depending on the tray material—whether thermoformed sheet or chemoplastics. What is crucial to both techniques, however, is the shaping of the tray edges. If the tray is kept slightly longer than the depth of the vestibular fornix, the edge can be in-dividually reworked in the mouth. To do this, the edge is shortened until it does not lift off during check movements and does not create any pres-sure points. The edges can be reinforced with wax after correction in order to mold lip shields and buccal rests as well as the length of the sublin-gual roll and the paralingual wings.Possible impression materials are heavy- and light-body silicones; thermoplastic materials allow long-term impression-taking in which the edges ABBCDFig 8-10 An impression of edentulous jaws is usually taken in two working steps: The mucostatic impression deliv-ers a preliminary model (A) on which the custom functional trays are made (B). They show the path of the periphery of the eventual denture. Undercuts are blocked out on the models (C). The vibrating line area and the paralingual and sublingual areas are individually reinforced on the functional tray before impression-taking in order to exploit these important parts of the jaw for special prosthetic purposes. The nished functional impressions are given a horizontal wax rim above the impression of the valve margin (D). This produces the model rim thickness with functional margin. 249Interocclusal Registrationare harmoniously rounded in the border area. Various methods can be used to take a practical functional impression in order to record the vari-able contours of the mucosa.A chewing impression is an impression of the surface of the dental arches during the muscle ac-tivity involved in chewing. This is taken to record the mucosal loading that would be caused under denture functioning conditions. A custom tray with bite planes in the correct vertical dimension of occlusion is coated with thermoplastic impres-sion material and placed in the mouth. Chewing movements are then performed for about 30 minutes.A swallowing impression takes an impression of the jaw’s border to the oor of the mouth, which is important in recording the sublingual spaces for the sublingual roll and the paralingual wings.An impression taken when the patient is pro-nouncing certain groups of vowels and conso-nants records the variable range of movement of the lips, cheeks, tongue, muscles of mastication, vestibule, and soft palate.A closed-mouth impression involves taking a simultaneous impression of the maxilla and the mandible with preliminary registration of occlu-sal position. Prefabricated stock trays are used for the anatomical impression; they can be xed in their position relative to each other. For this purpose, bite plate trays are prepared, which are used when determining the occlusal position for the functional impression (Fig 8-11). The function-al movements can be performed actively by the patient or passively by the operator.The functional model made from dental stone shows the functional periphery to the dimensions required for fabricating a valve margin with an adequate outer valve. To do this, the edge of the model is raised about 3 to 4 mm outward on the impression. A broad wax pad can be stuck onto the impression at that distance from the valve margin so that the base plaster can be raised up to this stop.The vestibular fornix, the border of the oor of the mouth, and the vibrating line can be clearly identied and must not be damaged. On these functional models, the bite plates are now pre-pared in the dimensions of the eventual denture base and used for interocclusal registration.Interocclusal RegistrationInterocclusal registration is intended to establish the positional relationship of the jaws to each other and their position relative to the joints. The aim is to regain the former centric occlusion or habitual intercuspation position in which the con-dyles lie pressure free and tension free deep in the mandibular fossae. In an edentulous mastica-tory system, the equivalent of the former centric occlusion will have to be determined in the verti-cal and horizontal relationships.The vertical dimension of occlusion is mea-sured in various ways. It can be assumed to be a statistical average, namely a 38- to 42-mm dis-tance from the mandibular to the maxillary for-nix. It can be assumed to be the position of the smallest speaking distance when pronouncing test words (eg, counting from one to ten). It can be deduced from the facial proportions as a har-monious length, whereby the facial prole lines yield three facial sections of equal length: the upper, mid-, and lower face. The distances from the root of the nose to the lower nasal point and from the lower nasal point to the tip of the chin are equal.20–22 mm18–20 mmFig 8-11 The occlusion rims are placed on rm bite plates following the course of the center of the alveolar ridge. The vertical dimension of occlusion is measured from the lowest point in the fornix to the occlusal plane. The occlusal plane runs roughly parallel to the contour of the maxillary ridge; in the mandible, it runs dorsally through the upper third of the retromolar triangle; anteriorly, the occlusion rims may be pad-ded by the dentist to match full lip volume or in the course of the vertical anterior arch. 250Complete DenturesThe horizontal relationship encompasses the transverse and sagittal positional relationship of the jaws. This relationship can be registered us-ing various methods. One possibility is to get the patient to adopt the most retruded mandibular position, for example by guiding the mandible back by hand or getting the patient to swallow. However, the most retruded position of the man-dible, in which the condyles are in contact with the dorsal joint limit about 1 mm behind the nor-mal position, is a forced position in most patients.Gothic arch tracing offers another means of de-termining the horizontal relationship. A tracing stylus mounted centrally on the maxillary (or mandibular) bite plate marks what is known as the Gothic arch on the tracing plate of the man-dibular (or maxillary) bite plate. The intersection of the marked lines derived from the horizontal mandibular excursions indicates the centric hori-zontal relationship (Figs 8-12 and 8-13). The point of intersection lies about 1 mm in front of the arrowhead. Using the facebow and Gothic arch tracing technique, the precise position of the man-dible relative to the joint points can be established and thus transferred to the articulator. The bite plate has a rm base that matches the dimen-sions of the denture base. The occlusion rims are placed exactly on the center of the alveolar ridge and are roughly 10 mm wide by 10 mm high. The exact height depends on the position of the occlusal plane. For instance, the mandibular oc-clusion rim—measured from the deepest point in the fornix (next to the labial frenum)—will be between 18 and 20 mm high, follow the occlusal plane, and pass through the upper third of the alveolar tubercle of the mandible. The maxillary occlusion rim extends from the deepest point of the fornix (next to the labial frenum) 20 to 22 mm up to the occlusal plane.Interocclusal registration is intended to deter-mine the relationship of the mandible to the maxilla and the joints and to provide guidance for eventual tooth setup. For this purpose, the maxillary occlusion rim to beyond the canine position is padded up to about 7 mm before the midline of the papilla, corresponding to the con-tour of the vertical anterior arch, until normal lip volume is achieved with wrinkles smoothed out.The markings on the occlusion rims are also intended to provide pointers for tooth setup and tooth proportions (Fig 8-14):• The midline is based on the middle of the face and indicates the middle of the dental arch.• The occlusal plane runs parallel to the pupil line and Camper plane, or it is marked as the lip clo-sure line.• The mandibular incisal point arises as the inter-section point between the midline and lip clo-sure line and provides xation for the incisal pin on articulators.• The smile line is marked as the position of the upper lip when smiling or maximum raising of the upper lip. The length of the teeth is deduced from the lip closure line and smile line.Fig 8-12 Intraoral occlusal registration involves marking the centric occlusion position by using a centrally placed tracing point to trace mandibular movement on a tracing plate in the form of a Gothic arch. The point where the arch intersects indi-cates the position of centric occlusion.Fig 8-13 To get the mandible into centric relation, in which both condyles lie in the most retruded position, a wax bead can be placed at the dorsal edge of the plate, where it will be touched with the tip of the tongue. This means the mandible is pulled evenly into the most posterior position. 251Tooth Setup for Complete Dentures• The canine points or labial angle points for de-termining tooth width are obtained by transfer-ring the extension line of the width of the wings of the nose to the occlusion rims or by indicat-ing the position of the angle of the mouth.• The lower lip line is obtained with the mouth re-laxed and open. This line may indicate the path of the maxillary incisal edges. The base of the nose line is often traced as well for this purpose.Tooth Setup for Complete DenturesA number of orientation guides and measures are available for reconstructing the positions of the teeth (Fig 8-15), which dental technicians must be familiar with and able to use. The descriptive models of the dental arches in a normal denti-tion are generally valid pointers to the position of teeth. They provide guidance for reconstructing the inclinations of axis and dental arch forms. The dental arch forms are parabolic in the mandible and ellipsoid in the maxilla. The occlusion follows the antagonist rule, an overjet being formed from overlap and overbite of the anterior teeth, and the anterior teeth forming the vertical anterior den-tal arch. The Bonwill circle, Bonwill tangent, and Pound lines can be used when shaping the dental arch of the mandible. The maxillary arch shows the premolar tangent.Dentists’ instructions on tooth positions are the markings on the occlusion rims that are placed during interocclusal registration. In addition, ana-tomical casts of the original position of the teeth or photographs of the patient may be used. Notes on the patient’s physiognomy, from which indi-vidual tooth positions may be deduced, may also be provided.Measures are taken to ensure that the static po-sitional stability of complete dentures takes into account the position of the teeth relative to the center of the alveolar ridge, denture body height, tooth position within the compensating curves for all-round sliding contact, and balance of the tone of tongue and cheek.Findings of model analysis are the link between anatomical xed points and the position of teeth. They provide a symmetric grid of static lines by which the tooth positions are aligned. Tooth posi-tion instructions to take account of phonetics and esthetics can also be used.The setup for a complete denture is done in an average-value articulator, in which the basic man-dibular movements are possible. Setup in a fully adjustable simulator of masticatory movements requires individual surveying of condylar paths and cranium-related interocclusal registration for adjusting the models.Setup in an average-value articulator after average-value adjustment of the models in the articulator can be conclusively legitimized: In most clinical cases for which a complete denture is to be pre-pared, there is extensive pathologic deformation 12 345Fig 8-14 After occlusal registration, the operator can make the following markings to indicate tooth shape, tooth size, and position: (1) Smile line: The upper lip raised when laughing, the smile line, and the occlusal plane establish the tooth length. (2) Position of the occlusal plane (lip closure line). (3) The canine points, labial angle points, and midline points determine the tooth width. (4) Midline: The midline of the face is not neces-sarily the same as the midline of the jaw. (5) The lower smile line or nasal base line indicates the position of the central to the lateral incisors and establishes the length of the mandibular teeth. 252Complete DenturesDescriptive models of dental archesDentition patternOverjetPremolar tangent Bonwill circleAntagonist rule Dental arch formsDentist’s positional instructionsFindings of model analysisMeasures to ensure static positional stabilityStatic position Compensating curveFixed pointsStatic linesEstheticsOcclusal registrationFig 8-15 Range of orientation possibilities. 253Statics of Denture Designof the TMJs, which can be treated by a standard-ized complete denture (ie, fabricated according to average values).Setup aid is provided by templates (calottes) in which the radii of curvature are laid out according to average condylar paths. These average-value templates can be adjusted in an average-value articulator to the height of the occlusal plane to enable the mandibular teeth to be set up within compensating curves.For template setup, the mandibular posterior teeth are placed with their cusp tips on the tem-plate so that the occlusal surfaces lie within the sagittal and transverse compensating curves. The exception is the mandibular rst premolar, which only contacts the buccal cusp of the calotte. When the maxillary dentition is opposed accord-ing to the antagonist rule, an occlusal eld may arise that exhibits all-round sliding contact during translative movements.Template systems are available with templates showing different curves that represent different condylar path inclinations. Matching sets of pos-terior teeth are supplied in which slopes of cusp surfaces are referenced to different joint values.Statics of Denture DesignA complete denture lies on the jaw without me-chanical anchorage so it can be moved on the tissue foundation while functioning. Denture stat-ics involve constructing the denture so that it lies evenly on the whole alveolar ridge under loading as well as during chewing and speaking. It would be statically unsatisfactory if the denture moved to and fro on the alveolar ridge and were tipped off during functioning. The static relationships af-fecting a denture are inuenced by the following factors:• The denture-bearing area of the jaws• The height of the denture body• Tooth position relative to the alveolar ridge (see Fig 8-17)• Tooth position relative to the occlusal planeThe denture-bearing area inuences denture statics in the described way: A minimally atro-phied, rm alveolar ridge with adequate mechan-ical retentions is favorable; a severely atrophied jaw whose connective tissue support forms a mobile, abby ridge without undercut retention areas is unfavorable. The form of shrinkage and progression of that shrinkage also inuence the size of the denture body.A denture body acts like a lever arm: The more the alveolar ridges have been resorbed, the taller the denture body will be. Hence, the denture body as a lever arm for occlusally acting forces be-comes longer, and the resulting torque becomes greater (Fig 8-16). The conclusion is to keep the denture body at, which can only be achieved by shortening the vertical dimension of occlusion.The tooth position relative to the center of the alveolar ridge has a signicant inuence on den-ture statics (Fig 8-17). On one-sided masticatory loading, as a result of the tooth being positioned on the ridge center, the denture can be either pressed down on the opposite side or levered off. Three static states are identied: neutral, unsta-ble, and stable tooth position.atLLb cFig 8-16 The statics of a complete denture are determined by the state of shrinkage of the alveolar ridges: (a) Where the ridges are well developed, even loading occurs in centric occlu-sion. (b) On transverse loading (t), the denture body acts as a lever arm (L) so that torque (T) tips the denture. (c) If the ridges are severely atrophied, the lever arm is longer because of the height of the denture body, and the torque is correspondingly greater. The vertical dimension of occlusion has a direct inu-ence on denture stability.T = t · Lt 254Complete Dentures• Neutral tooth position (neutral state) shows the arrangement of the articial teeth on the center of the alveolar ridge. On functioning, the den-ture is initially pressed only onto the side of the loading.• Unstable tooth position (unstable state) exists if the teeth are located outside the middle of the alveolar ridge. On masticatory pressure, the denture is levered off on the opposite side.• Stable tooth position (stable state) arises when the articial teeth are positioned lingually rela-tive to the ridge midline. A torque then acts on the denture body around a pivot on the middle of the alveolar ridge. The denture is pressed onto the opposite side by the masticatory forces. The stable tooth position guarantees secure reten-tion of the complete denture and produces even pressure distribution to the underlying tissue. The stable tooth position has two serious draw-backs. First, the normal processes of shrinkage widen the ridge line in the mandible while nar-rowing it in the maxilla. As a result, the ridge lines no longer lie one on top of each other (Fig 8-18). If the maxillary posterior teeth are now set up slightly inside the ridge line, the mandibular pos-terior teeth will lie well inside the ridge line if they are arranged in normal occlusion. They stand far more lingually than the natural teeth did previ-ously. This means unacceptably severe crowding of the tongue; the patient would be constantly bit-ing his or her tongue and having pronunciation problems.Second, if the maxillary anterior teeth are set up in the stable position inside the ridge line, lip support is lost and the patient’s facial expression is greatly altered—as in an edentulous senile face. Fig 8-17 The position of the articial teeth relative to the ridge midline has a decisive inuence on the statics of a complete den-ture: (a) The stable state denotes the position of the articial tooth inside the ridge line; here loading causes downward pressure on the opposite side because of the eccentric tooth position. (b) In the unstable state, the tooth is positioned outside the ridge line, which leads to the denture being lifted off on the opposite side. (c) The neutral state refers to the tooth position over the middle of the alveolar ridge; here only the loaded side is pressed on.ααFig 8-18 Arranging the teeth in a statically favorable position is difcult because the fol-lowing anatomical features have to be taken into account: (a) In a fully dentate dentition, the ridge lines lie almost on top of each oth-er. (b) After the jaws have shrunk, the ridge lines are displaced relative to each other, de-pending on how advanced the shrinkage is. The interalveolar line is inclined toward the occlusal plane at an angle α. (c) The inclina-tion of the interalveolar line increases if the vertical dimension of occlusion is altered. If the teeth are arranged inside the interal-veolar line, they will be displaced toward the middle of the ridge.a b ca b c 255Statics of Denture DesignTherefore, the maxillary anterior teeth are placed labially in front of the middle of the alveolar ridge for esthetic reasons. The posterior teeth in the maxilla are positioned in the neutral position for functional reasons, there-by placing the mandibular posterior teeth in nor-mal occlusion in a minimally stable tooth position (Fig 8-19). If atrophy is very advanced, however, the neutral tooth position in the maxilla can give rise to an extremely stable tooth position in the area of the mandibular posterior teeth, with the aforementioned drawback of crowding of the tongue.Crossbite position becomes necessary in shrunk-en dental arches if the maxillary ridge is extreme-ly narrowed and the mandibular ridge is widened vestibularly (Figs 8-20 and 8-21). This arrangement is used when the angle between the interalveolar line (the vertical line connecting the ridge mid-lines) and the occlusal plane is smaller than 80 Fig 8-19 The interalveolar line can be used as a reference line for setting up teeth in the posterior region. If the teeth are ar-ranged in normal occlusion, the mandibu-lar central incisors are in a stable position and the maxillary central incisors are in an unstable position. If the mandibular teeth are moved closer to the middle of the al-veolar ridge, taking into account the space required for the tongue, the change to the static relationships is extremely disadvan-tageous for the maxillary teeth.Fig 8-20 Static relationships in severely atrophied alveolar ridges can be improved by setting up the posterior teeth in a crossbite position, moving the mandibular teeth upward and the maxillary teeth downward in a crosswise fashion so that the left teeth are on the right side and the right teeth on the left side. The space for the tongue is enlarged, and the teeth are moved toward the middle of the alveolar ridge.Fig 8-21 If the alveolar ridges shrink in the direction of inclina-tion because the teeth are missing, this also has repercussions for lip volume. In the normal physiologic rest position of the mandible, the lips attain their natural fullness in a fully dentate jaw because of support from the maxillary incisors. If the man-dible is brought into this position in an edentulous situation, the mouth will cave in. Thus, the anterior teeth must be brought into the original position. To do this, the maxillary anterior teeth are positioned anterior to the shrunken alveolar ridge. 