Part Two: Interpretation










R Localization ofObjects (SLOB Rule) 109
Fig.R2 (a) Illustration of the SLOB rule: vertical angulation shift of the PID. A. Central ray directed perpendicular to the
receptor superimposes both objects (
B
). B. Central ray directed from superior position projects
B
inferiorly (i.e. opposite
direction). C. Central ray directed from the inferior position projects
B
superiorly (i.e. opposite direction). Conclusion:
B
is on the buccal and is on the lingual. (b) A. Central lateral view (nos 7 and 8). B.Increased vertical angulation resulted
in a shift of the unerupted cuspid superiorly (same direction as the PID movement). Simultaneously, a horizontal shift of
the PID to the midline resulted in a shift of the cuspid toward the midline (same direction as the PID). Conclusion: the
cuspid is on the lingual aspect.
A
(a)
B
C
X-ray image
Centr
al ray
Central ray
Buccal
Buccal
Buccal
Central ray
B
B
B
B
B
B
Object on lingual side
Object on buccal side
AB
(b)
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110 Fundamentals of Oral and Maxillofacial Radiology
comparison to the first image and the object in
question appears to move superiorly, the object
of interest is positioned on the buccal. If the
object of interest moves in the same direction as
the PID, then the object is positioned more
towards the lingual.
In situations where a foreign object is located
in an edentulous region, the practitioner
maystill be able to apply the SLOB rule simply
by utilizing dental anatomic landmarks as a
guide. In this scenario, one must study the
position of the object in relation to a reference
landmark. If the object moves either away from
the landmark or in the same direction as the
landmark, its position can be determined
within either jaw. Similarly, when multiple
images have already been exposed as in a full
mouth series of images, the practitioner should
focus on specific landmarks to determine an
alteration in either the horizontal or vertical
position to localize an object. In either case,
the practitioner should first attempt to use
pre‐existing images for diagnosis prior to pre-
scribing additional images.
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Companion website: www.wiley.com/go/hubar/radiology
111
Recommendations
forInterpreting Images
S
Interpretation of dental x‐ray images is inte-
gral to oral diagnosis and treatment planning.
The best technology cannot correct for visual
miscues. When examining x‐ray images,
dental professionals all too often focus solely
on the teeth and fail to see alterations to the
surrounding structures, unless, of course, they
are too obvious to miss. The accompanying
panoramic image outlines multiple anatomic
structures (Fig.S1). In any order, the observer
should systematically evaluate each structure
or pair of structures independently: the maxil-
lary sinuses, the orbits, the border of the man-
dible, the temporomandibular joint, the border
of the maxilla, the dentition, etc. Doing so will
reduce the number of anomalies missed. The
author’s recommendation is for the observer
to consistently use one sequential visual pat-
tern and simply adapt it for each type of image
viewed (i.e. intraoral, panoramic, cephalomet-
ric and CBCT images). It is also recommended
that evaluation of the teeth and large osseous
lesions be diagnosed toward the end of the
interpretation. At that time, the observer can
solely focus on alterations to the dentition
and include large osseous anomalies. This
should improve the diagnostic proficiency of
the clinician.
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112 Fundamentals of Oral and Maxillofacial Radiology
Systematic observation order:
1. Red: maxillary sinuses (right and left)
2. Purple: mandible (exclude the teeth)
3. Yellow line: alveolar crestal bone, both
maxilla and mandible
4. Green: zygomatic arch
5. Magenta: hyoid bone
6. Yellow shading: surrounding structures
7. Blue: maxillary and mandibular teeth
A
B
Fig. S1 Interpretation of a panoramic image. Red, maxillary sinuses; purple, mandible; yellow line, maxilla; green,
zygomatic arch; magenta, hyoid bone; yellow shading, surrounding structures; blue, dentition.
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Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar.
© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/hubar/radiology
113
X‐ray Puzzles: Spot
theDifferences
T
The following section contains eight pairs of
extraoral dental images. The object of this
exercise is for the observer to locate subtle
differences between two near‐identical x‐ray
images. The changes are highlighted in the
accompanying image. The intent of the author
is to demonstrate that a thorough analysis of
every image is critical to find all of the anoma-
lies. Hopefully these puzzles and the interpre-
tation recommendations previously mentioned
will help train the observer to more critically
examine every x‐ray image and become a
better diagnostician.
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114 Fundamentals of Oral and Maxillofacial Radiology
Puzzle 1
Spot ten differences between the panoramic images
Please see page 122 for solution
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T X‐ray Puzzles: Spot theDifferences 115
Puzzle 2
Spot ten differences between the panoramic images
Please see page 122 for solution
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116 Fundamentals of Oral and Maxillofacial Radiology
Puzzle 3
Spot ten differences between the coronal images
Please see page 122 for solution
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T X‐ray Puzzles: Spot theDifferences 117
Puzzle 4
Spot ten differences between the coronal images
Please see page 122 for solution
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118 Fundamentals of Oral and Maxillofacial Radiology
Puzzle 5
Spot nine differences between the panoramic images
Please see page 123 for solution
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T X‐ray Puzzles: Spot theDifferences 119
Puzzle 6
Spot nine differences between the mid-sagittal images
Please see page 123 for solution
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120 Fundamentals of Oral and Maxillofacial Radiology
Puzzle 7
Spot eight differences between the sagittal images
Please see page 123 for solution
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T X‐ray Puzzles: Spot theDifferences 121
Puzzle 8
Spot nine differences between the sagittal images
Please see page 123 for solution
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Puzzle 1 key
Puzzle 2 key
Puzzle 3 key
Puzzle 4 key
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Puzzle 5 key
Puzzle 6 key
Puzzle 7 key
Puzzle 8 key
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© 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/hubar/radiology
124
Radiographic Anatomy
U
Interpretation of abnormalities requires a thorough
knowledge of normal anatomy. A comprehensive
study of skull osteology cannot be covered within
the scope of this textbook. Only the major land-
marks commonly found on conventional dental
x‐ray images will be presented here.
Note: Natural skeletal variations between one
patient and another can dramatically alter ana-
tomic appearances. Variations in the operators
techniques, from positioning of the receptor to
alignment of the PID, can dramatically distort
or even obscure a landmark. Two‐dimensional
images of three‐dimensional structures auto-
matically result in object superimposition and
panoramic imaging inherently produces ghost
images which can easily lead to misinterpreta-
tion of normal anatomic landmarks.
1. DENTAL ANATOMY
Enamel (Fig. U1) is the most mineralized
substance in the human body. Its 90% plus min-
eralization content is very effective at absorbing
x radiation and as a result enamel typically
appears as a thin radiopaque shell surrounding
the crown of a tooth. It gradually tapers in
thickness to a fine edge at the level of the
cementum. It is noteworthy that the density
and thickness of enamel is quite variable due to
age, environment, congenital hypoplasia, etc.
