Particulate Membrane Grafting/Guided Bone Regeneration










933
36
Particulate Membrane grafting/
Guided Bone Regeneration
C. STEPHEN CALDWELL
T
he eld of restorative dentistry has been through a para-
digm shift in recent years that has completely changed
treatment planning and the prospects for reconstruction
of severely compromised dental cases. e use of dental implants
in most treatment plans today oers the possibility of restorative
success using xed prostheses in many situations that would have
previously been impossible. Meeting the demands and expecta-
tions of our enthusiastic patient population requires the multidis-
ciplined implant team to perform at new and challenging levels of
sophistication. As we attempt to restore these progressively more
dicult cases, the severely compromised bony ridge defects that
we encounter will continue to challenge team members to develop
new and predictable grafting techniques (Fig. 36.1).
e goal of any dental implant procedure is to restore the patient
to optimal form, function, and esthetics. rough the combined
eorts of a great number of clinicians and researchers, guidelines
have been established in regard to proper implant numbers and
positioning based on possible prosthetic designs. e patient’s
existing bone volume often makes the proper placement and posi-
tioning of implants dicult, if not impossible. Ideal treatment
planning in implant dentistry often requires the correction of sig-
nicant alveolar ridge defects in regions where dental implants are
indicated to support critical prostheses. Alveolar ridge defects are
caused by a variety of factors including developmental anomalies,
trauma, and most commonly, tooth extraction. After tooth loss a
predictable resorptive process of the alveolar bone occurs in both
a horizontal and a vertical dimension
1
(Fig. 36.2).
e loss of alveolar bone can pose a challenge both from the
perspective of supporting a conventional removable prosthesis
or placement of dental implants in an ideal position for func-
tional and esthetic results. Before development of eective bone-
grafting techniques, implants were placed in regions where there
was available bony support, often leaving the restorative dentist
with the task of restoring an implant in a less than ideal position
within the arch. e success of implant dentistry today has been
largely related to the advent of bone augmentation techniques
that allow regeneration of an ideal ridge form and placement of
implants in their ideal functional and esthetic positions
2–6
(Fig.
36.3).
e augmentation of bone volumes through grafting is an
eective, but technique-sensitive process. It requires meticulous
surgical skill, practice, and knowledge to become procient in
creating predictable bone growth before implant placement.
Complications are plentiful in this discipline, leading to treat-
ment delays, patient and provider frustration, as well as possible
neurosensory, vascular, and infectious issues. e dental implant
surgeon must have a rm understanding of the limitations
encountered in various bone-grafting techniques to develop
appropriate treatment plans. Clinicians must be able to not only
prevent complications during the procedure, but also properly
address complications related to these issues should they arise
(Box 36.1).
Indications for Bone Grafting
e presence of an adequate volume of available bone is one of
the most important prerequisites for predictable implant place-
ment and osseointegration. Although loss in bone volume may
result from trauma, bone deciency is most frequently due to the
normal physiologic process that occurs after tooth loss or extrac-
tion. Studies have shown that resultant bone resorption after tooth
removal can be approximately 1.5 to 2 mm vertically and 3.8 mm
in the horizontal plane within 6 months.
7,8
Currently, bone regeneration procedures are widely accepted
as a viable option for the treatment of edentulous deciencies to
be restored with an implant-supported prosthesis. Implant clini-
cians have a wide range of bone-grafting materials and procedures
at their disposal. For years the gold standard in bone regenera-
tion has been the use of autogenous (autograft) bone because
of its inherent osteoconductive, osteoinductive, and osteogenic
properties (Box 36.2). Because autogenous bone is composed of
the patient’s own tissue, there is a reduction in the likelihood of
immunoreactions and possible infectious transmission. However,
autogenous bone grafting has disadvantages, including the need
for a secondary surgical site, a potential increase in pain and dis-
comfort, bone-harvesting quantity restrictions, increased costs,
and longer surgical procedures. Studies have shown that only
61% of patients accept grafting with autogenous bone.
9
Methods

934
PART VII Soft and Hard Tissue Rehabilitation
that minimize the inconvenience related to autogenous bone har-
vests allow the surgical team the opportunity to use the boost of
autogenous grafts without putting their patients through excessive
discomfort. As tempting as it may be, the lack of incorporation
of at least some autogenous bone in a large ridge augmentation
(> 3 mm) can ultimately change the density of the nal graft,
its resistance to unpredictable remodeling, the overall ability to
regenerate vertical volume, and to some degree the width of a
A
B
C
D
Fig. . Careful planning and surgical execution can provide patients with the opportunity to replace
their missing teeth with restorations that are not only functional, but also esthetically pleasing. (A Preopera-
tive CBCT Cross-section of severely compromised central incisor B) Cross-section of the same site after
completing a large ridge augmentation. (C and D) Final restorations in the anterior graft site.
Fig. . The progressive resorption of the bony ridge after an extraction leads to a situation that com-
promises all aspects of the restorative process. As resorption advances, less bone is available for implant
placement, thus compromising the final result.

935
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
large horizontal graft site. erefore ideally 50% autogenous bone
should be used in vertical regeneration cases and in large-volume
horizontal grafts.
Success in any implant prosthesis requires the implants to be
placed in positions that provide ideal esthetics, function, comfort,
and support. To be successful in the development of a favorable
prosthesis, the number and positions of implants in an edentulous
space must be determined with a careful analysis of the relationship
between the restorative prosthesis and the forces that will be exerted
on the nal prosthesis. is is then combined with the functional
and esthetic aspects of the case, ultimately dictating the relationship
between the implants, bone, and opposing forces. All of these factors
must be considered in planning support for a prosthesis that func-
tions well while maintaining the bone volume around its implant
abutments. Clinicians too often try to bypass the grafting process,
either to save time or because they are not experienced in advanced
grafting techniques. Insucient bone in recipient sites leads to place-
ment of implants with inadequate diameters, shorter lengths, insuf-
cient numbers, or less than ideal angulations. Compromises such
as these can eventually lead to signicant damage around an implant
and the prosthesis it supports. Due to the fact that resorption and
remodeling occur in every edentulous site, the need for adjunctive
bone grafting must be considered and is often vital for a successful
outcome.
Failure to recognize the need for bone grafting leads to
numerous treatment issues, ranging from esthetic complica-
tions to implant and prosthetic failure. Placing implants of
suboptimal sizes or in less than ideal numbers to bypass the
grafting process is a compromise that often leads to force-
related failures of implant components, failure of the prosthe-
sis itself, or accompanied bone loss. Ultimately, prosthetic and
implant morbidities may result. A multidisciplinary approach
should be taken to assess the optimal prosthetic solution for
the patient, based on the patient’s wishes, available bone, and
other factors. After a prosthetic plan has been established, the
clinician should begin planning the implant positions required
to execute the prosthetic option. Once the sites for the spe-
cic implants have been determined, the associated regions are
evaluated for bony foundational support in that specic site.
If inadequate bone is available to successfully place an implant
in a key location for the prosthesis, grafting should then be
included in the treatment plan to build the appropriate bone
volumes (Fig. 36.4).
Cellular Bone Regeneration Process
e cellular development of bone in a decient site involves a
delicate process that occurs over an extended period. is series
of steps can be easily disrupted by cellular ingrowth, micromove-
ment, infection, or bacterial contamination. erefore the process
of guided bone regeneration (GBR) is always carried out in a pro-
tected space where the natural step-by-step process of bone devel-
opment can occur. e rst phase of this regeneration process
involves the recruitment of osteoblast precursors and growth fac-
tors to the recipient area. is is accomplished primarily through
the existing bony recipient bed, its vasculature, and the graft mate-
rial (i.e., autograft, allograft, xenograft). e second phase of the
process is the resorption/deposition process. Host osteoprogeni-
tor cells will inltrate the graft within 7 days, and resorption and
deposition will occur via creeping substitution and osteoconduc-
tion. e osteoblast precursors dierentiate into mature osteo-
blasts under the inuence of osteoinductors and synthesize new
bone during the rst weeks. Growth factors involved in the bone
formation process act on broblast and osteoblast proliferation,
extracellular matrix deposition, mesenchymal cell dierentiation,
and vascular proliferation (Fig. 36.5 and Box 36.3).
Fig. . Loss of Soft and Hard Tissue. After tooth loss, bone loss
occurs with respect to the prosthesis position. As the bone resorbs, the
vertical and horizontal soft tissue support around teeth and implants dis-
appears. This results in the exposure of the failing implant body, together
with a future nonesthetic implant prosthesis.
Alveolar ridge width
Alveolar ridge height
Alveolar ridge angulation
Available restorative space
Maxillary/Mandibular alveolar ridge relationship
Proximity to vital structures
Bony undercuts/defects
Maxillary Sinus pneumatization
Available autogenous donor sites
BOX
36.1
Hard Tissue Considerations With Implant
Treatment Planning
1. Osteogenic Grafts
Osteogenic bone grafts originate from autogenous origin and are
comprised of live, viable cells capable of differentiation and formation of
bone.
2. Osteoinductive Grafts
Osteoinductive grafting materials provide a biological stimulus (proteins
and growth factors) that induce the progression of mesenchymal stem
cells and other osteoprogenitor cells toward osteoblast lineage.
3. Osteoconductive Grafts
Osteoconduction is the process that allows the bone graft to be
conducive to forming bone, thereby acting as scaffolding for bone
growth.
BOX
36.2
Biologic Bone Healing Classication

936
PART VII Soft and Hard Tissue Rehabilitation
A
B
C D
E
Fig. . Malpositioned Implants. (A) Implants placed in compromised bone sites result in a compro-
mised final prosthesis. (B and C) Implants positioned too far facially will increase prosthesis morbidity and
compromise esthetics. (D and E) Implants positioned too far lingual will result in an overcontoured prosthe-
sis, but also will place the implants at a biomechanical disadvantage.
Fig. . Guided bone regeneration combines the science of bone regeneration with the management
of space maintenance for development of planned bony configurations. With the use of bone screws and
a barrier membrane, bone regeneration may take place.

937
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
Treatment Planning in the Compromised
Edentulous Ridge
Treatment planning for implant-supported restorations in
edentulous spaces requires a clear understanding of the resorp-
tive patterns of bone loss. As a ridge resorbs, available bone for
support of dental implants disappears, preventing placement of
implants in key locations for restorative success. After tooth loss
the initial pattern of bone resorption starts with loss of the lateral
(buccal) aspect of the ridge, eventually leading to a decrease in
vertical ridge height. As this resorptive process occurs, the posi-
tion of implant-supported restorations can change substantially
secondary to the new interarch relationship between the maxilla
and the mandible. For instance, the loss of maxillary posterior
teeth with the accompanied loss of the buccal bony ridge width
will often lead to development of a posterior crossbite. is is
compounded as the mandible deteriorates into a division C or
D ridge, resorbing until the remaining mandibular basal bone
is actually positioned laterally, away from the remaining maxil-
lary bone. Treatment planning must combine nal restorative
loading of implants in a manner that will not place unreason-
able forces on the implant-bone interface leading to excessive
bone remodeling and implant failure. e current ability of the
implant team to regenerate bone in critical sites has increased the
predictability of nal prostheses and in doing so has reduced the
number of implant failures (Fig. 36.6).
Edentulous Site Assessment
e treatment planning process begins with a reasonable assess-
ment of the extent of the bony deciency and the capacity of a
regenerative procedure to create adequate support for implants in
their ideal positions for comfort, esthetics, function, and support.
As the extent of bone regeneration is evaluated, care must be taken
in the beginning stages to identify the expected positions of each
restoration or prosthesis using accurate restorative wax-ups. Evalu-
ation of the relationship between the required restorative positions
and the bony deciency will then provide insight into the volume
and shape of the bone that will need to be regenerated. At this
Bone Remodeling—the natural phenomena in which old bone is
continually replaced with new bone. This balanced process is critical for
maintenance of healthy bone mass.
Bone Modeling—these changes in size and shape of bone in a region are
adaptations in response to stress or loading forces directed to the bone.
Bone Repair—the physiologic process in which the body facilitates the
repair of a bone fracture.
Bone Regeneration—the development of new bone growth in deficient
sites using surgical protocols that apply the principles of osteogenesis,
osteoinduction, and osteoconduction for directed bone growth.
Guided Bone Regeneration (GBR): technique to reconstruct alveolar bone
deficiencies via the use of a barrier membrane to exclude epithelial cells
and allow slower-growing cells to form bone.
Guided Tissue Regeneration (GTR): technique to regenerate lost
periodontal structures via the use of a barrier membrane to exclude
epithelial or connective tissue ingrowth.
BOX
36.3
Bone Healing and Grafting Denitions
A B
C
D
Fig. . Resorptive Pattern in Posterior Mandible. (A) The normal bony contours in a coronal view of the
maxillary and mandibular arches. (B) The initial resorption of bone in the mandibular arch from Division A to
Division B. (C) As bone resorbs further (Division B to Division C), the resultant mandibular position is more
lingually (medially) inclined in comparison with the maxillary arch. Further loss in the lower arch leaves the
remaining bone in a more lateral position than the maxillary arch. (D) Often when bone resorbs, the posi-
tion of the implant is compromised, as can be seen by the cross-sectional image depicting a perforation.

938
PART VII Soft and Hard Tissue Rehabilitation
stage the most predictable surgical approach and bone graft mate-
rial (e.g., autograft, allograft, xenograft) is selected to ensure ade-
quate bone support can be developed for ideal implant placement.
In site assessment treatment planning, complications often
result when the clinician fails to understand the relationship
between the limitations of various regenerative grafting tech-
niques and the predictable development of the required bone
contours and bone volume needed for overall restorative suc-
cess. It is not possible to treat every bony defect with simple
or limited techniques that a clinician learns early in his or her
learning curve. is discipline requires a variety of approaches
to meet the reality of advanced bone resorption, and as the
surgeon gains experience, correct application of techniques will
lead to predictable outcomes. When the incorrect technique
is used, inadequate bone volume will be regenerated, leading
to either compromised restorative results or a potential fail-
ure of the prosthesis. ese problems not only compromise the
local grafting site, but they can also destroy bone around sur-
rounding teeth, creating a worse situation than was originally
encountered (Fig. 36.7).
AB
CD
E
Fig. . (A) Maxillary left lateral and canine implants were placed in a poorly executed bone graft site,
leading to a devastating esthetic situation. (B) Because of the malpositioned implants, a removable partial
denture was placed to hide the implant position. (C) Maxillary left lateral incisor replacement resulted in a
defect after two unsuccessful attempts to graft a missing facial cortical plate. (D) The loss of the cortical
bone raised the defect to the level of the apices of the adjacent teeth. (E) The only remaining bone is found
along the palatal cortical plate.

939
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
In an ideal setting, prevention of ridge resorption starts with aware-
ness of ridge preservation and limiting bone loss before major ridge
defects occur. is starts with atraumatic extraction techniques, aggres-
sive socket grafting, and communication among the members of the
implant team in respect to the need for timely preservation of the
ridge. e longer the patient remains without an implant in an extrac-
tion site, the greater the chance that adjunctive grafting procedures will
be necessary. Use of eective grafting materials is critical for successful
results. For patients with long-term edentulism, the surgeon needs to
be fully aware of the patterns of bone resorption to understand the
current underlying bony architecture and to correctly choose a grafting
protocol that will build the correct volume for the intended prosthesis.
is working knowledge of ridge resorption and expertise in the use
of eective diagnostic imaging to accurately assess bone volumes gives
the clinician the opportunity to correctly organize a reasonable and
predictable implant treatment plan (Fig. 36.8).
e use of cone beam computed tomographic (CBCT) imaging,
together with proper diagnostic digital or cast models, allows the cli-
nician to create a clear prosthetic plan. e restorative wax-up can
easily be interlaced into computed tomographic (CT) imaging soft-
ware for assessment of the bone volumes needed for proper implant
support in key positions. is whole process has been advanced with
digital scans and virtual crowns/implants. e digital plans, once inte-
grated into CBCT images, allow the team to visualize the relation-
ships between bone volume and restorative components. Once the
dimensions and volume of the graft have been determined, proper
application of bone-grafting techniques and materials is necessary
to ensure that the intended volume can be achieved. At this point
the patient should be educated on the details of the regenerative pro-
cedures and a timeline of treatment. Advanced grafting procedures
delay completion of the nal prosthesis, and patients should be aware
of the extent of the inconveniences that will need to be tolerated dur-
ing this surgical sequence (Fig. 36.9, Fig. 36.10).
1 Division B2. Small diameter
Osteoplasty
3G
raft
Fig. . Treatment Planning Decision Tree. In a Division B ridge,
various treatment options are possible, including osteoplasty, Division
B implants, or bone grafting. However, each treatment plan has advan-
tages and disadvantages that should be taken into consideration with
respect to the final prosthesis (e.g., type 1 fixed prosthesis [FP-1], FP-2,
or FP-3).
ABC
Fig. . (A) Use of three-dimensional imaging allows the implant team the opportunity to visualize the
relationship between the osteotomy and the surrounding bone and teeth. (B) Examination of cone beam
computed tomography cross sections allows assessment of proposed implant sites and their relationship
to available bone. In this case there is not enough bone to support an implant without additional grafting in
the site. (C) The absence of adequate buccal bony support indicates the need to regenerate at least 5mm of
bone. Bone around this coronal 5mm of the implant is critical for functional support during loading.

940
PART VII Soft and Hard Tissue Rehabilitation
AB
CD
E
Fig. . (A) Planning a case in three-dimensional software starts with incorporation of the restorative
wax-up into the cone beam computed tomographic image. (B) Implants are then introduced in posi-
tions that will support the crowns in their required restorative positions. (C and D) As the cross sections
are evaluated in this particular case, it is apparent that there is not enough ridge width for placement of
implants in the existing bone. This preliminary view indicates that augmentation of the ridge will be neces-
sary for proper implant alignment and support. (E) Evaluation of the actual bony ridge at the time of surgery
confirms the previous digital assessment of the bony deficiency.

941
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
Bony Defect Morphology Considerations and
Classification
One of the most dicult components of bone augmentation
treatment planning is learning how to predict the amount of bone
that will actually be required to develop the proper foundational
support that the restorative treatment plan requires. Evaluation
of the clinical situation, review of two-dimensional radiographs,
assessment of models with restorative wax-ups, and information
from CBCT all play a role in determining where bone will be
required and how much bone will be needed to successfully graft
the site. e concept of determining graft volume is even more
important when autogenous bone is incorporated into the regen-
erative process. e location of an autogenous bone harvest often
determines how much volume of bone can be retrieved. e chin
and ramus are the primary sites for signicant donor volumes used
in block grafting, but these sites can provide only a limited volume
of bone. If these local donor sites are inadequate, bone can be
taken at the apex of many osteotomy sites. In addition, the use of
a Piezosurgery unit and bone scrapers may be utilized to harvest
cortical shavings. (Fig. 36.11)
In cases where a previous procedure fails to properly develop
adequate bone volumes for ideal implant positioning, reection of
tissue over the grafted site will reveal inadequate bony support for
the intended implant size and position. At this time, critical deci-
sions must be made to prevent the chance of compromising the
overall case success because of this shortfall. e easiest solution is
to stop and regraft the site, but this causes inconvenience for the
patient, embarrassment for the surgeon, and an overall increase in
the treatment time and expense. e alternative is to either ignore
the deciency, placing the implant in a decient site or attempt-
ing supplemental grafting around the exposed implant sur-
faces. Implant placement in compromised sites without grafting
ultimately limits the implant size or forces improper positioning of
the implant in the alternative position. is option then leads to a
compromised result and incurs unnecessary risk for future failure.
For more experienced surgeons, simultaneous implant placement
with additional grafting can be attempted, but this is limited to
cases where the surrounding basal bone allows proper implant
positioning application of grafting principles. (Fig. 36.12),
(Fig. 36.13).
Bony Defect Classification
Determining if an edentulous site will require augmentation
should start with an initial assessment of the bony defect.
Careful review of the topography of the recipient site includes
review of the bone levels on adjacent teeth, bony protuberances,
the depth of the actual defect itself, variations in the vertical
height of the remaining walls of the ridge, and the condition of
the surrounding soft tissue. A successful graft depends on the
passage of various cellular components from the surrounding
recipient sites bony walls and vascular components into the
developing graft site. e larger the distance from these bony
surfaces to the peripheral graft components, the greater is the
challenge for the various cells to migrate to the outer limits of
the particulate graft. e surrounding prominent bony con-
tours also provide additional support and protection for the
graft particles, limiting micromovement that usually results in
compromised bone growth. ese xed bony surfaces can also
help with containment of graft particles and eventual support
of membranes. Depending on the morphology and topography
of the defect, the clinician may determine the diculty and
potential success of augmentation procedures. e following
classication system is based on the bony contours of the de-
cient area.
Fig. . This series of cross sections was prepared from a mandible showing a patient who has a very
thin overall ridge width throughout the anterior and posterior regions. As this case is considered for aug-
mentation, concern should be directed to the potential for graft failure because of the overall discrepancy
between the thin basal bone width and the required width for implant positioning.