256Complete Denturesdegrees. Practically speaking, the maxillary left incisors beyond the second premolars are moved down and to the right and reversed, and the max-illary right incisors are similarly placed down and to the left and reversed. The posterior teeth are swapped crosswise.Position of teeth relative to the occlusal planeThe position of teeth relative to the occlusal plane also inuences the statics of a complete denture, which can be depicted in relation to the Chris-tensen phenomenon (Fig 8-22) and Bennett side shift.On lateral movements of the mandible, the idling condyle on the nonworking side drifts down and forward on its condylar path, while the working-side condyle rotates around its vertical axis and slips outward and often backward in the direction of the lateral movement. This lateral movement of the condyle is the Bennett side shift (or laterotru-sion). In a normal dentition, the posterior teeth on the working side are rmly pressed together while the posterior teeth on the nonworking side gape. This is the transverse Christensen phenom-enon (Fig 8-23).On protrusive excursions, there is a gap be-tween the two rows of teeth while the anterior teeth are in incisal contact. This sagittal Chris-tensen phenomenon arises because, during pro-trusive movements, the condyles on both sides slide downward and forward on the condylar paths and the mandible is dorsally lowered. In normal occlusion, the separation into working and nonworking sides is an expression of the functional orientation of the rows of teeth in the form of sagittal and transverse occlusal curves, whereby faulty contacts in dynamic occlusion are avoided.Preparing plano-parallel occlusion rims for in-terocclusal registration at the level of the occlu-sal plane will give rise to an extreme Christensen phenomenon. If the teeth are set up parallel to the occlusal plane, the rows of teeth will gape on functional chewing movements; this results in the denture tilting and lifting off.All-round sliding contact of all the teeth dur-ing lateral and protrusive movements would be advantageous because the denture would be re-peatedly stabilized against possible tipping off (Fig 8-24). How can such all-round sliding contact be achieved?In the normal dentition, complete and rm oc-clusal contact between posterior teeth occurs during a lateral movement on the working side, while anterior teeth and the opposite side remain without contact. This rm and complete occlu-sal contact of the posterior teeth on the working side comes about because the occlusal surfaces are inclined inside a gently arched sagittal and transverse occlusal curve (Fig 8-25); on the oppo-site side, however, these occlusal curves prevent tooth contact. It is worth checking whether or not the shape of the occlusal curves might be exploit-ed to gain all-round sliding contact with complete dentures because full occlusal contact or selec-tive tooth contact arises at least on the working side because of the occlusal curves.With strongly arched curves, all-round sliding contact can be achieved, and the Christensen phe-Fig 8-22 The Christensen phenom-enon occurs when two occlusion rims arranged in parallel in the occlusal plane (a) are meant to be kept in contact dur-ing protrusive movement, but instead a large gap is created in the posterior re-gion while the anterior teeth remain in contact (b).a b 257Statics of Denture Designnomenon and the positional defect of the Bennett side shift can be compensated for. This is why these curves are called compensating curves. They have basically the same shape as the famil-iar occlusal curves but are more strongly arched.Disturbances in the occlusal plane move the denture against the mucosal base, which may ac-celerate resorption of the bony foundation. For instance, a one-sided increase in the vertical di-mension of occlusion—if it is not remedied—will cause that side to be particularly stressed via re-ex movements, which may lead to deformation of the TMJ.In this context, a similar aspect applies to guid-ance from groups of teeth, for example canine guidance in the case of complete dentures. The maxillary canine—including those in complete dentures—can guide the mandibular denture into centric occlusion but only in interaction with the cusps of the posterior teeth (Fig 8-26). If neces-sary, the canine must be ground back to allow for the individual movement pattern.Fig 8-23 During lateral movements and the transverse Christensen phenom-enon, the Bennett movement also inu-ences the curvature of the compensating curve. The teeth should be positioned so that tooth contact exists in the balancing position (a) and the working position (b).a bFig 8-24 All-round sliding contact can be ensured in the transverse plane by means of a compensating curve arched caudally. From the central articulator po-sition (a), the maxilla is moved relative to the mandible to the side (b) so that the calotte-shaped, curved occlusion rims move against each other in sliding con-tact.a bFig 8-25 The occlusal plane can take on a curved shape (a), which favors sliding contact on mandibular excursions (b). The arrangement of the occlusal curves in space may result in a calotte shape.a b 258Complete DenturesIn summary, the following may be concluded regarding denture statics: The articial teeth should be set up over the middle of the alveo-lar ridge, the mandibular posterior teeth may be placed slightly inside the ridge line, and the max-illary anterior teeth must be placed in the origi-nal tooth position (hence anterior to the alveolar ridge) for esthetic reasons and to aid pronuncia-tion. To secure denture statics, the posterior teeth should be set up inside the sagittal and transverse compensating curves (Fig 8-27). In the process, the denture body should be kept as at as pos-sible. The articial teeth should exhibit a statically stable form to avoid transferring horizontal shear-ing forces to the denture.Articial Teeth for Complete DenturesModern articial teeth are precisely matched to their natural counterparts in terms of shape and color. This acknowledges the fact that the natural tooth represents the optimum functional form with which the functions of the masticatory sys-tem can be best performed. These tooth shapes, reproduced according to the natural model, are in themselves stable and more functionally reliable (Fig 8-28). For the anterior region, a vast array of different tooth shapes are available, enabling in-dividual restoration of any possible case.Posterior teeth are supplied in a few selected shapes and sizes. The occlusal surfaces are ana-tomically precisely shaped, which makes it easy to locate their position in centric occlusion and produces a favorable esthetic impression. Some manufacturers include a certain theory of occlu-sion; for example, the Physiodens from Vita has simultaneous and uniform point contacts with oc-clusal clearances.Abrasion surfaces on the occlusal surfaces are re-created in a few forms. These surfaces are re-lated to condylar paths based on variable values. This makes setting up the teeth easier, based part-ly on average values but also on individual joint values. Using these teeth, problem-free setup is Fig 8-26 If teeth whose occlusal surfac-es have slanting cusps (a) are mounted, these slanting cusp surfaces will nd sliding contact on protrusion (b) while the mandible can be moved without tilting.Fig 8-27 Increasing the curvature of the compensating curves in the sagittal plane so that the condyles and teeth move on a shared arc of a circle is in line with Ferdi-nand Graf von Spee‘s diagrams. The curve of Spee (or anteroposterior curve), which is named for him, is often used as a synonym for the occlusal and compensating curves. The curve of Spee is a special type of sagittal occlusal curve in that occlu-sal curves typically follow a atter course. The compensating curves are also not so sharply arched that extension of the curves touches the condyles. More importantly, the condylar path—as a guide variable for the condyle—is not arched in the path of the curve of Spee.a b 259Articial Teeth for Complete Denturespossible in multipoint contact during functional chewing movements.Variations from the natural tooth shape can be found in the ranges of posterior teeth supplied by certain manufacturers (Fig 8-29). These are usu-ally modications of the original shape down to statically more favorable reduced forms. Dur-ing the development of articial tooth forms, at-tempts have been made to diverge from the natu-ral functional form and develop greatly reduced forms that are intended to support the statics of the denture.Hiltebrandt’s mortar-and-pestle tooth is the most successful modication of the natural tooth shape, which was further developed into a differ-entiated form such as the Condyloform teeth de-veloped by Gerber. According to this principle of form, the punctiform occlusal contacts of natural teeth are simplied into a at mortar-and-pestle contact in which the contact surfaces are displaced lingually and the vestibular contacts are designed merely as supporting and balancing contacts to position each individual posterior tooth so that it is statically stable (Fig 8-30); no balancing contact is required on the opposite side.Fig 8-28 Articial posterior teeth differ from natural teeth, especially in terms of static suitability. Manufacturers usually offer a smaller form that meets the special static demands placed on a complete denture. The process starts with replication of puncti-form occlusal contacts of natural tooth shapes (a) and moves on to pronounced abrasion of occlusal surfaces with variably inclined cusps, which are derived from average condylar paths (b). Modication into a trough-shaped tooth in which a pestle-like occlusal surface engages (c) then leads to a different form in which the condylar path–related parts of the abrasion surface are combined with mortar-and-pestle sections (d).a b c dFig 8-29 Modern posterior teeth have cusp slopes that re-late to different types of occlu-sion, as is the case here with the posterior tooth from Ivo-clar Vivadent. The cusp groove angles relate to the condylar forward glide path; there is a difference between deep bite (approximately 29 degrees), normal occlusion (26 degrees), and crossbite (25 degrees). The cusp surfaces have punctiform contacts.Fig 8-30 In the case of Gerber Condyloform molars and pre-molars, the maxillary posterior teeth have a palatal occluding cusp in the form of a pestle, which engages in the mortar-like occlusal surface of the mandibular teeth; these cusps involved in chewing are posi-tioned inside the middle of the alveolar ridge. The vestibular cusps have a stabilizing effect on chewing; the bulbous buc-cal tooth surfaces have cheek contact. 260Complete DenturesFig 8-31 Bilabial sounds (B and P) are impeded if the lip position is altered by incorrect tooth positioning. If the anterior teeth are placed too far lingually, the lips will cave in and the consonants will be poorly formed.Fig 8-32 Apart from the position of the teeth, the shape of the denture base also inuences pronunciation. In the case of large faults, malpositioning of teeth, and incor-rect denture shape, the patient may never get used to the denture and may always retain a speech impediment. The tongue’s position relative to the anterior teeth when pronouncing various consonants shows the area in which the most common problems occur due to denture design: (a) The voiced consonants C and Z are formed when the tip of the tongue is pressed against the maxillary anterior teeth and lies close to the mandibular incisal edges. (b) S also arises as a fricative when air is squeezed through the narrow gap formed by the tip of the tongue and the palatal surfaces of the maxil-lary incisors. Incorrect tooth positions often result in lisping.B; PC; ZSa bFig 8-33 A forward rolled R is formed when the tongue is moved behind the anterior teeth in a powerful tremolo and produces a vibrating plosive sound. Er-rors in tooth position and incorrect den-ture base shapes impede the formation of this consonant.RFig 8-34 The tongue lies on the palatal plate directly behind the anterior teeth when pronouncing T and D. If the base is too thick or angular in this area, the tongue will shift and T or D will become a G.Fig 8-35 The same applies to the con-sonant L, which is formed in the same place, with the tongue also lying against the premolar region. Replication of the plicae palatinae will make it easier to ori-ent the tongue.LT; D 261Position of Teeth and PhoneticsPosition of Teeth and PhoneticsThe unstable tooth position must always be cho-sen for the maxillary anterior teeth for esthetic reasons. Restoring the natural lip volume is the primary aim so that the patient is not identiable as a denture wearer. However, the functional im-portance of the natural position of the maxillary anterior teeth is also closely linked to the patient’s speech. The formation of sounds is a complex interplay between tongue, lips, and teeth. Most consonants are inuenced by the teeth and their position during the sound. It is not uncommon for patients to complain of having difculty forming certain sounds with their new teeth.Bilabial sounds, such as B, P, and M, become possible on normal lip closure (Fig 8-31). The cor-rect position of the anterior teeth and hence the correct lip position have functional signicance for pronunciation. If the vertical dimension of oc-clusion is too big, lip closure is prevented; if the maxillary anterior teeth are placed too far palatal, the lips will cave inward. In both cases, this leads to weak formation of bilabial sounds.Sibilants (dentoalveolar sounds), such as C, S, and Z, are formed when the tongue is pressed against the palatal surfaces of the maxillary ante-rior teeth and the anterior palate. Gaps between the teeth lead to spluttering; if the teeth are tipped in the oral direction or if the transition from den-ture base to the teeth is too thick or worked too smoothly, the patient will lisp (Fig 8-32). Repro-duced plicae palatinae provide orientation for the tongue (Fig 8-33).Glottal stops (palatoalveolar sounds), such as D, T, or L, arise when the tongue is pressed onto the palate behind the teeth. If the teeth are tipped orally or placed too far lingual, a glottal stop is not possible (G instead of D); a thick base will press the tongue downward and prevent pronunciation of these sounds (Figs 8-34 and 8-35).Fricatives (labiodental sounds), such as V and F, arise when the lower lip contacts the maxillary incisal edges. If the maxillary anterior teeth are too short, the sounds V and F will be distorted into B (Fig 8-36).Postpalatal sounds, such as J, K, and G, arise when the tongue is supported on the posterior teeth. If the dental arch is too narrow, this will impede tongue movements (Fig 8-37). If the tran-sition from the denture base to the teeth is too rough, too angular, or worked too thickly, the space for the tongue will be impeded and nar-rowed.Fig 8-36 If the maxillary anterior teeth are too short or the occlusal plane is dis-placed, the weak fricatives (V and F) are distorted into a blurred glottal stop.Fig 8-37 The “ck” consonant group is palatally formed. This fricative is impeded if the dental arch is too narrow.V; F“ck” 262Complete DenturesModel Analysis of Edentulous JawsPoints and lines can be xed on the dental arches, allowing individual tooth positions relative to an-atomical landmarks to be located later. The pur-pose of model analysis is to locate and trace points on the edentulous jaws that remain unaffected by the normal atrophy that occurs after tooth loss. From these, a symmetric grid is created from static lines, and this grid is used when setting up the teeth and shaping the dental arches.Statics analyses have shown the relationship between these points and normal tooth position. Based on these lines and xed points, the original tooth position can be reconstructed. The setup for complete dentures can then be claried with the aid of topographic features from the description of the normal dentition. The position and form of the model analysis xed points are presented here; their references to natural tooth position are explained, and other prosthetic references are identied.Model analysis of the maxillaFigure 8-38 shows the xed points in model anal-ysis of the maxilla. The median palatine suture xes the middle of the jaw or the model midline. The symmetry axis of the maxillary dental arch along the median palatine raphe is generally the rst to be traced on the model. On this midline, the labial frenum is located in the anterior ves-tibular area, while the dorsal end is formed by the posterior nasal spine of the palatine bone.The incisive papilla appears to be labially dis-placed in an edentulous jaw because the alveolar ridge is resorbed in the palatal direction. The raphe- papillary cross-line runs transversally through the middle of the incisive papilla (about 2 mm from the tip backward) through the canine tips and in the fully dentate jaw touches the lingual edges of the maxillary central incisors. The labial contours of the incisors are located approximately 7 mm labially.The rst pair of large plicae palatinae end about 2 mm anterior to the palatal edges of the maxillary canines. In an edentulous jaw, the canine points can therefore be xed on the alveolar ridges (ie, approximately 5 mm from the plicae palatinae toward the raphe-papillary cross-line) (Fig 8-39). This value is variable, depending on the extent of ridge atrophy.The maxillary tuberosity marks the dorsal end of the alveolar ridge, which is not resorbed after tooth loss. The middle of the tuberosity is indicated by the attachment of the pterygomandibular raphe.The centers of alveolar ridges in the posterior region are identied by the canine points and the midpoints of the maxillary cusps. The middle of the ridge in the anterior region can be drawn from the canine point to the tip of the incisive papilla.Model analysis of the maxilla therefore encom-passes the following steps:1. Mark all the xed points (incisive papilla, rst large pair of plicae palatinae, median palatine suture, and midline of the maxillary tuberosity).Fig 8-38 The reference points of model analy-sis must be present on each dental arch, must always be located at the same place and be un-affected by resorptive atrophy of the jaws, and must be clearly visible and clearly related to tooth position. The gure shows the xed points in model analysis.Anterior vestibular fornixIncisive papillaFirst pair of large plicae palatinaeMedian palatine rapheMaxillary tuberosity 263Model Analysis of Edentulous Jaws2. Mark the middle of the model and extend the tracing onto the edge of the model.3. The canine point must be constructed: Draw a diagonal from the midline of the maxillary tu-berosity through the tip of the opposing rst large plica palatinae. To do this, select the xed points that are clearly visible. To obtain a sym-metric grid, reect the clear xed points and the found canine point over the axis of sym-metry.4. Trace the centers of the alveolar ridges in the posterior and anterior region and extend the tracing onto the model edges.5. Draw the raphe-papillary cross-line and extend it to the model edges. On the model edges, this produces a typical image of model analysis markings.Application of model analysis ndingsThe static reference lines (model midlines, cen-ters of ridges) as well as the position points for the canines and maxillary central incisors are found by means of model analysis (Figs 8-40 and 8-41); this also establishes the position of the maxillary lateral incisors. The position of the posterior teeth is located via the center of the alveolar ridge. The lines of the central developmental grooves of the posterior teeth lie over the middle of the ridge. To ensure that the mouth does not look overfull and that the buccal corridor is created, the premolars are placed inside the premolar tangent (ie, the connecting line between the labial marginal ridge of the canine and the mesiobuccal cusp ridge of the rst molar).Fig 8-39 The canine point is constructed with the aid of model analysis xed points. The model midline is rst drawn through the median palatine raphe; then the maxillary tuberosity and the rst pair of large plicae palatinae (which can clearly be seen) are selected. A diagonal line is drawn from the center of the maxillary tuberosity over the tip of the opposing rst large plica. The canine point lies on this line approximately 5 mm vestibularly. The found canine point is reected over the axis of symmetry.Fig 8-40 The static lines through the model analysis xed points are the model midline over the median palatine raphe, the raphe-papillary cross-line through the middle of the papilla, the midlines of the anterior alveolar ridges through the canine points and to the tip of the papilla, and the midlines of the posterior alveolar ridges through the center of the maxillary tuberosities and the canine points.Fig 8-41 The static lines are carried over to the model edges so they can still provide orientation during setup on a nontrans-parent base. Twelve markings must appear on the edge of the maxillary model, and these produce a symmetric grid. 264Complete DenturesModel analysis of the mandibleFigure 8-42 shows the xed points in model anal-ysis of the mandible. The retromolar triangle or pad can be used for constructing various static lines. It is not resorbed after tooth loss, so half the height (or the upper third) of the triangle con-tinues to indicate the dorsal position of the occlu-sal plane. Half the height of the triangle serves in many template setup devices and average-value articulators as a xed point for the appropriate calibration keys, which are adjusted to the trian-gles and the mandibular symphysis point.The symphysis point is located directly on the center of the alveolar ridge and is the equiva-lent of the mandibular incisal point. (Assuming that the anterior apex of the Bonwill triangle tips downward at the mandibular incisal point after tooth loss, this apex will describe a section of an arc and, after shrinkage of the alveolar ridge, will lie on the middle of the ridge, namely on the sym-physis point, without the length of the sides of the Bonwill triangle having changed.) The symphysis point is found on the middle of the alveolar ridge contour where labial and lingual frena attach-ments can be joined.The axis of symmetry of the mandibular dental arch or the jaw midline runs through the symphy-sis point and half the distance of the triangle (Fig 8-43). To put it another way, a triangle is spanned through the centers of the retromolar pads and the symphysis point; its midline drawn through the symphysis point indicates the middle of the model or midline of the jaw.Canine points on the mandible lie clearly on the corner of the edentulous alveolar ridge, which is resorbed into a trapezoidal basic shape because of its direction of inclination.The alveolar ridge centers in the posterior re-gion run through the centers of the triangle and the canine points (Fig 8-44). In the anterior region, the center of the ridge runs through the canine points.Vestibular fornices in the anterior region of the maxilla and mandible are xed points for the ver-tical anterior arch, which touches the labial sur-faces of the maxillary central incisors; this arc of a circle runs 7 mm away from the middle of the papilla. The labial surfaces of the incisors thus give the upper lip its necessary volume, while the cutting edges of these maxillary teeth support the lower lip.The inferior vestibular fornix is a reference point for the position of the occlusal plane, which lies about 18 to 20 mm above the deepest point of the vestibular fornix directly next to the labial frenum. In addition, this lowest point of the fornix is used as the approach for some calibration keys.Molar points can be seen in the posterior re-gion as a clear depression in the region of the mandibular rst molar, from where the ridge pro-le increases very steeply dorsally and relatively gently ventrally. This depression arises because of the natural shape of the dental arch inside the sagittal occlusal curve and is further accentuated by severe resorption of the bone material after loss of the largest posterior tooth.Retromolar triangleMolar pointSymphysis pointCanine pointAnterior vestibular fornixFig 8-42 The model analysis xed points on the mandible must have the same quality as those in the maxilla. They must always be present in the same place on each jaw, remain unaf-fected by resorptive atrophy, be clearly visible, and be clearly related to tooth position. The gure shows the xed points in a model analysis. 