Dentin (Fig.U1) is situated between the enamel
and pulp and it is approximately two‐thirds
as mineralized as enamel. As a consequence,
dentin will appear less radiopaque than enamel.
It has a density comparable to bone. Generally
the junction between enamel and dentin is
distinguishable on x‐ray images. However an
x‐ray image with poor contrast will make it dif-
ficult to differentiate dentin from enamel. Similar
to enamel, dentin’s density and thickness may
be quite variable due to environmental and
congenital factors.
Cementum is a thin calcified layer covering the
root surface. It is approximately 50% mineral-
ized. Differentiating cementum from dentin on
an x‐ray image is very difficult because the
cementum layer is quite thin and its mineral
content is similar to that of dentin. Hyperce-
mentosis, which is visible on x‐ray images, is an
alteration in the shape of a root. It occurs as a
result of the deposition of variable amounts of
secondary cementum.
Pulp (Fig. U1) is composed of vascularized
and innervated soft tissue (i.e. connective tissue,
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U Radiographic Anatomy 125
blood vessels, nerves). The term pulp is often
used in lieu of pulp chamber or pulp canals. The
pulp chamber and canals are hollowed cavities
within the center of the tooth that extend from
the coronal portion of the tooth to the apex of
the root(s) which contains the pulpal tissue.
A healthy pulp appears radiolucent in compari-
son with the dentin and enamel. The chamber
and canals may become partially or fully calci-
fied over time and as a result become radiopaque.
Congenital maladies, natural aging and trauma
contribute to dentin production, thus reducing
the size of the pulp chamber. In addition, calci-
fied denticles
may form resulting in a reduc-
tion in the size of the pulp chamber.
Lamina dura (Fig.U2) is a thin radiopaque line
that normally outlines the border of the entire
tooth socket. It is merely a manifestation of x‐ray
beam absorption as the x rays pass through the
socket wall and is not any more mineralized
than normal trabecular bone. Many factors can
alter the appearance or cause the disappear-
ance of the lamina dura. It will typically appear
very distinct and uniform if the horizontal
AB
Fig.U1 Tooth structure. Red, enamel; grey, dentin; yellow, pulp chamber.
Fig.U2 Radiographic anatomy: a, outline of the soft tissue
of the nose; it encompasses the uniformly faint radiopaque
shadow superimposed over the roots of the maxillary
central and lateral incisors; b, floor of the nasal fossa; c,
anterior nasal spine (V‐shaped radiopacity). The black
arrows point to a thin radiopaque line which is the lamina
dura. The red arrows point to a thin radiolucent line
which is the periodontal ligament space.
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126 Fundamentals of Oral and Maxillofacial Radiology
angulation of the x‐ray beam directly passes
through the width (i.e. bucco‐lingually) of the
socket walls; whereas if the x‐ray beam passes
tangentially through the tooth socket, a smaller
quantity of x rays will be absorbed and the
lamina dura would be much less obvious or
may not even be visible on an x‐ray image.
Additionally, if other anatomic structures are
superimposed over the socket, these structures
may disrupt the continuity of the lamina dura.
Complete absence of the lamina dura may also
be a sign of pathosis such as Paget’s disease,
fibrous dysplasia, osteopetrosis, osteosarcoma
and hyperparathyroidism.
Periodontal ligament space (Fig.U2) is a thin
radiolucent line located between the lamina
dura and the root of a tooth on an x‐ray image.
It extends mesiodistally around the entire root,
beginning and ending at the level of the alveo-
lar crest. This radiolucent space contains the
collagenous periodontal ligament which is not
visible on x‐ray images. The width of the peri-
odontal ligament space (PDL space) can be
quite variable even within the same individ-
ual. Similar to the variability in the thickness
of the lamina dura, the PDL space may vary in
width simply as a result the operator’s
intraoral technique. Modification of the hori-
zontal angulation of the x‐ray beam can alter
the appearance of the PDL space. Occlusal bit-
ing forces or pathosis such as an osteosarcoma
may also lead to abnormal widening of the
PDL space.
Alveolar bone refers to the anatomic bone com-
prising the mandible and maxilla that surrounds
and supports the dentition. Cortical bone (aka
compact bone) is the dense shell of bone that
forms the outer plates of both the maxilla and
the mandible. Cortical bone appears as a thin
radiopaque line of variable thickness. Trabecular
bone (aka cancellous bone or spongy bone) is the
bone that lies between the buccal and lingual
cortical plates. Trabecular bone typically has a
lace‐like radiopaque appearance.
Alveolar crest is the superior aspect of the
interproximal cortical plate of bone. It appears
as a thin radiopaque line at the height of the
alveolus spanning between adjacent teeth or
along edentulous ridges. It may be horizontal
or angled vertically. In a healthy dentition the
alveolar crest runs parallel to and approxi-
mately one millimeter inferior to the cemento‐
enamel junction. Deviations from normal may
be as a result of periodontal disease, etc. which
may alter the height, angulation and thickness
of the alveolar crest.
2. ANATOMIC LANDMARKS OF THE
MAXILLARY REGION
Radiopaque landmarks
Anterior nasal spine (Fig.U2) is a midline bony
projection located at the floor of the nasal cav-
ity. It appears as a small v‐shaped radiopacity.
It is more easily observed on intraoral central
incisor and lateral cephalometric projections.
On panoramic images, the anterior nasal spine,
the soft tissue of the nose and the oropharynx
are frequently superimposed, which makes it
difficult to discern.
Inverted “Y” or “X” (Fig.U3) produced by the
intersection of the floor of the maxillary sinus
and the nasal fossa. The radiolucent area to the
right is the maxillary sinus and the radiolucent
area to the left is the nasal fossa.
Nose (soft tissue) (Fig.U2) will often appear
as a faint radiopaque shadow superimposed
over the roots of the maxillary incisors on
intraoral images. The anterior nasal spine
will generally be superimposed over the soft
tissue of the nose.
Nasal septum (Fig. U4) is the dividing wall
composed of bone and cartilage that runs down
the middle of the nasal fossa.
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U Radiographic Anatomy 127
Fig.U3 (a) Characteristic inverted “Y” landmark produced by the intersection of the floor of the maxillary sinus
and the nasal fossa. (b) Characteristic inverted “X” landmark produced by the intersection of the floor of the
maxillary sinus (MS) and the nasal fossa (NF).
A
NF
MS
B
(a)
AB
(b)
NF
MS
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128 Fundamentals of Oral and Maxillofacial Radiology
Nasolabial folds (Fig. U5) are the bilateral
folds of soft tissue extending from the lateral
aspect of the nose to the corner of the mouth.