942
PART VII Soft and Hard Tissue Rehabilitation
Bone Defect Classication
1. Depression
2. Concavity
3. Trough
4. Elevation/Prominence
5. Vertical (Height)
6. Buccal & Lingual Cortical Destruction
7. Complex/Multi-Dimensional
(Fig. 36.14), (Fig. 36.15).
Depression
A simple depression in a potential implant site is a bony defect
measuring less than 3.0 mm. If these types of defects are left
untreated, they can contribute to either a ridge dehiscence or
a fenestration when an implant is placed in the region. ese
depressed areas are usually grafted at the time of implant
placement and they do not require the use of extensive space
maintenance techniques. When a depression is noted, it can
A
B
C
D
E
F
Fig. . Osseous Defects. (A) When evaluating osseous defects, the three-dimensional relationship of bone
loss versus adjacent tooth positioning is crucial. (B) Severe vertical resorption requires regeneration to avoid
complications with support, esthetics, and poor healing. (C) The position of the adjacent teeth and roots should
be evaluated to determine the prognosis of an implant-related restoration. (D) Defects that destroy both the
facial and palatal cortical plates limit the choice of regenerative procedures that can be used. (E and F) When
there is a sharp declining ridge adjacent to a natural tooth, placement of an implant 1.5 mm away creates a
failing situation beginning at time of the initial implant placement. As time passes, both the tooth and the implant
will be compromised. Positioning the implant away from the natural tooth can limit this proximity problem; how-
ever, the implant body position will be too apical, which affects the esthetics and biomechanics.

943
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
AB
Fig. . Cone Beam Computed Tomography (CBCT) Evaluation of Osseous Defects. (A) The use
of interactive treatment planning should be completed to determine any possible bony deficiencies. (B)
Three-dimensional CBCT can be used to obtain a better ideal of the bone morphology.
AB
Fig. . (A) Evaluation of the clinical appearance of an edentulous space can easily mislead clinicians
with respect to the underlying bony contours. (B) Flap reflection reveals a severely resorbed facial aspect
of the edentulous ridge.
BA
Fig. . (A) Facial and palatal ridge resorption with coronal and apical defects. This will require facial
and palatal regeneration. (B) Severe facial resorption with some remaining palatal bony cortical plate.

944
PART VII Soft and Hard Tissue Rehabilitation
be covered with a layer of allograft material and covered with
a collagen membrane. Long-term isolation of the particles is
not as critical in these situations as compared to larger defects
where brous in-growth can be catastrophic. Depression type
bony defects are the most predictable types of grafts and
advanced surgical expertise is not as critical as in other defect
types.
Concavity
e concave shaped ridge defect has a signicant horizontal
depression or bony defect in the middle of the ridge that exceeds
3.0 mm in overall depth. ese defects have reasonable remnants
of bone surrounding the site that can be used for graft support,
containment of particles, and delivery of an adequate supply of
cells for angiogenesis. Regeneration in these sites is relatively
predictable and most of the implant support will still be pro-
vided by the surrounding autogenous bone. A concave defect
will require adequate space maintenance for the development of
signicant horizontal bony growth requiring the use of a static
support system (e.g. bone screws, a titanium supported mem-
brane) that is maintained for at least 5 months. (Fig. 36.16A,
Fig. 36.16B).
Trough
Severe ridge defects may on occasion destroy the ridge to the depth
of the lingual/palatal cortical plate. ese are most commonly
seen in single tooth defects, especially after a traumatic extraction.
e resulting defect provides clearly dened lateral walls of bone
formed by the roots of the adjacent teeth and most of these sites
also have an apical wall of bone that approximates the prior apex
of the tooth. Although these are deep and involved defects, they
provide protection for the graft components through their actual
conguration. Fixation of tenting screws in the middle of these
defects assures maintenance of the needed space for regeneration.
e presence of four actual bony walls provides a ready source
of cellular components and the resulting regenerative potential is
excellent. erefore, grafting in these defects can be completed
more predictably than a wide and exposed concave defect that
requires complex vertical support for development of graft depth,
protection from removeable prostheses, and general exposure to
micromovement (Fig. 36.17).
Elevation/Prominence
When ridge defects extend across the span of several teeth, the
topography of the lateral and vertical surfaces of potential graft sites
can vary signicantly. A horizontal concavity or isolated depression
in a recipient site can be complicated by adjacent elevated promi-
nences of cortical bone. e maxillary cuspid region would be a
typical site where the original tooth extended beyond the surround-
ing basal bone. e loss of the cortical plate on an adjacent premolar
would be a distinct contrast to the prominent cortical support over
a cuspid. Other examples would be changes in the overall facial con-
tours created by malpositioned teeth. Situations like this also can
develop as various teeth are lost over an extended period of time and
the resulting loss of ridge support emphasizes the facial contours of
the remaining compromised teeth. Grafting around these promi-
nent regions does not require much support in the elevated area, but
good space maintenance is needed directly adjacent to the elevated
portion of the recipient site (Fig. 36.18).
Vertical (Height)
Accurate assessment of the vertical ridge height in a potential aug-
mentation site is critical from a treatment planning standpoint.
As the vertical defect height is increased, the crown-implant ratio
becomes problematic with respect to esthetics and biomechani-
cal factors. Regeneration of vertical height is a complex grafting
procedure and that is usually reserved for clinicians with advanced
experience and skills in complex soft tissue manipulation. A true
vertical defect is in essence a through and through defect with
the loss of both cortical plates. ese defects will require that the
concept of space maintenance be moved into a 3
rd
dimensional
skill. A thin sharp-edged ridge top is usually present, with two
dense cortical surfaces approximating each another with little to
no medullary component between them. e resulting surface
area requiring regeneration involves the palatal/lingual aspect, the
vertical height defect region, and the highly resorbed facial/buccal
portion of the ridge. e limiting factor with these types of defects
is the level of the bone on the interproximal aspect of the adjacent
A B
Fig. . (A). Concave Ridge Defect: This ridge has multiple contours to the generalized horizontal
defect. There is an angular coronal defect at the top of the ridge, as well as a serious apical defect that
leaves a large region that will need to be regenerated. (B). This Concave defect requires significant support
for the membrane to regenerate adequate bone in the deeper portions.

945
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
B
C
A
Fig. . Trough Defect Type: (A) 3D CBCT image demonstrating the loss of interproximal bone. This
will greatly limit development of adequate height of the interproximal papilla in the final restoration. (B and
C) Three-dimensional and clinical images of severe horizontal defect with loss of bone on adjacent teeth.
There is still fairly good vertical height of the palatal cortical plate.
Fig. . This ridge defect has a complex nature to its topography.
The prominent portions of the facial aspect of the ridge will help with sup-
port and regenerative components to the more compromised adjacent
areas. Careful evaluation of the remaining surfaces demonstrate examples
of other defect types.
MM
II III IV
VV
I
25
20
15
10
5
Anterior Mandible
Fig. . Vertical Ridge Defect Type: Lower anterior complex ridge defect
with serious vertical component that destroyed both the facial and lingual
cortical plates. The precipitous vertical drop in bone height from the inter-
proximal tooth bone to the base of the defect requires correction of the verti-
cal defect for reasonable implant placement and esthetics. Placement of an
implant in the middle of the depressed region would still involve a horizontal
deficiency. Preservation of the bone levels on the adjacent teeth is a priority.

946
PART VII Soft and Hard Tissue Rehabilitation
teeth. Clinicians must understand that it is not possible to raise a
ridge higher than the adjacent bony level. In complex cases, this
limitation can often require removal of an adjacent tooth to pro-
vide a higher adjacent interproximal height for potential vertical
development. is is most often seen in anterior areas of the max-
illa and mandible where the aesthetic demands of a case require as
much vertical regeneration as possible (Fig. 36.19).
Buccal/Lingual (Palatal)
Ridge assessment must include a three-dimensional review of the
bony resorption on the lingual/palatal aspects as well as on the
facial and vertical regions. Severe ridge defects can often include a
signicant lingual/palatal component that moves the regenerative
procedure into a complex surgical category. e most common
site for a true “Hour Glass” ridge defect is in the anterior portion
of the maxilla or mandible. Unfortunately, these sites are techni-
cally challenging with respect to tissue release, space maintenance,
and graft containment. In general, the palatal tissue is very thick
and dense, limiting any signicant stretching or expansion of tis-
sue over a graft and membrane. For example, the lingual tissue in
the mandible is paper-thin and procedures to release and extend
lingual tissue over a graft has a potential for button-holing a ap
or for potential complications in the region of vessels, salivary
components, and muscle attachments. Fixation of tenting screws
in palatal defects requires extensive reection of the palatal tissue
and accurate anchorage of the membrane beyond the borders of
the bony defect. Membrane xation on the lingual aspect of the
mandible is a delicate process and awareness of the vital structures
if critical. Regeneration in these sites is limited to clinicians with
extensive surgical and bone grafting experience (Fig. 36.20 A, B).
Complex/Multi-Dimensional
Complex ridge defects are made up of a combination of the con-
gurations described above. ese sites will more than likely have
deep horizontal destruction that is combined with at least one
vertical component. ese type of defects vary from a severe single
tooth site to a complete section of a quadrant. It is the recognition
of the complexity of these situations that is critical for success. e
sheer volume of bone that needs to be regenerated can only be
determined with advanced integration of 3D Imaging and CBCT
surveys. e restorative requirements then dictate the actual loca-
tions for implant support and subsequently the areas where spe-
cic volumes of bone will be need to be regenerated. At that point,
the specic technique can be chosen by its potential for devel-
opment of large volumes of bone. ese cases require harvesting
signicant volumes of autogenous bone and use of isolating mem-
branes capable of separating the developing graft sites from soft
tissue inltration. Complex cases should be avoided until a clini-
cian has extensive experience in development of bone in each of
the basic situations described above (Fig. 36.21).
A
B
Fig. . Hour-glass Ridge Defect: The images in examples (A) and
(B) demonstrate the destruction of the facial and palatal cortical plates.
Regeneration in these sites will require growth in both dimensions. Failure
to regenerate the palatal portion of the site will lead to facial positioning of
the implant and most likely, a facial bony deficiency.
A B
Fig. . Complex Ridge Defect: The images in (A) and (B) demonstrate the severity of bone loss that
can occur over time and in highly destructive situations. These defects require advanced training and
experience for predictable grafting success.

947
CHAPTER 36 Particulate Membrane grafting/Guided Bone Regeneration
Soft Tissue Considerations
Patient-to-patient comparisons of the soft tissue drape surround-
ing the natural teeth often demonstrate signicant dierences in
color, surface consistency, tissue thickness, and overall esthetics.
is is emphasized when a very thin and friable tissue drape sur-
rounds an anterior tooth. Dierentiation of patients into either a
thick biotype” or a “thin biotype” is a critical tool that should be
used during routine restorative care and anterior implant–related
treatment planning. Cook etal.
10
demonstrated the simplest way to
determine a patient’s tissue biotype is through the evaluation of the
visibility of a periodontal probe in the sulcus of an anterior tooth. A
patient with a thick biotype will not show any translucence of the
probe through the sulcular tissue. In contrast, a thin biotype will
allow visualization of the coloration of a probe through the sulcular
tissue.
10
A patient with a thick biotype has tissue with a robust pink
stippled appearance. is dense tissue drape forms a thick layer
of tissue that is very forgiving when dental restorations are placed
around natural teeth and when dental implants are involved. e
thin biotype patient, however, presents a much more dicult
challenge. ese patients often have a thinner labial plate thick-
ness, a narrower keratinized tissue width, and a greater distance
from the cement-enamel junction to the initial alveolar crest. is
delicate layer of tissue is so thin that the periodontal probe can be
visualized when it is lightly placed in the sulcus. Patients with a
thin biotype are also more prone to tissue recession, complicating
the predictability of restorative esthetics around anterior teeth. As
teeth migrate out of position or rotate in the arch, the prominence
of the roots can increase, complicating the soft tissue situation
even more. in layers of tissue around the maxillary anterior
teeth require meticulous planning to hide underlying crown mar-
gins (Box 36.4 and Fig. 36.22).
Patient biotype and bony architecture must be considered early in
all implant treatment planning to avoid a variety of issues that become
very complex compared with similar situations around natural teeth.
is early planning allows the surgical team the opportunity to incor-
porate tissue grafting into each surgical stage, allowing deciencies to
be avoided or to at least be minimized. ese problems can be sig-
nicantly complicated when major bone grafting has been completed
in the region, resulting in elevation of the mucogingival junction
and repositioning of the mucosa into the zone surrounding implant
restorative margins. e tissue thickness in postoperative graft sites is
often very thin, and development of an adequate emergence prole
for crowns requires development of at least 3 mm of keratinized tis-
sue thickness over the top of the implant body prior to restoring the
implant. Restorative dentists often nd it dicult to mask the dark
tones in the coronal portions of natural teeth with endodontic-related
color changes. is problem is compounded in a patient with a thin
biotype as the color passes through the thin facial bone and thin tis-
sue consistency. is problem with translucence is a reoccurring issue
with implant restorations. Problems related to the translucence of the
dark hue of the implant body and the abutment through thin tis-
sue can signicantly complicate the esthetics surrounding the nal
restoration.
11
A patient with a thick biotype and thick facial cortical
Gingival biotype
Width of keratinized tissue
Soft tissue thickness
Vestibular depth
Smile Line
Frenum attachments
BOX
36.4
Soft Tissue Evaluate and Assessment
Considerations
A
DE
BC
Fig. . (A) Thin biotype exhibiting metal show-through. Tissue biotype can be defined by the trans-
lucence of a probe through the sulcus. (B) Thick biotype yellow probe (i.e., no-show through). (C) Thick
biotype with dark probe (i.e., no show-through). (D) Intermediate biotype with visible probe through sulcular
tissue (i.e., show-through). (E) Thin biotype with probe (i.e., show-through).

948
PART VII Soft and Hard Tissue Rehabilitation
bone makes an ideal implant patient when restorations are placed and
minor deciencies can be hidden behind the thickened tissue mass. A
patient with a thin biotype does not usually have a robust facial bone
thickness, and any remodeling changes in facial bone density or thick-
ness can greatly alter the restorative esthetics (Fig. 36.23).
Additional problems related to tissue thickness develop in
implant cases as time passes and bony changes occur around
the implant body. Esthetics around an implant restoration
often change because there is an active bone remodeling pro-
cess around implants that often results in a loss of facial cor-
tical thickness. is can be a serious problem if an implant is
placed in a site with very thin facial bone or in a site where the
quality of bone lateral to the implant resorbs as the prosthesis is
loaded and the functional forces are centered on the coronal 5
mm of the implant body. If recession or slight bone loss occurs,
the facial aspect of the implant can be exposed, creating a dark
hue that shows through the overlying tissue and contributes to a
poor esthetic situation.
As anterior immediate implants are considered, recommenda-
tions for the actual location of the implant in the socket have changed
signicantly as resorptive patterns in immediate implants have been
studied over time. An immediate implant currently should be placed
signicantly palatal to the facial cortical plate to allow for bone
remodeling. is paradigm shift has occurred over time as the rec-
ommendations for implant diameters in anterior spaces have steadily
decreased to accommodate for these changes in facial bone thickness
and complications related to color translucence through the soft tis-
sue. Current recommendations specify that the facial aspect of the
implant body should be placed at least 3 mm palatal to the inner edge
of the facial cortical plate. Additional authors currently recommend
grafting on the facial aspect of anterior immediate implant sites with
bovine particulate grafts and connective tissue graft to minimize long-
term changes.
When a clinician is preoperatively aware of a problem related to
tissue biotype, it is possible to plan ahead procedurally to maintain
or possibly change the biotype, leading to optimal esthetic out-
comes. Patients with a very thin biotype can be evaluated for intra-
operative supplementation using connective tissue grafts and facial
bone grafts to create a more forgiving tissue drape over the implant
site. Because thicker cortical bone volumes promote thicker bio-
types, the bony architecture and soft tissue drape may be modi-
ed in an esthetic zone before implant placement and restoration.
Advance planning also provides the implant team an opportunity
to inform the patient about these issues and to point out potential
esthetic complications before commencing treatment. Any com-
promise in a patient’s expectations must be addressed, especially if
the patient is not interested in grafting to modify the tissue type.
Implant restorative care in thin biotypes often requires tis-
sue augmentation as the case ages to create a thick, dense layer of
brous tissue over the implant body and any deciencies involving
the adjacent natural teeth. Connective grafting procedures are read-
ily available to increase the thickness of the tissue drape in situations
such as this. Subepithelial connective grafting procedures may use
palatal connective tissue, dense connective tissue from the maxillary
tuberosity, or acellular dermal matrix (i.e., OrACELL [Salvin Den-
tal Specialties], AlloDerm [BioHorizons IPH, Inc.], PerioDerm)
as the source of donor tissue. A thick layer of connective tissue is
inserted into the decient regions with tunneling procedures, allow-
ing the repositioned tissue ap to provide the blood supply to the
developing graft site. e use of the subepithelial approach allows
the implant clinician to produce a nal tissue tone and color that
matches the adjacent natural tissue (Fig. 36.24A, B and C).
AB
C
Fig. . Tissue Biotypes. (A and B) Thick biotype. (C) Thin biotype.