265Model Analysis of Edentulous JawsThis deep point in the prole of the alveolar ridge serves as a reference point for calibration keys by the average-value technique in order to align mandibular jaw models in an average-value articulator (Fig 8-45). This also provides a direct reference for reconstructing original tooth posi-tions: the mandibular rst molar is set up above this lowest point.Model analysis of the mandible therefore en-compasses the following steps:1. Trace all the model analysis xed points again (symphysis point, retromolar triangle, and ca-nine points).2. Construct the model midline and continue to the model edge. To do this, halve the distance of the triangles and draw a connecting line to the symphysis point. The halved distance be-tween the molar points can also be used for locating the midline.3. Mark the ridge centers in the posterior and anterior region and extend them to the model edges. On the model edges, this again pro-duces the typical picture of the model analysis markings.Application of model analysis ndingsOnce again, the static reference lines (model mid-lines, centers of ridges) as well as the position points for the canines and the rst molars are found (Fig 8-46). The posterior teeth lie with their central developmental grooves exactly over the middle of the ridge.Fig 8-43 The midline of the model has to be constructed in the mandible: The xed points are rst traced, then the distances between the molar points and the retromolar triangles are halved. The midline runs from the symphysis point between these arithmetically averaged points.Fig 8-44 The centers of the alveolar ridges run anteriorly between the canine points and posteriorly between the ca-nine points and the middles of the retro-molar triangles. The actual ridge contour deviates in a vestibular direction at the molar points. The midlines of the alveolar ridges form a trapezium.Fig 8-45 The mandibular alveolar ridge shrinks most around the position of the rst molar so that the prole of the ridge dips most here from the vestibular view. This point, known as the molar point, serves as a reference point for calibration keys in average-value articulators and helps to reconstruct the original tooth position as the mandibular rst molar is set up directly above this lowest point.Fig 8-46 In the mandible, the static lines have to be carried over to the model edges so that they can be used for ori-entation during setup. Ten markings are made, including the position of the rst molar, which identies the deepest point of the alveolar ridge contour. 266Complete DenturesThe mandibular parabolic dental arch can be described by the Bonwill circle and its premolar tangents. The size of the Bonwill circle is xed by the canine points; the buccal boundary of the tri-angles establishes the path of the tangents (Figs 8-47 and 8-48).General Setup RulesComparison of different descriptions and illustra-tions of complete dentures shows that there are a few fundamental rules governing the setup of articial teeth. These fundamentals, drawn from the various interpretations, are applied here. No particular method is given priority, but essential advice is taken from all the depictions of tooth setups. As most setup compendia relate to spe-cic tooth shapes, no single method can claim to be universally valid.An average-value articulator is the minimum requirement for setting up two complete den-tures in order to perform check movements and arrange the teeth inside the compensating curves. A setup in a fully adjustable articulator would re-quire the condylar path to be surveyed in the pa-tient. Whether it is appropriate to carry out time-consuming condylar path surveying for complete dentures is a matter for the dentist to decide, es-pecially because determination of an average-value occlusal eld can also be used therapeuti-cally for the TMJs.The ndings of model analysis are the primary orientation guides and the static lines that the dentist draws in place. On the other hand, the familiar descriptive models of normal occlusion can also provide orientation.Static positional stability of the denture is achieved if the articial teeth are positioned on the center of the alveolar ridge. If they are placed outside the ridge middle, that is called vestibular placement, and adverse lever effects will arise in response to eccentric mandibular movements. Instead, the mandibular posterior teeth can be placed slightly lingually, provided that they do not crowd the tongue. The maxillary anterior teeth are the exception to this principle; these teeth are placed anterior to the alveolar ridge to provide support to the lips (Figs 8-49 to 8-54).The compensating curves have to be created. The teeth should be set up inside sagittal and transverse compensating curves. The term three-point contact claries this point: On lateral and protrusive movements, the denture may be le-vered off on the nonworking side if tipping is not avoided by means of antagonist contacts on the nonworking (balancing) side.Fig 8-47 The mandibular dental arch can be described by the Bonwill circle (yellow), where the mandibular anterior teeth and the rst premolar lie on an arc of the circle. Tangents (teal) placed at the rst premolars intersect the buccal cusps and buccal border of the triangle. The central incisors are positioned slightly lingually inside the arc of the circle if the alveolar ridge is severely atrophied.Fig 8-48 The Pound line touches the lingual border of the tri-angle and runs over the lingual cusps of the posterior teeth up to the mesial edge of the canine. The simplest and most reliable method of setting up the posterior teeth is to align the central developmental grooves with the middle of the alveolar ridge. 267General Setup Rules7 mm2 mm5 mmFig 8-49 The maxillary anterior teeth can be reconstructed in their original arrangement with the aid of model analysis to improve the esthetic impression. The central incisors are placed with the labial contour about 7 mm in front of the raphe-papillary cross-line. The canines can be brought into their original position with relative accuracy by reference to the rst pair of large plicae palatinae; in the process, the canine tips touch the raphe-papillary cross-line.7 mmFig 8-50 The labial contours of the maxillary incisors should be about 7 mm in front of the middle of the papilla so that a natural lip volume is created.Fig 8-51 The lips will cave in if the maxillary incisors are placed on the center of the ridge. The impression of an aging face is accentuated if the vertical dimension of oc-clusion is reduced.Fig 8-52 If the denture body is reinforced to tighten the wrinkles around the mouth, the vermilion of the lips is pulled inward and the lips ap-pear very thin.Fig 8-53 The natural lip vol-ume with adequate vermilion is restored if the maxillary an-terior teeth are arranged in-side the vertical anterior arch approximately 7 mm in front of the middle of the incisive papilla and the denture body only compensates for the at-rophy of the alveolar ridge. The vestibule is a capillary gap in a fully dentate dentition, but this is widened by the denture base so that this part of the mouth is altered.Fig 8-54 The incisive papilla in conjunction with the raphe-papillary cross-line is used as a xed point in model analysis. In a fully dentate dentition, it is clearly located behind the alveolar ridge. It apparently drifts as far as the center of the alveolar ridge, depending on how advanced the atrophy is (A and B).A B 268Complete DenturesWhen chewing food, there is no guarantee that the balancing side will have contact. The highest masticatory pressure and hence the risk that the denture will be levered off occurs immediately before gliding into terminal occlusion, or directly before tooth contact on the balancing side; stabi-lization is then instantly possible.The direction of movement when sliding into terminal occlusion can also help stabilize the denture (Fig 8-55). During chewing, the move-ment stroke is always guided into centric occlu-sion coming from the vestibular toward the lin-gual; the direction of movement is then toward the palate (Fig 8-56). Hence the maxillary denture presses on the dental arch on the opposite side (Fig 8-57). If the mandibular teeth lie slightly in-side the alveolar ridge line, the force vector pass-es inside the center of rotation and the denture presses onto the jaw.During speaking and normal play movements, the teeth are also moved against each other un-der contact, and the denture might be levered off if teeth have not been set up inside the compen-sating curves. If the teeth are placed inside these curves, however, the patient can readily be guar-anteed stabilization. The embarrassment of inse-cure denture retention is particularly highlighted when the wearer is speaking, which is why a den-ture should have balancing contacts for this pur-pose.Canine guidance (or guidance from a group of teeth), which lifts the posterior teeth out of occlu-sal contact when protrusive or lateral movements are performed, is inappropriate for complete prosthodontics because even the best functional impression and positional stability provided by the mechanical retentions of undercuts can never offer the type of secure retention a xed restora-tion can provide. Even if canine guidance would not lever off the denture, the dentures will still be moved transversally against the underlying mucosa. Over the long term, these usually trans-verse, forced movements will damage the tissue base and accuracy of t will be lost, which in turn means dynamic loading increases on the mucosa (Figs 8-58 and 8-59). Relining becomes necessary, but it is often not done promptly enough, result-ing in remarkably fast breakdown of the bony foundation; the necessary denture-bearing area is lost.Fig 8-55 In terminal occlusion, it does not matter what path is followed because the opposite side is also in tooth contact. Patients adapt their movement habit when chewing so masticatory forces stabilize the denture. Biting-off movements and reex-checking movements are critical.Fig 8-56 The chewing cycle in the nal phase is directed toward the palate. The mandible presses the food in that direc-tion against the maxillary teeth. In the maxillary denture, the resultant force (Res) passes the center of rotation on the middle of the alveolar ridge, and the den-ture is stabilized on the opposite side.Fig 8-57 Shortly before terminal occlu-sion, when masticatory force is greatest and is applied rather vertically, the resul-tant directed palatally goes past the cen-ter of rotation. As a result, the denture is pressed onto the opposite side.ResRes 269Ways to Check Tooth PositioningWays to Check Tooth PositioningThe teeth are set up tooth by tooth while check movements (lateral and protrusive excursions) are constantly performed to ensure that all-round antagonist contact exists. The incisal guide pin must always maintain contact with the incisal guide plate, especially when a certain plate slope is specied.On lateral movements, the buccal cusps of the posterior teeth on the working side lie on top of each other, while the cutting edges of the ante-rior teeth on this side have edge-to-edge contact. The anterior teeth on the balancing side have no antagonist contact, while the buccal cusps of the mandibular posterior teeth on this side lie on the palatal cusps.On protrusive movements, the anterior teeth have edge-to-edge contact, and in the posterior region individual cusp tips on the molars touch each other. In some circumstances, the incisal guide pin may lose contact with the guide plate.The position of the individual teeth is checked in three spatial directions: from the occlusal, vestib-ular, and approximal directions. From the occlu-sal aspect, rotation inside the dental arch should be checked and corrected. The reference point is the central developmental groove for posterior teeth and the incisal edge for anterior teeth. The central developmental grooves form a straight line that lies directly over the alveolar ridge. The incisal edges form the dental arch.From the vestibular aspect, the mesial or distal inclination of the axis is checked and corrected. This involves checking the height of the tooth rel-ative to the adjacent tooth; a correct interdental embrasure must result, in which the antagonist contacts are evenly distributed to both teeth. On lateral movements, the antagonist cusps glide along in these embrasures.From the approximal aspect, the lingual inclina-tion of axis of the alveolar ridge is checked. In the mandible, the teeth are inclined lingually in keep-ing with the tooth inclination; in the maxilla, the teeth have a vestibular inclination, which gives rise to the transverse curve.The length of the maxillary anterior teeth is denitely dependent on the length of the upper lip. The safest way of establishing this length is for the dentist to make markings on the occlusion rims. If the lip closure line is marked, the anterior teeth should project 1 to 2 mm beyond it. Fig 8-58 Guidance for a group of teeth in the anterior region can be constructed for complete dentures if adequate mechan-ical retentions are available; these are recorded by an accurate functional impression. In the posterior region, occlusal contact is broken on eccentric movements of the mandible. However, transverse forced movements of the denture occur that non-physiologically load the denture-bearing area and damage it.Fig 8-59 If the mechanical retentions are inadequate, the dentures will be levered off their rest area by guidance from a group of teeth. This positional instability lessens the dentures’ functional value and leads to dynamic stresses on the underly-ing tissue. Progressive breakdown of the bony foundation oc-curs, which further reduces positional stability. For complete dentures, bilaterally balanced occlusion should be attempted. 270Complete DenturesIn principle, an overjet is formed; that is, the anterior teeth, including the canines, have no antagonist contact in centric occlusion (Figs 8-60 to 8-62). If this overjet is not formed, the denture may lever off when biting off food or during pro-trusive movements.Individual tooth positions are always positive if they are prepared according to the dentist’s instructions or based on an anatomical model of the original tooth positions, with any extreme positional anomalies obviously being alleviated. An individual tooth position must not impede the statics of the denture (Figs 8-63 to 8-68).It is advisable to carry out individual variations from normal tooth position after setup of all the teeth has been fully completed; a better overview is then possible because dynamic occlusion al-ready functions with all-round sliding contact. Then interferences only need to be sought on the repositioned teeth. The following variations from normal tooth position may be selected: Fig 8-60 The term overjet denes the overbite and is equiva-lent to the amount of protrusive occlusion; that is, the incisors are placed in relation to each other so that the maxillary incisal edges reach beyond the mandibular teeth by the amount to which the maxillary teeth stand anterior to the mandibular in-cisal edges.Fig 8-61 The degree of overjet should ensure that, on protru-sion, the anterior teeth glide past each other while the poste-rior teeth simultaneously remain in sliding contact. With this balanced occlusion, the dentures are stabilized on the denture-bearing area and are not levered off.Fig 8-62 The position of the dental arch-es relative to each other inuences the overjet: If the mandible lies in front, a small amount of overjet is selected. As a result, the anterior teeth achieve sliding contact after only short movement deections.Fig 8-63 Abrasion edges can be ground into the anterior teeth, along which these teeth glide during eccentric movements. Many prefabricated teeth already have abrasion edges; canines usually have to be ground in.Fig 8-64 The overbite may be extended if the upper lip is long. As a result, the mandibular teeth must be placed far back or the maxillary teeth placed far forward to achieve a balanced amount of overjet. This jeopardizes positional stability. 271Ways to Check Tooth PositioningFig 8-65 For checking purposes, the lateral movement is executed until the approximal edges between the central and lateral incisors of the maxilla and mandible lie above one another. Then the incisors on the working side have edge-to-edge contact (A). On the working side, the posterior teeth then have cusp-to-cusp contact (B), while on the balancing side the palatal mandibular cusps have sliding con-tact with the buccal cusps of the mandibular teeth (C). The incisal guide pin will not lift off the guide plate.Fig 8-66 Rotation of the posterior teeth from the occlu-sal view. As a basic principle, the central developmental grooves form a line. If this criterion is applied, it is no-ticeable when a tooth tips out or is twisted out of the arch. This indicates that the interdental niche is disrupted and the dental arch form is defective, which has esthetic drawbacks, especially in the case of the premolars.Fig 8-67 The position of the tooth axes can be checked when viewed from the vestibular aspect. Although more esthetic as-pects come to the fore in the anterior region, in the posterior region it is a matter of shaping the interdental embrasures be-cause this is where the contact areas of the antagonist cusps lie. Otherwise, gliding interference may arise in the embrasure area on lateral excursions.Fig 8-68 (right) It is important to check the approximal incli-nation of the teeth because it determines the position of the teeth relative to the occlusal curves. (a) If a mandibular tooth is tipped in the vestibular direction, an inverted curve rather than a transverse compensating curve will arise. (b) If a maxillary tooth is tipped lingually, the palatally placed occlusal contacts will be lost; however, if it is placed too far vestibularly, this will lead to static and esthetic disadvantages.abACB 272Complete Dentures• The contour of the incisal edges of the ante-rior teeth follows the lower lip contour or the nasal baseline. The dentist can mark both lines on the occlusion rims. The shape and width of the wings of the nose can be used to select the width of the anterior teeth (Fig 8-69).