Insertion of an intraoral receptor holder in the
canine–premolar region will compress the soft
tissue. Superimposition of this thick soft tissue
over the teeth and bone will attenuate suffi-
cient radiation so as to appear as a diffuse
oblique radiopaque shadow extending posteri-
orly from the cuspid–premolar intraoral
region. A sharp demarcation line will be
observed at the anterior border of the nasola-
bial fold. The region anterior to the nasolabial
fold will appear more radiolucent in compari-
son. In edentulous patients, this landmark can
assist the operator in determining the right and
left sides of the patient.
Pterygoid plates (medial and lateral) of the
sphenoid bone (see Fig. M24) are best visualized
on axial images. Intraoral images may or may
not capture them because the plates are located
posterior to the maxillary tuberosity. They will
appear as uniform radiopacities without any
Fig.U4 Anatomic landmarks: a, nasal septum; b, mid‐palatine
suture appearing as a thin radiopaque line located between
the maxillary central incisors; c, nasal fossa, which is the radi-
olucency extending superior to the incisors and bisected by
the nasal septum.
AB
Fig.U5 Nasolabial fold (highlighted in B).
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U Radiographic Anatomy 129
trabecular pattern. The hamular process extends
off the medial pterygoid plate.
Palatine torus (pl. tori) (Fig. U6) is a bony
protuberance located in the midline of the
hard palate. It is quite a common phenomenon,
occurring in approximately 20% of the popu-
lation. A torus is typically less than 2 cm in
diameter and may consist of several lobes of
dense bone. A palatine torus usually appears as
a dense radiopacity that may be partially super-
imposed over the roots of posterior maxillary
teeth. It often is misdiagnosed as the zygoma.
Synonyms include torus palatinus and palatal
torus.
Zygomatic arch (Fig. U7) is comprised of the
zygoma and zygomatic process. The zygomatic
process is actually an extension of the maxilla,
temporal bone and frontal bone. In periapical
images it appears as a U‐shaped radiopacity in
the first and second molar region. Generally, a
portion of the maxillary sinus will be visible
behind it. Over‐ and underangulation of intraoral
imaging techniques can dramatically vary the
appearance of the zygomatic process. The
zygoma appears as a uniform radiopacity con-
tinuing posteriorly from the zygomatic process.
On intraoral images the inferior border of the
zygoma will only be visible.
Radiolucent landmarks
Incisive foramen (Fig.U8) is the opening of the
incisive canal located immediately behind the
maxillary central incisors. The nasopalatine
nerve and sphenopalatine artery exit through
this foramen and supply the oral mucosa and
hard palate. On periapical x‐ray images, the
Fig.U6 Palatine torus (highlighted).
A
B
Fig.U7 Zygomatic arch (highlighted in B).
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130 Fundamentals of Oral and Maxillofacial Radiology
incisive foramen is located in the midline
between the roots of the central incisors. Its
appearance is quite variable due to normal ana-
tomic variation and due to the operator’s angu-
lation of the x‐ray beam. Typically it appears as
a well‐defined, round or elliptical radiolucency
measuring up to 1 cm in diameter. Abnormal
enlargement of the incisive foramen may be
indicative of a nasopalatine cyst. Synonyms
include nasopalatine foramen and anterior
nasopalatine foramen.
Lateral fossa (Fig.U9) is a mild skeletal depres-
sion in the region of the maxillary lateral inci-
sor. On a periapical image, the region may or
may not appear slightly more radiolucent than
the surrounding area. It should not be misdiag-
nosed as periapical pathology associated with a
tooth. The lamina dura will typically be intact
and clinically the patient will be asymptomatic.
A synonym is incisive fossa.
Maxillary sinus (FigsU10 and U11) is the larg-
est of the paranasal sinuses and is bilaterally
located within the body of the maxilla. Each
sinus is bounded by the zygoma and the body
of the maxilla. The maxillary sinus extends
anteriorly toward the canine. Posteriorly it may
extend into the tuberosity region, often seen
dipping interproximally between the roots of
multiple teeth. Its size and shape is variable in
appearance. Age and the loss of teeth contrib-
ute to increased pneumatization
of a sinus,
with the floor of the maxillary sinus possibly
extending to the crest of the alveolar ridge.
Within the maxillary sinus there is an ostium
that connects the sinus to the middle concha
of the nasal cavity. The maxillary sinuses typi-
cally appear as large radiolucencies outlined
by a thin radiopaque border. Extraoral images
such as panoramic and CBCT images project a
full sinus view. However, with the limited field
Fig.U8 Incisive foramen: appears as an elliptical radiolu-
cency located between the roots of the central incisors
(highlighted).
Fig. U9 Lateral fossa: appears as a diffuse radiolucency
located around the root of a lateral incisor with an intact
lamina dura (highlighted).
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U Radiographic Anatomy 131
of view on periapical images, only the inferior
aspect of the maxillary sinus will be visible.
Superimposition of the floor of the nasal cavity
over the maxillary sinus is often seen in periapical
views of the canine. The intersection of the
radiopaque borders of the sinus and the nasal
cavity produces an inverted “Y” or “X” land-
mark. If the top of the image cuts off a segment
of the intersecting lines, the intersecting lines
will appear as a “Y”; if the intersecting lines are
fully visible on the image, the result appears
more like an “X”. This landmark is useful to
the operator to determine if a periorbital image
belongs either to the right or left quadrant.
This is particularly helpful for arranging x‐ray
images of edentulous patients. Actual inter-
pretation of the intersecting inverted “Y” or
“X” landmark is as follows: the oblique radiolu-
cent region towards the anterior demarcates the
nasal fossa, while the posterior radiolucency is
the maxillary sinus.
The relationship of the maxillary sinus to the
maxillary molars in particular is often misinter-
preted. Two‐dimensional images of teeth often
appear to project the roots into the maxillary
sinus when in fact the sinus is simply envelop-
ing the roots and it is only superimposed over
it. An analogy would be to poke your finger
into a fully inflated balloon and then observe it
from the side. Viewing the balloon from the
side, it would give the illusion that your finger
was actually inside the balloon, when in fact it
was merely being enveloped by it. Advanced
imaging techniques can accurately show their
true relationship. An additional complicating
effect that often is misdiagnosed as pathology
where none exists also occurs when a sinus is
A
B
Fig.U10 Maxillary sinus (lower border highlighted in B).
Fig.U11 Maxillary sinus (highlighted).
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132 Fundamentals of Oral and Maxillofacial Radiology
superimposed over a root. The effect is an illu-
sionary widening of the PDL space around the
apex. A normal radiolucent PDL space and
the superimposed sinus together exaggerate
the appearance of the PDL space. This may lead
to misinterpretation as non‐existent periapical
pathology. Further clinical testing is necessary
to rule out possible periapical pathology.