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93336Particulate Membrane grafting/Guided Bone RegenerationC. STEPHEN CALDWELLThe eld of restorative dentistry has been through a para-digm shift in recent years that has completely changed treatment planning and the prospects for reconstruction of severely compromised dental cases. e use of dental implants in most treatment plans today oers the possibility of restorative success using xed prostheses in many situations that would have previously been impossible. Meeting the demands and expecta-tions of our enthusiastic patient population requires the multidis-ciplined implant team to perform at new and challenging levels of sophistication. As we attempt to restore these progressively more dicult cases, the severely compromised bony ridge defects that we encounter will continue to challenge team members to develop new and predictable grafting techniques (Fig. 36.1).e goal of any dental implant procedure is to restore the patient to optimal form, function, and esthetics. rough the combined eorts of a great number of clinicians and researchers, guidelines have been established in regard to proper implant numbers and positioning based on possible prosthetic designs. e patient’s existing bone volume often makes the proper placement and posi-tioning of implants dicult, if not impossible. Ideal treatment planning in implant dentistry often requires the correction of sig-nicant alveolar ridge defects in regions where dental implants are indicated to support critical prostheses. Alveolar ridge defects are caused by a variety of factors including developmental anomalies, trauma, and most commonly, tooth extraction. After tooth loss a predictable resorptive process of the alveolar bone occurs in both a horizontal and a vertical dimension1 (Fig. 36.2).e loss of alveolar bone can pose a challenge both from the perspective of supporting a conventional removable prosthesis or placement of dental implants in an ideal position for func-tional and esthetic results. Before development of eective bone-grafting techniques, implants were placed in regions where there was available bony support, often leaving the restorative dentist with the task of restoring an implant in a less than ideal position within the arch. e success of implant dentistry today has been largely related to the advent of bone augmentation techniques that allow regeneration of an ideal ridge form and placement of implants in their ideal functional and esthetic positions2–6 (Fig. 36.3).e augmentation of bone volumes through grafting is an eective, but technique-sensitive process. It requires meticulous surgical skill, practice, and knowledge to become procient in creating predictable bone growth before implant placement. Complications are plentiful in this discipline, leading to treat-ment delays, patient and provider frustration, as well as possible neurosensory, vascular, and infectious issues. e dental implant surgeon must have a rm understanding of the limitations encountered in various bone-grafting techniques to develop appropriate treatment plans. Clinicians must be able to not only prevent complications during the procedure, but also properly address complications related to these issues should they arise (Box 36.1).Indications for Bone Graftinge presence of an adequate volume of available bone is one of the most important prerequisites for predictable implant place-ment and osseointegration. Although loss in bone volume may result from trauma, bone deciency is most frequently due to the normal physiologic process that occurs after tooth loss or extrac-tion. Studies have shown that resultant bone resorption after tooth removal can be approximately 1.5 to 2 mm vertically and 3.8 mm in the horizontal plane within 6 months.7,8Currently, bone regeneration procedures are widely accepted as a viable option for the treatment of edentulous deciencies to be restored with an implant-supported prosthesis. Implant clini-cians have a wide range of bone-grafting materials and procedures at their disposal. For years the gold standard in bone regenera-tion has been the use of autogenous (autograft) bone because of its inherent osteoconductive, osteoinductive, and osteogenic properties (Box 36.2). Because autogenous bone is composed of the patient’s own tissue, there is a reduction in the likelihood of immunoreactions and possible infectious transmission. However, autogenous bone grafting has disadvantages, including the need for a secondary surgical site, a potential increase in pain and dis-comfort, bone-harvesting quantity restrictions, increased costs, and longer surgical procedures. Studies have shown that only 61% of patients accept grafting with autogenous bone.9 Methods 934PART VII Soft and Hard Tissue Rehabilitationthat minimize the inconvenience related to autogenous bone har-vests allow the surgical team the opportunity to use the boost of autogenous grafts without putting their patients through excessive discomfort. As tempting as it may be, the lack of incorporation of at least some autogenous bone in a large ridge augmentation (> 3 mm) can ultimately change the density of the nal graft, its resistance to unpredictable remodeling, the overall ability to regenerate vertical volume, and to some degree the width of a ABCD• Fig. . Careful planning and surgical execution can provide patients with the opportunity to replace their missing teeth with restorations that are not only functional, but also esthetically pleasing. (A Preopera-tive CBCT Cross-section of severely compromised central incisor B) Cross-section of the same site after completing a large ridge augmentation. (C and D) Final restorations in the anterior graft site.• Fig. . The progressive resorption of the bony ridge after an extraction leads to a situation that com-promises all aspects of the restorative process. As resorption advances, less bone is available for implant placement, thus compromising the final result. 935CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationlarge horizontal graft site. erefore ideally 50% autogenous bone should be used in vertical regeneration cases and in large-volume horizontal grafts.Success in any implant prosthesis requires the implants to be placed in positions that provide ideal esthetics, function, comfort, and support. To be successful in the development of a favorable prosthesis, the number and positions of implants in an edentulous space must be determined with a careful analysis of the relationship between the restorative prosthesis and the forces that will be exerted on the nal prosthesis. is is then combined with the functional and esthetic aspects of the case, ultimately dictating the relationship between the implants, bone, and opposing forces. All of these factors must be considered in planning support for a prosthesis that func-tions well while maintaining the bone volume around its implant abutments. Clinicians too often try to bypass the grafting process, either to save time or because they are not experienced in advanced grafting techniques. Insucient bone in recipient sites leads to place-ment of implants with inadequate diameters, shorter lengths, insuf-cient numbers, or less than ideal angulations. Compromises such as these can eventually lead to signicant damage around an implant and the prosthesis it supports. Due to the fact that resorption and remodeling occur in every edentulous site, the need for adjunctive bone grafting must be considered and is often vital for a successful outcome.Failure to recognize the need for bone grafting leads to numerous treatment issues, ranging from esthetic complica-tions to implant and prosthetic failure. Placing implants of suboptimal sizes or in less than ideal numbers to bypass the grafting process is a compromise that often leads to force-related failures of implant components, failure of the prosthe-sis itself, or accompanied bone loss. Ultimately, prosthetic and implant morbidities may result. A multidisciplinary approach should be taken to assess the optimal prosthetic solution for the patient, based on the patient’s wishes, available bone, and other factors. After a prosthetic plan has been established, the clinician should begin planning the implant positions required to execute the prosthetic option. Once the sites for the spe-cic implants have been determined, the associated regions are evaluated for bony foundational support in that specic site. If inadequate bone is available to successfully place an implant in a key location for the prosthesis, grafting should then be included in the treatment plan to build the appropriate bone volumes (Fig. 36.4). Cellular Bone Regeneration Processe cellular development of bone in a decient site involves a delicate process that occurs over an extended period. is series of steps can be easily disrupted by cellular ingrowth, micromove-ment, infection, or bacterial contamination. erefore the process of guided bone regeneration (GBR) is always carried out in a pro-tected space where the natural step-by-step process of bone devel-opment can occur. e rst phase of this regeneration process involves the recruitment of osteoblast precursors and growth fac-tors to the recipient area. is is accomplished primarily through the existing bony recipient bed, its vasculature, and the graft mate-rial (i.e., autograft, allograft, xenograft). e second phase of the process is the resorption/deposition process. Host osteoprogeni-tor cells will inltrate the graft within 7 days, and resorption and deposition will occur via creeping substitution and osteoconduc-tion. e osteoblast precursors dierentiate into mature osteo-blasts under the inuence of osteoinductors and synthesize new bone during the rst weeks. Growth factors involved in the bone formation process act on broblast and osteoblast proliferation, extracellular matrix deposition, mesenchymal cell dierentiation, and vascular proliferation (Fig. 36.5 and Box 36.3). • Fig. . Loss of Soft and Hard Tissue. After tooth loss, bone loss occurs with respect to the prosthesis position. As the bone resorbs, the vertical and horizontal soft tissue support around teeth and implants dis-appears. This results in the exposure of the failing implant body, together with a future nonesthetic implant prosthesis. • Alveolar ridge width • Alveolar ridge height • Alveolar ridge angulation • Available restorative space • Maxillary/Mandibular alveolar ridge relationship • Proximity to vital structures • Bony undercuts/defects • Maxillary Sinus pneumatization • Available autogenous donor sites • BOX 36.1 Hard Tissue Considerations With Implant Treatment Planning1. Osteogenic Grafts • Osteogenic bone grafts originate from autogenous origin and are comprised of live, viable cells capable of differentiation and formation of bone. 2. Osteoinductive Grafts • Osteoinductive grafting materials provide a biological stimulus (proteins and growth factors) that induce the progression of mesenchymal stem cells and other osteoprogenitor cells toward osteoblast lineage. 3. Osteoconductive Grafts • Osteoconduction is the process that allows the bone graft to be conducive to forming bone, thereby acting as scaffolding for bone growth. • BOX 36.2 Biologic Bone Healing Classication 936PART VII Soft and Hard Tissue RehabilitationABC DE• Fig. . Malpositioned Implants. (A) Implants placed in compromised bone sites result in a compro-mised final prosthesis. (B and C) Implants positioned too far facially will increase prosthesis morbidity and compromise esthetics. (D and E) Implants positioned too far lingual will result in an overcontoured prosthe-sis, but also will place the implants at a biomechanical disadvantage.• Fig. . Guided bone regeneration combines the science of bone regeneration with the management of space maintenance for development of planned bony configurations. With the use of bone screws and a barrier membrane, bone regeneration may take place. 937CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationTreatment Planning in the Compromised Edentulous RidgeTreatment planning for implant-supported restorations in edentulous spaces requires a clear understanding of the resorp-tive patterns of bone loss. As a ridge resorbs, available bone for support of dental implants disappears, preventing placement of implants in key locations for restorative success. After tooth loss the initial pattern of bone resorption starts with loss of the lateral (buccal) aspect of the ridge, eventually leading to a decrease in vertical ridge height. As this resorptive process occurs, the posi-tion of implant-supported restorations can change substantially secondary to the new interarch relationship between the maxilla and the mandible. For instance, the loss of maxillary posterior teeth with the accompanied loss of the buccal bony ridge width will often lead to development of a posterior crossbite. is is compounded as the mandible deteriorates into a division C or D ridge, resorbing until the remaining mandibular basal bone is actually positioned laterally, away from the remaining maxil-lary bone. Treatment planning must combine nal restorative loading of implants in a manner that will not place unreason-able forces on the implant-bone interface leading to excessive bone remodeling and implant failure. e current ability of the implant team to regenerate bone in critical sites has increased the predictability of nal prostheses and in doing so has reduced the number of implant failures (Fig. 36.6).Edentulous Site Assessmente treatment planning process begins with a reasonable assess-ment of the extent of the bony deciency and the capacity of a regenerative procedure to create adequate support for implants in their ideal positions for comfort, esthetics, function, and support. As the extent of bone regeneration is evaluated, care must be taken in the beginning stages to identify the expected positions of each restoration or prosthesis using accurate restorative wax-ups. Evalu-ation of the relationship between the required restorative positions and the bony deciency will then provide insight into the volume and shape of the bone that will need to be regenerated. At this Bone Remodeling—the natural phenomena in which old bone is continually replaced with new bone. This balanced process is critical for maintenance of healthy bone mass.Bone Modeling—these changes in size and shape of bone in a region are adaptations in response to stress or loading forces directed to the bone.Bone Repair—the physiologic process in which the body facilitates the repair of a bone fracture.Bone Regeneration—the development of new bone growth in deficient sites using surgical protocols that apply the principles of osteogenesis, osteoinduction, and osteoconduction for directed bone growth.Guided Bone Regeneration (GBR): technique to reconstruct alveolar bone deficiencies via the use of a barrier membrane to exclude epithelial cells and allow slower-growing cells to form bone.Guided Tissue Regeneration (GTR): technique to regenerate lost periodontal structures via the use of a barrier membrane to exclude epithelial or connective tissue ingrowth. • BOX 36.3 Bone Healing and Grafting DenitionsA BCD• Fig. . Resorptive Pattern in Posterior Mandible. (A) The normal bony contours in a coronal view of the maxillary and mandibular arches. (B) The initial resorption of bone in the mandibular arch from Division A to Division B. (C) As bone resorbs further (Division B to Division C), the resultant mandibular position is more lingually (medially) inclined in comparison with the maxillary arch. Further loss in the lower arch leaves the remaining bone in a more lateral position than the maxillary arch. (D) Often when bone resorbs, the posi-tion of the implant is compromised, as can be seen by the cross-sectional image depicting a perforation. 938PART VII Soft and Hard Tissue Rehabilitationstage the most predictable surgical approach and bone graft mate-rial (e.g., autograft, allograft, xenograft) is selected to ensure ade-quate bone support can be developed for ideal implant placement.In site assessment treatment planning, complications often result when the clinician fails to understand the relationship between the limitations of various regenerative grafting tech-niques and the predictable development of the required bone contours and bone volume needed for overall restorative suc-cess. It is not possible to treat every bony defect with simple or limited techniques that a clinician learns early in his or her learning curve. is discipline requires a variety of approaches to meet the reality of advanced bone resorption, and as the surgeon gains experience, correct application of techniques will lead to predictable outcomes. When the incorrect technique is used, inadequate bone volume will be regenerated, leading to either compromised restorative results or a potential fail-ure of the prosthesis. ese problems not only compromise the local grafting site, but they can also destroy bone around sur-rounding teeth, creating a worse situation than was originally encountered (Fig. 36.7).ABCDE• Fig. . (A) Maxillary left lateral and canine implants were placed in a poorly executed bone graft site, leading to a devastating esthetic situation. (B) Because of the malpositioned implants, a removable partial denture was placed to hide the implant position. (C) Maxillary left lateral incisor replacement resulted in a defect after two unsuccessful attempts to graft a missing facial cortical plate. (D) The loss of the cortical bone raised the defect to the level of the apices of the adjacent teeth. (E) The only remaining bone is found along the palatal cortical plate. 939CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationIn an ideal setting, prevention of ridge resorption starts with aware-ness of ridge preservation and limiting bone loss before major ridge defects occur. is starts with atraumatic extraction techniques, aggres-sive socket grafting, and communication among the members of the implant team in respect to the need for timely preservation of the ridge. e longer the patient remains without an implant in an extrac-tion site, the greater the chance that adjunctive grafting procedures will be necessary. Use of eective grafting materials is critical for successful results. For patients with long-term edentulism, the surgeon needs to be fully aware of the patterns of bone resorption to understand the current underlying bony architecture and to correctly choose a grafting protocol that will build the correct volume for the intended prosthesis. is working knowledge of ridge resorption and expertise in the use of eective diagnostic imaging to accurately assess bone volumes gives the clinician the opportunity to correctly organize a reasonable and predictable implant treatment plan (Fig. 36.8).e use of cone beam computed tomographic (CBCT) imaging, together with proper diagnostic digital or cast models, allows the cli-nician to create a clear prosthetic plan. e restorative wax-up can easily be interlaced into computed tomographic (CT) imaging soft-ware for assessment of the bone volumes needed for proper implant support in key positions. is whole process has been advanced with digital scans and virtual crowns/implants. e digital plans, once inte-grated into CBCT images, allow the team to visualize the relation-ships between bone volume and restorative components. Once the dimensions and volume of the graft have been determined, proper application of bone-grafting techniques and materials is necessary to ensure that the intended volume can be achieved. At this point the patient should be educated on the details of the regenerative pro-cedures and a timeline of treatment. Advanced grafting procedures delay completion of the nal prosthesis, and patients should be aware of the extent of the inconveniences that will need to be tolerated dur-ing this surgical sequence (Fig. 36.9, Fig. 36.10). 1 Division B2. Small diameterOsteoplasty3Graft• Fig. . Treatment Planning Decision Tree. In a Division B ridge, various treatment options are possible, including osteoplasty, Division B implants, or bone grafting. However, each treatment plan has advan-tages and disadvantages that should be taken into consideration with respect to the final prosthesis (e.g., type 1 fixed prosthesis [FP-1], FP-2, or FP-3).ABC• Fig. . (A) Use of three-dimensional imaging allows the implant team the opportunity to visualize the relationship between the osteotomy and the surrounding bone and teeth. (B) Examination of cone beam computed tomography cross sections allows assessment of proposed implant sites and their relationship to available bone. In this case there is not enough bone to support an implant without additional grafting in the site. (C) The absence of adequate buccal bony support indicates the need to regenerate at least 5mm of bone. Bone around this coronal 5mm of the implant is critical for functional support during loading. 940PART VII Soft and Hard Tissue RehabilitationABCDE• Fig. . (A) Planning a case in three-dimensional software starts with incorporation of the restorative wax-up into the cone beam computed tomographic image. (B) Implants are then introduced in posi-tions that will support the crowns in their required restorative positions. (C and D) As the cross sections are evaluated in this particular case, it is apparent that there is not enough ridge width for placement of implants in the existing bone. This preliminary view indicates that augmentation of the ridge will be neces-sary for proper implant alignment and support. (E) Evaluation of the actual bony ridge at the time of surgery confirms the previous digital assessment of the bony deficiency. 941CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationBony Defect Morphology Considerations and ClassificationOne of the most dicult components of bone augmentation treatment planning is learning how to predict the amount of bone that will actually be required to develop the proper foundational support that the restorative treatment plan requires. Evaluation of the clinical situation, review of two-dimensional radiographs, assessment of models with restorative wax-ups, and information from CBCT all play a role in determining where bone will be required and how much bone will be needed to successfully graft the site. e concept of determining graft volume is even more important when autogenous bone is incorporated into the regen-erative process. e location of an autogenous bone harvest often determines how much volume of bone can be retrieved. e chin and ramus are the primary sites for signicant donor volumes used in block grafting, but these sites can provide only a limited volume of bone. If these local donor sites are inadequate, bone can be taken at the apex of many osteotomy sites. In addition, the use of a Piezosurgery unit and bone scrapers may be utilized to harvest cortical shavings. (Fig. 36.11)In cases where a previous procedure fails to properly develop adequate bone volumes for ideal implant positioning, reection of tissue over the grafted site will reveal inadequate bony support for the intended implant size and position. At this time, critical deci-sions must be made to prevent the chance of compromising the overall case success because of this shortfall. e easiest solution is to stop and regraft the site, but this causes inconvenience for the patient, embarrassment for the surgeon, and an overall increase in the treatment time and expense. e alternative is to either ignore the deciency, placing the implant in a decient site or attempt-ing supplemental grafting around the exposed implant sur-faces. Implant placement in compromised sites without grafting ultimately limits the implant size or forces improper positioning of the implant in the alternative position. is option then leads to a compromised result and incurs unnecessary risk for future failure. For more experienced surgeons, simultaneous implant placement with additional grafting can be attempted, but this is limited to cases where the surrounding basal bone allows proper implant positioning application of grafting principles. (Fig. 36.12), (Fig. 36.13).Bony Defect ClassificationDetermining if an edentulous site will require augmentation should start with an initial assessment of the bony defect. Careful review of the topography of the recipient site includes review of the bone levels on adjacent teeth, bony protuberances, the depth of the actual defect itself, variations in the vertical height of the remaining walls of the ridge, and the condition of the surrounding soft tissue. A successful graft depends on the passage of various cellular components from the surrounding recipient site’s bony walls and vascular components into the developing graft site. e larger the distance from these bony surfaces to the peripheral graft components, the greater is the challenge for the various cells to migrate to the outer limits of the particulate graft. e surrounding prominent bony con-tours also provide additional support and protection for the graft particles, limiting micromovement that usually results in compromised bone growth. ese xed bony surfaces can also help with containment of graft particles and eventual support of membranes. Depending on the morphology and topography of the defect, the clinician may determine the diculty and potential success of augmentation procedures. e following classication system is based on the bony contours of the de-cient area.• Fig. . This series of cross sections was prepared from a mandible showing a patient who has a very thin overall ridge width throughout the anterior and posterior regions. As this case is considered for aug-mentation, concern should be directed to the potential for graft failure because of the overall discrepancy between the thin basal bone width and the required width for implant positioning. 942PART VII Soft and Hard Tissue RehabilitationBone Defect Classication 1. Depression 2. Concavity 3. Trough 4. Elevation/Prominence 5. Vertical (Height) 6. Buccal & Lingual Cortical Destruction 7. Complex/Multi-Dimensional(Fig. 36.14), (Fig. 36.15).DepressionA simple depression in a potential implant site is a bony defect measuring less than 3.0 mm. If these types of defects are left untreated, they can contribute to either a ridge dehiscence or a fenestration when an implant is placed in the region. ese depressed areas are usually grafted at the time of implant placement and they do not require the use of extensive space maintenance techniques. When a depression is noted, it can ABCDEF• Fig. . Osseous Defects. (A) When evaluating osseous defects, the three-dimensional relationship of bone loss versus adjacent tooth positioning is crucial. (B) Severe vertical resorption requires regeneration to avoid complications with support, esthetics, and poor healing. (C) The position of the adjacent teeth and roots should be evaluated to determine the prognosis of an implant-related restoration. (D) Defects that destroy both the facial and palatal cortical plates limit the choice of regenerative procedures that can be used. (E and F) When there is a sharp declining ridge adjacent to a natural tooth, placement of an implant 1.5 mm away creates a failing situation beginning at time of the initial implant placement. As time passes, both the tooth and the implant will be compromised. Positioning the implant away from the natural tooth can limit this proximity problem; how-ever, the implant body position will be too apical, which affects the esthetics and biomechanics. 943CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationAB• Fig. . Cone Beam Computed Tomography (CBCT) Evaluation of Osseous Defects. (A) The use of interactive treatment planning should be completed to determine any possible bony deficiencies. (B) Three-dimensional CBCT can be used to obtain a better ideal of the bone morphology.AB• Fig. . (A) Evaluation of the clinical appearance of an edentulous space can easily mislead clinicians with respect to the underlying bony contours. (B) Flap reflection reveals a severely resorbed facial aspect of the edentulous ridge.BA• Fig. . (A) Facial and palatal ridge resorption with coronal and apical defects. This will require facial and palatal regeneration. (B) Severe facial resorption with some remaining palatal bony cortical plate. 944PART VII Soft and Hard Tissue Rehabilitationbe covered with a layer of allograft material and covered with a collagen membrane. Long-term isolation of the particles is not as critical in these situations as compared to larger defects where brous in-growth can be catastrophic. Depression type bony defects are the most predictable types of grafts and advanced surgical expertise is not as critical as in other defect types. Concavitye concave shaped ridge defect has a signicant horizontal depression or bony defect in the middle of the ridge that exceeds 3.0 mm in overall depth. ese defects have reasonable remnants of bone surrounding the site that can be used for graft support, containment of particles, and delivery of an adequate supply of cells for angiogenesis. Regeneration in these sites is relatively predictable and most of the implant support will still be pro-vided by the surrounding autogenous bone. A concave defect will require adequate space maintenance for the development of signicant horizontal bony growth requiring the use of a static support system (e.g. bone screws, a titanium supported mem-brane) that is maintained for at least 5 months. (Fig. 36.16A, Fig. 36.16B). TroughSevere ridge defects may on occasion destroy the ridge to the depth of the lingual/palatal cortical plate. ese are most commonly seen in single tooth defects, especially after a traumatic extraction. e resulting defect provides clearly dened lateral walls of bone formed by the roots of the adjacent teeth and most of these sites also have an apical wall of bone that approximates the prior apex of the tooth. Although these are deep and involved defects, they provide protection for the graft components through their actual conguration. Fixation of tenting screws in the middle of these defects assures maintenance of the needed space for regeneration. e presence of four actual bony walls provides a ready source of cellular components and the resulting regenerative potential is excellent. erefore, grafting in these defects can be completed more predictably than a wide and exposed concave defect that requires complex vertical support for development of graft depth, protection from removeable prostheses, and general exposure to micromovement (Fig. 36.17). Elevation/ProminenceWhen ridge defects extend across the span of several teeth, the topography of the lateral and vertical surfaces of potential graft sites can vary signicantly. A horizontal concavity or isolated depression in a recipient site can be complicated by adjacent elevated promi-nences of cortical bone. e maxillary cuspid region would be a typical site where the original tooth extended beyond the surround-ing basal bone. e loss of the cortical plate on an adjacent premolar would be a distinct contrast to the prominent cortical support over a cuspid. Other examples would be changes in the overall facial con-tours created by malpositioned teeth. Situations like this also can develop as various teeth are lost over an extended period of time and the resulting loss of ridge support emphasizes the facial contours of the remaining compromised teeth. Grafting around these promi-nent regions does not require much support in the elevated area, but good space maintenance is needed directly adjacent to the elevated portion of the recipient site (Fig. 36.18). Vertical (Height)Accurate assessment of the vertical ridge height in a potential aug-mentation site is critical from a treatment planning standpoint. As the vertical defect height is increased, the crown-implant ratio becomes problematic with respect to esthetics and biomechani-cal factors. Regeneration of vertical height is a complex grafting procedure and that is usually reserved for clinicians with advanced experience and skills in complex soft tissue manipulation. A true vertical defect is in essence a through and through defect with the loss of both cortical plates. ese defects will require that the concept of space maintenance be moved into a 3rd dimensional skill. A thin sharp-edged ridge top is usually present, with two dense cortical surfaces approximating each another with little to no medullary component between them. e resulting surface area requiring regeneration involves the palatal/lingual aspect, the vertical height defect region, and the highly resorbed facial/buccal portion of the ridge. e limiting factor with these types of defects is the level of the bone on the interproximal aspect of the adjacent A B• Fig. . (A). Concave Ridge Defect: This ridge has multiple contours to the generalized horizontal defect. There is an angular coronal defect at the top of the ridge, as well as a serious apical defect that leaves a large region that will need to be regenerated. (B). This Concave defect requires significant support for the membrane to regenerate adequate bone in the deeper portions. 945CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationBCA• Fig. . Trough Defect Type: (A) 3D CBCT image demonstrating the loss of interproximal bone. This will greatly limit development of adequate height of the interproximal papilla in the final restoration. (B and C) Three-dimensional and clinical images of severe horizontal defect with loss of bone on adjacent teeth. There is still fairly good vertical height of the palatal cortical plate.• Fig. . This ridge defect has a complex nature to its topography. The prominent portions of the facial aspect of the ridge will help with sup-port and regenerative components to the more compromised adjacent areas. Careful evaluation of the remaining surfaces demonstrate examples of other defect types.MMII III IVVVI252015105Anterior Mandible• Fig. . Vertical Ridge Defect Type: Lower anterior complex ridge defect with serious vertical component that destroyed both the facial and lingual cortical plates. The precipitous vertical drop in bone height from the inter-proximal tooth bone to the base of the defect requires correction of the verti-cal defect for reasonable implant placement and esthetics. Placement of an implant in the middle of the depressed region would still involve a horizontal deficiency. Preservation of the bone levels on the adjacent teeth is a priority. 946PART VII Soft and Hard Tissue Rehabilitationteeth. Clinicians must understand that it is not possible to raise a ridge higher than the adjacent bony level. In complex cases, this limitation can often require removal of an adjacent tooth to pro-vide a higher adjacent interproximal height for potential vertical development. is is most often seen in anterior areas of the max-illa and mandible where the aesthetic demands of a case require as much vertical regeneration as possible (Fig. 36.19). Buccal/Lingual (Palatal)Ridge assessment must include a three-dimensional review of the bony resorption on the lingual/palatal aspects as well as on the facial and vertical regions. Severe ridge defects can often include a signicant lingual/palatal component that moves the regenerative procedure into a complex surgical category. e most common site for a true “Hour Glass” ridge defect is in the anterior portion of the maxilla or mandible. Unfortunately, these sites are techni-cally challenging with respect to tissue release, space maintenance, and graft containment. In general, the palatal tissue is very thick and dense, limiting any signicant stretching or expansion of tis-sue over a graft and membrane. For example, the lingual tissue in the mandible is paper-thin and procedures to release and extend lingual tissue over a graft has a potential for button-holing a ap or for potential complications in the region of vessels, salivary components, and muscle attachments. Fixation of tenting screws in palatal defects requires extensive reection of the palatal tissue and accurate anchorage of the membrane beyond the borders of the bony defect. Membrane xation on the lingual aspect of the mandible is a delicate process and awareness of the vital structures if critical. Regeneration in these sites is limited to clinicians with extensive surgical and bone grafting experience (Fig. 36.20 A, B). Complex/Multi-DimensionalComplex ridge defects are made up of a combination of the con-gurations described above. ese sites will more than likely have deep horizontal destruction that is combined with at least one vertical component. ese type of defects vary from a severe single tooth site to a complete section of a quadrant. It is the recognition of the complexity of these situations that is critical for success. e sheer volume of bone that needs to be regenerated can only be determined with advanced integration of 3D Imaging and CBCT surveys. e restorative requirements then dictate the actual loca-tions for implant support and subsequently the areas where spe-cic volumes of bone will be need to be regenerated. At that point, the specic technique can be chosen by its potential for devel-opment of large volumes of bone. ese cases require harvesting signicant volumes of autogenous bone and use of isolating mem-branes capable of separating the developing graft sites from soft tissue inltration. Complex cases should be avoided until a clini-cian has extensive experience in development of bone in each of the basic situations described above (Fig. 36.21). AB• Fig. . Hour-glass Ridge Defect: The images in examples (A) and (B) demonstrate the destruction of the facial and palatal cortical plates. Regeneration in these sites will require growth in both dimensions. Failure to regenerate the palatal portion of the site will lead to facial positioning of the implant and most likely, a facial bony deficiency.A B• Fig. . Complex Ridge Defect: The images in (A) and (B) demonstrate the severity of bone loss that can occur over time and in highly destructive situations. These defects require advanced training and experience for predictable grafting success. 947CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationSoft Tissue ConsiderationsPatient-to-patient comparisons of the soft tissue drape surround-ing the natural teeth often demonstrate signicant dierences in color, surface consistency, tissue thickness, and overall esthetics. is is emphasized when a very thin and friable tissue drape sur-rounds an anterior tooth. Dierentiation of patients into either a “thick biotype” or a “thin biotype” is a critical tool that should be used during routine restorative care and anterior implant–related treatment planning. Cook etal.10 demonstrated the simplest way to determine a patient’s tissue biotype is through the evaluation of the visibility of a periodontal probe in the sulcus of an anterior tooth. A patient with a thick biotype will not show any translucence of the probe through the sulcular tissue. In contrast, a thin biotype will allow visualization of the coloration of a probe through the sulcular tissue.10A patient with a thick biotype has tissue with a robust pink stippled appearance. is dense tissue drape forms a thick layer of tissue that is very forgiving when dental restorations are placed around natural teeth and when dental implants are involved. e thin biotype patient, however, presents a much more dicult challenge. ese patients often have a thinner labial plate thick-ness, a narrower keratinized tissue width, and a greater distance from the cement-enamel junction to the initial alveolar crest. is delicate layer of tissue is so thin that the periodontal probe can be visualized when it is lightly placed in the sulcus. Patients with a thin biotype are also more prone to tissue recession, complicating the predictability of restorative esthetics around anterior teeth. As teeth migrate out of position or rotate in the arch, the prominence of the roots can increase, complicating the soft tissue situation even more. in layers of tissue around the maxillary anterior teeth require meticulous planning to hide underlying crown mar-gins (Box 36.4 and Fig. 36.22).Patient biotype and bony architecture must be considered early in all implant treatment planning to avoid a variety of issues that become very complex compared with similar situations around natural teeth. is early planning allows the surgical team the opportunity to incor-porate tissue grafting into each surgical stage, allowing deciencies to be avoided or to at least be minimized. ese problems can be sig-nicantly complicated when major bone grafting has been completed in the region, resulting in elevation of the mucogingival junction and repositioning of the mucosa into the zone surrounding implant restorative margins. e tissue thickness in postoperative graft sites is often very thin, and development of an adequate emergence prole for crowns requires development of at least 3 mm of keratinized tis-sue thickness over the top of the implant body prior to restoring the implant. Restorative dentists often nd it dicult to mask the dark tones in the coronal portions of natural teeth with endodontic-related color changes. is problem is compounded in a patient with a thin biotype as the color passes through the thin facial bone and thin tis-sue consistency. is problem with translucence is a reoccurring issue with implant restorations. Problems related to the translucence of the dark hue of the implant body and the abutment through thin tis-sue can signicantly complicate the esthetics surrounding the nal restoration.11 A patient with a thick biotype and thick facial cortical • Gingival biotype • Width of keratinized tissue • Soft tissue thickness • Vestibular depth • Smile Line • Frenum attachments • BOX 36.4 Soft Tissue Evaluate and Assessment ConsiderationsADEBC• Fig. . (A) Thin biotype exhibiting metal show-through. Tissue biotype can be defined by the trans-lucence of a probe through the sulcus. (B) Thick biotype yellow probe (i.e., no-show through). (C) Thick biotype with dark probe (i.e., no show-through). (D) Intermediate biotype with visible probe through sulcular tissue (i.e., show-through). (E) Thin biotype with probe (i.e., show-through). 948PART VII Soft and Hard Tissue Rehabilitationbone makes an ideal implant patient when restorations are placed and minor deciencies can be hidden behind the thickened tissue mass. A patient with a thin biotype does not usually have a robust facial bone thickness, and any remodeling changes in facial bone density or thick-ness can greatly alter the restorative esthetics (Fig. 36.23).Additional problems related to tissue thickness develop in implant cases as time passes and bony changes occur around the implant body. Esthetics around an implant restoration often change because there is an active bone remodeling pro-cess around implants that often results in a loss of facial cor-tical thickness. is can be a serious problem if an implant is placed in a site with very thin facial bone or in a site where the quality of bone lateral to the implant resorbs as the prosthesis is loaded and the functional forces are centered on the coronal 5 mm of the implant body. If recession or slight bone loss occurs, the facial aspect of the implant can be exposed, creating a dark hue that shows through the overlying tissue and contributes to a poor esthetic situation.As anterior immediate implants are considered, recommenda-tions for the actual location of the implant in the socket have changed signicantly as resorptive patterns in immediate implants have been studied over time. An immediate implant currently should be placed signicantly palatal to the facial cortical plate to allow for bone remodeling. is paradigm shift has occurred over time as the rec-ommendations for implant diameters in anterior spaces have steadily decreased to accommodate for these changes in facial bone thickness and complications related to color translucence through the soft tis-sue. Current recommendations specify that the facial aspect of the implant body should be placed at least 3 mm palatal to the inner edge of the facial cortical plate. Additional authors currently recommend grafting on the facial aspect of anterior immediate implant sites with bovine particulate grafts and connective tissue graft to minimize long-term changes.When a clinician is preoperatively aware of a problem related to tissue biotype, it is possible to plan ahead procedurally to maintain or possibly change the biotype, leading to optimal esthetic out-comes. Patients with a very thin biotype can be evaluated for intra-operative supplementation using connective tissue grafts and facial bone grafts to create a more forgiving tissue drape over the implant site. Because thicker cortical bone volumes promote thicker bio-types, the bony architecture and soft tissue drape may be modi-ed in an esthetic zone before implant placement and restoration. Advance planning also provides the implant team an opportunity to inform the patient about these issues and to point out potential esthetic complications before commencing treatment. Any com-promise in a patient’s expectations must be addressed, especially if the patient is not interested in grafting to modify the tissue type.Implant restorative care in thin biotypes often requires tis-sue augmentation as the case ages to create a thick, dense layer of brous tissue over the implant body and any deciencies involving the adjacent natural teeth. Connective grafting procedures are read-ily available to increase the thickness of the tissue drape in situations such as this. Subepithelial connective grafting procedures may use palatal connective tissue, dense connective tissue from the maxillary tuberosity, or acellular dermal matrix (i.e., OrACELL [Salvin Den-tal Specialties], AlloDerm [BioHorizons IPH, Inc.], PerioDerm) as the source of donor tissue. A thick layer of connective tissue is inserted into the decient regions with tunneling procedures, allow-ing the repositioned tissue ap to provide the blood supply to the developing graft site. e use of the subepithelial approach allows the implant clinician to produce a nal tissue tone and color that matches the adjacent natural tissue (Fig. 36.24A, B and C).ABC• Fig. . Tissue Biotypes. (A and B) Thick biotype. (C) Thin biotype. 949CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationLarge edentulous regions in the posterior portions of both arches often have little, if any, remaining keratinized tissue. ese decient regions can be augmented “before” the bone grafting procedure using “free tissue grafting techniques.” In these cases, the epithelial layer of the palate is used as the source of the donor tissue. is usually creates large zones of thicker keratinized tissue with a distinct pinkish white color, duplicating the color of the tissue where the graft was harvested. is dense tissue is not always acceptable from an esthetic standpoint when it is placed in the anterior maxilla. Some of this color issue can be reduced by taking the graft from the posterior portion of the vault of the palate, away from the rugae found in the anterior palate. Use of thinner palatal grafts can also limit some of these annoying color issues. It is still important to keep in mind that the actual “thickness of the tissue” is important in the development of an emergence prole for the nal restorations. At least 3 mm of tissue thickness is needed for not only this emergence pattern but is also important from the standpoint of implant health as the implant is restored and maintained.e importance of the depth of soft tissue above the platform height has been described by Linkevicius etal.12 in respect to maintenance of crestal bone height. Implants with less than 3 mm of tissue height over an implant were shown to be suscep-tible to crestal bone loss. e authors compared both regular root form implant and platform switch designs, and all implants were shown to be susceptible to this specic soft tissue related bone loss.12Most anterior treatment plans involving major bone-grafting today incorporate the addition of layers of connective tissue, allograft, or bovine graft particles with membrane coverage to limit excessive bone remodeling in these critical regions. ese concepts are critical in “immediate implant” cases, where many cases require both soft tissue and hard tissue supplementation.Augmentation and implant treatment planning should include a careful assessment of any frenum attachments that could inter-fere with the grafting process. Grafting in regions where there is still a highly placed frenum can be compromised during the healing phase when remnants of the frenum place tension on the closed incision line, contributing to incision line opening. e maxil-lary frenum should routinely be removed if it appears to be prob-lematic for future tissue health. e lower frenum and lateral frenum attachments can create a similar tension eect, but the routine perios-teal release incision in these graft sites usually eliminates this particular problem in most cases (Fig. 36.25). Guided Bone Regeneration ProtocolRegeneration of bone in a specied area requires that a protected zone be created where the development process can be completed with-out interference. Block grafting and other approaches have previously been described for development of signicant amounts of bone regen-eration in appropriate sites. is chapter describes various protocols that use the principle of “space maintenance and tissue exclusion” for dened bone development. One of the most important components of the GBR process is space maintenance via the use of barrier mem-branes. Dahlin etal.13 and many other authors have described the ACB• Fig. . Soft Tissue Augmentation over the facial aspect of an implant site with “grey tone” to the overlying soft tissue. (A). Grey coloration over the facial of the implant site. (B) A connective tissue graft is drawn into a tunnel prepared over the facial of the implant site. (C). The final restoration in place following the successful grafting procedure. 950PART VII Soft and Hard Tissue Rehabilitationdevelopment of new bone growth using membranes that contained grafts materials, allowing only neighboring bone or bone marrow cells to migrate into the bony defect, without ingrowth of competing soft tissue cells from the overlying mucosa.In general, membranes are used in GBR procedures to act as biological and mechanical barriers, preventing the invasion of non–bone-forming cells (e.g., epithelial cells), whereas slower-migrating bone-forming cells are drawn into the defect sites.14 As bone defects heal over time, there is a competition between soft tissue ingrowth and slower action bone-forming cells that are trying to migrate into the area. Soft tissue cells tend to migrate at a much faster rate than bone-forming cells and if left unchecked, they will inltrate the developing site. erefore the primary goal of barrier membranes is to allow for selective cell repopulation and to guide the proliferation of various tissues during the heal-ing process.15 Below the protective membrane, the regeneration process proceeds with angiogenesis and migration of osteogenic cells into the site. is initial blood clot is replaced by woven bone after vascular ingrowth, and later is transformed into load-bearing lamellar bone. is ultimately assists in the support of hard and soft tissue regeneration.16 If a barrier membrane is not used, the bony defect will ll in with soft tissue, resulting in compromised bone growth (Boxes 36.5 and 36.6).In the following guided bone regeneration protocol, there exists nine distinct steps for successful and predictable outcomes; 1. Incision and Flap Design 2. Flap Reection 3. Removal of Residual Soft Tissue 4. Recipient Bed Preparation 5. Tissue Release 6. Membrane Placement 7. Space Maintenance 8. Bone Graft Placement 9. ClosureStep 1: Incision and Flap DesignIncision design is one of the keys to a predictable regenera-tive result. Ideal incision designs provide complete access to the surgical site without compromising the integrity of the ABDC• Fig. . (A) High frenum attachment. (B to D) Removal of frenum and placement of healing abutment.Primary closureAngiogenesis for necessary blood supply and undifferentiated mesenchymal cellsSpace maintenance/creation to facilitate adequate space for bone ingrowthStability of wound to induce blood clot formation • BOX 36.5 “PASS” Principles for Predictable Bone Regeneration69Woven bone = 60–100 μm/dayLamellar bone = 1 μm/dayFibrous tissue = 1000 μm/day (1 mm/day) • BOX 36.6 Growth Rates of Soft Tissue Versus Hard Tissue 951CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationsurrounding tissue. As the incision is planned the anatomy of the adjacent papilla must be considered to prevent any dam-age that will compromise the esthetics and function of the tis-sue postoperatively. e patient’s biotype and the amount of keratinized tissue is always reviewed, and any deciencies in attached tissue must be accounted for in the incision design. e incision must be planned in a way that keeps incision lines away from critical regions where graft particles or blocks could become exposed. Observation of sound surgical principles in preparation of incisions is critical for maintenance of the blood supply to all of the involved tissues. Wide-based incisions are always important to prevent interruptions in the vascular sup-ply to the ap.Failure to properly plan the incision design of a ap during grafting can pose numerous issues, mainly related to incision line opening postoperatively. Incision line opening exposes the regen-eration site to an inux of oral pathogens, soft tissue ingrowth, and loss of the graft materials that were intended to be isolated during the maturation process (Fig. 36.26A, B and C and Box 36.7).e coronal incision is usually placed on the crest of the ridge, favoring a location closer to the palatal aspect if pos-sible. It is important that the scalpel make a continuous full-thickness cut through the tissue and the periosteum, ending on the actual bone. Incisions that are irregular and leave regions of attached tissue and periosteum will lead to maceration of the ap as it is reected. is shredding of tissue also compromises the periosteal layer that is the primary source for blood to the underlying bone. A survey of the available keratinized tissue must be completed before making an incision. In regions of bountiful attached tissue, the surgeon can use his discretion in the location of the incision through the keratinized regions. In regions where the keratinized tissue is limited, the incision should at least “split” the distance between the two edges of the keratinized tissue. It is always best to try to keep incision lines away from areas that are key to regenerative volume and protection (Fig. 36.27A,B, C, D).When possible, the papillae should be preserved while inci-sions are prepared. If there is a good papilla adjacent to a graft site, the incision should be designed to avoid involvement of the papilla or it should be moved to the adjacent interproxi-mal space. If the papilla is absent or is at, the incision can be directed to the root approximating the graft or it can be moved to the adjacent space. It should be kept in mind that regeneration of a compromised interproximal papilla is still one of the most dicult endeavors in soft tissue surgery today. An incision in the middle of an anterior space of a “thin bio-type” patient can either permanently scar the region or can completely destroy the papilla form and esthetics in the nal restoration.e positioning of vertical releasing incisions is one of the most important parts of the incision. A broad-based releasing incision should be prepared to maintain the blood supply to the ap and to allow elevation, retraction, repositioning, and suturing without tension. It should be kept in mind that most graft sites have a compromised soft tissue component that becomes a greater issue as the complexity of the underlying architecture increases. Most of these sites have a minimal keratinized band of tissue at the crest of the ridge, tapering quickly to the mobile mucosa of the vestibule. Full-thickness vertical release incisions should generally be planned to extend to the apical portion of mucogingival junc-tion. In larger bone graft sites the vertical release will often extend deeper into the vestibule to help with complete release of the ap ABC• Fig. . Incision Design. (A) Ideal crestal incision when adequate attached tissue is present. (B) Crestal or more lingually placed incision that preserves the limited amount of keratinized tissue. (C) Crestal full-arch incision designed to preserve the limited facial zone of keratinized tissue. • Consideration of tissue biotype as incision is planned • Maintain ideal papilla forms and levels • Preservation and utilization of keratinized tissue in region • Maintain the integrity of the full-thickness flap during reflection • Design of lateral releasing incisions in locations that minimize exposure of graft particles • Maintaining wide-based incisions to provide adequate blood supply to flap • BOX 36.7 Principle Concepts to Be Practiced in Grafting Incisions 952PART VII Soft and Hard Tissue Rehabilitationduring a tension-free closure. e location of vertical releases should be moved away from the most critical zones of the graft, limiting encroachment of the incision closure on the bulk of the graft particles and membrane margin. is is very important in cases where the barrier membrane is nonresorbable and exposure of a margin of the membrane can contribute to graft failure. In those cases, it is best to completely move the release to a com-pletely dierent interproximal space. Properly placed incisions will position the margins of the ap over host bone instead of the graft particles and the membrane (Figs. 36.28 A and B). Vertical incisions have been related to scar formation in the surgical sites after healing. Most scars are related to irregular incisions and poor adaptation of the wound edges at the time of suturing.e goal of any implant treatment plan would be placement of restorations in the middle of a zone of attached keratinized tissue that is at least 3 mm thick from the level of the platform of the implant to the margin of the tissue surrounding the implant. Few resorbed ridges have an abundance of keratinized, and in most situations the surgeon will need to incorporate development of a thick tissue zone that will provide an emergence prole for the restoration and protection of the implant-bone interface. As the incision is prepared, the keratinized tissue dictates the path of the ABC D• Fig. . Design for Papilla Preservation. (A and B) Ridge incision, making sure to “score” the bone to obtain full-thickness flap; (C and D) incision continued to include a vertical release.AB• Fig. . Papilla-Sparing Incision. (A) Initial incision. (B) Full-thickness reflection. 953CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationincision line and often determines how easily the wound will be to close and to withstand the strain on the incision line during heal-ing. If adequate attached tissue is not present, soft tissue grafting should be completed either before the augmentation procedure, as a portion of the grafting protocol, or after the implants are placed. Tissue development options include autogenous free tissue grafts, autologous connective tissue grafts, acellular dermal matrix (Allo-Derm, OrACELL), or combinations of Mucograft and soft tissue grafts. In addition, when inadequate keratinized tissue is present, the incision should be placed toward the lingual portion of the remaining keratinized tissue, preserving as much attached tissue on the facial as possible. is allows for greater resistance to mus-cle pull and will decrease incision line opening (Fig. 36.29 A and B) (Fig. 36. 30). Step 2: Flap Reflection and Site PreparationFull-Thickness ReflectionElevation of the tissue to expose the recipient site requires reection of a full-thickness mucoperiosteal ap. is should be completed in an uninterrupted release of the ap that includes the surface mucosa, submucosa, and periosteum. is initial release is accomplished with an angled curette or a scalpel that is used to score the bone, ensuring complete penetration through the tissue layers and the periosteum. As the tissue is reected, the underlying bone should be “scraped” with the curette or periosteal elevator in a side-to-side motion. It is important to conrm at this stage that the complete ap has been freed from the bone and that it is freely drawing away from the bony surface. Partial-thickness reection leads to tissue trauma or shred-ding of the ap itself. Tissue that has been compromised in this man-ner results in slower healing and a higher morbidity. When using a periosteal elevator (i.e., 2–4 Molt) for this ap release, the edge should always rest on the bone to prevent tearing through of the tissue ap.e tissue thickness on the lingual aspect of the mandible is very thin and friable. is tissue can be easily torn during reec-tion of the ap and manipulation of the tissue during the graft-ing procedures. Resulting “buttonhole” openings compromise the blood supply to the surrounding tissue that is needed for coverage over the graft site, leading to compromised results postoperatively. Tearing or buttonholing the lingual ap may also expose the graft site and increase the possibility of margin necrosis coronal to the tear. is exposure may lead to a total graft failure (Fig. 36.31 A and B).If the lingual ap is torn during the procedure, it can some-times be repaired using 5–0 chromic suture, approximating the edges of the tear and preventing tension on the weak site. It is rec-ommended to use a collagen membrane below these fenestrations to assist with healing and to isolate the graft materials. Mainte-nance of the blood supply to the tissue ap is important, requiring that all tension on the ap be minimized.A ap covering a graft that does not have complete release of pressure on the two margins of the ap will often pull open dur-ing the healing process (incision line opening). Tension on the ap compromises the blood supply to the tissue along the suture line that is under pressure. is pressure leads to necrosis and even-tual separation of the two edges of the ap closure. Once this has occurred the ap cannot be sutured back into place, and the graft site is open for contamination and tissue ingrowth. e success of bone grafting is largely dependent on the maintenance of space for bone development and isolation of the graft particles during the slow process of osteogenesis. Soft tissue ingrowth, bacterial contamination, and migration of graft particles predictably com-promise regenerative results.A B• Fig. . Alternative Release Incisions. (A) The vertical releasing incision is often moved laterally to the adjacent papilla space to obtain adequate access. This will minimize incision line opening when larger graft volumes are obtained. (B) Extending the incision to an adjacent tooth also minimizes the possibility of the incision over top of the graft site.• Fig. . Poorly Placed Release Incision. The incision should be posi-tioned away from the graft site and also be more lateral to obtain a more broad-based flap design. 954PART VII Soft and Hard Tissue Rehabilitatione typical graft site requires that the overlying ap be released enough for extension of the ap at least 5 mm beyond the edge of the adjacent margin for a tension-free ap closure. e only way to achieve this free ap release is complete release of the periosteal layer, allowing the elastic bers of the underlying ap to stretch as the ap is drawn over the graft site. Step 3: Removal of Residual Soft Tissue and PathologyBefore bone grafting, all evidence of soft tissue remnants should be eradicated. Soft tissue bers left on the recipient site can limit proper attachment of the newly regenerated bone to the underly-ing basal layer. ese brous tissue remnants are the same tissue that the barrier membrane is attempting to exclude from the site. Early brous tissue growth in the wound simply bypasses that crit-ical barrier and starts fresh tissue development right in the center of the graft site (Fig. 36.32 A and B). Step 4: Recipient Bed PreparationPreparation of the recipient site for an augmentation is very important in the development of a healthy ridge. e recipient site is usually covered with a dense layer of cortical bone that does not easily provide a blood supply to a developing graft. e process of decortication of the recipient base is used to open multiple pathways through this thick layer of bone. ese pilot holes create an open pathway to the underlying trabecular bone where blood ow into the graft site will increase revasculariza-tion (angiogenesis) and introduce bone growth factors into the graft site.17 e decortication is usually accomplished with the use of cross-cut ssure burs or small, round burs that are used to perforate the cortical plate. Copious amounts of chilled saline should be used to prevent thermal trauma (Fig. 36.33 A and B).e decortication process initiates the regional acceleratory phenomenon, which describes the cellular stimulating technique used to accelerate the healing rate of a graft site. In this process, bone decortication is used as a “noxious stimulus,” and it has been shown that the healing rate of a graft site can be increased 2 to 10 times the normal healing rate by initiating the regional accel-eratory phenomenon (RAP).18 is acceleration is accomplished by the introduction of platelets to the area that ultimately release growth factors including platelet-derived growth factor (PDGF) and transforming growth factor (TGF). Ultimately the decortica-tion process will lead to better integration of the graft to the host bone. AB• Fig. . Lingual Flap Design and Exposure. (A) The lingual should be reflected to expose the entire lingual surface; however, care must be exercised not to tear the flap. Perforating or a buttonhole in the flap will compromise the graft site. (B) If this occurs, it is very difficult to mend the tear, potentially compromis-ing the closure of the graft site or predisposing the region to incision line opening over the healing graft. Incision line opening leads to an increased morbidity of the graft site.A B• Fig. . (A and B) Removal of fibrous/soft tissue with course barrel bur. 955CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationStep 5: Tissue ReleaseSuccessful augmentation procedures require maintenance of an intact tissue closure along the incision line during the healing pro-cess. One of the most common surgical complications that clini-cians will experience early in their learning curve is incision line opening. e failure of maintaining this tissue union is directly related to an inadequate release of tension on the tissue ap as it is stretched over the widened graft space. Clinicians will nd that it is highly unlikely to pull a tissue ap over any sizable graft site without rst altering the integrity of the ap itself.e most important concept in augmentation procedures is total membrane coverage of grafting materials from the time of membrane placement to completion of the graft maturation pro-cess. Success is directly related to the overall management of the soft tissue ap during ap closure. A successful case starts with the incision and continues with proper ap reection of an intact periosteal layer, proper membrane positioning, and completion with a tension-free ap closure.Tissue Release TechniqueExamination of the exposed inner surface of a reected ap will reveal a smooth, shiny layer of the periosteum. e periosteum is composed of a thin, rm layer of dense tissue that has no elastic bers. is binding layer limits any signicant elongation of the ap as it is stretched over a graft site. A shallow incision through the dense tissue “releases” the tight band of pressure on the under-lying tissue ap. e tissue directly below the periosteum is pri-marily composed of elastic-type bers, and once the periosteum has been released, the entire ap can be stretched. is simple releasing incision ultimately allows tension-free closure over the graft site (Fig. 36.34 A B and C) site (Fig. 36.35 A and B). Step 6: Membrane Selection and PlacementBarrier membranes are generally used in guided bone regen-eration procedures to act as biological and mechanical barriers against the invasion of brous tissue into the developing graft site. e membrane also will allow for the migration of the slower-migrating bone-forming cells into the defect sites During the bone regeneration process, there is a competition between soft-tissue and bone-forming cells to invade the surgical site. In general, soft-tissue cells migrate at a much faster rate than bone-forming cells. erefore, the primary goal of barrier membranes is to allow for selective cell repopulation and to guide the pro-liferation of various cells during the healing process. Below the protection of the membrane, the regeneration process is allowed to continue unchecked with early angiogenesis and migration of osteogenic cells. e initial blood clot is replaced by woven bone after vascular ingrowth, which later is transformed into load-bearing lamellar bone. is will ultimately support the hard- and soft-tissue regeneration. If a barrier membrane is not utilized, lack of isolated space maintenance will result in soft-tissue inte-gration and compromised bone growth.Types of MembranesMembranes are typically classied as resorbable or nonresorbable. Nonresorbable membranes have included titanium foils, expanded polytetrauoroethylene (e-PTFE), and dense polytetrauoroeth-ylene (d-PTFE) with or without titanium reinforcement. Resorb-able membranes are typically made of polyesters (e.g., polyglycolic acid, polylactic acid) or tissue-derived collagens (e.g., AlloDerm GBR, Pericardium, Ossix Plus). Non-resorbable membranes are bio-inert materials and require a second surgical procedure for removal after bone regeneration is complete. Resorbable mem-branes are naturally biodegradable and have varying resorption rates. However, all membranes, non-resorbable or resorbable, dif-fer in their biomaterial and physical characteristics. ese varied characteristics can often be associated with advantages and disad-vantages in various clinical situations (Box 36.8).Non-Resorbable Membranes. Non-resorbable membranes exhibit excellent biocompatibility, superior mechanical strength, increased rigidity, and generally achieve more favorable space maintenance than unsupported resorbable membranes. How-ever, wound dehiscence is more common with non-resorbable membranes, and these membranes have the disadvantage of the need for a second surgery. is second procedure can result in an increased morbidity, higher costs, and over-all patient discomfort. e most common types of non-resorbable membranes include polytetrauoroethylene (PTFE) and titanium mesh. a. Expanded PTFE membranes — e expanded PTFE mem-brane (e-PTFE) was the rst type of membrane used in implant dentistry and was the gold standard for bone regeneration in the 1990s. e e-PTFE membrane was advantageous as it pre-vented broblasts and connective-tissue cells from invading the BA• Fig. . Host Site Decortication. (A) The host site is prepared with a tapered cross-cut fissure bur (e.g., 169 L) to initiate angiogenesis. (B) The decortication must be deep enough to initiate bleeding, thus allowing blood vessels into the area (i.e., angiogenesis). 956PART VII Soft and Hard Tissue Rehabilitationbone defect, yet they allowed the osteogenic cells to repopu-late the graft area. e most common e-PTFE membrane in implant dentistry was GORE-TEX® (W.L. Gore & Associates, Inc.; Flagsta, Ariz.).e two sides of e-PTFE membranes were composed of dif-ferent layers. One side was approximately 1 mm thick with 90 percent porosity, which impeded the growth of epithelium; e other side was approximately 0.15 mm thick with 30 percent ABC• Fig. . Tissue Release Procedure. (A) Adequate flap release around bone graft sites is the most criti-cal step for tension-free flap closure and predictable graft success. (B) A single shallow incision through the periosteum is prepared inside the flap while maintaining tension from elevating the flap. (C) The clear separation of the periosteal edges as the flap is extended and the elastic fibers allow the flap to stretch (i.e., tension-free).AB• Fig. . Extended Periosteal Release Procedures. (A) The incision may be extended on the mesial and distal aspect of the graft site to allow increased mobility of the flap when it is extended. (B) After blunt dissection of the periosteal release with scissors (i.e., scissors should be parallel to the flap), the flap can be freely extended over the graft site. This release must be completed until the flap can be repositioned at least 5 mm beyond the lingual aspect of the graft site. 957CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationporosity, which provided space for new bone growth and lim-ited brous tissue ingrowth.19e e-PTFE membranes had a high incidence of exposure, thereby resulting in an increased infection rate because of the ingrowth of bac-teria into the highly porous structure. Additionally, the porous struc-ture, with an approximate pore size of 5–20 micrometers, allowed for soft-tissue ingrowth, leading to increased diculty in removal. b. High-density PTFE membranes — Because of the associated complications of e-PTFE membranes, a higher density material — less than 0.3 microns — was developed in the early 1990s under the name Cytoplast™ (Osteogenics Biomedical; Lubbock, Texas). is high-density PTFE (also termed dense PTFE or d-PTFE) has been shown to have a lower risk of bacterial colonization in comparison to e-PTFE membranes, therefore resulting in fewer infections. e high density and small pore size of the membrane prevents passage of bacteria through the membrane, while allowing oxygen diusion and passage of small molecules. Because of the lack of tis-sue ingrowth into the 0.3 micron pores, d-PTFE membranes are much easier to remove. Clinical use of d-PTFE has demonstrated that localized membrane exposure does not always dictate failure of the developing graft. If the d-PTFE membrane can be main-tained for at least 6 weeks, removal at that time or later will often be followed with development of a reasonable bony ridge. (Fig. 36.36). c. Titanium-reinforced PTFE membranes — e addition of a Titanium strut to a PTFE membrane allows the membrane to be shaped into a form that will develop bone in the con-tour and volume required by the restorative plan. ese types of membranes are especially useful in the treatment of large os-seous defects where varied thicknesses of bone are dictated by an irregular recipient topography. Studies of GBR procedures using titanium-reinforced nonresorbable membranes have shown great success with horizontal and vertical alveolar ridge augmentation because of their ability to maintain space, mini-mize graft mobility, and exclude soft tissue ingrowth.20–24 (Fig. 36.37 ) (Fig. 36.38). d. Titanium Mesh Titanium mesh is a non-resorbable barrier that has been shown to be eective in maintaining space with-out collapsing. Titanium foils are exible and can be bent and manipulated to mold around a bony defect. Titanium mesh has demonstrated predictable biocompatibility and features holes within the mesh that allow for maintenance of the blood supply from the periosteum. e primary disadvantage of tita-nium mesh is related to an increased incidence of wound dehis-cence’s and overall diculty in maintaining soft-tissue coverage during the lengthy healing process. Exposure of the mesh may lead to an increased rate of infection and patient discomfort, leading to early removal of the mesh. Resorbable Membranes. Resorbable membranes exhibit the advantage of no second-stage surgery for removal, thus decreas-ing discomfort and morbidity to the patient. However, the draw-backs of collagen include an unpredictable resorption time, which may adversely aect the amount of bone formation. Resorbable membranes derived from xenogeneic collagen for use in GBR pro-cedures are the most popular membranes utilized in implant den-tistry today. e various types of resorbable membranes include collagen, pericardium, and acellular dermal matrix.Resorbable collagen membranes consist of either type I or type III collagen from bovine or porcine origin. Collagen membranes are easy 1. Tissue compatibility — Ideally, the membrane should be biocompatible, resulting in no inflammation or interaction between the membrane and the host tissue that could lead to wound dehiscence or a local infection. 2. Space maintenance — The membrane should have a generally firm consistency to help maintain the regenerative space and to prevent loss of the defined ridge shape required by the restorative plan. 3. Stabilization of the blood clot — The membrane should provide stabilization of the blood clot, allowing the regeneration process to progress and reducing connective tissue integration into the defect. 4. Cell Occlusiveness — The porosity of the membrane should prevent fibrous tissue from invading the graft site. A larger pore size may inhibit bone formation by allowing the in-growth of faster-growing soft tissue cells. When the pore size is too small, limited cell migration inhibits collagen deposition and ultimately contributes to poor graft development. 5. Mechanical Strength — The membrane should have high durability and mechanical strength to protect the blood clot and resist passage of unwanted cells and bacteria. This same material strength is important when the membrane is tacked to the apical portion of the recipient site. A fragile membrane can easily tear around the fixation tack, releasing the anchorage of the membrane. 6. Predictable resorption rate — The resorption time of the membrane should coincide with the regeneration rate of bone tissue. The continued presence of the membrane is dependent on the location of the graft, the available vascularity in the region, and the quantity of graft material. 7. Easy to modify and manipulate — The membrane should be capable of size and shape alteration while maintaining adequate stiffness to prevent collapse into the graft site. • BOX 36.8 Ideal Barrier Membrane Characteristics• Fig. . D-PTFE membrane with titanium reinforcement depicting space maintenance principle, which allows for angiogenesis and the bone regeneration to progress. (Image adapted from Osteogenic Biomedical).• Fig. . Polytetrafluoroethylene (d-PTFE) Membrane. Clinical view of d-PTFE membrane. 958PART VII Soft and Hard Tissue Rehabilitationto manipulate and have favorable eects on coagulation and wound healing, variable cross-linking, low antigenicity and high tensile strength.25 Additionally, they inhibit epithelial cells, promote the attachment of connective-tissue cells, and increase platelet aggre-gation, which leads to wound stabilization and increased healing.Collagen constitutes over 50 percent of the proteins in the human body. As the collagen membrane is degraded through enzy-matic reactions, the process resembles normal tissue turnover.26–33 Today, most collagen membranes are derived from allogenic or xenogeneic sources, which have become popular in implant den-tistry. ey act as scaolding for osteoconduction, increase plate-let aggregation and stability of clots, and allow for the attraction of broblasts for healing. Collagen membranes are manufactured with a variable resorption rate, which occurs through inamma-tory cell biodegradation. e resorption rate is altered via the manufacturing process by the amount of cross-linking.Collagen barriers are available in various forms: a. Collagen tape / plugs are mainly used to control bleeding and maintain the blood clot within extraction sites. Collagen tape/plugs are usually a soft, pliable, sponge-like material that rapidly absorbs blood, thereby creating an articial clot. e collagen allows aggregation of platelets, which results in the degranulation and release of bone-growth factors. Collagen tape/plugs have a resorption time of approximately 10–14 days are not indicated for guided bone regeneration procedures. b. Regular collagen membranes resorb in three to four months and are mainly used in guided bone regeneration for small- to medium-size bony defects. Ideally, primary closure is recom-mended to decrease graft morbidity. d. Extended collagen membranes resorb in four to six months and are used for larger bony defects that require longer heal-ing periods. ese membranes are modied by increasing the cross-link density. Cross-linked collagen membranes are most commonly used in guided bone regeneration procedures for larger bony defects requiring longer healing time and graft con-tainment. e. Pericardium Membranes are most commonly of either bovine or porcine origin, with bovine having a greater collagen content. ey generally consist of three layers with collagen and elastic bers in an amorphous matrix. eir surface is porous, which allows for cellular attachment and proliferation, yet has an increased density for soft-tissue exclusion. (Fig. 36.39 A, B, and C). f. Acellular Dermal Matrix (ADM) is a biocompatible human (allograft) connective-tissue matrix derived through a process of removing all cells within the dermis. Because of the cells being removed during the manufacturing pro-cess, no viruses may be transmitted. Additionally, because of the acellular nature of this membrane, no inammatory reactions or rejection will occur. e inert allograft, when used as a membrane, acts as an architectural framework that allows for broblast migration and vascularization. Allo-Derm is an acellular dermal matrix originally developed in 1994 to be used as a skin allograft for burn patients.34 It has been used in the medical and dental literature as an allograft for various procedures because of its ability to rapidly vascularize and to increase soft tissue thickness. In the dental literature, AlloDerm has been successfully used for root coverage, thickening of soft tissues, and GBR.35,36 AlloDerm GBR is a thinner version (thickness ranges from 0.5 to 0.9 mm) of the original AlloDerm product (thickness ranges from 0.9–1.6 mm), specically designed for GBR. AlloDerm GBR has been successfully used as a barrier mem-brane and has also been shown to signicantly increase soft tissue thickness by 45% and 73% from baseline at 6 and 9 months, respectively (baseline 0.55 ± 0.16 mm to 0.80 ± 0.26 mm at 6 months and 0.95 ± 0.28 mm at 9 months; P < 0.0033), when used as a barrier membrane for GBR of horizontal alveolar ridge deciencies.37,43 (Fig. 36.40 A, B, and C). Sizing and Positioning of Membranese selection of the membrane type is one of the most impor-tant aspects of bone regeneration protocol. e choice of a specic type of barrier membrane is directly related to the ultimate success of the regenerative process. With numerous resorbable and non-resorbable membranes available, each one has specic properties that either help or hinder the isolation properties of the proce-dure. ese properties relate ultimately to the workability of the material and the longevity of its protection of the underlying graft particles.e size of the membrane must be large enough to com-pletely cover the entire graft site after the bulk of the graft has been placed in the recipient site. As the membrane is then stretched over the graft, it must be wide enough and long enough to guarantee that all of the graft particles will be iso-lated from any soft tissue or bacterial ingrowth. Experience indicates that the minimum membrane will be 20 × 20 mm and in almost all large graft sites, use of a 20 × 40 mm mem-brane will be needed. Attempting to piecemeal two or three small membranes together is not only dicult, but also intro-duces another variable into the concept of graft isolation over an extended time frame. e most ecient way to trim and shape a large piece of dermal matrix or connective tissue is to wet a tongue depressor in saline and then use this as a “cutting board” for the membrane (Fig. 36.41).Positioning of membranes around teeth is very critical to reduce complications. e use of d-PTFE requires a minimum of 2 mm between the edge of the membrane and the side of an adjacent root surface. d-PTFE membranes with titanium struts should be trimmed in a manner that prevents a lateral extension of the strut • Fig. . Polytetrafluoroethylene (PTFE) Membrane: Clinical image depicting dense PTFE membrane prior to modification of the 2mm free zone adjacent to each tooth (Photo courtesy of Dr. John Hamrick). 959CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationin the region of the coronal aspect of the graft site. Titanium struts that are positioned close to the interproximal root surfaces will often lead to membrane exposure and a compromised graft volume in the region. Newer d-PTFE membranes are designed to keep these lateral extensions located away from these critical regions. Specic elimination of all sharp edges or rough margins is critical in the elimination of membrane perforation through thin regions of the overlying ap. GBR techniques using titanium mesh require 2 mm of clearance from the root of a tooth because of similar issues.When using resorbable membranes around teeth, the 2-mm rule is not a critical factor, and resorbable membranes can be placed directly against the roots of the adjacent teeth without causing a membrane failure. Acellular dermal matrix does not need to be separated from root surfaces, keeping in mind that this same membrane is used in routine periodontal procedures for root coverage. e only complication with placing resorbable mem-branes directly against natural roots is related to primary wound closure in the root proximity. Membranes must be smooth, and they should allow the overlying ap to be adapted evenly around the neck of a tooth root. Initial Placement of MembraneAfter preparation of the recipient site, the barrier membrane may be initially xated. e initial xation may be completed either apically or on the lingual aspect of the ridge. Fixation of the membrane before placing the particulate graft assures that the membrane will not shift after the bulk of the graft has been placed and that it denes the apical extent of the graft itself. In situations where tacks cannot be used the membrane can be xed both apically and palatally/lingually with sutures. It should be kept in mind that denition of this space is established by the membrane. If the thickness of the graft narrows as the graft extends toward the apex of the regenerative site, the thickness of the bony support of the implant itself will also be reduced. In that instance an apical fenestration often occurs, introducing one of a number of variables that can complicate the predictabil-ity of an implant over time (Figs. 36.42 and 36.43. Step 7: Space MaintenanceAside from the soft tissue exclusion and clot stability, space main-tenance is key to the success of the GBR process. e creation and continued unmoving support of the graft “space” can be accomplished with membranes supported by tenting screws/pins, titanium-reinforced membranes, molded titanium mesh, block grafts, dental implants, or the bulk of particulate graft mate-rial.44–48 Most of the new techniques in GBR protocols require specic support of this area where bone is needed. Simply lling the defect space with bone particles has been shown to greatly limit the nal bone volumes, and denition of the actual shape of the ridge is really not predictable. As this protected “free zone” is dened, possibilities of successful development of new bone have been greatly improved.ABC• Fig. . Pericardium Membrane. (A) Fixation of membrane. (B) Autogenous bone being placed under tent screws. (C) Final veneer graft of allograft bone. 960PART VII Soft and Hard Tissue RehabilitationSpace Maintenance Options 1. d-PTFE integrated with titanium struts 2. Titanium Mesh 3. Tent Screws Tent Screw TechniqueTo support the membrane support and prevent collapse of the graft in most particulate membrane techniques, tenting screws are used. e principle of tenting screws utilizes the “head” of the screw for vertical and horizontal support. is support system literally creates the surface countour of the membrane and bone graft material, which allows for the bone regeneration process to proceed in a predictable manner.Size of Fixation Screws. Bone xation screws on the market today are generally non-resorbable screws that either have threads from the head to the tip of the screw or a smooth neck with 3 mm of thread design at the tip of the screw.47,48,50,51 Use of resorbable screws has been described, and this possibility gives the surgeon the option to avoid a reentry procedure to remove the xation screws.41 As the variety of xation screws is explored, choices of screws with large-head diameters are preferred. e wide head is important with this technique because the primary purpose of the screw is to support the membrane during the complete bone maturation process. If the head of the screw perforates through the membrane, the vertical support will be lost and the particulate graft is subject to pressure and micromovement. When support is lost, the nal volume and consistency of the matured ridge will be altered.Use of narrow-diameter (small) screw heads that are used in block grafting procedures was found to periodically result in com-promised and decreased bone growth. Most likely, the membrane will lose its vertical support after the small screw head perforates through the membrane.Ideally, bone xation screws with a shaft diameter of 1.5 mm are recommended instead of thicker screws because it decreases the • Fig. . Modification of membrane to encompass defect using a #15 blade.AB C• Fig. . Collagen Membranes. (A) Bone screws placed in defect area. (B) Collagen membrane hydrated and fixated with tacks. (C) Site grafted and membrane positioned over graft. 961CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationoverall post-grafting bone volume when larger-diameter screw shafts are used. Most screws today are self-threading and are easily inserted into decortication holes. e most common length of tent screws is approximately 6 mm, however the clinician should anticipate screw lengths of 10 -12 mm for larger osseous defects (Fig. 36.44). Tent Screw Numbers. e amount of support required to maintain the spatial dimensions of the graft site determine the number and positioning of these screws. Screws are anchored in the recipient site as needed to form a dome over the graft site that replicates the height of bone needed for ideal implant placement. Ultimately the tenting screws act as “tent poles” to support the membrane, decrease graft mobility, and relieve external pressure on the graft.49 Placement of simple mem-branes over graft materials without dening space maintenance will usually lead to variable postoperative bone volumes and often decient bony support on the facial and lingual aspect of the coronal aspects of the implant platform (i.e., membrane collapse) (Fig. 36.45). Tent Screw Positioning. e positioning of the screws should be planned in a manner that will result in a dome shape that is formed by the “heads of the screws” matching the required con-tour of the nal ridge form. e use of multiple screws in this technique creates very specic ridge forms that cannot be attained with unsupported membranes. Screws are placed 3 to 4 mm apart to allow solid bone formation between the screws. Basically, the number and position of tent screws is directly related to the size and the required contour of the bone graft.Clinical situations where screws have been placed too close together periodically demonstrate weaker zones of bone forma-tion which may result in dicult implant positioning. is can be important because lateral forces are placed on mature bone graft sites during implant osteotomy preparation and implant place-ment. Postoperative bony ridges using this specic technique have been found to easily tolerate the lateral forces of bone spreaders and wide body implants without any signicant problems related to aking or granular bony ridge forms. e only problem encoun-tered with respect to screw positioning has been related to screw positions that were too close to the crest of the ridge. In these situ-ations, an osteotomy diameter can encroach on the unlled screw hole and the thin fragment of bone can become detached (Figs. 36.46 A, B, C, and D) (Figs. 36.47 A, B, C, and D).Care should also be exercised in placing tent screws in approxi-mation to adjacent teeth. e location and trajectory of adjacent tooth roots should be determined to prevent screw placement into a tooth root. Ideally, post-operative radiographs should be taken to verify ideal positioning in relation to tooth roots. Step 8: Bone Graft Placemente success of a bone graft is very dependent on the proper appli-cation of the basic principles of bone development. is has been emphasized as surgeons attempt to regenerate large bony defects that require development of a viable graft that can be far from the recipient bone, where all of the regenerative components originate. CBA• Fig. . Membrane Placement in Proximity to Teeth. (A) Titanium-reinforced membrane. (B) Extended collagen membrane. (C) Acellular matrix. 962PART VII Soft and Hard Tissue Rehabilitationis is even more important in vertical regeneration because the graft particles contact the host bone only at the base of the defect, and the other three sides of the graft are totally separated from this natural source of cells for angiogenesis and cellular ingrowth.Prior to placement of the graft material, the recipient site should be free of soft tissue remnants, bone decorticated, and initial xa-tion of the membrane should be completed. When placing graft material into a bony defect, ideally a systematic layered approach should be utilized consisting of three layers which is dependent on the size and location of the graft site.Layer # 1: Autograft (Optional)e rst layer of the guided bone regeneration graft is comprised of autogenous bone. Autogenous bone is usually indicated in any bony defect which requires horizontal bone growth of greater than 3 mm or in all cases of vertical regeneration. Autogenous bone harvesting today is typically harvested from any exposed region of cortical/cancellous bone present in the oral cavity. In the maxilla, donor sites are often available apical to most implant sites and in the tuberosity area. In the mandible, in the lateral aspect of the ramus provides a bountiful source of cortical bone which may be harvested via numerous techniques.Ramus Graft HarvestIncision and Reection. e incision for harvesting a graft in the ramus region starts at the level of the occlusal plane and proceeds down the external oblique ridge a short distance until it extends medially to the distal buccal aspect of the second molar or that same region if the area is edentulous. e incision continues anteriorly, following the crest of the ridge or following the sulcus to the distal aspect of the rst molar or premolar, where a vertical release is usually prepared. e incision should always be located lateral to the retromolar pad to avoid any possible damage to the lingual nerve. e ap is reected laterally to expose the cortical bone distal to the terminal molar and a minimal exposure of the lateral aspect of the ramus. Ramus Harvesting Techniques. To harvest cortical bone from the ramus, numerous techniques are available;Lateral Ramus Block: A cortical block may be harvested from the ramus and broken into smaller cortical particles. e amount of surface area obtained from smaller particles is much greater than what could be obtained by xating an entire harvested block. e harvested block is processed by breaking the block into small pieces using double-action rongeurs. Use of large particles is not recommended, and complete destruction of the block with a bone mill has also not produced the results found with reasonable sized particles. e preparation of dense cortical bone has always pre-sented a challenge in block grafting when an irregularly surfaced cortical graft needs to be trimmed and reshaped for adaptation in a graft site. In the case of particulate grafting, the complete piece of cortical bone must be broken into small pieces before it can be used. Control of the graft particles during this process is critical because loose particles can be easily lost or contaminated as the graft is processed. Autogenous bone harvests are challenging, and loss of critical bone particles or blocks can cause unnecessary time delays and patient discomfort if additional bone needs to be har-vested to replace a contaminated block.e particulate grafting technique described in this chapter requires that a piece of a cortical block be completely broken up into small particles that are then packed into irregular bony defects. ese small particles tend to “shoot out” of the rongeurs if they are not carefully contained. e best way to eliminate the loss of these cortical particles is to ll a clear, shallow glass beaker or bowl with saline. e block is then submerged in the saline, and double-action rongeurs are used to break it up into the particle size needed for the procedure. e saline slows escaping particles in the same manner that water slows the movement of a bullet that is red into water. e bone is typically broken up into 1 × 2 mm particles for placement in the graft site. (Figs. 36.48).Scraping Technique: Another option of obtaining autogenous bone is removing cortical bone chips from the external oblique ridge. A double action rongeur may be used to remove small frag-ments from the exposed bone. e scrapings may be placed into a sterile surgical bowl with sterile saline. Another option of obtain-ing cortical chips is with the use of specic manufactured “scrap-ers”, which not only harvest the bone, but also collect it within the scraper device. And lastly, piezosurgery units may be used with dedicated scraper tips. (Fig. 36.49).Trephine Technique: e use of trephine burs (i.e. cylindrical end-cutting burs) have been advocated to harvest bone from the ramus area. ese end-cutting burs that are available in various diameters, with the 6–8 mm trephine being the most popular for AResorbed ridge/Horizontal and vertical deficiencyBony socket with all wallsE. Urban mattress design closureTitanium supporting strutsSoft tissueParticulate graftparticlesParticulate graft particlesPTFEmembraneResorbablemembrane/No verticalsupportB• Fig. . Resorbable vs. Non-resorbable membrane (A)This figure rep-resents a nonresorbable dense polytetrafluoroethylene (d-PTFE) barrier membrane (provided by Osteogenics Biomedical) that has titanium sup-porting struts to prevent collapse into the regenerative space fill the under-lying space with a bony matrix that can be replaced with viable bone as the regenerative process is completed. (B) This figure demonstrates the use of a resorbable barrier membrane with no supporting components. In this situation the membrane functions as a protective layer that prevents ingrowth of soft tissue into the underlying space. Membranes should gen-erally be elevated above the ridge deficiency with screws or titanium to prevent collapse into the space or shifting of the graft particles. 963CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationharvesting bone from the ramus. One half of the trephine bur is placed over the external oblique bony ridge, while the other half is lateral to the bone and above the reected masseter muscle, which is elevated o the anterior lateral aspect of the ramus. e trephine bur is used with an angled surgical drill at 2,000 rpm with copious saline irrigation, to a depth of approximately 5–8 mm, making sure the cuts are above and lateral to the position of the inferior alveolar nerve (IAN), artery and vein. e IAN position should be identied via a CBCT exam survey. Ramus Recipient Site Closure. After removing the harvested donor bone the donor site is lled with a double layer of collagen tape before closing the wound with a combination of interrupted and mattress sutures. is closure is monitored as each suture is tied to conrm that there is no ap tension. e use of Vicryl or Teon (Cytoplast) sutures is recommended to allow the implant clinician the opportunity to remove the sutures when he or she feels the wound has adequately healed. Due to the nature of soft tissue in the ramus region, overlapping tissue margins can contribute not only to post-operative opening of wounds, but also to a lengthy recovery process. Additional Harvest Sites. Maxillary Tuberosity Donor Site: e maxillary tuberosity oers a variable amount of trabecular bone, which is dependent on the extent of maxillary bone atro-phy and maxillary sinus pneumatization. e cancellous nature of the bone allows it to be molded into the extraction socket. e tuberosity should be evaluated with a CBCT survey to determine the maxillary sinus location and the amount of host bone present.Tori: e use of cortical bone harvested from lingual tori has been shown to produce excellent results. is is dense cortical bone, and large amounts of bone can be harvested from the typical lin-gual donor site. e use of Piezosurgery techniques allows the tori to be separated from the mandible without the threat of injury to underlying anatomic regions. ere has been no noted dierence AB• Fig. . Tent Screw Size (A) Older generation tent screws of various diameters and head size, (B) Newer tent screws with larger, convex head which allow for more ideal space maintenance.A BB• Fig. . (A). Tent screws used to stabilize membrane to achieve desired contour. (B) Postoperative results of bone growth to ideal contours. ABCD• Fig. . (A-D) The screws have been used in these varied surfaced defects to define a smooth final ridge contour that will allow implant placements in proper locations specified by the restorative wax-up.ACDDB• Fig. . (A to D) Screw placement literally determines the final contours of the augmented graft site. The screw head should never be placed higher than the level of the adjacent interproximal bone. When large head screws are used on the buccal aspect, the uppermost edge should be angled slightly to prevent its sharp edge from perforating the membrane. The best location for the largest diameter screw heads is lower down in the graft site where lateral support is needed. in the nal graft quality when tori were used as the donor source in regeneration cases (Fig. 36.50). Placement of Layer # 1. e small autograft chips or small par-ticulate pieces are placed directly on the host bone surrounding the bone screws. Because of the extensive nature of grafts requir-ing autogenous bone, at least 50% of the graft volume should be made up of this autogenous bone, with allograft compromising the second layer. Graft particles are transferred from the bowl to the graft site with cotton forceps or a Molt curette. A bone or amalgam plugger with a small end can be used to manipulate the particles between the various screws. is process lls most of the defect and voids, regardless of the topography of the recipient site. It should be kept in mind that the volume of this graft is clearly dened by the levels of the heads of the bone screws. e screws have been positioned in a manner that denes the outermost bor-ders of the desired bony ridge, corresponding to the requirements of the restorative plan and the needed sites for implant placement (Fig. 36.51). Particulate Graft Material Options. ere are many optional techniques and materials for use in regenerative graft procedures. Successful application of these techniques requires that the clini-cian have a comprehensive understanding of the various types of bone grafts and bone substitutes available, and the inherent advan-tages and disadvantages of each material. e ideal characteristics of a bone substitute include biocompatibility, low incidence of infection and immunogenicity, predictable maintenance of space over time, and the ability to be replaced entirely with new, viable bone growth. To comprehend the concept of bone regeneration and to select the ideal bone graft material, the implant clinician should have a strong understanding of bone biology.Allograft Bone. Allogenic bone is harvested from an indi-vidual of the same species and transplanted to a genetically dif-ferent individual. Allografts are considered to be one of the best sources for supplementation of an autograft or as an alternative to an autograft. Allografts are available in many dierent prepa-rations, with the most common being FDBA and demineralized FDBA (DFDBA). Although their biological properties vary, they ABCD• Fig. . Ramus Autograft Harvest With Piezosurgery Unit. (A) Piezo cuts made in ramus bone. (B) Block removed. (C) Harvested block. (D) Block bone made into particulate chips.AB• Fig. . Alternative Bone Scraper. (A) Disposable bone scraper. (B) Harvested bone inside scraper. 966PART VII Soft and Hard Tissue Rehabilitation• Fig. . Tori Bone Harvest: (A) Tori Exposure (B) Harvested Tori.A BCD• Fig. . Delivery of bone particulate around the tenting screws: (A) Autogenous cortical particles have been placed around the screws on each side of the defect. The allograft application has been started in the center region and it will then be placed over the autogenous particles. (B) Autogenous bone particles have been placed around the fixation screws and the screw lengths are visible in the adjacent region where graft has not been positioned yet. (C) The allograft is placed over the autogenous bone on the right side before the layers are started on the opposite side. (D). The particulate has been placed over the entire recipient site and the membrane is ready to be drawn over the entire region.generally exhibit osteoconductive qualities with reduced osteoin-ductive properties found in DFDBA. FDBA and DFDBA oer the advantage of decreased patient morbidity secondary to the elimination of the need for a second surgical site.Allografts undergo extensive and rigorous processing proce-dures. First, allografts are processed by freeze-drying the graft at approximately −15°C to −20°C, allowing for easier handling and a decreased antigenicity. e main drawbacks of freeze-dried bone include the potential risk for cross-infection and the possibility of immunologic reactions because of its protein content. e possibil-ity of disease transmission cannot be completely eliminated; how-ever, there are no documented cases of disease transmission related 967CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationto the use of allografts in dentistry after completion of more than 1 million cases in a 25-year period.57 In addition, allografts have been related to variations in sample quality related to age and the health variations of the donor. ese variations in the regenerative proper-ties of a specic sample indicate the possible importance of using a sample from a single donor rather than a donor pool. Allografts are primarily osteoconductive materials, with some reduced osteo-inductive properties in demineralized bone matrix preparations.Types of Allografts. e most common allografts used in implant dentistry have varying characteristics. For example: • DFDBA is osteoconductive and osteoinductive. e material con-sists of highly processed bone with at least 40% of the mineral content of the bone matrix being removed by 0.5 to 0.6 M hydro-chloric acid until the calcium content is reduced to less than 2%.58 is allows for increased availability of matrix-associated BMPs or growth factors that allow the graft to become osteoinductive. • FDBA is an allogenic bone that does not undergo the demin-eralization process. Also referred to as “mineralized” because the mineral content has not been reduced, FDBA has the same BMP content in its organic matrix. However, it does not have the same osteoinductive capability as DFDBA. FDBA has been shown to be a better scaold for osteocon-duction than DFDBA, which allows for superior space main-tenance.59 Eventually osteoclasts break down the mineral content of FDBA until demineralization occurs, inducing new bone formation and a prolonged protein release. Particle Form and Size. e allograft particle form and size contribute to the predictability of bone regeneration. • Ideal particle form: Allografts are available in three particle forms: cortical, cancellous, and cortico-cancellous. Cortical allografts are associated with an increased density and greater space maintenance properties, subsequently allowing a slower resorption rate. Cancellous chips are advantageous because they allow for osteoconductive scaolding and deposition of osteoblasts while also allowing a faster resorption rate. e cortico-cancellous mixture allows for the benets of both can-cellous and cortical bone. • Ideal particle size: e particle size of the allograft material is very important in the bone regeneration process, because a particle size that is too small (less than 125 μm) leads to fast resorption with inconsistent bone formation. A larger particle size (greater than 1000 μm) restricts resorption and may be sequestered or result in delayed healing. Studies have shown an ideal particle size for predictable bone regeneration to be approximately 250 to 1000 μm.60 Xenografts. Xenografts are bone grafts originating from a dif-ferent species. Most commonly, xenografts are derived from bovine (cattle) origins, with less common sources including equine (horses) and porcine (pigs). e most common xenografts are natu-ral hydroxyapatite (HA) derived from animal bone and anorganic bone matrix produced from bovine sources. Xenogenic bone grafts exhibit excellent osteoconductive properties and act as a scaold for newly deposited bone. Although xenografts are available in greater supply than allograft materials, they have been shown to exhibit elevated inammatory responses, along with a slow and inconsis-tent resorption process. Consideration must also be given to the risk for cross-contamination with bovine spongiform encephalopa-thy or porcine endogenous retroviruses. Unfortunately it has been shown to be dicult to adequately screen xenografts for the pos-sibility of a viral presence61 (Fig. 36. 