• The anterior teeth can be rotated within the den-tal arch. For instance, the central incisors can be twisted with their distal edges out of the den-tal arch or conversely with their mesial edges twisted out of the dental arch. The anterior teeth can also be moved with their vestibular axes so that the teeth partly overlap at the incisal edges. Spaces between individual teeth can also be set up, although the central incisors are excluded from this if the patient experiences vocalization problems afterward.The dentist chooses the tooth color, taking into consideration the patient’s age, complexion, lip color, and facial hair. The shape of the anterior teeth should be established by the dental prac-titioner in order to select the basic shapes that match the patient’s physical type (Fig 8-70).Position of Mandibular Anterior TeethThere is no hard and fast rule about which teeth to start with in a complete denture setup. If start-ing from the model analysis markings on the maxilla, supplemented by the markings and pad-ding of the occlusion rims, it makes sense to be-gin by setting up the maxillary teeth. If this pad-ding is absent and an average-value template is used for the setup, it is advisable to set up the mandibular teeth rst, for which the static lines from the model analysis of the mandible provide reliable guides. In any case, the parabolic dental ab c dFig 8-69 The shape of the nose can be used to determine the width of the anterior teeth: (a) The vertical tooth axes of the canines line up with the outer edges of the wings of the nose. (b) The incisors can be aligned with the baseline of the nose; a long, pointed nose invites stepped positioning of the anterior teeth. (c) A normally curved base of the nose allows harmonious positioning of the anterior teeth. (d) A relatively uniform line of incisal edges ts well in a patient whose nose has a broad base.Fig 8-70 The Kretschmer constitutional typology is reected in the shape of the maxillary central incisors, as illustrated here: (a) The athletic constitution is well balanced, powerful, and represented by an angular, almost square tooth shape. (b) The leptosomic or asthenic type, rather lanky, nervous, and panicky, is characterized by a triangular tooth shape. (c) The round and trusting pyknic type is best represented by an oval basic tooth shape.a b c 273Position of Mandibular Anterior Teetharch shape is easier to reproduce than the semi-ellipse in the maxilla.The procedural approach to setup being adopt-ed here starts with the mandibular anterior teeth, followed by the maxillary anterior teeth and shaping of the overjet. The posterior teeth are set up in xed pairs of antagonists (tooth to tooth): mandibular premolars and maxillary rst premo-lars in order to determine possible tooth spacing between canines and the rst premolars. This is followed by the mandibular rst molar and the opposing maxillary second premolar, then the mandibular second molar and nally the maxil-lary molars.The mandibular anterior teeth invariably stand on the alveolar ridge. Seen from the incisal as-pect, they form the start of the Bonwill circle, the arc of the circle whose tangents form the refer-ence lines for the posterior teeth (Figs 8-71 and 8-72). As the alveolar ridge of the mandible is generally straight in the anterior region, the arc must be created by the approximal inclination of the anterior teeth and by rotation around the tooth axis. It is inadvisable to use the tooth axis for aligning in the approximal inclination; the la-bial contours of the anterior teeth provide better orientation.OPFig 8-71 The mandibular anterior teeth stand exactly on the occlusal plane (OP), and their incisal edges form a straight line. The tooth axes display a mesial tendency when seen from the labial aspect. The dental arch, seen from the occlusal aspect, forms the Bonwill circle with the canines positioned over the canine points.Fig 8-72 The approximal inclinations are varied to form the dental arch in keeping with the Bonwill circle. All the anterior teeth stand on the center of the alveolar ridge. The approximal inclination can be checked by looking at the path of the labi-al contour: The labial contour of the cen-tral incisor stands vertically, that of the lateral incisor is inclined slightly lingual-ly, and that of the canine shows a pro-nounced lingual inclination. These match the correct inclinations of the tooth axes. 274Complete DenturesThe incisal edges of the mandibular anterior teeth form a straight line congruent with the lip closure line (occlusal plane), while the canine may exceed this line slightly at its tip (Fig 8-73). From the vestibular view, the central and lateral inci-sors stand perpendicular with a slight mesial ten-dency, while the canine is inclined mesially.The mandibular central incisors stand with their tooth axis inclined strongly toward the vestibular aspect; the labial contour runs vertically, and its extension points into the mandibular vestibular fornix (Figs 8-74 and 8-75). The mandibular lateral incisors stand with their tooth axis almost per-pendicular on the center of the ridge; the labial contours are inclined slightly in the lingual di-rection. The mandibular canines stand with their tooth axis vertical and slightly toward the lingual aspect, while the labial contours show a marked Fig 8-73 From the labial view, the incisal edges form a straight line corresponding to the occlusal plane, beyond which the tips of the canines protrude slightly. In a symmetric setup, the mandibular anterior teeth appear to be inverted because of the aforementioned approximal inclinations.Fig 8-74 (left) The mandibular central incisor has a vestibular inclination in a normal dentition; its labial contour, extended vertically, points into the mandibular vestibular fornix. On total tooth loss, the vertical dimension of occlusion is reduced so that the middle of the anterior alveolar ridge of the mandible is displaced forward. If the mandibular central incisor is brought into its original position, it stands slightly in front of the center of the ridge.Fig 8-75 (right) When setting up the central incisor in the man-dible, the mandibular vestibular fornix may provide good orien-tation: The labial contour points vertically downward into the depth of the vestibular fornix, and the incisor stands slightly in front of the middle of the alveolar ridge and displays the neces-sary vestibular inclination. The maxillary vestibular fornix is not suitable for orientation because the shift in the jaw relation will also shift the relationship of the maxillary vestibular fornix to the position of the mandibular teeth. 275Position of Maxillary Anterior Teethlingual inclination. The position of the canines is determined by the canine point, as dened by model analysis.An individual tooth position caused by rotation and overlapping is permissible and should be formed so that no interference in occlusion occurs and sliding contact is always maintained during lateral movements. The mandibular anterior teeth can be set up irregularly to create a favorable es-thetic impression (Fig 8-76). If the teeth are twist-ed in their vertical tooth axes and pushed togeth-er, the anterior width from canine to canine may also be reduced. The anterior width can be in-creased by leaving spaces between the mandibu-lar anterior teeth.Error analysisIt is difcult to make proper use of the orienta-tion lines and positional guidance provided. The requirement for tooth positioning on the center of the alveolar ridge is difcult to carry out. When is an inclined incisor actually on the ridge middle? Must the cervical margin and the ridge contour show, or should the incisal edge lie above the ridge middle, or should the base overlap the ridge contour? For static reasons, the incisal edges should be placed over the middle of the ridge, but then it is not possible to form the Bonwill circle.By way of compromise, the cervical margins of all the mandibular anterior teeth form a roughly straight line parallel and approximately 2 mm in front of the ridge middle; the dental arch is shaped by the previously described vestibular inclination of the teeth and their rotation around the tooth axis. The advice to let the extension of the labial contour of the mandibular rst incisor point into the vestibular fornix is a good guide. This advice also allows considerable leeway. The labial contour can point into the depth of the for-nix at the outer or the inner edge; another varia-tion will arise if the contour does not lie vertically. A ruler held against the contour can show this variation clearly.Position of Maxillary Anterior TeethThe maxillary anterior teeth should form the overjet. Thus, the mandibular anterior teeth are placed up to the lip closure line, while the maxil-lary anterior teeth overhang this line by about 2 mm. The maxillary anterior teeth lie in front of the mandibular anterior teeth by the same amount. If the mandibular anterior teeth have been set up rst, the maxillary teeth can rst be placed with the appropriate overbite to the mandibular ante-rior teeth, and provided the wax is still soft, a lat-eral movement can be performed until edge-to-edge contact is achieved, which means pressing the maxillary incisor in the vestibular direction. If the maxillary anterior teeth are allowed to glide back into centric occlusion, normal overjet to the correct extent will emerge, and protrusive occlu-sion will be equivalent to overbite.The maxillary central incisor stands in front of the alveolar ridge, in keeping with the occlusion rim padding or, based on the average from model analysis, 7 mm from the center of the papilla as far as the contour of the labial surface (Fig 8-77). The vestibular inclination, checked from the approxi-mal aspect, shows the following: It is vestibularly inclined with the neck of the tooth at the alveolar ridge, and the labial contour follows the vertical anterior arch. The incisal edge overhangs the lip Fig 8-76 The mandibular anterior teeth can be set up irregularly to create a favorable esthetic impression. If the teeth are rotated in their vertical tooth axes and pushed together so that they partly overlap, the anterior width from canine to canine may be reduced. Spacing the mandibular anterior teeth can enlarge the anterior dental arch, which can also create a favorable esthetic impression. 276Complete DenturesFig 8-77 The maxillary central incisor stands in front of the alveolar ridge so that the labial surface is about 7 mm in front of the middle of the incisive papilla. It has a vestibular inclination. When seen from the labial aspect, the mesial inclination of axis can be seen. The tooth projects about 1 to 2 mm beyond the occlusal plane or the lip closure line. Seen from the occlusal aspect, both central incisors stand in the dental arch.Fig 8-78 The lateral incisor has a more pronounced approximal inclination, is set up to be slightly shorter, and is tipped more mesi-ally. The lateral incisors stand anterior to the alveolar ridge and continue the dental arch. 277Position of Maxillary Anterior Teethclosure line by about 2 mm, and hence an over-bite over the mandibular anterior teeth is formed that corresponds to the overjet. The mesial axis of inclination is checked from the vestibular aspect, although this inclination is very weak. From the occlusal aspect, there must already be a sugges-tion of the dental arch when looking at the incisal edges of both central incisors.The maxillary lateral incisor also stands an-terior to the alveolar ridge, like the central inci-sor, and hence is in keeping with the vertical an-terior arch or follows the occlusion rim contour (Fig 8-78). The inclinations of axes are more pro-nounced: seen from the labial aspect, there is a stronger inclination, but from the approximal aspect, the neck of the tooth shows more at the alveolar ridge. The lateral incisor is shorter than the central incisor but still projects beyond the lip closure line. From the incisal aspect, the dental arch is visible.The maxillary canine also stands in front of the alveolar ridge (Fig 8-79). The canine point has been located by model analysis or xed by mark-ings on the occlusion rim. The canine is inclined mesially. Its approximal inclination is in the ves-tibular direction, which means the tip of the canine and the cervical margin lie roughly vertically on top of each other; as a result, the bulbous canine appears very dominant. The canine is not longer than the central incisor, which is checked with a at plate parallel to the occlusal line. Canine guid-ance is not attempted. At best, antagonist contact exists with the mandibular rst premolar, hence distally; the mandibular canine has no contact in centric occlusion. It may become necessary to prepare the maxillary canine for interference-free lateral movement.The incisal edges of the maxillary anterior teeth can be ground in, as they are beveled labially to palatally and abrasion surfaces are created. This may even become necessary if the ash on fac-tory teeth is not adequately buffed. Usually, it then becomes necessary to bevel these areas of ash toward the labial aspect in the case of the mandibular anterior teeth. This results in a regu-lar sliding contact.Fig 8-79 The canine is also located in front of the alveolar ridge. The canine point is xed by the rst pair of large plicae palatinae. The canine, like all the anterior teeth, displays a vestibular tendency and is inclined slightly mesially. Its length corresponds to that of the central incisor. From the occlusal view, the canine must be given an exposed position. It is the corner in the dental arch, 2 mm in front of the rst pair of large plicae palatinae.2 mm 278Complete DenturesFig 8-80 Subtle, deliberate irregularities in tooth position en-hance the natural effect of the dentures. Based on this knowl-edge, it is possible to deviate from regular positioning (A) and create a harmonious individuality seen from the labial aspect by means of convergence and divergence of the tooth axes (B and C).Fig 8-81 Positional changes achieved by rotation around the vertical tooth axis, so that some of the teeth may overlap, will also increase the natural impression (B and C).Individual tooth positionsSubtle, deliberate irregularities in tooth position enhance the natural effect of dentures (Fig 8-80). Based on this knowledge, it is possible to deviate from regular positioning and create a harmoni-ous individuality seen labially by convergence and divergence of the tooth axes. Positional changes achieved by rotation around the vertical tooth axis, so that some teeth may overlap, will also in-crease the natural impression (Fig 8-81).Error analysisThe canine is often placed with the neck of the tooth facing vestibularly for esthetic reasons. However, inverted placement of a canine, where the cutting edge is tipped inward, causes massive interference in lateral movements; as a result, the canine will be pressed out in the vestibular direction by forced movements. The canine is de-formed by corrective preparation. Therefore, the canine should be set up so that the neck and inci-sal edge overlie each other vertically. The degree of overjet has esthetic aspects and functional val-ue. The sagittal distance of all the teeth must be uniform. The distance often increases on the lat-eral incisor and canine. This error arises if the ar-ticial teeth have the wrong vestibular inclination or are placed inverted; this error will also arise if the maxillary teeth are placed too close together.Position of Mandibular Posterior TeethFor static reasons, the mandibular posterior teeth are placed on the middle of the alveolar ridges. Provided that the tongue is not crowded, it is possible to move the posterior teeth slightly lin-gually. The compensating curves are formed by the position of the posterior teeth. The curves are achieved in an average-value articulator with a template (calotte) by placing the teeth against the mounted template. If the posterior teeth are set up without accessories—hence without tem-ABCABC 279Position of Mandibular Posterior Teethplates—the following points should be kept in mind.Setup starts with the mandibular posterior teeth, and the maxillary posterior teeth are set against them. This is because the static lines in the mandible are clearer when the anterior teeth are in place, which makes setup easier. Setup is done tooth by tooth in antagonist pairings; the necessary corrections always relate to all the teeth involved.The mandibular second molar stands with its distobuccal cusp at the same height as the tip of the canine, which means level with the occlusal plane. This occlusal plane runs from the mandib-ular incisal point to half the height of the retro-molar triangle (Figs 8-82 and 8-83). This occlusal plane is marked in every average-value device so that this plane can be readily identied by simple placement of a ruler. Stretching a rubber band is not accurate because it can be shifted by the standing teeth or the occlusion rim.The sagittal compensating curve must emerge when viewed from the vestibular aspect: Only the canine and the distobuccal cusp of the sec-ond molar touch the occlusal line. The premolars stand below this line. The rst molar stands per-pendicular and is the lowest within the curve (Fig 8-84).Fig 8-82 The second molar is set up with a mesial inclination inside the compensating curve, and its distobuccal cusp tip touches the occlusal plane.Fig 8-83 The occlusal plane is xed by half the height of the retromolar triangle and by the lip closure line, which in turn is represented by the incisal indicator on the articulator. The compensating curve intersects the occlusal plane at the canine and at the distobuccal cusp of the second molar. The curve arises because the rst premolar lies lower than the canine, the second premolar lower than the rst premolar, and the rst molar lower than the second premolar, while the second molar is tipped so steeply that it touches the occlusal plane again.Fig 8-84 The rst molar is placed at the lowest part of the sunken alveolar ridge, where the center of masticatory force is located. 280Complete DenturesThe transverse compensating curve is formed when the tooth inclination of the mandibular pos-terior teeth is reproduced; that is, all the posterior teeth are inclined lingually (Fig 8-85). The central developmental grooves of the mandibular poste-rior teeth form a straight line that aligns with the middle of the alveolar ridge; as a result, the buc-cal cusps lie on the tangent of the Bonwill circle. The lingual cusp tips lie on the Pound line. Check movements show whether an antagonist contact exists with the maxillary canine, without the inci-sal guide pin lifting off.The mandibular rst premolar stands with its buccal cusp tip slightly lower than the canine. This cusp tip should point exactly to the interden-tal embrasure between the canine and rst pre-molar in the maxilla. Inclination of axis from the vestibular view is slightly distal (Fig 8-86).A space between the rst premolar and the ca-nine becomes necessary to compensate for the differing widths of the anterior teeth. To do this, the two mandibular premolars and the maxillary rst premolars are xed in their approximate po-sition to determine where the space is needed. If the maxillary set is too wide or the overjet is too small, a space is needed in the mandible; if the maxillary set is too narrow or the overjet is very wide, the space will arise in the maxilla.The mandibular second premolar stands with its buccal cusp again slightly lower than the rst premolar, approximately 0.75 mm below the oc-clusal plane; the sagittal curve is formed. From the vestibular view, the tooth axis is perpendic-ular, which supports the shape of the curve. So that a precise interdental embrasure is created, the mesial edge of the second premolar lies at the same height as the distal edge of the rst premolar. The approximal inclination shows the tooth inclination, whereby the transverse curve arises. In the tooth-by-tooth setup, the maxillary rst premolar is now set up to correct the sliding contacts during check movements.The mandibular rst molar in the vestibular view stands vertically at a distance of about 1 mm from the occlusal plane. It forms the lowest point on the sagittal compensating curve. Its central developmental groove forms a straight line with the rst and second premolars, running parallel to the ridge line. It stands with a slight tooth incli-nation lingually in order to shape the transverse curve. In the tooth-by-tooth setup, the maxillary second premolar must be set up to correct the sliding contacts during check movements.The mandibular second molar, seen from the buccal aspect, stands inside the sagittal com-pensating curve and is tipped mesially so that it forms a correct interdental embrasure with the rst molar and touches the occlusal plane with its distobuccal cusp. The transverse curve is very weakly developed at the terminal molar. In the tooth-by-tooth setup, the antagonists are now set up, and complete sliding contact is corrected.Fig 8-85 The approximal inclinations of the mandibular posterior teeth in the lingual direction produce the transverse compensating curve. This inclination can be found in a tooth-by-tooth setup by the check movements in which sliding contacts have to exist. The transverse curve decreases distally; that is, the rst premolar is the most strongly inclined lingually and the second molar the least inclined.Fig 8-86 The premolars are tted inside the compensating curve; their vestibular contours display the same inclination as the canine. 281Position of Maxillary Posterior TeethPosition of Maxillary Posterior TeethFor static reasons, placement of the maxillary posterior teeth on the middle of the alveolar ridge is compulsory. Slight deviations in the vestibular direction may arise because of the inclination of axis inside the transverse compensating curve (Figs 8-87 and 8-88). Nevertheless, secure reten-tion of the complete denture can be ensured by means of the functional impression and the me-chanical retentions.The dental arch is shaped into a semi-ellipse; the premolars stand inside the premolar tangent in order to shape the buccal corridor, for which the canine and rst molar serve as xed points (Figs 8-89 and 8-90). It makes sense to set up the mandibular pair of posterior teeth rst and then to align the maxillary antagonists accordingly (Fig 8-91). It is important to ensure that the posterior teeth are placed in normal occlusion according to the antagonist rule, where the cusp tips always lie in the interdental embrasures of the antagonists (Figs 8-92 and 8-93).If the mandibular teeth are set up, the maxil-lary antagonist can be xed with a little wax in its correct intercuspation position on this row of teeth (Figs 8-94 and 8-95). It is then pressed into the maxillary softened wax rim by closing the ar-ticulator. The maxillary and mandibular occluding cusps each engage in their antagonist contact ar-eas. The correct sliding contact is checked by lat-eral and protrusive movements.The maxillary premolars stand perpendicular, and their lingual cusps touch the antagonists in the interdental embrasures. The correct position should also be checked intraorally. The palatal cusps appear longer than the buccal cusps and form the transverse compensating curve. The pre-molars have only a slight overbite buccally and glide past each other in antagonist contact with-out interference and without losing the sliding contact of the anterior teeth.The maxillary rst molar is brought into the correct intercuspation position by resting the me-siolingual occluding cusp in the central develop-Fig 8-87 (top) In a complete denture setup, the inclinations of the tooth axes of the maxillary (and obviously the mandibular) posterior teeth deviate from the natural inclinations of axis be-cause the sagittal compensating curve is more curved than the natural occlusal curve. The rst and second molars are tipped markedly in the distal direction. In addition, the posterior teeth project beyond the occlusal plane because of the shape of the curve.Fig 8-88 (bottom) The axes of the mandibular posterior teeth are inclined so that the sagittal compensating curve arises: The rst molar stands perpendicular, and the second molar is tipped mesially; the rst and second premolars have a slight distal tendency to the alveolar ridge. 282Complete DenturesFig 8-89 The maxillary dental arch forms a semi-ellipse. To achieve this, the second molar is twisted distally into the den-tal arch. Ellipsoid shaping of the dental arch is necessary so that the cheek is not pulled between the rows of teeth on mas-tication in the narrow buccal vestibular space.Fig 8-90 Two principles apply to setting up the maxillary inci-sors: placement on the center of the alveolar ridge and follow-ing the premolar tangent. The vestibular edges of the rst mo-lar and the canine are touched by a straight line, behind which the premolars stand; the buccal corridor should emerge.Fig 8-91 The approximal inclinations of the maxil-lary posterior teeth should be selected so that the palatal occluding cusps have occlusal contact in the central areas of the mandibular teeth. The rst pre-molar stands over the ridge line so that its palatal cusp is shorter than its buccal cusp; in the case of the second premolar, both cusps are at the same height; the occluding cusp of the rst molar is lon-ger than the buccal nonsupporting cusp (shear), a relationship that is further accentuated on the second molar. From the vestibular view, the buccal cusps follow the compensating curve and project beyond the occlusal plane caudally.Fig 8-92 If the overjet is small but the maxillary anterior width is large, a space between the man-dibular canines and rst premolars will become necessary on both sides. If the anterior teeth are set up rst, the mandibu-lar premolars and the max-illary rst premolar must be placed in an antagonist pairing to identify where and how much of a space needs to be left.Fig 8-93 If the maxillary anterior teeth are too nar-row and the overjet is very wide, a space will form between the maxillary ca-nine and the rst premolar. This space is often referred to as a primate space. In any case, it is advisable to leave a slight gap between the posterior teeth during setup so that the individual antagonist pairings can be placed in an interference-free intercuspation position. 