Within a healthy sinus there may appear to
be thin radiolucent and radiopaque lines. The
narrow radiolucent lines are called nutrient
canals
, which carry the superior alveolar
nerves and vessels, while the thin radiopaque
lines are typically septa, which are simply undu-
lating folds of cortical bone within the sinus.
Neither should be considered pathogenic.
The maxillary sinuses are lined with a thin
mucosal membrane. Inflammation of this
mucosal lining can contribute to dental symp-
toms due to the close proximity of the apices of
the molars to the inferior border of the sinus.
Depending upon the degree of mucosal inflam-
mation, the inferior portion of one or both
maxillary sinuses may appear to be radiopaque.
A thorough clinical examination of patients
experiencing dental pain may reveal a healthy
dentition with associated acute sinusitis.
Inadequate alveolar bone height for dental
implant placement often calls for a sinus lift
procedure with bone augmentation using
autogenous or alloplastic materials (see Fig. Y14).
In post‐sinus lift surgery, the inferior aspect of
the grafted sinus material typically appears as a
uniformly dense, irregular or dome‐shaped
radiopacity. This radiopacity must not be con-
fused with a mucocele within the sinus, which
is a simply a build‐up of fluids. On rare occa-
sions, there may be aplasia
of the maxillary
sinus or complete opacification of the sinuses.
Mid‐palatine suture (Fig.U4) is the line of union
between the horizontal plates of the palatine
bone. It typically appears as a thin radiolucent
line extending from the incisive canal posteri-
orly. On a periapical x‐ray image of the central
incisors, it will often appear to extend from the
alveolar crest superiorly up to the anterior nasal
septum. However, its visibility on an x‐ray
image is particularly dependent upon the hori-
zontal angulation of the x‐ray beam. Directing
the x‐ray beam diagonally through the thin
mid‐palatine suture may obscure it because the
suture line will now be superimposed with the
denser surrounding palatal bone. Synonyms
include intermaxillary suture, median palatine
suture and palatomaxillary suture.
Nasal fossa (Fig. U4) is the large midline air
space that extends anteroposteriorly from the
nares into the nasopharynx. It is divided into
two compartments by the nasal septum. It is
bounded superiorly by the cribiform plateof
the ethmoid bone and inferiorly by the pro-
cesses of the maxilla and the horizontal portion
of the palatine bone. The lateral walls of the
fossa each have three conchae
(synonym:
turbinates): the superior, middle and inferior
conchae. Anterior periapical x‐ray images
often will capture a portion of the inferior
aspect of the nasal fossa. Its presence or absence
will vary greatly depending on the extent of
the vertical angulation of the x‐ray beam. In the
central incisor region, the inferior border of the
fossa will typically appear as a V‐shaped radi-
opaque line located well above the apices of
the teeth. The nasal septum appears in the mid-
line as a radiopaque line rising vertically from
the inferior border of the nasal fossa. The
adjoining air space of the nasal cavity will
appear radiolucent and it will be bisected by
the nasal septum. The maxillary cuspid peria-
pical view often contains the floor of the nasal
fossa intersecting with the floor of the maxil-
lary sinus, forming an inverted “Y” or “X” con-
figuration (Fig. U3). The nasal conchae will be
more visible on extraoral imaging of the nasal
fossa. The conchae will appear as elongated
radiopacities extending the length of the nasal
cavity in sagittal views, while in cross‐sectional
views the conchae appear more semicircular,
like the musical symbol “bass clef.” Synonyms
include nasal cavity and nasal antrum.
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U Radiographic Anatomy 133
3. ANATOMIC LANDMARKS OF THE
MANDIBULAR REGION
Radiopaque landmarks
Coronoid process (Fig.U12) is the thin, tri-
angular‐shaped process of the anterosuperior
aspect of the ramus. Its triangular shape resem-
bles the dorsal fin of a shark. This mandibular
landmark is typically observed in extraoral
images. However, it may also appear in maxil-
lary molar periapical images. This can occur
because the mandible must swing open to
accommodate the intraoral receptor holder.
In so doing, the coronoid process rotates anter-
oinferiorly and often becomes superimposed
over the maxillary molar tuberosity region. The
coronoid process appears as a homogeneous
triangular radiopacity.
Genial tubercles (Fig.U13) are small bony pro-
jections in the midline on the lingual aspect of
the mandible. The genioglossus and geniohyoid
muscles attach at these points. They are quite
variable in appearance. On mandibular incisor
periapical images, the genial tubercles may
appear as a donut‐shaped radiopacity several
millimeters in diameter with a pin‐point radio-
lucent center (i.e. lingual foramen
). On axial
CBCT images and mandibular occlusal images,
the genial tubercles will typically appear as
small projections emanating from the lingual
cortical plate. A synonym is mental spine.
Inferior border (i.e. cortical plate) of the
mandible (Fig.U14) appears as a uniformly dense
radiopaque band. On periapical x‐ray images,
it should not be confused with either the exter-
nal or the internal oblique ridges. Generally, the
inferior border of the mandible is not observed
on periapical images unless there was excessive
negative vertical angulation of the x‐ray beam.
Lip line (Fig.U15) is the result of the soft tissue
of the lip attenuating enough radiation to be
visible on a periapical image of the anterior
teeth. The lip line is recognized by a uniform
change in density horizontally across the coro-
nal portions of teeth. The more radiolucent
portion of the crown is superior to the lip line.
Mental ridge (Fig.U16) is a dense elevation on
the anterolateral aspect of the body of the man-
dible. On anterior periapical images, it appears
AB
Fig.U12 Coronoid process: appears as a triangular‐shaped radiopacity located in a maxillary molar periapical
(highlighted in B).
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134 Fundamentals of Oral and Maxillofacial Radiology
as a thin radiopaque line extending posteriorly
from the midline (i.e. bilaterally). It usually is
located inferior to the teeth, but if excessive
negative vertical angulation of the x‐ray beam
occurs, the mental ridge will be superimposed
over the mandibular anterior teeth. A synonym
is mental process.
External oblique ridge (Fig. U17) is the bony
protuberance that extends off the anterolateral
AB
C
Fig.U13 Genial tubercles. A. The genial tubercles appear as a radiopaque circle. The small radiolucency within the genial
tubercles is the lingual foramen. B. Increased vertical angulation of the PID results in the genial tubercles appearing as a
spiny process. C. The genial tubercles appear as a spiny process in an axial view.
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U Radiographic Anatomy 135
border of the ramus and runs diagonally
towards the area of the first molar. It serves as
an attachment site of the buccinator muscle.
The external oblique ridge typically appears to
run parallel and superior to the internal oblique
ridge. It appears as a thin oblique radiopaque
line that gradually disappears as it extends
from the ramus to approximately the location
of the first molar.