52). Alloplasts. Because of the remote possibility of disease trans-mission from allografts and xenografts, some in the literature have advocated alternative bone substitute options. Alloplasts, which are synthetic, are a biocompatible option for the implant clini-cian. Alloplasts have the advantage of relatively no immunogenic responses, and there is no risk for disease transmission. ese materials have been shown to be osteoconductive, with an inter-connecting pore system that serves as a scaold for the migration of bone-forming cells.62 Unfortunately many alloplastic grafts do not allow the graft material to be replaced with vital bone cells, which results in nonvital bone at the implant interface.Types of Alloplasts. A wide range of synthetic materials for allografts have been developed, such as synthetic HA, β-tricalcium phosphate, calcium-phosphate cements, and glass ceramics. • HA is the basic component of inorganic bone and exhibits a similar chemical composition to natural bone. HA is most com-monly processed from natural reef coral skeletons or homoge-nized calcium-phosphate powder. It is not only biocompatible and osteoconductive, but also has excellent space-maintaining qualities. However, synthetic HA has shown unpredictable and slow degradation after approximately 1 to 2 years.63 • Tricalcium phosphate has a calcium-to-phosphate ratio of 1.5, which is much lower than HA and results in less compressive strength. Calcium phosphates resorb 10 to 20 times faster than HA, and their macroscopic mechanical properties are inadequate for load-bearing surfaces because of their inherent brittleness. Because of the fast biodegradation rate, this bone can be unpre-dictable and is not consistent with adequate bone deposition. • Carbonate apatite with collagen has been shown to resemble bone more than any other calcium phosphate available. e inorganic content of bone contains approximately 7% carbon-ate by weight.64 Studies have shown that carbonate apatite exhibits a more controlled resorptive pattern, as well as excel-lent osteoconductivity and biocompatibility.65 When carbon-ate apatite is combined with collagen, the biological stability and strength are increased, which allows the scaolds to act as a delivery vehicle for growth factors and living cells for bone formation.66 Scanning electron microscopy studies have shown that the highly porous and interconnected structure ensures a biological environment that is conducive to cell attachment, proliferation, angiogenesis, and tissue growth.67 • Bioactive glasses are ceramic substitutes that are reinforced by oxides—sodium oxide, calcium oxide, phosphorus pentoxide, and silicon dioxide—and exhibit questionable mechanical strength. ey are absorbable and have no risk for disease trans-mission or immune responses. e bioactive ceramics exhibit improved mechanical properties relative to bioactive glass, but they are still brittle enough to fracture when subjected to cyclic loading. To improve their resistance to fracture, methods of incorporating stainless-steel and zirconia fibers have been per-formed. Studies have shown questionable efficacy of bioactive glasses with respect to osteoconduction qualities and the ability to bond to tissues (bioactivity).68 Layer # 2 Summary. e second layer of the graft is ideally made up of particulate allograft that is placed over the top of the autograft (i.e. or 100% allograft for smaller defects < 3 mm). e allograft should veneer over the screw heads, however care should be exercise to not “overll” the graft site. e recommended allograft bone type is either 70% mineralized / 30% demineral-ized or a cortical/cancellous mixture of mineralized bone. It is highly recommended that the ridge be overdeveloped rather than underdeveloped. Excessive overlling of the graft site may lead to dicult tissue closure and increases the possibility of incision line opening. 968PART VII Soft and Hard Tissue RehabilitationLayer # 3: Final Implant PlacementAfter the graft material (Layers # 1 and # 2) is ideally positioned, the membrane (previously xated apically or lingually) is stretched over the graft site. e membrane should be of sucient size to totally encompass the entire graft. e goal of the membrane xa-tion is to not allow any movement, which could negatively aect the wound healing. In most cases, the nal xation is on the pala-tal aspect of the ridge with two tacks. Additional xation can be used as needed in large graft sites to limit membrane movement. Bone Growth FactorsBone growth factors can be a signicant part of the bone-grafting process as they may enhance the formation and mineralization of bone. In addition, bone growth factors may induce undierenti-ated mesenchymal cells to dierentiate into bone cells that trigger a cascade of intracellular reactions for the release of additional bone growth and cell-enhancing factors. ese growth factors actually bind to specic receptors on the surface of target cells directing a more timely healing process. More than 50 known growth factors have been identied and categorized according to their specic contributions to the functions in bone healing. e two most common bone growth factor techniques utilize blood concen-trates and recombinant human Bone Morphogenetic Protein-2.Blood Concentrates. Most blood concentrates used in implant dentistry today are direct derivatives of platelets. e platelet, also called a thrombocyte, are blood cells that are primarily involved in the blood clotting process. A unique secondary function of a platelet is to release a wide range of growth factors that enhance collagen production, cell mitosis, blood vessel growth, cell recruit-ment, and cell dierentiation.69e two most utilized and studied platelet concentrates in implant dentistry today are platelet-rich plasma (PRP) and plate-let-rich brin (PRF). e rst-generation blood concentrate, platelet-rich plasma, was rst introduced by Marx in 1998. His studies showed bone maturity to be twice as eective with the use of PRP in grafted sites, and the addition of PRP increased bone density up to 30% in healed sites.70A second-generation blood substitute, platelet-rich brin, was rst described by Choukroun in 2001. is concentrate has been shown to exhibit a much simpler processing protocol in compari-son to PRP. PRF is very eective in the release of important growth factors present in platelets, such as platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-ß), insulin-like growth factor (IGF), broblast growth factor (FGF), and epithelial growth factor (EGF). 71 (Box 36.9) Multiple clinical studies have shown increased soft tissue healing, enhanced healing of grafted bone, promotion of angiogenesis, and faster wound healing.72–74e internal organization make-up of platelet rich brin is rather unique as it contains three adhesive molecules (brin, bronectin, and vitronectin) that result in a highly elastic, matri-cial mesh architecture. is complex three-dimensional struc-ture allows for a longer release of growth factors. As the platelets degranulate, a sustained release of growth factors may range from a time period of one to four weeks.75DCAB• Fig. . There can be very substantial variations in the density of matured graft sites, depending on what type of graft was used initially. The delayed turn-over of bovine particulate can greatly affect the den-sity when an implant is placed before the complete substitution cycle has been completed. (A) PepGen15. (B) OsteoGraf 300/FDBA. (C) 90% autogenous/FDBA. (D) Mix of autogenous/bovine/FDBA. 969CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationPRF is an autologous brin matrix that incorporates platelets, leukocytes, cytokines, and circulating stem cells that are gradually released to accelerate physiologic healing. It is easily obtained and does not require any biochemical blood handling.52 After drawing blood and placing in a centrifuge for 12 minutes, the coagula-tion cascade will be triggered. e end result is a brin clot in the middle layer, situated between the acellular platelet-poor plasma and the red blood cells. When this brin clot (PRF) is used as a membrane, it will help isolate and protect the wound while serv-ing as a matrix to accelerate healing. When the PRF is mixed with the graft material (allograft), the brin clot acts as a biological connector between all of the elements of the graft, while also act-ing as a matrix that initiates angiogenesis, stem cell accumulation, and migration of osteoprogenitor cells to the graft. us the syn-ergistic eects of the brin matrix and growth factors allow for the enhanced healing of the hard and soft tissues. Studies have shown that PRF with freeze-dried bone allograft (FDBA) heals faster than FDBA alone.53e second-generation blood concentrate platelet rich brin (PRF) has been shown to be advantageous in comparison to plate-let rich plasma (PRP): • Is naturally polymerized and requires no chemical use • Requires a conventional, single spin centrifuge • Has a slower release of growth factors • Is more ecient with cell migration and proliferation • More advantageous brin network that stores cytokines and growth factors • Better healing properties • Less disposables required resulting in less expensePlatelet Rich Fibrin Uses. With bone augmentation proce-dures, PRF may be used as either a membrane or added to the particulate bone grafting material. Studies have shown that PRF is advantageous in healing during regenerative procedures either as a membrane or when added to particulate bone.76 Because the PRF membrane resorbs rather fast (∼ 7 days), it is not the most ideal membrane to be used to prevent soft tissue invasion. erefore, usually the PRF membrane is placed over the primary membrane (e.g. collagen) to aid in hard and soft tissue healing (Figs. 36.53). Recombinant human bone morphogenetic protein-2. Recombinant human bone morphogenetic proteins (rhBMPs) are a group of sequentially arranged amino acids and polypeptides that are osteoinductive proteins, acting to initiate, stimulate, and amplify bone morphogenesis. BMPs stimulate mesenchymal stem cells to induce bone formation via dierentiation to osteoblasts, which form and mineralize new bone. BMP-2 has been puried, sequenced, and cloned, and is marketed as rhBMP-2 (recombi-nant human bone morphogenetic protein-2; Infuse; Medtronic, Inc., Minneapolis, Minn.). Infuse bone graft consists of two com-ponents: a 1.5 mg/mL concentration of rhBMP-2 and an absorb-able collagen sponge. Studies have shown rhBMP-2 with titanium mesh to be an eective treatment for augmentation of the decient bony ridge before implant placement.54 e new bone formed by rhBMP-2 has been shown to be similar to native bone and can with-stand the stresses of implant placement and prosthetic function.55 Step 9: Closuree nal closure of the bone graft site is one of the most important steps of the grafting process. Ideally, a tension-free ap adaptation is the key to predictable results. If a poor suturing technique is used, incision line opening may result, which signicantly increases the morbidity of the procedure. erefore, meticulous principles should be adhered to with respect to a tension-free ap, ideal suture tech-nique, and the close post-operative evaluation of the surgical site.e type of suture selected should include a high tensile strength material. e most common suture materials used today include vicryl (absorbable) or PTFE (nonmabsorbable). e primary prin-ciple of wound closure in GBR cases is attaining a completely “tension-free” closure over the submerged graft. Specic attention must be directed to proper approximation of the margins of the ap to conrm there is no overlapping of the tissue aps.Usually the combination of horizontal mattress and inter-rupted sutures are used to close these graft sites. One of the pri-mary advantages of using the horizontal mattress sutures is the ability to “evert” the tissue margins. By everting the margins of the ap outward, the connective tissue layers will be approximated against each other. A ap closure that “overlaps” two aps is actu-ally placing the connective tissue layer of the rst ap over the epi-thelial layer of the adjacent ap. is type of poor approximation leads to at best a weak suture line and most often an open margin postoperatively. Additional interrupted sutures may be used to approximate all edges of the wound. e vertical incisions may be closed with 5-0 Chromic, as they may greatly reduce the post-op formation of tissue scars.(Fig. 36. 54). (Fig. 36.55 A, B, and C) (Fig. 36. 56). Postoperative TreatmentProvisional Restoratione successful maturation of a bone graft site requires that the area be completely protected from micromovement of the iso-lating membrane and the underlying graft material. A success-ful graft is totally dependent on blood clot adhesion, capillary ingrowth, and the introduction of associated growth factors for predictable healing. It has been estimated that micromovement of 25 μm over a graft site can decrease the nal graft volume as much as 40%. erefore, disruption of any kind will consis-tently yield compromised results in mature graft development, if not full graft failure.e most common source of daily pressure on a site occurs when the patient’s transitional appliance has contact with the surface of the graft site. If possible, a xed bonded transitional bridge should be placed over the graft site because it totally prevents contact with the underlying graft site. If this is not possible and the patient insists on a temporary prosthe-sis, plans for a carefully constructed removable partial denture should be formulated. A transitional prosthesis (ipper or removable partial 1. Platelet-derived growth factor (PDGF)- Stimulates fibroblast mitogenesis and collagen synthesis 2. Transforming growth factor beta (TGF-ß)- Enhances wound healing via endothelial angiogenesis 3. Insulin-like growth factors (IGF)- Enhances rate and quality of wound healing via bone matrix formation and cell replication 4. Epithelial growth factor (EGF)- Increases angiogenesis and epithelial mitogenesis 5. Fibroblast growth factor (FGF)- Increases angiogenesis, epithelialization, and fibroblasts 6. Vascular Endothelial Growth Factor (VEGF)- Increases endothelial growth factor and angiogenesis • BOX 36.9 Growth Factors Released by Platelets 970PART VII Soft and Hard Tissue Rehabilitationdenture) must be modied to eliminate any signicant contact with the graft site. If a removable prosthesis is absolutely necessary, all buccal anges should be removed, and if possible, the acrylic should be altered to create regions of support on the lingual surfaces of the adjacent teeth. Occlusal rests should be used, or in cases where this is not possible, there must be good adaptation of the prosthesis to direct the forces to alternative stress-bearing areas (i.e., tissue areas away from the graft site that take the pressure o the graft site).Essix appliances allow temporary replacement of teeth in narrow span regions, allowing long-term prostheses to be fabricated after the initial healing process has been completed. However, the Essix appliance does have disadvantages related to esthetics, fracture, wear issues, and discoloration. e Snap-On Smile appliance (Den-Mat Holdings, LLC) has been used successfully over longer-span edentulous regions with more pleasant esthetics that and increases patient acceptance (Figs. 36.57) (Fig. 36. 58) (Fig. 36.59). Development of Ideal Bone Density in Regeneration Sitese sole purpose of ridge augmentation and bone grafting is to develop a dense, stable volume of bony support for implants of appropriate sizes and numbers that are placed in the locations specied by the restorative plan. e quality and density of the nal graft development are important because a weak and granu-lar implant osteotomy site is more susceptible to crumbling dur-ing implant insertion. ese granular ridges can also resorb when the implant is loaded and stress is placed on the coronal aspect of the implant-bone interface. As clinicians plan augmentation procedures, they must understand the limitations of the materials that they are using and the techniques that are going to be used. • Fig. . Bone Graft Suturing. Polytetrafluoroethylene (PTFE) sutures over ridge with minimal tension from the vertical release incisions.ABCD• Fig. . (A) PRF used as a secondary membrane over the primary membrane, (B) PRF may be added to the graft material, (C) Sticky Bone, (D) Platelet Poor Plasma may be used to hydrate the primary (col-lagen) membrane 971CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationMisch56 created a system of bone densities for implants, rang-ing from D1 (hardest) to D4 (softest/most porous). ese divi-sions encompass the acceptable ranges for the placement and rigid xation of implants. Successful regeneration procedures develop a nal osteotomy site that provides adequate bone volume in a dense, rm, manageable form that has a large number of vital bone cells that will easily integrate with the titanium implant body.Success in bone grafting requires a thorough knowledge of the variety of grafting materials that are available and their capacity to be readily replaced with vital bone on a timely basis. e ultimate goal is a clear understanding of the concepts of osteoinduction and osteoconduction, which is critical for predictable grafting suc-cess. It is easy in the incorporation of regeneration into a practice routine to simply open a bottle of bone for use in a surgical pro-cedure, instead of preparing to open a second site for a cortical bone harvest. Unfortunately, the characteristics of dierent types of bone graft vary greatly and in the long term this can signi-cantly aect the volume and quality of the regenerated bone. It is vitally important that the clinician have a strong understanding ABC• Fig. . (A, B, C) Polytetrafluoroethylene sutures over ridge with minimal tension from the vertical release incisions.AB• Fig. . Alternative Lingual Suture Membrane Fixation. (A) Tack placed in palatal cortical plate with suture started through the palatal flap, passing below the flap and back through the membrane. (B) The suture is then passed back from beneath the flap and out again. ACB• Fig. . Interim Prosthesis Modification. (A and B) The buccal flange and the grafted area should be modified to remove any possible pressure areas. (C) Post adjusted prosthesis showing minimal flange and ridge area relieved.A BCD• Fig. . Interim Prosthesis-Related Pressure. (A) Fixation screw exposed with associated bone loss (B) caused by interim prostheses with protrusion placing pressure on graft. (C) Essix appliances allow temporary replacement of teeth in narrow span regions. However, the Essix appliances do have disadvan-tages in respect to limited esthetics, fractures, and discoloration. If adjusted properly, it will not allow any pressure on the graft site. (D) Essix appliance with added acrylic that encompasses the soft tissue defect and potentially may place undue pressure on the grafted area. 973CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationand foundation of the use and indications of the available bone grafting materials (Box 36.10). Graft Maturation Healing TimesAs time frames for graft maturation are considered, it must be kept in mind that this whole approach to grafting is a “substitution” pro-cess where the grafted bone is eventually going to be replaced with newly developed natural bone. For adequate healing the graft must be given sucient time to resorb and for new bone to be regener-ated in its place. is process varies considerably as dierent graft types are considered. A common issue with clinicians early in their learning curve is trying to use a “xed” healing time period for all particulate grafts.Ideally many factors must be taken into consideration when determining the healing time. One of the most important factors is the number of remaining walls of bone that surround the recipient site. In general the larger the number of walls sur-rounding the graft, the shorter the healing time. e second fac-tor is the use of autogenous bone within the graft. e more autogenous bone used, the shorter is the healing time. e quantity of allograft is a signicant factor because the greater the amount of allograft, the longer the required healing period. is is directly tied to the time needed for adequate angiogenesis. e type of bone used is also signicant with the healing time: autog-enous (fast), allograft (moderate), xenograft (slow), and alloplast (slow to unpredictable bone turnover). Lastly, systemic diseases such as diabetes, hyperparathyroidism, thyrotoxicosis, osteoma-lacia, osteoporosis, and Paget’s disease may all aect the healing response. (Box 36.11)In summary, it is always best to err on the side of safety and allow for more bone healing time. For most cases involving graft sites composed entirely of allograft, 6 to 8 months is recommended when graft volumes are less than 4 mm in dimension. In similar sites with larger graft volumes (>4 mm), 6 to 10 months is highly recommended. Premature reentry into the graft may initiate many complications. In cases of poor or delayed healing, the quality of bone will be very weak and granular, similar to D5 bone. is type of bone is very soft and prone to overpreparation, ultimately result-ing in a poor bone-implant contact. If this situation is encountered, the surgical implant placement protocol should be altered with underpreparation of the osteotomy, osseodensication techniques ABC• Fig. . Alternative Interim Prosthesis. (A) Large grafting site. (B) Final closure of ridge augmentation. (C) Placement of Snap-On Smile over the closed graft site to protect augmentation site during the healing process. 1. Autogenous Grafts: a graft removed from one anatomic location and placed in another location in the same individualDonor sites: tuberosity, ramus, symphysis, iliac crest, etc. (coagulum, particulate, block grafts)Indications: used as the 1st layer in GBR procedures which require > 3 mm of bone growth (horizontal) or vertical bone growth 2. Allograft: grafts taken from the same species—human cadaver a. Osteoinductive Allografts: grafting materials that provide a biological stimulus (proteins and growth factors) that induce the progression of mesenchymal stem cells and other osteoprogenitor lineage. (Example: Demineralized Freeze Dried Bone Allograft {DFDBA}) b. Osteoconductive Allografts: relatively inert filling materials that integrate with new forming bone. Osteoconduction is the process that permits osteogenesis when cells already committed to bone formation are also present in a closed environment.(Example: Mineralized Freeze-Dried Bone Allograft {FDBA})Indications: used as 2nd layer for grafts > 3 mm or as sole grafting material for grafts < 3 mmOptions: 1. 70% FDBA / 30 DFDBA2. 100% FDBA (Cortico-Cancellous) 3. Xenograft: osteoconductive graft from another species(Examples: Bovine {Bio-Oss, Bio-Oss porcine, and equine)Indications: rarely used in GBR protocols 4. Alloplast: osteoconductive—a chemically or naturally derived nonanimal material(Examples: Hydroxyapatite, Bioglass, calcium sulfate)Indications: rarely used in GBR protocols 5. Biologics: cell-based therapies, growth factors, and osteoconductive matrices, that clinically enhance bone regeneration(Example: Emdogain, recombinant human bone morphogenetic protein-2, platelet-rich plasma, platelet-rich fibrin)Indications: elective use, however highly recommended in larger graft cases • BOX 36.10 GBR Bone-Grafting Options 974PART VII Soft and Hard Tissue Rehabilitationand/or the use of osteotomes. e concepts of ridge remodeling after loading should be seriously considered, and placement of additional layers of xenograft with membrane coverage should be used. Overall, patience in graft maturation is critically important. Bone-Grafting ComplicationsIncisive Canal Involvement in Regeneration SitesImplant restorations in the anterior maxillary region present one of the most dicult challenges in dentistry today. e combina-tion of esthetic demands, biomechanical/functional issues, and phonetic challenges require implant placement in ideal positions. e incisive foramen is the exit point of the nasopalatine canal, where the terminal branch of the descending palatine artery and nasopalatine nerve pass into the oral cavity. e proximity of the incisive foramen and the path of the canal must be evaluated in all maxillary incisor implant treatment plans because there can be signicant variations in the size, position, and angulation of the nasopalatine canal and the exiting foramen. As the bone around the maxillary central incisors resorbs, the zone of available bony support moves palatally, frequently encroaching on the incisive foramen.Dening the dimensions and pathway of the nasopalatine canal with CBCT imaging allows the surgeon to decide whether implants can be placed within the required restorative space or whether aug-mentation will be needed for ideal placement. is is particularly important in cases involving immediate implants because the lin-gual angulation of the immediate implant osteotomy could poten-tially fenestrate into the incisive canal. A fenestration in the side of an osteotomy allows neural/brous tissue invasion into the oste-otomy, retarding bone growth and rigid xation of the implant.Axial CBCT images provide the most accurate view of the size, shape, and location of the canal in respect to the possible implant sites. Use of CBCT cross sections and three-dimensional images can also help determine the positions and dimensions of this important anatomic variant. e clinician must be aware of a possible widening of the canal above the level of the foramen, creating a fenestration between the canal and the osteotomy in the more apical regions of the osteotomy. As the cross sections of the CBCT are reviewed, the possible presence of a nasopalatine cyst should be ruled out, and edentulous arches should be reviewed for an enlarged foraminal dimension, as is often noted. e posi-tions of implants in central incisor regions where the foramen is involved should be adjusted distally where an FP-1 restoration does not require a specic placement. is slight adjustment dis-tally prevents fenestration on the mesiopalatal line angle, where this deciency most likely will occur.Severe bone resorption on the facial aspect of the maxilla reduces the ridge thickness to surprising extents, often leaving only a thin ridge that is positioned well to the palatal aspect of the required location for a central incisor implant. It should be kept in mind that a line between the cingula of the two cus-pids passes directly over the incisal foramen. Subsequently, if an implant is placed this far palatally, the emergence prole will originate at a signicantly proclined angle and the complete res-toration will be palatally positioned. Cases such as this require that the seriously decient ridge be regenerated before implant placement.Regions that are determined to be decient will require facial augmentation using techniques that are capable of generating suf-cient lateral/vertical bone volume for proper implant placement and restorative success. Cases where the implant can be moved slightly in a distal direction can sometimes prevent the