283Position of Maxillary Posterior TeethA C DA BFig 8-95 The size of overjet can vary within the aforementioned excursion if the contact situations of the abraded incisal edges are altered: (a) Setting the abraded incisal edges exactly to edge-to-edge contact will produce an average amount of overjet. (b) If the maxillary central incisor is placed with the vestibular edge of its abrasion facet on the lingual edges of the abraded cutting edges of the mandibular antagonists, a very small overjet will be created. (c) If, on the other hand, the maxillary central incisor is placed with the lingual edge of its abrasion facet on the vestibular edges of the abraded cutting edges of the mandibular teeth, a wide overjet will result.a b cFig 8-94 The overjet is constructed by reference to a dened excursion: Once the mandibular anterior teeth have been set up, the maxillary central incisor is placed in the soft wax in its position, precisely on the midline with an overbite (ap-proximately 2 mm) (A). A lateral movement guided by the in-cisal guide table is then performed until the distal approximal edges of the maxillary and mandibular central incisors are in alignment (B). In the process, the maxillary central incisor is pressed in a vestibular direction; in this lateral position, it is pressed to the edge-to-edge position in the soft wax (C). If the excursion is reversed, the maxillary central incisor will lie in the correct overjet (D). 284Complete Denturesmental groove of its antagonist. Its distolingual occluding cusp lies in the interdental embrasure between the mandibular rst and second molars. The mesiobuccal facet with the labial contour of the canine forms the premolar tangent on which the premolars lie.The second molar is tted into its correct in-tercuspation position. Keeping the second molar inside the ellipsoid dental arch can pose prob-lems. If a buccal overbite is dispensed with and an edge-to-edge position is chosen instead, the correct position within the dental arch can be achieved. The compensating curves are deter-mined by the position of the mandibular teeth. If a complete antagonist contact is created, the transverse compensating curve is clearly identi-able from the maxillary teeth.The central developmental grooves of the max-illary posterior teeth—as in the mandibular denti-tion—form a roughly straight line that lies over the middle of the alveolar ridge.As a departure from tooth-to-tooth setup, the mandibular dentition can be set up and ready, and then the maxillary rst molar can be placed in its position so that the premolars can be brought into the space. This gives rise to a space between the canine and rst premolar if the occlusion or the different widths of the anterior teeth demand it; if a space becomes necessary in the mandible, the setup of the mandibular posterior teeth must be repeated.Error analysisTo check tooth position, lateral and protrusive movements are executed, during which the de-scribed sliding contacts must arise without the incisal guide pin lifting off the guide table. Each antagonist pairing is checked and corrected until sliding contact exists during all eccentric move-ments; only then is another antagonist pairing set up. The interdental embrasures, the oral and ves-tibular intercuspation, and the curvature of the compensating curves are checked and corrected.If balancing contacts are missing, the oral in-tercuspation may be defective, or the transverse compensating curve will have to be strengthened. If working-side contacts are missing, the vestibu-lar intercuspation may be defective, or both com-pensating curves are too pronounced. The rst antagonist pairing (mandibular premolars and maxillary rst premolars) may already point to this error. If the buccal cusp of the maxillary rst premolar glides into the interdental embrasure, it should retain contact with both antagonists. If the sagittal curve is too pronounced, a gap with the mandibular second premolar will occur, which should be raised by exactly the width of the gap. In this way, the sagittal compensating curve can be corrected.Retention of Complete DenturesThe main problem when restoring edentulous jaws lies in ensuring that the complete denture has secure enough retention when in the rest po-sition and when functioning. Complete dentures are supported on the dental arch without mechan-ical anchorage, whereby static relationships and dynamic processes inuence functioning capabil-ity. Retention of the complete denture is affected by anatomical and physical realities, including the quality of the underlying tissue (Fig 8-96). Ad-equate retention must be provided against with-drawal forces.These withdrawal forces may be lever forces arising from masticatory function, traction forces due to sticky foods, or the weight of the denture itself. Denture retention onto the dental arch can usually be achieved without additional aids, pure-ly by the effect of suction, forces of adhesion and cohesion, and mechanical retentions from under-cut parts of the jaw.The denture margins and body can be prepared with such accuracy of t by means of a precise functional impression that the denture is rmly retained. The quality of the retention can be mea-sured by the way in which the denture rest area—the tissue of the jaw—is protected and how effec-tively the denture is protected against withdrawal forces.The following physical factors inuence reten-tion of a complete denture:• Adhesive and bonding effect• Accuracy of t• Stable support• Mechanical retentions 285Retention of Complete Dentures• Effect of suction• Statics of denture designAdhesive and bonding effects due to forces of adhesion and cohesion are crucial to retention of a complete denture. There is saliva in the gap be-tween the mucosa and the denture base, which creates adhesive forces to the denture acrylic on the one hand and to the tissue on the other. This form of retention can be illustrated by the exam-ple of two glass microscope slides.Adhesion refers to the forces of attraction be-tween the molecules of two bodies. The closer these two bodies are brought together, the great-er the force. The size of the gap between the bod-ies can usually be lled with the easy-to-move molecules of a liquid substance, so that the ad-hesive effect happens via these molecules and, as shown by two wet glass slides, can produce enormous forces. The adhesive force of the den-ture base is consequently greater if the gap is very small (that is, the accuracy of t of the den-ture is very great).Cohesion refers to the force of attraction be-tween the molecules of a substance. Cohesive force arises through the saliva. This cohesive force is relatively strong with a thick viscous sa-liva but can be further increased by suitable ad-hesive agents (adhesive powder). Adhesive and bonding effects always act together, namely ad-hesive force between saliva and the denture or tissue and cohesive force in the saliva.Accuracy of t increases the capillary action of the aforementioned forces due to adhesion and cohesion. The more tightly the denture base ts to the mucosa, the more effective is the capillary action and the effect of suction. Good accuracy of t also prevents any adverse dynamic behavior of the denture while functioning; that is, during chewing function or when the wearer is speaking, a very accurately tting denture will not slip to and fro on the mucosal support as much as an ill-tting denture, which will produce sore spots.Stable support from a relatively rm denture-bearing area is necessary for secure retention of a complete denture. A bony alveolar ridge with minimally resilient mucosal covering is best suit-ed as support for a denture. On a mobile support (abby ridge) comprising tough connective tis-sue, a denture will be displaced and levered off. Denture movements counter to jaw movements produce areas of opposing pressure loading, leading to substantial pressure sores.Mechanical retentions are undercut areas of the alveolar ridge on the jaws into which the denture bases have to be extended. In the maxilla, these Fig 8-96 Horizontal positional stability depends on the underlying tissue. In the case of abby ridges (a), where the ridges consist of tough connective tissue only, the dentures can be displaced transversally and sagittally on very strong compression of the mu-cosa. High, well-preserved alveolar ridges are the prerequisite for good denture retention. This is because the denture can still be shifted when the bony support with uniform mucosal covering is not high and its shape offers no mechanical retentions (b). Denture movements and compression of the mucosa will accelerate bone resorption.a b 286Complete Denturesareas include parts of the left and right tubercles, between tubercle and anterior alveolar ridge, and sometimes the entire vestibular area (Fig 8-97). In the mandible, the undercuts include the ante-rior parts of the alveolar ridge and the retromolar wings (Fig 8-98). These morphologic features of the jaws can be described as extension options.Suction EffectA suction effect arises because a space lled with rareed air gets smaller because of the effect of normal atmospheric pressure. The effect can be illustrated by a suction pad: If a rubber pad is pressed onto a smooth surface, its edges offer a tight marginal seal. The pressure difference arises because the rubber pad that is deformed when it is pressed will try to upright itself because of its elasticity. Hence a small gap of rareed air is formed between the pad and smooth surface. At-mospheric air pressure presses the edges of the rubber pad onto the smooth surface. If the pad is pulled perpendicular to the surface, the rareed air space and hence the pressure difference will get bigger and the pad will stick more.The functional margin in a denture acts like the edges of the suction pad, producing a space that is closed on all sides (Fig 8-99). To achieve this suction effect with a denture requires this closed space on all sides, which can be made bigger by withdrawal forces and gives rise to the rareed air space. Atmospheric air pressure becomes effective because of withdrawal force as it tries to restore the original spatial dimensions. If the denture is pulled off vertically, the space between the jaw and the denture base will increase. In the small amount of air found in the saliva within this space, a pressure difference occurs in response to higher outer pressure and creates a suction ef-fect. This suction effect is greatest when subject to axial forces (withdrawal forces perpendicular to the suction surface); in other words, at jaws Fig 8-97 In the maxilla, the mechanical retentions on well-preserved alveolar ridges are found in the undercut anterior vestibular areas and the buccal vestibular areas. These areas act as mechanical retentions but only interact when the width of the vestibular fornix (Vf) is less than the tuberosity width (Tw); there-fore, the anterior areas do not become effective until the dorsal retentions are also present.VfTwVfTwFig 8-98 In the mandible, well-preserved alveolar ridges in the anterior vestibular area are undercut and offer mechanical retentions. If the denture base is extended into the sublingual areas, the downward pressure of the tongue may serve as me-chanical retention. The paralingual areas are always undercut and can be used as mechanical retentions if appropriate im-pressions are taken. 287Suction Effectare not unfavorable but need to be better protect-ed against axial forces.A valve-type margin is a specially shaped func-tional margin to a complete denture base. The vestibular fornix in the rest position is a narrow space in which the mucosal parts touch each oth-er (Fig 8-100). Therefore, a denture margin in the transitional area from attached to mobile mucosa, having been shaped, smoothed, and rounded ac-cording to a functional impression, may slightly displace the mucosa that is pulling toward the vestibule. The mucosa is slightly stretched and remains at the denture margin during denture movements. The denture margin forms the valve-type seal throughout its course, with a distinction being made between an outer valve and an inner valve. The inner valve is the area of the immobile mucosa from the depth of the vestibular fornix up to the alveolar ridge. The outer valve is formed when the mucosa is displaced out of the rest po-sition toward the vestibule by the broad denture margin and is stretched around the functional margin. The denture margins should not be so wide that they cause pressure points to develop on loading because of the space they occupy.The more accurately and more extensively the valve margin (especially the outer valve) is shaped according to the functional impression, the more effective the valve margin. The surface of the out-er valve can be enlarged by suitable shaping of the outer surface of the denture so that the pressure-equalizing air travels a longer distance. The inner valve can be effectively created if the mucosa in this vestibular fornix area is also dis-placed out of the rest position toward the bony support and is thereby placed under tension.Etched lines marking the vibrating line on the dorsal edge of the baseplate of the maxillary den-ture complete the valve margin (Fig 8-101). The vibrating line is etched in place so that the edge of the plate presses into the mucosa. The etch-ing can be shaped in various ways. To prevent retching by the patient, the contour of the etch-ing should ideally be adapted to the bony sup-port; that is, it should be at, should rise dorsally, and then should be sunk into the transition from hard to soft palate. The etching should be about 2 to 3 mm wide and about 1 to 1.5 mm deep. The acrylic resin plate can be gently tapered so that a smooth, dorsal transition is formed from den-Fig 8-99 In the same way as a normal suction cup, the suction effect of a complete denture arises as the space between the denture and tissue is enlarged when the denture is pulled off its support. In the case of a suction cup, pre-tension caused by the elasticity of the pressed-on rubber holds the cup onto the smooth surface. In the case of a denture, the suction force only ensues when external pulling forces increase the size of the space. The denture margin in the vestibular fornix must provide an airtight seal, as with a suction cup. It therefore becomes necessary to shape the functional margins as valve margins.O IFig 8-100 In the rest position, the vestibular fornix is a nar-row space in which the mucosal parts touch each other (a). The entire functional margin of the denture (b) must be shaped as a valve margin. A distinction is made between the outer valve and the inner valve. The outer valve (O) arises when the mucosa is displaced out of the rest position in the vestibular direction by the wide denture margin and is stretched around the functional margin. The inner valve (I) is the area of immo-bile mucosa from the depth of the vestibular fornix up to the alveolar ridge.a b 288Complete Denturesture to mucosa. Etching of the vibrating line, as well as the effect of the valve margin, should also compensate for any inaccuracy of t of the dorsal plate edge caused by shrinkage of the acrylic resin. Even if shrinkage is largely offset by re-pressing devices for acrylic polymerization and accuracy of t is improved, it is still advisable to etch a vi-brating line to complement the valve margin.Additional etchings on the surface of the palate can increase retention of the maxillary denture base. Etching additional ridges will divide the en-tire retentive surface into several compartments with their own separate retentive effect. Tools with different proles may be chosen for this pur-pose. Etched lines should be placed so that the bony support is not damaged.Extension OptionsExtension options are the design principles in-volved in extending denture bases into mucosal areas so that masticatory forces are distributed according to the snowshoe principle and addi-tional retention is created for the denture base.In the maxilla, it is mandatory to encompass the entire vestibule with the denture base right into the buccal vestibular spaces. This includes the maxillary tubercle, which is not affected by at-rophy after tooth loss and can offer excellent sup-port. In individual cases, the denture body may be extended buccally into the cheek area to ac-commodate the posterior teeth, so that the buc-cal mucosa creates additional retention for the denture.Shaping the outside of the denture to ensure denture retention includes the sparing, smooth reproduction of the alveolar eminences as well as the creation of a circumferential channel di-rectly above the valve or functional margin. Al-lowing for reduction needs, the buccal and labial mucosae, along with their muscle bundles, can settle here and support the denture. The outer surface of the denture body in the anterior re-gion is shaped to grip muscle; this is done by constructing lip shields for the orbicular muscle of the mouth. In the posterior region, buccinator rests should be created, and the muscle tracts to the buccal frena should be traced (Figs 8-102 and 8-103). Due regard should be given to reduction needs (Fig 8-104).ABFig 8-101 The dorsal edge of the maxillary complete denture is etched to complete a circumferential valve margin. As in the vestibular area of the margin, the mucosa must be displaced out of the rest position. For this purpose, a 3-mm-wide and 1.5-mm-deep groove falling continuously in the dorsal direction is etched directly at the transition to the soft palate. The path of the vibrating line becomes visible in the functional impression if the soft palate is moved during impression-taking by the pa-tient’s swallowing or pronouncing “ah” or by the nose-blowing effect. As a result, the position of the posterior nasal spine of the palatal bone becomes visible; this should denitely be taken into account because the palatine suture is thickened here (A). This etching of the vibrating line (ah line) must follow the dorsal edge of the bone precisely to avoid pressure points. It is worth noting that the dorsal edge of the bone is beveled cranially and ends in a sharp edge (B), which meets the etching of the vibrating line. 289Extension OptionsIn the mandible, the retromolar triangle or the mandibular tubercle is enclosed on both sides to support the denture and enlarge the base. These dorsal ridge areas can be slightly restricted by a well-developed pterygomandibular raphe, which is tightened when the mouth is opened and le-vers off the denture. Therefore, the dorsal limit of the margin must be suitably reduced here.Sublingual pockets (in the anterior sublingual space) can be covered with a so-called sublingual roll (Figs 8-105 and 8-106). This is a horizontal ex-tension of the denture margin under the tongue into the area of the premolars. Vertical extension would have the opposite effect and would actu-ally cause the denture to lift off during tongue movements. Horizontal extension of the margin considerably increases the retentive effect of the denture. The functional impression involves tak-ing an extension impression of the anterior sub-lingual space without impeding tongue move-ment and while sparing the lingual frenum.Paralingual pockets (posterior sublingual spac-es) are located on both sides in the dorsal lingual area under the retromolar triangle. These are usu-ally undercut areas behind the mylohyoid line into which retromolar wings of the denture base engage and, as mechanical retention in combina-tion with the undercut ridge parts of the anterior region, can secure retention of the mandibular denture (Fig 8-107). The size and the shape of this retromolar region are limited by the movement of the root of the tongue.MoABDEGGGFCMa12 Fig 8-102 The outer surfaces of the denture body are shaped to grip the muscles; that is, lip shields are prepared for the or-bicular muscle of the mouth, in the posterior region buccinator rests are created, and the muscle tracts to the buccal frena are traced. Reduction needs should be taken into consideration.Fig 8-103 The course of the muscle tracts originating from the modiolus (Mo) allows shaping that grips the muscles: The tract of the orbicular muscle of the mouth (A + B) engages in the lip shields. The levator and depressor anguli oris (C + D) pull toward the buccal frena. The major zygomatic muscle (E) pulls with parts of the buccinator (G) toward the zygomatic crest. The risorius muscle (F) also runs with parts of the buccinator (G) backward and toward the oblique line. The masseter (Ma) overlays the buccal vestibular space.Fig 8-104 A normally shaped mandibular denture that makes allowance for reduction needs ([1] mylohyoid line, [2] oblique line) has a slim mucosal rest. If the denture base is enlarged into the extension spaces, excellent mechanical retentions are achieved in undercut areas of the jaw. 290Complete DenturesBuccinator pockets are the posterior buccal spaces into which the denture margin can be ex-tended by buccinator supports. In the same way as the sublingual roll, a horizontal extension can be created above the plate edge that has been trimmed in keeping with the oblique line; this ex-tension takes the form of a rest for the cheeks, whereby the denture is pressed onto the dental arch (Fig 8-108).Balanced muscle tone between the tongue and the cheek can aid retention of the mandibular denture if the teeth are set up so that the den-ture cannot be moved by these muscles and so that the patient does not bite his or her tongue or cheek (Fig 8-109). Typically, the teeth stand fur-ther lingually than they did before tooth loss for static reasons. Therefore, the space for the tongue is always slightly restricted. This is why manufac-Fig 8-105 The sublingual space can be lled by an extended denture margin so that the tongue can stabilize the man-dibular denture by its own weight. It is inadvisable to extend the denture margin vertically because this will displace the oor of the mouth and impede move-ment of the tongue.Fig 8-106 Extending the denture mar-gin in the horizontal plane under the tongue does not impede the oor of the mouth and therefore fullls the function of an additional retentive aid because the weight of the tongue can press the denture downward. A denture margin extended in this way is known as a sub-lingual roll.Fig 8-107 An individual impression must be taken of the paralingual areas (A), which provide space for the retromo-lar wings on the denture. The vestibular undercuts on the anterior ridges form us-able supports for the retromolar wings. The sublingual spaces (B) can be used for the sublingual roll.AABFig 8-108 In the posterior region, the denture body can be extended into the buccal space so that the cheek can lie on these convexities and give the denture additional retention. The bucci-nator support starts above the vestibular fornix. In the mandible, the buccinator support can be extended vestibularly over the oblique line. A suit-able impression is always the foundation for shap-ing these accessory retentive aids.Fig 8-109 The posterior teeth are placed so that they do not impede the cheeks or tongue. Thus, they are positioned over the middle of the alveolar ridge and are accompanied by balanced tongue and cheek tone. Balanced tone is the position of equilibrium between the resting tension of the tis-sues of the tongue and cheek. When the posterior teeth are accompanied by balanced tone, the pa-tient cannot bite the cheeks or tongue. 