Internal oblique ridge (Fig. U17) is the bony
protuberance located on the lingual surface of
mandible extending diagonally downward
from the ramus and ending anteriorly near the
apices of the premolars. Its function is to serve
as an attachment site for the mylohyoid muscle
of the floor of the mouth. The appearance of the
internal oblique ridge can be quite variable. On
periapical images, it may appear to be a well‐
defined, thin radiopaque line located inferior to
Fig.U14 Inferior border of the mandible (highlighted).
Fig.U15 Lip line (highlighted).
Fig.U16 Mental ridge (arrows).
Fig.U17 External oblique ridge (a) and internal oblique
ridge (b) (synonym: mylohyoid ridge).
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136 Fundamentals of Oral and Maxillofacial Radiology
the external oblique ridge. It runs obliquely at
the level of the apices of the molars and premo-
lars from the ramus. In some individuals, the
internal oblique ridge may be quite diffuse and
indistinguishable from the surrounding alveo-
lar bone. A synonym is mylohyoid ridge.
Mandibular torus (pl. tori) (Fig.U18) is a bony
protuberance located on the lingual side of
the mandible, typically found bilaterally in
the cuspid and premolar region. It occurs less
commonly than the palatine torus (i.e. in
approximately 8% versus 20% of the popula-
tion). A mandibular torus typically appears as a
rounded uniform radiopacity. The size of a
torus is quite variable. Occasionally, bilateral
tori together may fill the floor of the mouth.
Placement of solid‐state receptors for intraoral
images may be physically impossible due to
space limitation. PSP plates, which are compar-
atively thinner and more flexible, may be an
alternative if available. Otherwise extraoral
imaging (e.g. panoramic image) may be the
only practical method to image the teeth. A syno-
nym is torus mandibularis.
Radiolucent landmarks
Lingual foramen (Fig.U13) is a small foramen
that the lingual artery passes through. It is
situated on the lingual side in the midline of
the mandible. Typically on periapical images of
the mandibular anterior region, the lingual
foramen will appear as a pinpoint radiolucency
surrounded by the radiopaque genial tuber-
cles. The small size and location of the lingual
foramen often make it difficult to visualize on
x‐ray images.
Mandibular canal (FigsU19 and U20) extends
from the mandibular foramen to the mental
foramen through the ramus and body of the
mandible. The inferior alveolar nerve and
artery travel within this canal. An extension of
the mandibular canal can sometimes be seen
AB
Fig.U18 Bilateral mandibular tori (highlighted in B).
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R Localization ofObjects (SLOB Rule) 109Fig.R2 (a) Illustration of the SLOB rule: vertical angulation shift of the PID. A. Central ray directed perpendicular to the receptor superimposes both objects ( B). B. Central ray directed from superior position projects B inferiorly (i.e. opposite direction). C. Central ray directed from the inferior position projects B superiorly (i.e. opposite direction). Conclusion: B is on the buccal and is on the lingual. (b) A. Central lateral view (nos 7 and 8). B.Increased vertical angulation resulted in a shift of the unerupted cuspid superiorly (same direction as the PID movement). Simultaneously, a horizontal shift of the PID to the midline resulted in a shift of the cuspid toward the midline (same direction as the PID). Conclusion: the cuspid is on the lingual aspect.A(a)BCX-ray imageCentral rayCentral rayBuccalBuccalBuccalCentral rayBBBBBBObject on lingual sideObject on buccal sideAB(b)http://dentalebooks.com 110 Fundamentals of Oral and Maxillofacial Radiologycomparison to the first image and the object in question appears to move superiorly, the object of interest is positioned on the buccal. If the object of interest moves in the same direction as the PID, then the object is positioned more towards the lingual.In situations where a foreign object is located in an edentulous region, the practitioner maystill be able to apply the SLOB rule simply by utilizing dental anatomic landmarks as a guide. In this scenario, one must study the position of the object in relation to a reference landmark. If the object moves either away from the landmark or in the same direction as the landmark, its position can be determined within either jaw. Similarly, when multiple images have already been exposed as in a full mouth series of images, the practitioner should focus on specific landmarks to determine an alteration in either the horizontal or vertical position to localize an object. In either case, the practitioner should first attempt to use pre‐existing images for diagnosis prior to pre-scribing additional images.http://dentalebooks.com Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology111Recommendations forInterpreting ImagesSInterpretation of dental x‐ray images is inte-gral to oral diagnosis and treatment planning. The best technology cannot correct for visual miscues. When examining x‐ray images, dental professionals all too often focus solely on the teeth and fail to see alterations to the surrounding structures, unless, of course, they are too obvious to miss. The accompanying panoramic image outlines multiple anatomic structures (Fig.S1). In any order, the observer should systematically evaluate each structure or pair of structures independently: the maxil-lary sinuses, the orbits, the border of the man-dible, the temporomandibular joint, the border of the maxilla, the dentition, etc. Doing so will reduce the number of anomalies missed. The author’s recommendation is for the observer to consistently use one sequential visual pat-tern and simply adapt it for each type of image viewed (i.e. intraoral, panoramic, cephalomet-ric and CBCT images). It is also recommended that evaluation of the teeth and large osseous lesions be diagnosed toward the end of the interpretation. At that time, the observer can solely focus on alterations to the dentition and include large osseous anomalies. This should improve the diagnostic proficiency of the clinician.http://dentalebooks.com 112 Fundamentals of Oral and Maxillofacial RadiologySystematic observation order:1. Red: maxillary sinuses (right and left)2. Purple: mandible (exclude the teeth)3. Yellow line: alveolar crestal bone, both maxilla and mandible4. Green: zygomatic arch5. Magenta: hyoid bone6. Yellow shading: surrounding structures7. Blue: maxillary and mandibular teethABFig. S1 Interpretation of a panoramic image. Red, maxillary sinuses; purple, mandible; yellow line, maxilla; green, zygomatic arch; magenta, hyoid bone; yellow shading, surrounding structures; blue, dentition.http://dentalebooks.com Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology113X‐ray Puzzles: Spot theDifferencesTThe following section contains eight pairs of extraoral dental images. The object of this exercise is for the observer to locate subtle differences between two near‐identical x‐ray images. The changes are highlighted in the accompanying image. The intent of the author is to demonstrate that a thorough analysis of every image is critical to find all of the anoma-lies. Hopefully these puzzles and the interpre-tation recommendations previously mentioned will help train the observer to more critically examine every x‐ray image and become a better diagnostician.http://dentalebooks.com 114 Fundamentals of Oral and Maxillofacial RadiologyPuzzle 1Spot ten differences between the panoramic imagesPlease see page 122 for solutionhttp://dentalebooks.com T X‐ray Puzzles: Spot