need for major augmentation. Another option in a FP-3, RP-4, or RP-5 case is the obliteration and grafting of the nasopalatine canal, which can aid in providing signicant bone volume for implant placement into vital bone and potentially creating a better ridge consistency on maturation. (Fig. 36.60) Releasing the Tissue Flap From Underlying Tenting ScrewsFlap reection is a basic procedure that is common in all surgi-cal applications. Correct tissue manipulation allows the ap to be released and reected without tearing or damaging the underly-ing periosteal layer. e use of bone xation screws in particulate grafting techniques creates a complicated situation for ap reec-tion because the brous tissue layer of the periosteum surrounds the head of the screw and any exposed portion of the neck of the screw. As the ap is reected away from a screw insertion site, this brous layer must be released before the ap can continue to be drawn away from the region.is binding attachment cannot be easily drawn over the screw heads, and there is a potential to create perforations or tears in the ap as it is released. Flap reection in this situation starts with a simple full-thickness crestal incision that is prepared over the graft site. Flap release is initiated with a sharp curette that is used to release the ap and to reect the periosteum, scraping side to side until the full ap can be elevated. As the ap is released, the bone xation screws must be freed from the thick layer of brous tissue that adheres to the screw head. A #12 scalpel maybe used to sever the brous layer over the screw, and a sharp curette is then used to continue the ap release until another screw is encountered. Once the ap has been completely released, the xation screws are accessible for removal before placing the implants (Fig. 36.61). Exposure of the Bone Fixation Screw During the Healing ProcessBone xation screws in regeneration sites sometimes become exposed during the healing process, potentially leading to bacte-rial invasion around the neck of the screw. Careful attention to the time lines of the screw exposure and the type of regenera-tive process is important in these situations. It is not uncommon for the tissue covering the heads of the xation screws to become very thin. is paper-thin tissue allows the color and contour of the screw heads to be visible and palpable. is is of no sig-nicant concern, and the only precaution is directed to relief of any removeable appliance that could be placing pressure on the 1. Remaining number of bony walls 2. Use or exclusion of autogenous bone 3. Type of allograft material 4. Particle size of allograft material 5. Amount of blood supply at graft site 6. Use of bone growth factors 7. Presence of systemic diseases 8. Lifestyle issues (smoking, alcohol) 9. Post-operative complications • BOX 36.11 Factors That Aect the Healing Time of Particulate Grafts 975CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationalready tender and thin tissue. If at any time the actual head per-forates through the tissue, it should be considered for removal.Exposure of xation screws in particulate grafting occurs when the head of the screw works its way through the overly-ing membrane and eventually perforates through the thin layer of the mucosa that covers the graft site. is typically happens when the screw head has a thin diameter that perforates through the membrane and eventually through the tissue. Particulate grafting techniques use these xation screws to support the membrane and to dene the shape of the desired bony contours. e use of a screw with a “wide head” is found to be important for predictable results. e type of membrane used for graft isolation also makes a signicant dierence when perforation of the screw through the membrane is a concern. Acellular dermal matrix and pericardium tend to be very resistant to membrane perforation during the heal-ing process, whereas collagen membranes are soft when moistened and tend to perforate and tear if strain is placed on the hydrated membrane. Perforation of a membrane allows the ingress of for-eign matter and brous soft tissue cells into the graft site, causing a disruption in the bone regeneration process. If the head of the AB• Fig . Incisive Canal Approximation (A) Two implants in # 8 and # 9 positions after significant bone augmentation, note that even with augmentation, implant placement impinging on incisive canal, (B) After extensive maxillary grafting, anatomical limitations of the incisive canal contraindicates implant placement.ACDB• Fig. . Bone Screw Removal. (A and B) The flap has been completely released and the fixation screws are accessible for removal (before placing the implants). (C and D) Bone must be removed from inside the screws before attempting removal with either a 12 blade or periodontal scaler. 976PART VII Soft and Hard Tissue Rehabilitationscrew pushes through the soft tissue and is exposed, bacterial con-tamination may result, potentially leading to graft infection and possible failure.e head of the bone xation screws should have a wide and smooth diameter that provides enough surface area to support the membrane and to limit abrasion against the overlying mucosal layer. A small head will tend to work its way through a membrane when it is placed under tension or where a delicate membrane is being used. e typical bone xation screw has a diameter of 1.5 mm, and the head of the screw should be as wide as possible. Newer generations of xation screws have been designed specically for membrane graft-ing, and they provide a very wide surface area for even support of a membrane. ese larger heads also support such a large surface that the actual number of xation screws can be reduced signicantly.Exposed screw heads should be maintained with chlorhexidine rinses until the surrounding soft tissue has healed. It is recom-mended that the screws in particulate techniques be removed at this time to eliminate the possibility of contamination of the graft through the opening around the shaft of the screw. If the screw is preventing pressure on the graft in respect to the use of a remov-able prosthesis, retention of the screw could be considered. Under no circumstances should eorts be made to cover the screw by repositioning the soft tissue (Fig. 36.62). Incision Line Opening in Bone-Grafting SitesMaintenance of complete soft tissue coverage over healing bone-grafting sites is one of the most important principles that must be observed for predictable grafting success. Any time that the heal-ing graft site is exposed to the oral ora during the healing process, there will be some type of compromised change in the nal graft site volume and in its overall integrity. Incision line opening with compromised graft results can often be a major limiting factor in successful implant placement.Incision line opening can compromise even the most care-fully planned regeneration site, and most of these graft sites will require additional grafting at a later time if an actual complication develops. An open incision line introduces numerous potential complications into the healing process. First, the introduction of microorganisms into a graft site through an open incision can lead to an infection in the healing graft site. Exposure of the graft par-ticles and the presence of purulence is an indication of impending failure of the graft. e infection reduces the pH in the graft site, causing a breakdown of the graft particles and eventually com-promising the resulting ridge volume. Second, an open incision line may allow exposure and breakdown of the barrier membrane, contributing to brous tissue ingrowth into the graft site. Lastly, there exists a potential for particulate graft materials to escape the graft site, resulting in an inadequate bone volume in the nal pro-posed implant site.e most important concept in maintaining incision line integrity is consistent tension-free wound closure. is protective seal can be most eectively managed from the standpoint of over-all ap management throughout the surgical procedure. A clini-cian’s experience in manipulation of soft tissue aects this aspect of bone regeneration more than any other part of bone regen-eration surgery. As the clinician gains more experience in delicate tissue management and begins to understand the maintenance of a tension-free ap closure, problems with graft and membrane exposure will become an uncommon occurrence.All regeneration sites require that the overlying tissue ap be stretched over the wide bulk of the graft at the completion of the procedure. Unfortunately there is a nite distance that a tissue ap can be freely stretched, and at this point the wound closure is placed under tension. Even though pressure can be exerted on the stiches to force closure of the wound, the incision line is put under an unreasonable amount of stress. e continual tension and pressure will eventually lead to necrosis of the tissue around the sutures, leading to an open incision postoperatively.e inner surface of a reected ap is lined with the periosteum: a thin, dense binding layer of tissue that cannot be stretched. e tissue directly below the periosteum is very loose mobile tissue full of elastic bers. is disparity in tissue types can predictably be neutralized with a shallow incision through the dense periosteal layer. is “tissue release” is accomplished by preparing a clear and continuous releasing incision through the periosteum, exposing the underlying elastic layers of tissue that can then be released for expansion of the ap over the enlarged graft site. As this inci-sion perforates the periosteal layer, the two edges clearly separate, allowing the elastic tissue below the periosteum to stretch. A sharp pair of Metzenbaum scissors is then placed into the space below the periosteum, and as the scissor tips are opened, the tissue easily releases and the edges separate further. is is repeated until the complete ap is stretched over the graft site and 5 mm beyond the opposite ap margin.In the event of an incision line opening, the patient should be placed on a frequent monitoring protocol to observe the status of the graft material and any grafting hardware present. e oral micro-ora must be managed with the use of daily chlorhexidine rinses. e clinician must not attempt to suture the site again because healing margins along incision lines feature tissue that cannot, at that time, support the pressure of another suture under tension (Figs. 36.63 and 36.64). High Mucogingival Junction Following Ridge AugmentationMajor ridge augmentation requires that the soft tissue ap be stretched over the enlarged graft site. rough the process of extending this tissue laterally over a large and bulky graft, the mucogingival junction is elevated to a level that often surrounds the abutment with mucosa. Various approaches are available to prevent or repair this deciency of keratinized tissue, but the addition of pre-surgical procedures to an already involved series of surgical appointments often prevents implant teams from coping with this situation.e simplied approach is to place a very wide autologous tissue graft from the palate over the mucosal region prior to the actual augmentation procedure. e main complaint about this approach is the fact that palatal grafts like this have a whiter color after the graft is placed and it really does not match the thin and pink color of anterior restorative sites. ose grafts are better indi-cated for use in posterior regions.e best method available in this situation was described by Dr. Esteban Urban who recommends releasing the loose mucosal tis-sue with a split thickness ap, leaving the underlying periosteum and brous tissue intact. e released mucosal ap is sutured api-cally with multiple 5-0 Chromic sutures, creating an exposed zone of exposed tissue from the top of the ridge to the newly sutured tissue. A thin strip of palatal tissue is removed, and it is sutured along the apical suture line to xate the repositioned tissue. is technique will ultimately prevent relapse of the mucosal tissue level. A large piece of mucograft (i.e. resorbable collagen matrix - Geistlich Mucograft®) is placed over the exposed periosteum and 977CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationsutured with chromic sutures. is arrangement of tissue, muco-graft, and tissue graft create a predictable zone of keratinized tissue on the facial aspect of the implant restoration and the addition of the mucograft basically eliminates any discomfort related to the repositioning of the mucosal ap. (Fig. 36.65 A, B, C, D, and E) Graft InfectionGraft materials resorb rapidly at a lower pH condition, with HA crystals dissolving at pH 5.5 or less. Infectious environments may contain a pH of 2 or less, which can cause the rapid dissolution of a graft. Infection may be caused by lack of aseptic surgical tech-nique, incision line opening, or infection from adjacent dental sources. e presence of a localized infection in a bone graft will cause dissolution of the graft material, contributing to graft fail-ure. e severity of this failure can vary depending on the duration of the infection and the onset of the contamination.e use of proper surgical technique is vital in the preven-tion of surgical contamination. Preoperative antibiotic regi-mens, chlorhexidine scrubs, and aseptic technique will limit bacterial contamination at the time of surgery. Proper suture technique and ap design are grafting fundamentals that CDFEAB• Fig. . Membrane Tent Screws. (A) Larger screw heads are more likely to grow bone than smaller screw heads. Note the lack of bone around the small-headed screw on the far right side of the photo. (B) Wide-head bone screw. (C) Tent screws are available in various width shanks and lengths. (D) As the graft heals and the membrane resorbs, the head of the fixation screws are often visible through the thin mucosa covering the healing graft site. This is not a complication, and no special treatment is necessary. (E) Screw perforation through thin tissue. (F) Screw removal before implant placement. A BBC• Fig. . Membrane Exposure. (A) Acellular dermis exposure. (B) Collagen membrane exposure. (C) Dense polytetrafluoroethylene exposure through buccal mucosa and residual ridge. All membrane expo-sures should be maintained as long as possible.ABC• Fig. . Membrane Exposure. (A) Two weeks after surgery. (B) Three weeks after surgery. (C) By keep-ing the area clean with chlorhexidine, at 5 weeks postoperative closure is obtained. 979CHAPTER 36 Particulate Membrane grafting/Guided Bone Regenerationprevent incision line opening that can also expose the graft to the oral microora. Lastly, the clinician should ensure that all space maintenance components (nonresorbable membranes, titanium mesh, tenting screws) are free from sharp edges that may perforate the mucosa postoperatively, allowing the ingress of bacteria into the graft.Postoperative examinations must be routinely scheduled, especially during the initial stages of wound healing. e patient must be instructed in hygiene techniques that minimize strain on the incision line, and postoperative chlorhexidine rinses can be used to manage the bacterial microora. If incision line open-ing occurs, the patient must be placed on a chlorhexidine rins-ing protocol to keep the graft site clean until the granulation is complete. If the patient experiences purulence from the site or general malaise, antibiotic protocols must be commenced imme-diately. Nonresorbable membranes should be maintained for at least 6 weeks unless the site becomes infected. If this occurs, the membrane should be removed before the situation advances. ABCDE• Fig. . High mucosal attachment in the restorative space of the prosthesis: (A). Note the elevated mucogingival junction, particularly on the distal implant. (B). Free Tissue harvest. (C). Split thickness release of the mucosa, with apical fixation using 5 0 Chromic sutures. (D). Fixation of the free tissue graft at the depth of the newly defined vestibule. The exposed tissue between the tissue graft and the top of the ridge is covered with “Mucograft”. (E). Three week post operative image is graft site with new zone of keratinized attachment. 980PART VII Soft and Hard Tissue RehabilitationUltrasonic Piezosurgery-Related Tissue Injurye use of ultrasound technology in dentistry rst began in the 1950s, and newer Piezosurgery units have been developed using low-frequency ultrasound (10–60 kHz) for the selective cutting of bone. Traditional bone drilling with motorized drills is easily available to clinicians; how-ever, cutting bone with a drill can generate excessive amounts of heat in dense bone, potentially damaging the surrounding tissue. A surgical drill that comes in contact with blood vessels, nerves, or sinus mem-branes can also cut or damage adjacent vital structures. e use of Piezo-surgery in implant surgery has been a welcome alternative to motorized drills in many applications. At the lower ultrasonic frequencies used for Piezosurgery, surgical inserts cut through hard, mineralized bone but do not damage the surrounding soft tissue or generate high amounts of heat. Piezosurgery has been especially useful in implant surgery, where bone must be cut in close proximity to a nerve or blood vessel.As Piezosurgery has been performed, it has been reported by practitioners that the inserts should not be allowed to function while in direct contact with the soft tissue ap. Earlier surgical units were reported to “heat up the insert tip” during use, and irri-tations or burns on the soft tissue ap were sometimes detected. is altered tissue issue has not been evident in updated Piezosur-gery units, but careful attention must be directed to protection of surrounding soft tissue during ultrasonic insert use. Instruc-tors describe this as an abrasive phenomenon caused by the rapid ultrasonic movement of the tip against the soft tissue. Care must be taken to keep the tissue ap away from the ultrasonic inserts.Development of any abrasive or burn-type lesion should be treated symptomatically, just as any other oral burn or abrasive lesion would be treated. If there are any signs of more serious dam-age, more involved treatment may require appropriate referrals for wound care (Figs. 36.66 A, B, and C and 36.67). SummaryTo satisfy the ideal goals of implant dentistry, the hard and soft tissues need to be present in ideal volume and quality. After tooth loss, the resorption of the alveolar process occurs so often that augmentation procedures are often necessary to restore the hard and soft tissues. is becomes especially signicant when the edentulous areas are in the esthetic zone. Augmentation procedures not only enhance the nal esthetic result, but also will make a more predictable biomechanical foundation to minimize possible complications. In implant dentistry today, there exist a vast array or procedures and protocols to augment decient implants sites. is chapter presented an overview of the indications for guided bone regeneration techniques along with a classication of diering ridge morphology that will allow the clinician to understand the predict ability and di-culty based on the bony ridge deciency. e following images demonstrate the regenerative potential of current approaches to bone augmentation. Jensen and Terheyden78 in 2009 reviewed 108 articles and concluded that the mean average of particu-late grafting with a membrane was 2.6mm and 24.4% required additional grafting post operatively. As the concept of “Space Maintenance” has been explored over recent years, techniques and barrier materials have improved signicantly, changing the ability of surgeons to regenerate ridge defects. e following cases are examples of the ability of these techniques to regen-erate large amounts of bone in critical regions. ese are not a few “rare cases” that have been cherry picked for this publi-cation. Careful application of the principles described in this chapter have demonstrated similar results on a very predictable basis (Box 36.12 and Figs. 36.68-36.72).ABC• Fig. . Piezoelectric Handpiece Trauma. (A and B) The shaft of the handpiece (A) and the insert (B) should not be allowed to contact the soft tissue because soft tissue burns or trauma may result. (C) Ideal position of handpiece and insert with no contact to adjacent tissues. 981CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationA B• Fig. . Ideal Retraction. (A) The piezoelectric inserts are separated from the surrounding soft tissue with “Pritchard retractors” and wide flap access. (B) Two retractors retract the tissue, whereas the piezo insert prepares the bone.Step 1: Incision a. Position—ideally bisect the attached tissue; if compromised keratinized tissue, incision should be made more to the lingual b. Broad based—release incisions should always be broad based to maintain adequate blood supply to allow for ideal healing c. Papilla sparing—when possible around adjacent natural teeth, incisions should be made maintaining the papilla; this reduces the chance of altering or losing the papilla and the development of a “black triangle” Step 2: ReflectionA full-thickness reflection is recommended. The amount of reflection is related to development of adequate exposure to the graft site for placement of bone grafts and barrier membranes. It is also important in preparation of the site for tension-free primary closure. Step 3: Removal of Recipient Site Soft TissueIt is imperative that all soft tissue is removed from the recipient site because soft tissue remnants will prevent bone formation. This may be accomplished in various ways including: (1) hand instrument removal, (2) small round burs (#8 carbide), or (3) laboratory straight handpiece burs (carbide, diamond). Step 4: DecorticationThe recipient site should be decorticated to increase bleeding (angiogenesis) and to allow bone growth factors to enter the area, enhancing bone formation. When decorticated, bleeding must be visible through the decortication sites. Cross-cut fissure burs or small, round burs may be used to perforate the cortical plate. Step 5: Tissue ReleaseIt is imperative the tissue is prepared prior to graft placement to prevent disruption of the graft material. Therefore, the flap is prepared to minimize any tension on the incision line. Ideally, the facial flap should extend a minimum of 5 mm over the lingual flap. There are two techniques which include (1) periosteal release - # 15 blade, and (2) blunt dissection – Metzunbaum scissors. Step 6: Membrane Placement a. Membrane selection—the type of membrane will depend on the shape and volume of bone required, the predictability of soft tissue closure (resorbable vs. nonresorbable), and the experience of the surgeon. b. Hydration—most membranes will need to be hydrated to allow for proper placement and to minimize the possibility of poor closure c. Fixation—the membrane should be apically fixated with tacks or sutures to minimize movement. Usually the facial/buccal tacks are placed before grafting. This initial stabilization of the membrane allows the site to remain undisturbed after graft placement. It is highly recommended to fix the membrane on the lingual/palatal aspect with tacks or sutures. d. Adequate periosteal release over the graft site—the tissue should be released enough for the flap to be stretched freely, allowing tension-free closure. Ideally the facial flap should extend a minimum of 5 mm beyond the lingual flap. Step 7: Space MaintenanceFor predicatble bone growth, the space must be maintained to allow the bone grafting material to heal undisturbed. Placement of a support system (tenting screws, polytetrafluoroethylene (PTFE) membrane with titanium, titanium mesh) must be used. Collapse of the graft site will result in compromised bone growth. Step 8: Graft Material Placement a . Autogenous: Usually, autogenous bone is recommended when bone growth of greater than 3 mm is required. When indicated, autograft should be the first layer (against the host bone). The autograft shavings should cover the complete recipient bed below the screws. • BOX 36.12 Guided Bone Regeneration ProtocolContinued • BOX 36.12 Guided Bone Regeneration Protocol—cont’d b . Allograft: The allograft should be placed as the second layer in larger bone graft cases (> 3 mm). For smaller graft cases, 100% allograft may be used (i.e. 70% FDBA / 30 DFDBA or100% FDBA Cortico-Cancellous). The particulate bone should be densely packed to avoid air spaces which tend to harbor bacteria. • After the bone graft is placed, the membrane is drawn completely over the graft material with 2 to 3 mm of overlap over native bone to limit exposure of the particulate during the healing process. The membrane should be fixated (on the free end) with tacks or sutures. In situations where the membrane cannot be fixated, it can be tucked under the lingual flap and the coronal surface can be included in the closure sutures to limit movement. If platelet-rich fibrin or platelet-rich plasma is being used, it should be placed over the membrane (in between the tissue and membrane). Step 9: Closure a . Suture selection: The most ideal sutures for tissue closure are Vicryl (resorbable) or PTFE (Cytoplast, nonresorbable). The PTFE suture allows adjustment of the suture tension as the knot is being tied, and results in minimal inflammation around a healing incision line. b . Primary sutures: the crest or ridge area should be closed first with a tension-free suture line. Mattress sutures should be placed at intervals that distribute the pressure on the incision over a large surface area. Mattress suture evert the tissue flaps, thereby decreasing the possibility of incision line opening. Interrupted sutures may be used between the mattress sutures. A common mistake is to close the vertical releasing incisions first, thereby placing tension on the crestal suture line. c . Secondary sutures: After the crestal area has been closed, the releasing incisions may be closed passively. Care should be exercised not to place too much tension on the releasing flaps, thereny limiting tension on the crestal sutures.ACB• Fig. . (A – C) Posterior mandible augmentation for horizontal regeneration using autogenous , min-eralized freeze-dried bone allograft, and GBR acellular dermis membrane. 983CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationABC• Fig. . Advanced Vertical & Horizontal defect with loss of facial and palatal cortical plates following the loss of two implants. (A) Flap reflection showing the severe destruction caused by two failed implants. (B) The final ridge form following ridge augmentation with autogenous bone and allograft/acellular dermis, (C) Final ProsthesisA B• Fig. . Maxillary Anterior Horizontal Augmentation; (A) Exposed defect, note the papilla saving inci-sion design, (B) Post-op bone augmentation healing. ABC• Fig. . Maxillary Anterior Augmentation (A). Anterior regeneration using space maintenance for site development. (Autogenous bone, FDBA and Acellular dermis). (B). Post-augmentation ridge formAB• Fig. . Vertical Ridge Augmentation (A) Pre-op, (B) Post-op. 985CHAPTER 36 Particulate Membrane grafting/Guided Bone RegenerationReferences 1. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft tissue contour changes following single-tooth extraction: a clini-cal and radiographic 12-month prospective study. Int J Periodontics Restorative Den. 2003;23:313–323. 2. Clementini M, Morlupi A, Canullo L, et al. 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