291Extension Optionsturers supply articial teeth that have a smaller vestibular-lingual breadth than normal teeth.Hollowing out the papilla, the palatine raphe, and the torus can increase the suction effect of a maxillary complete denture in the short term (Fig 8-110). A kind of suction chamber is formed, but this closes after a short wearing time due to proliferation of the mucosa. If lines are etched and hollowing out is done at the same time, the foils are guided over the etched lines up to the hollowed-out area.The retentive force of the denture—due to the suction effect, the force of adhesion, and cohe-sion—is between 70 and 100 N if the accuracy of t is good and the valve margins are functioning properly (Fig 8-111); on vertical withdrawal, this force may be considerably higher.Fig 8-110 In the brous median area (palatine raphe and palatine torus), a rocking movement around the median palatine suture can occur when the denture is loaded on one side, and the denture margin may be lifted off on the unloaded side. Therefore, it may be advisable to hollow out this area so that the denture sinks in evenly and can be more heavily loaded. If the denture base is hollowed out in the area of the median palatine suture, an additional suction effect may arise because a vacuum chamber has been created. This effect is lost after a short time because the mucosa proliferates into the chamber.Fig 8-111 Retention of a maxillary complete denture can be improved by etching lines. The retentive surface is divided into areas of different sizes, forming separate retentive compartments. If air gets under the denture at the valve margin, the denture will still hold because the individual compartments can still have adequate negative pressure. The etching, in this case Frankfurt etching, is preferably done in the glandular and fat pad area. Vertical band etching is another method in which the whole alveolar ridge is encompassed by a circumferential ridge. The ridge is angular and about 1.5 mm deep. A vibrating line etching is also created. This form of etching has been used for abby ridges and is not recommended for normal dental arches.1 mm 0.5 mm 292Complete DenturesGysi’s Working Method The term articulation theory is closely linked to the name of Professor Gysi because he presented what he called the “articulation problem” in a 1908 publication. In that and subsequent publica-tions, as well as through his teaching work, he studied and was the rst to prove the functional relationship between tooth shape and tooth po-sition, the TMJ, and mandibular movement. The proof was provided by long-term studies, experi-mental research, and statistical analyses, all of which laid down the principles of modern dental research.Based on his research ndings, Gysi developed a comprehensive and, in the truest sense, com-plete theory, which was applied to create instruc-tions for the practical fabrication of dentures. According to Gysi, the chewing cycle involves a movement habit that depends on the consistency of the food and varies between individuals but follows a xed principle: Food is crushed as slid-ing occlusal surfaces grind against each other. To do this, the mandible is brought into a slightly lateral position from which a grinding, sliding movement takes place into terminal occlusion.According to Gysi, the four-phase round bite is the movement sequence involved in masticating food (Fig 8-112):1. The rst phase is opening the mouth to take in the food.2. The second phase is a slight sideways gliding of the mandible to the chewing side to grasp the food.3. The third phase involves closure of the mouth into approximate cusp-to-cusp contact, where-by the food is crushed but not ground.4. The fourth phase involves gliding out of the lat-eral position into terminal occlusion, when the food is broken down into small pieces by the constant increase in masticatory force.The single phases ow seamlessly into each other. Only the fourth phase is of interest, when the teeth on the chewing side glide into centric occlusion in full tooth contact and the mandible is guided not only by the joints but also by the oc-clusal pattern of the teeth. This tooth guidance be-comes even clearer when looking at the process of biting off food: The mouth is opened and the mandible pushed forward to grip the food. If the Opening the mouthMandible gliding sidewaysClosing on cusp contactGliding into terminal occlusionPhase 1 Phase 2Phase 3 Phase 4Fig 8-112 The movement sequence of the chewing cycle is described by Gysi as a four-phase round bite. The sequence of move-ments follows a xed principle but is depen-dent on the consistency of the food and is therefore variable. Four phases are identied. The phases merge seamlessly. The fourth phase is of interest: gliding into terminal oc-clusion under masticatory force, during which balanced articulation is required for a com-plete denture according to Gysi. 293Gysi’s Working Methodfood now has to be sheared off, the incisors glide into centric occlusion under contact. To glide into terminal occlusion, the anterior teeth and canines guide the mandible into the correct position.Guiding elements in mandibular movement are the TMJs and the occlusal patterns of the teeth (Fig 8-113). The occlusal patterns of all the teeth can be presented as a combined virtual guide plane: the incisal guide (surface).The mandibular movements can be understood from the condyles and a xed point on the inci-sors. It is noticeable that the condyle moves on a xed path both forward and to the side, namely on the sagittal and lateral condylar paths. In the process, the xed point on the mandibular inci-sors moves on the palatal surfaces of the maxil-lary incisors within what is known as the sagittal and lateral symphysis path. (The symphysis point and mandibular incisal point are considered syn-onyms for the anterior Bonwill triangle point.)Gysi describes the sagittal and lateral symphy-sis path and condylar path as a functional unit with the cusp slopes of the posterior teeth and the inclinations and positions of the teeth inside the occlusal curves. In this context, these curves con-tinued to be called curves of Spee, even though there was already evidence that the ideal form of the Spee curve, according to Spee’s description, must be regarded as a special case.Certain conclusions necessarily arise from these connections. If the chewing cycle involves xed, recurring movements and the mandible is guided by the TMJs and the tooth shapes and positions, fabricating a fully functioning denture should follow these steps: 1. Initiate the mandibular movement.2. Precisely reproduce the anatomical tooth shapes.3. Position teeth relative to mandibular movement.To put it simply, Gysi proved that precise repro-duction of specic parts of the functioning mas-ticatory system ensures the success of a denture.Articulators according to GysiGysi developed articulators for copying mandibu-lar movements, which made it possible to simu-late a close approximation of individual move-ments. The Simplex articulator is the best-known average-value device developed by Gysi (Fig 8-114). It allowed the essential mandibular move-ments to be executed on condylar paths with a sagittal inclination to the occlusal plane of about 33 degrees and a Bennett angle of roughly 15 to 17 degrees. Joint-related mounting of the models was possible in the average-value articulator. A key factor was that the incisal guide plate could be variably inclined between 0 and 55 degrees to handle patients’ asymmetric condylar path incli-nations.Gysi’s Trubyte articulator enabled the sagittal condylar path inclination to be set between 0 and 55 degrees, based on individual values, and an individual Bennett angle to be chosen between 0 and 20 degrees. These individual joint values had to be measured with a specially developed face-bow and special tracing plates.The tooth shapes Gysi went on to develop em-ulated the anatomical pattern and had cusp sur-faces with a slope that was adapted to the condy-Fig 8-113 The guiding elements of mandibular movement, ac-cording to Gysi’s mechanical explanatory model, are the joints and occlusal patterns of the teeth; the musculature is ignored. The occlusal patterns are combined in incisal guidance. With the joints, this forms a three-point support on which the upper arm of the articulator can be moved relative to the mandible. If the three guides are individually adjustable, each occlusal area can be reconstructed. 294Complete Dentureslar path inclination. The Anatoform articial teeth had a sagittal inclination of 32 degrees and a buccal and lingual inclination between 10 and 20 degrees; the molars based on Gysi had a sagittal inclination of 20 degrees and a lateral inclination of 3 degrees.Gysi described tooth positioning relative to mandibular movement with the term balanced articulation, dividing the rows of teeth into the working side and the balancing side (nonworking side) during chewing (Fig 8-115). During chewing, the working side is the loaded side; Gysi described the nonworking (idling) side as the balancing side because the tooth contacts on that side were sup-posed to prevent the denture from being levered off or tipping during the fourth phase of chewing.On protrusive movements, tooth contact in the anterior region is meant to be compensated for by balancing contacts on the terminal molars. The teeth must therefore have both a sagittal and a transverse occlusal curve, thereby compensating for the Christensen phenomenon. These dental arch forms that Gysi called compensating curves also had to be replicated when setting up the teeth. The aim was to achieve three-point contact during lateral and protrusive movements, which, distributed over the entire dentition, had one con-tact in the posterior region on each side and one contact in the anterior region.The static conditions affecting the denture body in relation to the shrunken alveolar ridges had to be taken into account during setup of the teeth. In the law of the ridge line, Gysi required the ar-ticial teeth to be set up over the center of the alveolar ridges in a statically stable position to prevent lever effects caused by the denture body (Fig 8-116).Crossbite setup in the posterior region be-comes necessary if the lines connecting the ridge centers are at an angle less than 80 degrees to the occlusal plane. This connecting line and angle are known as the interalveolar line and the interalve-Fig 8-114 The Simplex articulator is an average-value articula-tor in which the Bennett movement is produced by dorsally positioned joints; the crosspiece located on the upper arm in front of the joint surfaces serves as the marking of the hinge axis (A).Fig 8-115 The term balanced articulation in the fourth phase of Gysi’s round bite denes the working side (A) and the bal-ancing side (B). The working side is the side into which the mandible is pushed, while there are tooth contacts on the bal-ancing side that should prevent the unloaded parts of the den-tition from being levered off (a). When biting off food, sliding contacts on the posterior teeth in the protrusive position must prevent any tipping of the denture (b).AABa bα > 80°α < 80°Occlusal plane Interalveolar lineFig 8-116 The varied shrinkage of alveolar ridges can pose a problem when setting up the posterior teeth. If the teeth have to be arranged on the ridge line ac-cording to the law of ridge lines, normal intercuspa-tion may be disrupted. According to Gysi, a normal occlusion should be set up if the inclination of the in-teralveolar line to the occlusal plane is greater than 80 degrees, and a crossbite should be set up for inclina-tions less than 80 degrees. 295Gysi’s Working Methodolar angle, respectively. In conclusion, Gysi gave working instructions for fabricating complete dentures. A functional impression with custom trays is rst required, and then a precise interoc-clusal registration. Gysi described and recommended extraoral oc-clusal registration (Fig 8-117). This involved mold-ing occlusion rims out of stent material (thermo-plastic impression material) and setting them onto the bite plates over the center of the alveolar ridge to the exact vertical dimension of occlusion so that they contact in the occlusal plane. A trac-ing plate was then mounted on the mandibular occlusion rim and the tracing pin onto the maxil-lary occlusion rim.The tracing plate and tracing pin protruded out of the mouth and enabled mandibular movements to be checked, during which the Gothic arch was traced into the registration wax. The tip of the Gothic arch indicated the position of centric occlu-sion. The bite plates were xed in this position. As positional indicators for the teeth, the occlu-sion rims had to be padded to reect natural lip volume so that the middle of the face could then be traced on the occlusion rims as well as the lip closure line, the canine points, and the smile line of the upper lip, thereby establishing tooth length and width (Fig 8-118). These tracings then had to be transferred to the models, and the tracing of the sagittal inclination of the posterior mandibu-lar ridge had to be added.123456Fig 8-117 Extraoral occlusal registration is an attempt to regain centric occlusion with suitable registration kits and, using a face-bow, to carry out joint-related mounting of the casts in the articulator as well as survey the condylar paths. (a) The tracing pin (1) is mounted on the maxillary occlusion rim and the tracing plate (2) on the mandibular occlusion rim; the registration wax (3) for tracing mandibular movement is located on the mandibular tracing plate with the facebow mounting pins (4). (b) The facebow is mounted on the pins, and the exible condyle indicators (5) are aligned with the condylar points of the patient. Adjusting pins (6) are tted onto the facebow; these are height adjustable so that the bite plates can be brought into the correct height when plastering up in the articulator.Fig 8-118 The maxillary anterior teeth are placed on the oc-clusal line and stand with their labial contours on the outer contour of the wax occlusion rim, which has been padded to reect lip volume. The inclinations of axis are located. The man-dibular central incisor should be in contact with its antagonist without an overjet.a b 296Complete DenturesSurveying the condylar pathIt was possible to t a facebow onto the tracing plate of the mandibular bite plate in order to al-low joint-related mounting of the models in the articulator. The exible ends of the facebow were aligned with the patient’s condylar points and represented the spatial relationship between the condyles and the occlusal plane. The facebow could be adjusted in the articulator with the trac-ing plate, bite plate, and mandibular model in such a way that the exible ends pointed to the condyles of the device and the mandibular incisal point on the bite plate coincided with that of the articulator.The facebow technique permitted individual surveying of the condylar paths and occlusal reg-istration, the sagittal course of the condylar paths actually being traced with the exible ends of the facebow during Gothic arch tracing. To do this, two tracing plates were placed on either side of the patient’s head, and the black lead pencils on the exible ends of the facebow traced the sagit-tal course of the condylar path onto the tracing plates. The inclination of the condylar path to the occlusal plane could then be determined by sim-ply measuring the angle.This description of Gysi’s articulation theory only provides a historical perspective but also il-lustrates his thoroughness, consistency, and sys-tematic working method, which remains exem-plary to the present day. After phases of hostility and defamation, expert opinion now asserts the importance of his theory. The methods commonly used today for fabricating complete dentures—in terms of their compendium-type setup rules and their explanatory constructs—represent a rene-ment of Gysi’s ideas or partial concentration on certain working methods based on this theory.The criticisms of Gysi’s articulation theory arose because certain anatomical facts allow for other interpretations. For instance, Gysi considered the balancing contacts to be the ideal form, including in natural dentitions, and interpreted missing con-tacts as a degenerative deformation of the den-tition. Critics deduced from this that the theory was incorrect. The high-cusp teeth were criticized because they lacked the physiologic and func-tional abraded grinding surfaces. The position of the maxillary anterior teeth and the lack of overjet were also criticized because this supposedly gave rise to unsatisfactory esthetics and statics of the maxillary denture.Setup instructionsGysi developed precise instructions for fabricat-ing complete dentures, among which the setup rules are of interest to dental technicians. They establish the position of the teeth and the setup sequence: 1. The maxillary anterior teeth are placed on the occlusal line and stand with their labial con-tours on the outer contour of the wax occlu-sion rim, which has been padded to reect lip volume. The inclinations of axis visible from the vestibular aspect are identied. 2. The mandibular anterior teeth should stand in contact with their antagonists without overjet. Once again, the inclinations of axis visible ap-proximally and vestibularly are established.3. The approximal inclination of the maxillary anterior teeth is also established. Accordingly, the labial contours of the canines stand verti-cally, and their tooth axes have a clearly ves-tibular inclination (Fig 8-119).4. The rst premolar in the maxilla contacts the occlusal line with its buccal cusp; this line is simulated by a glass plate. A small space is possible between the canine and the rst pre-molar (Fig 8-120).5. The maxillary second premolar contacts the occlusal line with both cusps (Fig 8-121).6 The maxillary rst molar touches the occlusal line with its mesiopalatal cusp (Fig 8-122).7. The second molar has no contact with the oc-clusal line, in keeping with the compensating curve (Fig 8-123).8. The mandibular anterior teeth are placed on the ridge midline with their incisal edges at the same height. The labial inclination of axis shows a mesial tendency, and the approximal inclinations are established. The mandibular dental arch is thus developed (Fig 8-124).9. The mandibular rst molar is rst placed in its correct position (Fig 8-125).10. Only then are the remaining teeth set up (Fig 8-126). 