theDifferences 115Puzzle 2Spot ten differences between the panoramic imagesPlease see page 122 for solutionhttp://dentalebooks.com 116 Fundamentals of Oral and Maxillofacial RadiologyPuzzle 3Spot ten differences between the coronal imagesPlease see page 122 for solutionhttp://dentalebooks.com T X‐ray Puzzles: Spot theDifferences 117Puzzle 4Spot ten differences between the coronal imagesPlease see page 122 for solutionhttp://dentalebooks.com 118 Fundamentals of Oral and Maxillofacial RadiologyPuzzle 5Spot nine differences between the panoramic imagesPlease see page 123 for solutionhttp://dentalebooks.com T X‐ray Puzzles: Spot theDifferences 119Puzzle 6Spot nine differences between the mid-sagittal imagesPlease see page 123 for solutionhttp://dentalebooks.com 120 Fundamentals of Oral and Maxillofacial RadiologyPuzzle 7Spot eight differences between the sagittal imagesPlease see page 123 for solutionhttp://dentalebooks.com T X‐ray Puzzles: Spot theDifferences 121Puzzle 8Spot nine differences between the sagittal imagesPlease see page 123 for solutionhttp://dentalebooks.com Puzzle 1 keyPuzzle 2 keyPuzzle 3 keyPuzzle 4 keyhttp://dentalebooks.com Puzzle 5 keyPuzzle 6 keyPuzzle 7 keyPuzzle 8 keyhttp://dentalebooks.com Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology124Radiographic AnatomyUInterpretation of abnormalities requires a thorough knowledge of normal anatomy. A comprehensive study of skull osteology cannot be covered within the scope of this textbook. Only the major land-marks commonly found on conventional dental x‐ray images will be presented here.Note: Natural skeletal variations between one patient and another can dramatically alter ana-tomic appearances. Variations in the operator’s techniques, from positioning of the receptor to alignment of the PID, can dramatically distort or even obscure a landmark. Two‐dimensional images of three‐dimensional structures auto-matically result in object superimposition and panoramic imaging inherently produces ghost images which can easily lead to misinterpreta-tion of normal anatomic landmarks.1. DENTAL ANATOMYEnamel (Fig. U1) is the most mineralized substance in the human body. Its 90% plus min-eralization content is very effective at absorbing x radiation and as a result enamel typically appears as a thin radiopaque shell surrounding the crown of a tooth. It gradually tapers in thickness to a fine edge at the level of the cementum. It is noteworthy that the density and thickness of enamel is quite variable due to age, environment, congenital hypoplasia, etc.Dentin (Fig.U1) is situated between the enamel and pulp and it is approximately two‐thirds as mineralized as enamel. As a consequence, dentin will appear less radiopaque than enamel. It has a density comparable to bone. Generally the junction between enamel and dentin is distinguishable on x‐ray images. However an x‐ray image with poor contrast will make it dif-ficult to differentiate dentin from enamel. Similar to enamel, dentin’s density and thickness may be quite variable due to environmental and congenital factors.Cementum is a thin calcified layer covering the root surface. It is approximately 50% mineral-ized. Differentiating cementum from dentin on an x‐ray image is very difficult because the cementum layer is quite thin and its mineral content is similar to that of dentin. Hyperce-mentosis, which is visible on x‐ray images, is an alteration in the shape of a root. It occurs as a result of the deposition of variable amounts of secondary cementum.Pulp (Fig. U1) is composed of vascularized and innervated soft tissue (i.e. connective tissue, http://dentalebooks.com U Radiographic Anatomy 125blood vessels, nerves). The term pulp is often used in lieu of pulp chamber or pulp canals. The pulp chamber and canals are hollowed cavities within the center of the tooth that extend from the coronal portion of the tooth to the apex of the root(s) which contains the pulpal tissue. A healthy pulp appears radiolucent in compari-son with the dentin and enamel. The chamber and canals may become partially or fully calci-fied over time and as a result become radiopaque. Congenital maladies, natural aging and trauma contribute to dentin production, thus reducing the size of the pulp chamber. In addition, calci-fied denticles may form resulting in a reduc-tion in the size of the pulp chamber.Lamina dura (Fig.U2) is a thin radiopaque line that normally outlines the border of the entire tooth socket. It is merely a manifestation of x‐ray beam absorption as the x rays pass through the socket wall and is not any more mineralized than normal trabecular bone. Many factors can alter the appearance or cause the disappear-ance of the lamina dura. It will typically appear very distinct and uniform if the horizontal ABFig.U1 Tooth structure. Red, enamel; grey, dentin; yellow, pulp chamber.Fig.U2 Radiographic anatomy: a, outline of the soft tissue of the nose; it encompasses the uniformly faint radiopaque shadow superimposed over the roots of the maxillary central and lateral incisors; b, floor of the nasal fossa; c, anterior nasal spine (V‐shaped radiopacity). The black arrows point to a thin radiopaque line which is the lamina dura. The red arrows point to a thin radiolucent line which is the periodontal ligament space.http://dentalebooks.com 126 Fundamentals of Oral and Maxillofacial Radiologyangulation of the x‐ray beam directly passes through the width (i.e. bucco‐lingually) of the socket walls; whereas if the x‐ray beam passes tangentially through the tooth socket, a smaller quantity of x rays will be absorbed and the lamina dura would be much less obvious or may not even be visible on an x‐ray image. Additionally, if other anatomic structures are superimposed over the socket, these structures may disrupt the continuity of the lamina dura. Complete absence of the lamina dura may also be a sign of pathosis such as Paget’s disease, fibrous dysplasia, osteopetrosis, osteosarcoma and hyperparathyroidism.Periodontal ligament space (Fig.U2) is a thin radiolucent line located between the lamina dura and the root of a tooth on an x‐ray image. It extends mesiodistally around the entire root, beginning and ending at the level of the alveo-lar crest. This radiolucent space contains the collagenous periodontal ligament which is not visible on x‐ray images. The width of the peri-odontal ligament space (PDL space) can be quite variable even within the same individ-ual. Similar to the variability in the thickness of the lamina dura, the PDL space may vary in width simply as a result the operator’s intraoral technique. Modification of the hori-zontal angulation of the x‐ray beam can alter the appearance of the PDL space. Occlusal bit-ing forces or pathosis such as an osteosarcoma may also lead to abnormal widening of the PDL space.Alveolar bone refers to the anatomic bone com-prising the mandible and maxilla that surrounds and supports the dentition. Cortical bone (aka compact bone) is the dense shell of bone that forms the outer plates of both the maxilla and the mandible. Cortical bone appears as a thin radiopaque line of variable thickness. Trabecular bone (aka cancellous bone or spongy bone) is the bone that lies between the buccal and lingual cortical plates. Trabecular bone typically has a lace‐like radiopaque appearance.Alveolar crest is the superior aspect of the interproximal cortical plate of bone. It appears as a thin radiopaque line at the height of the alveolus spanning between adjacent teeth or along edentulous ridges. It may be horizontal or angled vertically. In a healthy dentition the alveolar crest runs parallel to and approxi-mately one millimeter inferior to the cemento‐enamel junction. Deviations from normal may be as a result of periodontal disease, etc. which may alter the height, angulation and thickness of the alveolar crest.2. ANATOMIC LANDMARKS OF THE MAXILLARY REGIONRadiopaque landmarksAnterior nasal spine (Fig.U2) is a midline bony projection located at the floor of the nasal cav-ity. It appears as a small v‐shaped radiopacity. It is more easily observed on intraoral central incisor and lateral cephalometric projections. On panoramic images, the anterior nasal spine, the soft tissue of the nose and the oropharynx are frequently superimposed, which makes it difficult to discern.Inverted “Y” or “X” (Fig.U3) produced by the intersection of the floor of the maxillary sinus and the nasal fossa. The radiolucent area to the right is the maxillary sinus and the radiolucent area to the left is the nasal fossa.Nose (soft tissue) (Fig.U2) will often appear as a faint radiopaque shadow superimposed over the roots of the maxillary incisors on intraoral images. The anterior nasal spine will generally be superimposed over the soft tissue of the nose.Nasal septum (Fig. U4) is the dividing wall composed of bone and cartilage that runs down the middle of the nasal fossa.http://dentalebooks.com U Radiographic Anatomy 127Fig.U3 (a) Characteristic inverted “Y” landmark produced by the intersection of the floor of the maxillary sinus and the nasal fossa. (b) Characteristic inverted “X” landmark produced by the intersection of the floor of the maxillary sinus (MS) and the nasal fossa (NF).ANFMSB(a)AB(b)NFMShttp://dentalebooks.com 128 Fundamentals of Oral and Maxillofacial RadiologyNasolabial folds (Fig. U5) are the bilateral folds of soft tissue extending from the lateral aspect of the nose to the corner of the mouth. Insertion of an intraoral receptor holder in the canine–premolar region will compress the soft tissue. Superimposition of this thick soft tissue over the teeth and bone will attenuate suffi-cient radiation so as to appear as a diffuse oblique radiopaque shadow extending posteri-orly from the cuspid–premolar intraoral region. A sharp demarcation line will be observed at the anterior border of the nasola-bial fold. The region anterior to the nasolabial fold will appear more radiolucent in compari-son. In edentulous patients, this landmark can assist the operator in determining the right and left sides of the patient.Pterygoid plates (medial and lateral) of the sphenoid bone (see Fig. M24) are best visualized on axial images. Intraoral images may or may not capture them because the plates are located posterior to the maxillary tuberosity. They will appear as uniform radiopacities without any Fig.U4 Anatomic landmarks: a, nasal septum; b, mid‐palatine suture appearing as a thin radiopaque line located between the maxillary central incisors; c, nasal fossa, which is the radi-olucency extending superior to the incisors and bisected by the nasal septum.ABFig.U5 Nasolabial fold (highlighted in B).http://dentalebooks.com U Radiographic Anatomy 129trabecular pattern. The hamular process extends off the medial pterygoid plate.Palatine torus (pl. tori) (Fig. U6) is a bony protuberance located in the midline of the hard palate. It is quite a common phenomenon, occurring in approximately 20% of the popu-lation. A torus is typically less than 2 cm in diameter and may consist of several lobes of dense bone. A palatine torus usually appears as a dense radiopacity that may be partially super-imposed over the roots of posterior maxillary teeth. It often is misdiagnosed as the zygoma. Synonyms include torus palatinus and palatal torus.Zygomatic arch (Fig. U7) is comprised of the zygoma and zygomatic process. The zygomatic process is actually an extension of the maxilla, temporal bone and frontal bone. In periapical images it appears as a U‐shaped radiopacity in the first and second molar region. Generally, a portion of the maxillary sinus will be visible behind it. Over‐ and underangulation of intraoral imaging techniques can dramatically vary the appearance of the zygomatic process. The zygoma appears as a uniform radiopacity con-tinuing posteriorly from the zygomatic process. On intraoral images the inferior border of the zygoma will only be visible.Radiolucent landmarksIncisive foramen (Fig.U8) is the opening of the incisive canal located immediately behind the maxillary central incisors. The nasopalatine nerve and sphenopalatine artery exit through this foramen and supply the oral mucosa and hard palate. On periapical x‐ray images, the Fig.U6 Palatine torus (highlighted).ABFig.U7 Zygomatic arch (highlighted in B).http://dentalebooks.com 130 Fundamentals of Oral and Maxillofacial Radiologyincisive foramen is located in the midline between the roots of the central incisors. Its appearance is quite variable due to normal ana-tomic variation and due to the operator’s angu-lation of the x‐ray beam. Typically it appears as a well‐defined, round or elliptical radiolucency measuring up to 1 cm in diameter. Abnormal enlargement of the incisive foramen may be indicative of a nasopalatine cyst. Synonyms include nasopalatine foramen and anterior nasopalatine foramen.Lateral fossa (Fig.U9) is a mild skeletal depres-sion in the region of the maxillary lateral inci-sor. On a periapical image, the region may or may not appear slightly more radiolucent than the surrounding area. It should not be misdiag-nosed as periapical pathology associated with a tooth. The lamina dura will typically be intact and clinically the patient will be asymptomatic. A synonym is incisive fossa.Maxillary sinus (FigsU10 and U11) is the larg-est of the paranasal sinuses and is bilaterally located within the body of the maxilla. Each sinus is bounded by the zygoma and the body of the maxilla. The maxillary sinus extends anteriorly toward the canine. Posteriorly it may extend into the tuberosity region, often seen dipping interproximally between the roots of multiple teeth. Its size and shape is variable in appearance. Age and the loss of teeth contrib-ute to increased pneumatization of a sinus, with the floor of the maxillary sinus possibly extending to the crest of the alveolar ridge. Within the maxillary sinus there is an ostium that connects the sinus to the middle concha of the nasal cavity. The maxillary sinuses typi-cally appear as large radiolucencies outlined by a thin radiopaque border. Extraoral images such as panoramic and CBCT images project a full sinus view. However, with the limited field Fig.U8 Incisive foramen: appears as an elliptical radiolu-cency located between the roots of the central incisors (highlighted).Fig. U9 Lateral fossa: appears as a diffuse radiolucency located around the root of a lateral incisor with an intact lamina dura (highlighted).http://dentalebooks.com U Radiographic Anatomy 131of view on periapical images, only the inferior aspect of the maxillary sinus will be visible. Superimposition of the floor of the nasal cavity over the maxillary sinus is often seen in periapical views of the canine. The intersection of the radiopaque borders of the sinus and the nasal cavity produces an inverted “Y” or “X” land-mark. If the top of the image cuts off a segment of the intersecting lines, the intersecting lines will appear as a “Y”; if the intersecting lines are fully visible on the image, the result appears more like an “X”. This landmark is useful to the operator to determine if a periorbital image belongs either to the right or left quadrant. This is particularly helpful for arranging x‐ray