297Gysi’s Working MethodFig 8-119 The approximal inclination of the maxillary anterior teeth is also estab-lished, Gysi referring to the labial contour in their inclination and not the tooth axis. Accordingly, the canines stand with their tooth axes showing a clear vestibular in-clination.Fig 8-120 The maxillary rst premolar touches the occlusal line with its buccal cusp. A small space between the canine and rst premolar is possible.Fig 8-121 The maxillary second premo-lar contacts the occlusal line with both cusps.Fig 8-122 The maxillary rst molar touches the occlusal line with its mesio-palatal cusp.Fig 8-123 The second molar has no contact with the occlusal line, in keeping with the curve of Spee.Fig 8-124 The mandibular anterior teeth stand on the center of the ridge with their incisal edges in a straight line. The labial inclination of axis shows a mesial tendency, and the approximal inclinations are established. The mandibular dental arch is thus developed.Fig 8-125 The mandibular rst molar is rst placed in its correct position.Fig 8-126 The remaining teeth are then set up. 298Complete DenturesHiltebrandt’s Working Method The interpretations by Dr Carl Wilhelm Hiltebrandt offer a cohesive theory with working instructions for fabricating complete dentures. In this case, the law of form and function is used to interpret the relationship between functional mandibular movements and the form of the masticatory sys-tem, thereby qualifying Gysi’s approach. Accord-ing to Hiltebrandt’s view, form and function make up a harmonious unit in which the form can adapt to functional disturbances. Mandibular move-ments are guided solely by the musculature, which does not follow xed pathways. The TMJs and occlusal patterns of the teeth have no signi-cance as elements that guide such movement.The purpose of the condylar path inclinations is to separate the rows of teeth during protru-sive and lateral movements in the area where no chewing activity is performed. The separation into working side and balancing side does not exist in a healthy, complete dentition. Only the canine guides the mandible into centric occlusion and is therefore referred to as the anterior jaw joint.Occlusal curves are interpreted according to the law of the smallest unit of force. The stepped positioning of the molars aids the stability of the alveolar bone. Mandibular movements are described as regu-latory control movements or as a crushing and grinding movement in the occlusal eld. Regu-latory check movements are slight lateral move-ments under tooth contact, whereby slight ir-regularities on the cusps standing in the way of articulation are ground off and the position of the teeth and dentitions are kept in constant balance. Crushing and grinding movement is the actual chewing movement with which food is broken down into small pieces. It is guided from the cen-tric to lingual aspect and takes place on one side only. According to Hiltebrandt, this results in the inclination of the teeth: vestibular at the top and lingual at the bottom.Physiologic abrasion arises because of the crushing and grinding movement and the regu-latory check movements. As a result, the teeth are ground down into trough-shaped and dome-shaped functional forms.The occlusal eld is the functional area of the chewing surface that is formed and extended by abrasion. The effective chewing movements take place in the occlusal eld as crushing and grind-ing movements; it is the area of complete tooth contact. All movements outside the occlusal eld are termed articulation; all movements within the eld are termed occlusion.Molar roots are aligned so that the masticatory forces are absorbed axially and transferred to the jawbone. The mandibular rst molar stands in-side a line that runs as an axis through the palatal root of the maxillary rst molar. The maxillary rst molar stands perpendicular to the occlusal plane (Fig 8-127). The ideal axis between the mandibu-lar and maxillary rst molars is the physiologic connecting line, which is at an angle of about 160 degrees to the occlusal plane. The occlusal eld lies within this axis.The basic statics law states that the maxillary rst molar stands perpendicular to the occlusal plane on the ridge midline and that the mandibu-lar molar stands with its longitudinal axis along the physiologic connecting line at an angle to the occlusal plane.Hiltebrandt’s conclusions include the following (Fig 8-128):• Chewing movements abrade the teeth into at functional forms; anatomically shaped, high-cusp posterior teeth are unfavorable.• Compensating curves are not necessary be-cause:– The stability of the denture is ensured by static tooth shapes– The chop bite is the effective chewing move-ment as a form of functional adaptation in den-ture wearers• The TMJs have no guiding functions; surveying joint values and their transfer to articulators is unnecessary, so:–Occlusion is merely reproducible– Setup of the teeth is done in an occluder with stable tooth positions and without support contacts on the opposite side• Guidance of effective chewing movements takes place in the occlusal eld; therefore, physiologi-cally domed and trough-shaped teeth are used.• For esthetic reasons, maxillary anterior teeth are placed in front of the alveolar ridge with an in- 299Hiltebrandt’s Working Methodcisal gap from the mandibular anterior teeth for effective chewing movements.• Posterior teeth are stable in themselves because of the typical inclination to the occlusal plane.• Setup inside the physiologic connecting line makes crossbite positioning unnecessary.abcdeOF90°Tipping zoneSupportzoneFig 8-128 According to Hiltebrandt, the setup rules are simpler and easier to understand: (a) Based on esthetic considerations, the anterior teeth are set up in the appropriate inclinations of axis. The canine stands perpendicular. (b) An overjet is left, and the anterior teeth support the lips. (c) The mandibular rst molar is placed at the lowest point of the alveolar ridge to contribute to the positional stability of the mandibular denture. The antagonist is precisely aligned with it. (d) The remaining teeth are accommodated in the space from canine to rst molar. The row of teeth ends at the rst molar. According to Hiltebrandt, any dorsally placed tooth could push the mandibular denture forward on the inclined plane of the sloping alveolar ridge.ab c dFig 8-127 According to Hiltebrandt, the maxillary rst molar stands perpendicular to the occlusal plane. The ideal axis of the man-dibular molar runs parallel to the palatal root axis of its antagonist. (a) The physiologic connecting line is derived from the ideal axes of the two rst molars and is bent at an angle in the occlusal plane. (b) The basic law of statics requires the posterior teeth to be placed on the alveolar ridge so that the ideal longitudinal axes intersect the ridge line. Tipping will occur outside the ridge line. (c) The occlusion rims already have a statically favorable position inside the physiologic connecting line. (d) The occlusal eld (OF) is a limited area of the occlusal surface with a xed relationship to the root arrangement. (e) The physiologically shaped posterior teeth have an enlarged occlusal eld into which the sagittally placed ridge of the antagonist engages. The mortar-and-pestle principle becomes clear here. 300Complete DenturesHaller’s Working MethodLudwig Haller’s working method is not a self-contained theory of masticatory function but deals with partial aspects of tooth positioning in prosthodontics. Certain distinct, individual mea-sures are intended to enhance the functionality of complete and partial dentures. The recommended measures specically relate to a tooth positioning that improves the statics and hence the retention of a complete denture.Haller calls his setup method a centripetal sys-tem for keying dentures. Retention of a complete denture is improved by the fact that the posterior teeth are notched within the occlusal line. The very at and wide molars (Haller molars) of the mandibular posterior regions are placed rooike against each other so that they form a roof ridge that ts into a notch inside the maxillary row of teeth. The incorporated notch is intended to key both dentures with each other and hold them in the right position on the dental arches (Fig 8-129). Functional performance is expected to increase as the patient gains condence in bringing the denture into the correct position by regulative movements.The TMJs are supported orthopedically by the centripetal setup as favorable stimuli during chewing function; this leads to regeneration of atrophic processes in the joints as a result of the securely xed centric occlusion. The keying en-sures retention of the denture to such an extent that greater chewing efforts are possible, which strengthen the muscles of mastication.The principle of keying is preferred to a setup inside compensating curves. This is because the denture would be pushed dorsally against the ascending ramus of the mandible as a result of the curves. Furthermore, true three-point guid-ance over the excessively at cusps of anatomical teeth is not considered possible.Notching of the posterior teeth and a pro-nounced anterior overbite give rise to centripetal force paths that are directed at one point and x Fig 8-129 According to Haller, a denture can be stabilized on the edentulous jaw (and in a partially edentulous dentition) by special positioning of the molars. (a) The four molars are set up in an exaggerated notch position to each other. In this positioning, the sec-ond molars are more inclined toward the occlusal plane than the rst molars. Angle α is smaller than angle β. (b) The force vectors at the molars, premolars, and incisors run centripetally, hence toward the middle of the denture or the denture-bearing area. The force diagram should yield a resultant that stands vertically on the jaw. (c) On biting off food, the notching of the molars prevents the denture from being completely levered off. The patient can immediately stabilize the prosthetic appliance. (d) The specially molded Haller molars are wider and longer than natural teeth and are entirely at on their occlusal surface. This produces a very large eld of action. (e) The force paths on the mandibular dentition show that the notching presses the denture against the dental arch and the ascending dorsal alveolar ridge. The mandibular denture should therefore sit stably.abcdeα < βα βbbLLM1M2M2M1SPPSM2M1PS 301Fehr’s Working Methodthe denture in a stable position. On the mandibu-lar denture, these force lines run directly to one point; on the maxillary denture, by parallel trans-lation, a force diagram xed at one point can be constructed.For better retention of a complete denture, Haller recommends reinforcing the labial edge of the denture directly in the vestibular fornix with ridges that are set against the denture body by a pronounced notch. The mucosa of the lip area ts into this notch or onto the ridge and protects the denture. Furthermore, a peripheral denture an-chor can be created on the mandibular denture. This roughly 5-mm-high, rounded ball anchor is placed vestibularly level with the second molars at the denture margin and is intended to wedge in the cheek muscles.Fehr’s Working MethodFehr’s working method is not a new approach to clarifying the static relationships; here the views about mandibular movements are stated in Gysi’s terms. For the interocclusal registration, the oc-clusion rims are shaped to the correct vertical dimension of occlusion in keeping with the com-pensating curves. The occlusion rims are then modeled to such a length that all-round surface contact exists during all translative movements and the bite plates lie stably on the dental arches. In other words, a smooth, curved, and individual occlusal eld is modeled with the occlusion rims that fully compensates for the Christensen phe-nomenon. The Fehr method uses a template (calotte) for interocclusal registration. A simple occluder and at-cusped teeth are used for the setup. Canines are trimmed at their tips, and the anterior teeth are arranged at a sagittal distance of about 1 mm. The working principle stipulates that the mandibular teeth should rst be placed on one half of the jaw precisely against the individually molded occlu-sion rim, then the antagonists should be placed against them (Fig 8-130). Afterward the other half of the jaw is set up in the same sequence. This produces a tooth setup that in principle will exhibit all-round sliding contact in the sense of three-point support.Other authors also offer concepts for setting up teeth using calottes (eg, Eichner, Monson, Hall, and Faber), and articulators with average-value calottes or calotte-shaped setup templates are available. All of these methods are based on the realization that the positional stability of a den-ture is achieved by three-point support and not by extreme keying of the dentures.Fig 8-130 According to Fehr, if occlusion rims have a calotte-like shape in the occlu-sal plane in maximal intercuspation and a suitable instrument is used to rework man-dibular lateral and protrusive movements in-dividually until the bite plates can be moved against each other without interference and without tipping, the mandibular teeth can be placed against the calotte-shaped oc-clusion rim. As a result, they are positioned inside an individual occlusal curve. At try-in in the mouth, lateral and protrusive move-ments can be performed without interfer-ence while maintaining complete denture stability. 302Complete DenturesSchreinemakers’s Working Method Another working technique for improving the re-tention of complete dentures is analysis of the denture-bearing area to ensure functional ef-ciency by individual contouring of the denture base. Analysis of the denture-bearing area, which is set against articulation theory, involves draw-ing up an individual treatment plan. Based on this plan, the shape of the denture body and the marginal contouring in the vestibule, on the oor of the mouth, and at the vibrating line are estab-lished. A form of denture is then produced that secures the positional stability of the prosthetic appliance. Tooth setup is performed based on static aspects: in the posterior region on the ridge midline and in the anterior region in front of the ridge for esthetic reasons.The working method of J. Schreinemakers is based on a theoretical model demonstrating what marginal contour, marginal length, and marginal thickness the denture should have (Figs 8-131 to 8-136).The action limit denes the transition from at-tached to mobile mucosa. No advice about the resilience of the movable mucosa is given here, but this is deemed to be noncompressible. The denture margin should extend beyond the action limit on all sides so that the tension of the close-tting mucosa is bound to create a valve margin that ensures negative pressure in the liquid layer under the denture base. Accordingly, a denture retained by suction is produced for each dental arch.By means of the functional impression, a den-ture margin is designed that creates a balanced state between tissue tension at the valve margin and levering muscle tension. The course of the muscle attachments is accurately established un-derneath the vestibular fornices, on the oor of the mouth, and in the soft palate. The direction of force and pull is also described to indicate the di-mensions of margin thickness.The marginal depth in the lingual area of the mandible at the tongue and oor of the mouth must be determined with the utmost accuracy. The marginal depth of the labial vestibular fornix area requires great accuracy as it must support the lip parts in a tension-free way during func-tioning. The path of the fornices and the position and extent of muscle attachments coincide with the described denture-bearing area in the maxilla and mandible.The anterior sublingual area is analyzed in de-tail so that the lingual groove around the genio-glossus muscle, measuring about 2 mm long and 3 mm deep, can be used for the sublingual roll. The seating for the tongue beyond this sublingual roll can be enlarged by hollowing out the lingual surface of the denture body from the teeth up to the denture margin. The aim is to create function-al clearance for the tongue that improves denture retention. In the buccal posterior region, how-ever, the denture body should bulge outward to enable self-cleaning; a buccinator support is not attempted.The border of the denture margin with the soft palate is placed at the vibrating line, where a groove about 2.5 mm deep and 2.5 mm wide is etched from the pterygomandibular raphe around the palatine processes of the maxillary tuberos-ity to the transition from hard to soft palate. The palatine foveae are indicated as reference points. The etched line must be probed individually with an instrument in the mouth.The retromolar triangle (pad) is also nished at its dorsal border by an etching that is 1 mm deep by 1 cm long. This means the plate edge ends to-ward the pterygomandibular raphe.In terms of the practical procedure, Schreine-makers offers a semi-individualized tray set for the rst impression. Custom trays are prepared on the anatomical casts from the rst impression. Occlusion rims to the exact vertical dimension of occlusion are simultaneously placed on the cus-tom trays. A functional impression is taken after rigorous marginal checks at the action limit and extremely accurate marginal correction of the bite plate. The custom trays/bite plates should already have a certain suction effect. An impression mate-rial is used that allows subsequent corrections to be made. The functional impression is therefore taken in various stages.The anterior setup is based on esthetic consid-erations. The Pound line is used for aligning the posterior teeth. If the mandibular posterior teeth are aligned with their lingual surfaces on this line, they will stand almost exactly over the ridge mid-line. 303Schreinemakers’s Working MethodFig 8-131 For Schreinemakers trays, the working instructions relate to impressions of the dental arches. The rst impres-sion is taken with prefabricated Clan-Trays, which are closely matched to the anatomical circumstances of edentulous arch-es.Fig 8-132 The mandibular Clan-Tray extends deeply into the oor of the mouth area to allow an impression to be taken of the sublingual area and the mylohyoid line.Fig 8-133 An initial impression with viscous-consistency al-ginate yields an extended representation of the mandibular denture-bearing area.Fig 8-134 The course of the lingual margin of the custom tray is traced in the rst impression and will appear on the plaster cast.Fig 8-135 An impression is taken of the dorsal palatal area into the soft palate. The denture margin should also pass in the soft palate area.Fig 8-136 The dorsal margin of the bony mass of the jaw is probed and etched into the jaw model as a semicircular, 2-mm-deep groove that extends into the tuberosity processes. 304Complete DenturesUhlig’s Working MethodThe working method of Professor Horst Uhlig sets the analysis of denture-bearing areas against Gysi’s articulation theory. Analysis of the denture-bearing area is put forward as the only essential requirement for fabricating a complete denture.Denture retention on the dental arch is present-ed as the interaction of capillary forces (adhesion and cohesion effect) and forces caused by pres-sure differences (suction effect), where the saliva acts as an adhesion promoter. The marginal seal comprises an inner and outer valve as well as the mechanical locking between the edge of the den-ture and the undercut areas of the jaw. The func-tional margin displays an inner valve at the outer surface of the jaw and an outer valve at the cheek; it also exploits all of the mechanical retentions, such as the maxillary tuberosity and anterior al-veolar ridge areas. Hollowing out of certain areas of the palate, Frankfurt etching, and etching of the vibrating line are recommended as accessory re-tentive aids.In practical terms, a formalized procedure for analyzing the denture-bearing area is proposed in which the tissue condition; the position of liga-ments, muscle attachments, and bony ridges; and the shape of the alveolar ridges are described and entered on a form. Based on this analysis, neces-sary surgical measures, such as tightening of a abby ridge, lowering of vestibular fornices, sep-aration and movement of ligaments, or smooth-ing of sharp-edged ridges, are undertaken. The resilient areas of the palate and the path of the vibrating line are then traced.For precise marginal locking of the denture base, a custom tray is prepared and used to take the functional impression. For tooth setup, tak-ing an impression of the “denture accommoda-tion” is recommended to establish the position of the cheeks, lips, and tongue so that the teeth can be set up while these tissues are in balance. In a “technique of individual ne adjustment,” the outer surfaces of the denture bodies should be adjusted to the position, shape, and dimensions of the cheeks and the tongue; that is, a circumfer-ential chamfer should be formed into which the mucosa settles. The result can be described as a dimensionally accurate dental prosthesis shaped to grip the muscle.In the maxillary labial area, the denture can be thickly padded to tighten the upper lip and com-pensate for the shrinkage of the jaw. The maxil-lary anterior teeth are positioned in front of the alveolar ridge to support the upper and lower lips (Fig 8-137). In the posterior region, a cross-bite position is presented to stabilize the position of the maxillary denture, together with a sagittal occlusal curve that is not constructed relative to the TMJ but emerges from the positioning of the teeth inside the interalveolar line.Jüde’s Working Method Professor Jüde established the course of the mar-gin of a mandibular prosthesis based on extreme-ly accurate studies. In particular, an extension into the retromolar area is specied to provide mechanical retention to the mandibular denture.M depressor anguli orisM orbicularis orisM Ievator anguli orisM zygomaticus majorM buccinatorM risoriusFig 8-137 The anterior teeth, especially the canines, are posi-tioned in front of the alveolar ridge to support the lips. Padding of the labial vestibule to tighten the upper lip must be rejected as inadequate. The canine position anterior to the ridge deter-mines the position and shaping of the angle of the mouth as the modiolus (insertion site for the illustrated muscles) is sup-ported. For this purpose, the mandibular canine must also be precisely mounted to tighten this tissue area. If the canines are placed too far lingually, the corner of the mouth will descend (as it does if the vertical dimension of occlusion is too small), saliva will leak, and the corner of the mouth may become in-amed. 305Jüde’s Working MethodThe muscle movements of the retromolar re-gion are determined by the activity of the tongue and can often give rise to an undercut mucosal pocket into which the retromolar wings of a man-dibular denture can engage. These wings should be dorsally guided caudally without impeding the activity of the myloglossus muscle.The genioglossus muscle described by Jüde originates below the mandibular tubercle on the inside of the mandible (Fig 8-138). The muscle bundle runs from there to the root of the tongue and thereby covers the posterior area of the my-lohyoid muscle. This limits the size of the retro-molar wings inferiorly. The retromolar (paralingual) areas should be individually determined by a functional impres-sion taken during tongue activity. The functional movements of the tongue for taking an impres-sion of the sublingual area are usually the same as those performed for dening the paralingual area.In practical terms, the length of the margin is incorporated into the custom tray before the functional impression is taken. In the process, the lingual edge of the tray follows the border of the oor of the mouth (Fig 8-139); trimming along the mylohyoid line is carried out, followed by extension into the paralingual area and sub-lingual lengthening for the sublingual roll. In the oral vestibule, the tray edge is guided along the vestibular fornix (Fig 8-140), trimmed in keeping with the oblique line, and spared at the ligaments.Fig 8-138 The position and shape of the mandibular tubercle is described as a tough mucosal ridge located in front of, but not above, the bony retromolar triangle. Therefore, the tubercle and triangle are not in the same position, but the mandibular tubercle on an edentulous jaw is located roughly at the position of the third molar and should be contained.Fig 8-139 The line of origin of the mylohyoid muscle indicates the border of the mobile oor of the mouth. Jüde described the limit of the oor of the mouth using a variety of shapes for the areas of origin. The most commonly found line of origin is depicted here. Any extension of the denture margin is sup-ported on the mylohyoid muscle in the paralingual region. It therefore becomes necessary to avoid pressing the retromolar wings against the mandible and instead to provide the mylohy-oid muscle with the space it needs to function.Area of the mandibular tubercleArea of the retromolar triangleMylohyoid lineRetromolar wingFig 8-140 The attachment of the mental nerve lies below the vestibular fornix; in the case of severe atrophy, it may shift to the middle of the anterior alveolar ridge in the denture-bearing area and may impair the positional stability of the mandibular denture. 306Complete DenturesGerber’s Working MethodIn recent years, the working method of Profes-sor Gerber has gained in signicance because it brings together the methods and theoretical prin-ciples outlined in the previous sections to create a successful synthesis that also incorporates the latest research ndings. Over the years, this has led to an almost closed, mechanically based the-ory of masticatory function with practical instruc-tions on fabricating complete dentures.The functional mandibular movements are analyzed using varied analysis methods, includ-ing radiographic sequences of joint movements and lm recordings of the chewing cycle in or-der to develop an articulator and static functional shapes of articial teeth. First, the relationship of the TMJs to tooth shapes and tooth positions is established and dened. Maximum tooth contact exists in centric occlusion in a normal dentition. The two condyles are located in the depth (zenith) of the mandibular fossae entirely pressure and tension free. In this position, masticatory forces are not transferred via the condylar heads.According to Gerber, the chewing cycle follows xed pathways (Fig 8-141). The loading phase is the start of the chewing cycle, for which the man-dible is guided to the chewing side to grasp the food. In the process, the condyle on the chewing side oats freely in the joint and can be pulled dor-sally and laterally by the musculature. A Bennett movement is performed. In the loading phase, the mandible is pushed out of the retruded lat-eral position forward and centrically to grind the food. Then the mandible can be seen to change position to the opposite side (balancing side) and to the anterior teeth before gliding back into the centric hinge position.Analysis of the chewing cycle demonstrates the basic movement sequence of the Bennett move-ment, but it also shows the position of the con-dyles during the movement sequence. In addi-tion, it becomes clear that the functional chewing movement, in contrast to the four-phase round bite, does not happen two-dimensionally in the transverse plane but three-dimensionally to the side and dorsally, after which it swerves over to the balancing side.Lip, cheek, and tongue activities during the chewing process prevent food particles from slip-ping down into the vestibule, while the tongue repeatedly presses the food between the rows of teeth. This muscle activity is one of the factors determining the excursions during mastication. Based on observations regarding functional man-dibular movements, Gerber sets out the following requirements:• The mandibular movement must be imitated in suitable articulators in order to fabricate dentures.Balancing side Working sideFig 8-141 According to Gerber, the chewing cycle follows xed pathways: (a) The mandible moves out of centric occlu-sion into the loading position. The condyle on the balancing side slips forward and downward. The condyle on the working side moves backward and outward in the Bennett movement and remains unloaded. (b) Out of the loading area, the active masticatory pressing and protrusive action occurs on the work-ing side. This involves the condyle slipping forward and inward into the fossa. In this active chewing phase, the maxilla moves in the direction of anterior contact and makes a contact-free change of position to the balancing side in order to glide back into centric occlusion. (c) During the active chewing phase, sliding balancing contacts occur on the balancing side in the molar region close to the joint.ac b 307Gerber’s Working Method• During occlusal registration, the centric, pressure-free position of the condylar heads in the zenith of the articular fossae must be relocated.• The condylar path must be surveyed so that in-dividual values can be transferred to the articu-lator.• The articial teeth must be referenced to the man dibular movement and satisfy static require-ments.• Tooth positioning on complete dentures must secure the positional stability of the appliance.• The denture body must be shaped to enable the muscles to support denture retention without impeding muscle activity.Gerber CondylatorThe Condylator is a semiadjustable articulator in which the condylar paths are adjustable from 0 to 60 degrees (Figs 8-142 and 8-143). The mandibu-lar fossa (Condylator aperture) and the condylar heads (Condylator body) take on the functions of guidance and limiting movement in all mandibu-lar excursions. They permit retral movement out of centric occlusion. This backward movement is not straight but curved in the Condylator aper-ture, in keeping with the natural hinge range. The Condylator body has a double-cone shape; the 17-degree inward-facing cone and the 13-degree Fig 8-142 The Gerber Condylator is an articulator in which the inclination of the condylar path is adjustable between 0 and 60 degrees. The Condylator aperture (A) is curved in keeping with the natural condylar path. The Condylator body (B) has a double-cone shape and takes on guidance in all lateral-eccentric move-ments. On the joint plate (C), the articulation can be raised from 0.3 to 1.0 mm using the Vario device (D). The xed table (E) opens the joint movements in the raised state but other-wise blocks the Condylator body, so only hinge movement is possible.Fig 8-143 A facebow (3) is available for the Condylator, with which the inclinations of the condylar paths can be surveyed. (a) The facebow is tted onto the tracing plate (1), and the tracing tips (2) trace the mandibular movements as condylar path tracings on registration ags. (b) The facebow can be used for joint-related mounting of the casts in the articulator. To do this, the facebow is xed onto the stand (4) and propelled around the articulator until the tracing tips point to the midpoint of the Condylator body.ABCDE13421342a b 308Complete Denturesoutward-facing cone undertake guidance of the Bennett movement.The incisal guide plate has an 18-degree incline for complete prosthodontics, but dentate arches can be modeled into an individual guide plate with self-curing acrylic resin by means of the in-tact incisal guidance of the arches. An optimized registration kit is recommended for the intraoral occlusal registration (Fig 8-144).Condyloform teethThe Condylator articulator was developed on the basis of observations of mandibular movements as well as TMJ shapes and movements. Accord-ing to Gerber, this functional relationship also ex-ists between joint and tooth shapes. During de-velopment of the dentition, there is a progressive adaptation between the sliding surfaces of the TMJs and tooth surfaces. This wearing process produces abraded surfaces on the molars, which have a shape similar to that of the articular fos-sae.The articular fossae and condyles t together like a mortar and pestle. It was based on this mortar-and-pestle principle that the maxillary pal-atal cusps and the mandibular occlusal surfaces on Gerber’s Condyloform posterior teeth were created (Fig 8-145). The palatal cusps form micro-condyles, and the lingual chewing depressions on the mandibular posterior teeth form microfossae.The static principle of mortar-and-pestle teeth according to Hiltebrandt is combined with the anatomical cusp slopes according to Gysi’s in-terpretation. The chewing surfaces are shaped as upside-down microjoints, in which one part of the joint is xed and the other is mobile. The mi-crojoint chewing surfaces display guide surfaces with the same slope and shape as real joint sur-faces (Fig 8-146).The chewing surfaces on the mandibular poste-rior teeth have their mortar-shaped occlusal fos-sae shifted lingually, while the buccal cusps have a noticeable abrasion surface that slopes down toward the vestibule.The palatal cusps of the maxillary teeth engage pestle-like into the mandibular occlusal fossae, while the maxillary buccal cusps engage with their adapted abrasion surfaces over the mandib-ular teeth. In their eventual shape, the occluding cusps resemble microcondyles that articulate in the microfossae.The condylar path inclinations and the move-ment patterns of the mandible are in the sloping surfaces of the buccal cusps in the sagittal and transverse direction, as reected in the curva-tures of the mortar-and-pestle cusps. Thus, pro-trusive movements on the long working facets and retrusive movements on the short balancing facets of the occlusal surfaces can be performed under tooth contact.The mortar-and-pestle teeth permit slight man-dibular movements under tooth contact in centric occlusion but do not result in dynamic denture movements or the need for slight changes to be made to mouth opening. In the case of normally shaped anatomical forms of abrasion, transla-tive movements are only possible if the mouth is opened slightly and the teeth are lifted out of centric occlusion.Fig 8-144 The intraoral occlusal registration described by Gerber follows the same principle as the Gysi extraoral regis-tration. In this case, however, the registration kit is mounted centrically over the dental arches so that tilting is ruled out. During mandibular movement, a Gothic arch also appears on the tracing plate. A perforated plexiglass disk is xed over the intersection point. The tracing stylus engages in the hole on the disk, and the mandible is established in centric occlusion. 309Gerber’s Working Method123456Fig 8-145 On the Condyloform posterior teeth, the maxillary occluding cusps engage like a mortar in the pestle-like occlusal sur-face of the mandibular teeth. (1) Occluding cusps resemble microcondyles that articulate in the microfossae. (2) Active masticatory microcondyles and microfossae are located in the lingual part of the teeth: The bulbous buccal tooth surfaces have cheek contact and stabilize the denture; positioning the active masticatory parts on the center of the alveolar ridge leaves adequate clearance for the tongue; and functional elements lie markedly lingually, so the teeth can be positioned more vestibularly. (3) The abraded buccal cusps aid statics and stability during mastication. (4) In crossbite, the molars are not swapped but the buccal cusps of the maxillary molars become active masticatory cusps; the palatal cusp must not impede chewing movement. (5) The buccal cusps can be ground back or placed out of contact. (6) To enlarge the space for the tongue, premolars can be used instead of molars in the mandible.Fig 8-146 The basic idea of interpreting the occlusal surfaces of the posterior teeth as microfossae and microcondyles is il-lustrated in this diagram. The sliding movements of the real joints are also possible on the posterior teeth. The occlusal sur-faces are interpreted as upside-down microjoints in which one part of the joint is xed and the other is mobile. The microjoint occlusal surfaces have the same guide surfaces as the real joints; this is the desired relationship. 310Complete DenturesThe lingually shifted occlusal fossae on the mandibular teeth and the abraded buccal cusps contribute to positional stability because these functional elements (microcondyles and micro-fossae) are displaced from the middle of the teeth in a pronounced lingual direction.The balanced tone of the tongue and cheek can be used because the teeth are kept wider in the lingual/vestibular direction. The anatomically shaped vestibular surfaces show a pronounced curvature, which makes good cheek contact pos-sible. Denture wearers are able to guide and sta-bilize their dentures with their cheeks and tongue.Condyloform teeth can be set up on the center of the alveolar ridge, leaving their antagonists in-dependently stable on chewing (Fig 8-147). As the functional elements are actually moved in a dis-tinctly lingual direction, the teeth can be placed very vestibularly. Positioning the active masti-catory parts on the center of the alveolar ridge leaves adequate clearance for the tongue. To enlarge the space for the tongue, premolars can even be used instead of molars in the mandible without impairing chewing activity.A crossbite, necessitated by advanced atrophy of the jaws, is not created by swapping the mo-lars. Instead the buccal cusps of the maxillary molars are turned into active masticatory cusps, while the palatal cusps must not impede articula-tion movement. This is why the teeth are tipped very buccally, whereby cheek contact is also re-stored. The buccal cusps can be ground back or placed out of contact if they hamper denture sta-bility or articulation.Stability during masticationAccording to Gerber, positional stability depends on tooth shape, the contouring of the denture body, and the positioning of the articial teeth relative to the alveolar ridges (Fig 8-148). The pos-terior teeth stand on the middle of the ridges. As Fig 8-147 Gerber also addressed the principle of placing the posterior teeth on the center of the alveolar ridge. In the case of Condyloform teeth, the active masticatory lingual parts of the surfaces must be positioned over the ridge line. In the mandible, because of the buccally overhanging shape, the tooth can be moved slightly lingually, which benets the statics of the mandibular denture but does not crowd the tongue. In the case of the rst premolar, the mortar-and-pestle principle is turned on its head. This aids masticatory stability and tooth shape in this area. The buccal cusps of the subsequent teeth are placed far enough out of contact that they do not interfere with denture statics but still provide balancing contact on lateral excursions. The maxillary second molar can usually be omitted, while the mandibular second molar can be the shape of a premolar that serves merely as a second-ary antagonist to the maxillary rst molar.First premolarSecond premolarSecond molarFirst molar 3 11Gerber’s Working Methodstipulated by Gysi’s law of the ridge line and by Hiltebrandt’s basic static law, this condition also applies to Gerber. If tooth positions are outside the ridge line, the denture may be levered off. On Condyloform teeth, the functional elements, such as the occlusal fossa and the lingual occlud-ing cusp, are moved markedly toward the lingual aspect. If these functional mortar-and-pestle parts are set up exactly over the ridge center, the buccal cusps will extend far in the vestibular direction.A crossbite position is only rarely necessary, as the space for the tongue is almost normal and not crowded and cheek contact can be used ex-tremely well for positional stability. All the teeth stand with their independently stable antagonists and permit slight movements under tooth con-tact. The requirement to position the teeth on the center of the alveolar ridge does not become a problem with Condyloform teeth, thereby satisfy-ing the rst criterion for positional stability of a complete denture.The instability of mandibular dentures on an al-veolar ridge rising dorsally can be contained by special tooth positioning. Hiltebrandt thought the solution was to shorten the dental arch up to the rst molar, and Haller recommended an upward notching of the posterior teeth. Gerber’s solution synthesizes these two views. The contour of the alveolar ridge in the mandible is deected down-ward and is generally at its lowest at the rst molar. This is where the masticatory center of a complete denture must lie, which is why Gerber describes this area as the stable center during mastication. This lowest point is marked on the edge of the cast, and the rst molar is arranged there.So that the masticatory center also remains on this stable center during mastication, the maxil-lary row of teeth stops at the rst molar, and the denture baseplates are kept a sufcient distance from each other. One premolar is now placed behind the mandibular rst molar, ending the arched curve as a secondary antagonist for the maxillary rst molar. The posterior teeth are set up in a steep curve deected downward, which produces a steep sagittal occlusal curve. The aim of this notching, shortening of the dental arch, and special tooth shape is to prevent the mandib-ular denture from slipping on the inclined plane of the alveolar ridge during mastication.To create balanced contacts on the nonworking side, the posterior teeth should be inclined inside the transverse curve. If no balancing contacts are possible when crushing food, these contacts will be achieved on functional mandibular move-ments during the swerve toward the balancing side. Furthermore, these balancing contacts pro-tect the jaws and joints during normal functional movements (eg, when speaking). According to Gerber, the posterior teeth should be set up in-side the transverse and sagittal curves, and these curves should create balancing contacts during mandibular movements. Therefore, strictly speak-ing, these are compensating curves.Another aspect of securing masticatory stabil-ity is supporting the denture in a particular way in the canine region. Denture wearers often bite food with the canines and premolars because the Fig 8-148 According to Gerber, stability during mastication (or masticatory stabil-ity) is linked to two facts: (a) The man-dibular rst molar must be placed at the lowest point on the shrunken mandible. The molar then stands between two in-clined planes whose contrary effect can-cels itself out. This stable position can be compared with a saddle, which is se-curely seated in the dip of a horse’s back. (b) The posterior teeth are set up inside a steep occlusal curve. This is supposed to compensate for positional defects due to the Christensen phenomenon and Ben-nett movement, but it also reinforces the contrary effect of the inclined plane.a b 312Complete Denturesdenture is usually more securely seated in this area than in the region of the incisors. If broad premolars are set up instead of maxillary canines, the mandibular antagonists in the occlusal fossa of the maxillary canine/rst premolar can produce an excellent cutting effect without pressing the maxillary denture outward and thereby levering it off (Fig 8-149). This is because the mandibular antagonists split up the food, like a knife between two parallel cuts would do.Finally, the positional stability of a complete denture should be supported by the contour-ing of the denture body. Schreinemakers, Uhlig, and Jüde recommend a thorough analysis of the denture-bearing area, whereas Gerber suggests molding lip shields on the maxillary and man-dibular dentures for mucosal support, based on a muscle relief impression of the perioral muscles, as well as modeling narrow channels in the di-rection of function of the ligaments for the buccal frena.Tooth setup according to GerberGerber explains the special tooth positioning for complete dentures by the special shape of the Condyloform teeth (Fig 8-150). The antagonist pairs of posterior teeth form harmonious mas-ticatory units that are meant to be independent-ly stable in their position in the dentition. This means that the teeth have only occluding cusp contact, and the abraded buccal cusps touch in order to increase masticatory stability. The maxil-lary antagonists are centered in their antagonists and do not have multiple cusp contact.Setup calls for four phases:1. Anterior teeth2. Mandibular posterior teeth3. Maxillary second premolar4. Rest of the maxillary posterior teethThe anterior teeth are set up by reference to the model analysis markings, tracings on the oc-clusion rims, and static considerations. The inci-sors have a sagittal distance of 1.5 to 2 mm; the cutting edges are abraded so they glide into an unimpeded edge-to-edge occlusion on protrusive movements.The canines are never placed with a pronounced overlap but permit free articulation move ments. If necessary, the tips of the canines inhibiting movement should be trimmed. The canines stand slightly outside the dental arch, hence in a domi-nant position. The decisive canine stability is achieved by placing a premolar instead of the maxillary canine. The tip of the mandibular canine engages in the mortarlike concavity of the maxil-lary canine/premolar, pressing the denture onto the dental arch.The broad posterior teeth are intended to gain cheek contact with their bulging buccal surfaces. The occlusal concavities and occluding cusps stand over the center of the alveolar ridge.The mandibular posterior teeth are rst set up, a gap being left between canine and rst premo-lar. The curve of Spee is distinctively shaped by imitating the occlusal line as a xed locator on the articulator using a ruler or a rubber band.Fig 8-149 The masticatory stability of the maxillary denture is jeopardized primarily by the canine because anterior contact is always sought in a chewing cycle. Gerber rst proposed set-ting up the incisors and canines so they could glide past one another. If the maxillary canine is replaced by a broad premolar, into whose chewing fossa the mandibular canine glides cen-trally, the effect of masticatory force could be used to stabilize the denture. The “canine premolars” exhibit a particular posi-tional stability. 313Biologic ProstheticsThe position of the maxillary posterior teeth is referenced to the maxillary second premolar. This tooth is the rst of the maxillary teeth to be set up, then the two teeth still missing are inserted. An oral check is done to see whether the pestle cusps have full mortar contact and whether the sloping abrasion surfaces permit unimpeded slid-ing movements.The maxillary second premolars stand with their lingual occluding cusps over the center of the ridge, while the maxillary antagonists stand with their markedly lingually displaced mastica-tory concavity in the middle. A comparable tooth setup is also adopted for the rst molars. T