images of edentulous patients. Actual inter-pretation of the intersecting inverted “Y” or “X” landmark is as follows: the oblique radiolu-cent region towards the anterior demarcates the nasal fossa, while the posterior radiolucency is the maxillary sinus.The relationship of the maxillary sinus to the maxillary molars in particular is often misinter-preted. Two‐dimensional images of teeth often appear to project the roots into the maxillary sinus when in fact the sinus is simply envelop-ing the roots and it is only superimposed over it. An analogy would be to poke your finger into a fully inflated balloon and then observe it from the side. Viewing the balloon from the side, it would give the illusion that your finger was actually inside the balloon, when in fact it was merely being enveloped by it. Advanced imaging techniques can accurately show their true relationship. An additional complicating effect that often is misdiagnosed as pathology where none exists also occurs when a sinus is ABFig.U10 Maxillary sinus (lower border highlighted in B).Fig.U11 Maxillary sinus (highlighted).http://dentalebooks.com 132 Fundamentals of Oral and Maxillofacial Radiologysuperimposed over a root. The effect is an illu-sionary widening of the PDL space around the apex. A normal radiolucent PDL space and the superimposed sinus together exaggerate the appearance of the PDL space. This may lead to misinterpretation as non‐existent periapical pathology. Further clinical testing is necessary to rule out possible periapical pathology.Within a healthy sinus there may appear to be thin radiolucent and radiopaque lines. The narrow radiolucent lines are called nutrient canals , which carry the superior alveolar nerves and vessels, while the thin radiopaque lines are typically septa, which are simply undu-lating folds of cortical bone within the sinus. Neither should be considered pathogenic.The maxillary sinuses are lined with a thin mucosal membrane. Inflammation of this mucosal lining can contribute to dental symp-toms due to the close proximity of the apices of the molars to the inferior border of the sinus. Depending upon the degree of mucosal inflam-mation, the inferior portion of one or both maxillary sinuses may appear to be radiopaque. A thorough clinical examination of patients experiencing dental pain may reveal a healthy dentition with associated acute sinusitis.Inadequate alveolar bone height for dental implant placement often calls for a sinus lift procedure with bone augmentation using autogenous or alloplastic materials (see Fig. Y14). In post‐sinus lift surgery, the inferior aspect of the grafted sinus material typically appears as a uniformly dense, irregular or dome‐shaped radiopacity. This radiopacity must not be con-fused with a mucocele within the sinus, which is a simply a build‐up of fluids. On rare occa-sions, there may be aplasia of the maxillary sinus or complete opacification of the sinuses.Mid‐palatine suture (Fig.U4) is the line of union between the horizontal plates of the palatine bone. It typically appears as a thin radiolucent line extending from the incisive canal posteri-orly. On a periapical x‐ray image of the central incisors, it will often appear to extend from the alveolar crest superiorly up to the anterior nasal septum. However, its visibility on an x‐ray image is particularly dependent upon the hori-zontal angulation of the x‐ray beam. Directing the x‐ray beam diagonally through the thin mid‐palatine suture may obscure it because the suture line will now be superimposed with the denser surrounding palatal bone. Synonyms include intermaxillary suture, median palatine suture and palatomaxillary suture.Nasal fossa (Fig. U4) is the large midline air space that extends anteroposteriorly from the nares into the nasopharynx. It is divided into two compartments by the nasal septum. It is bounded superiorly by the cribiform plateof the ethmoid bone and inferiorly by the pro-cesses of the maxilla and the horizontal portion of the palatine bone. The lateral walls of the fossa each have three conchae (synonym: turbinates): the superior, middle and inferior conchae. Anterior periapical x‐ray images often will capture a portion of the inferior aspect of the nasal fossa. Its presence or absence will vary greatly depending on the extent of the vertical angulation of the x‐ray beam. In the central incisor region, the inferior border of the fossa will typically appear as a V‐shaped radi-opaque line located well above the apices of the teeth. The nasal septum appears in the mid-line as a radiopaque line rising vertically from the inferior border of the nasal fossa. The adjoining air space of the nasal cavity will appear radiolucent and it will be bisected by the nasal septum. The maxillary cuspid peria-pical view often contains the floor of the nasal fossa intersecting with the floor of the maxil-lary sinus, forming an inverted “Y” or “X” con-figuration (Fig. U3). The nasal conchae will be more visible on extraoral imaging of the nasal fossa. The conchae will appear as elongated radiopacities extending the length of the nasal cavity in sagittal views, while in cross‐sectional views the conchae appear more semicircular, like the musical symbol “bass clef.” Synonyms include nasal cavity and nasal antrum.http://dentalebooks.com U Radiographic Anatomy 1333. ANATOMIC LANDMARKS OF THE MANDIBULAR REGIONRadiopaque landmarksCoronoid process (Fig.U12) is the thin, tri-angular‐shaped process of the anterosuperior aspect of the ramus. Its triangular shape resem-bles the dorsal fin of a shark. This mandibular landmark is typically observed in extraoral images. However, it may also appear in maxil-lary molar periapical images. This can occur because the mandible must swing open to accommodate the intraoral receptor holder. In so doing, the coronoid process rotates anter-oinferiorly and often becomes superimposed over the maxillary molar tuberosity region. The coronoid process appears as a homogeneous triangular radiopacity.Genial tubercles (Fig.U13) are small bony pro-jections in the midline on the lingual aspect of the mandible. The genioglossus and geniohyoid muscles attach at these points. They are quite variable in appearance. On mandibular incisor periapical images, the genial tubercles may appear as a donut‐shaped radiopacity several millimeters in diameter with a pin‐point radio-lucent center (i.e. lingual foramen ). On axial CBCT images and mandibular occlusal images, the genial tubercles will typically appear as small projections emanating from the lingual cortical plate. A synonym is mental spine.Inferior border (i.e. cortical plate) of the mandible (Fig.U14) appears as a uniformly dense radiopaque band. On periapical x‐ray images, it should not be confused with either the exter-nal or the internal oblique ridges. Generally, the inferior border of the mandible is not observed on periapical images unless there was excessive negative vertical angulation of the x‐ray beam.Lip line (Fig.U15) is the result of the soft tissue of the lip attenuating enough radiation to be visible on a periapical image of the anterior teeth. The lip line is recognized by a uniform change in density horizontally across the coro-nal portions of teeth. The more radiolucent portion of the crown is superior to the lip line.Mental ridge (Fig.U16) is a dense elevation on the anterolateral aspect of the body of the man-dible. On anterior periapical images, it appears ABFig.U12 Coronoid process: appears as a triangular‐shaped radiopacity located in a maxillary molar periapical (highlighted in B).http://dentalebooks.com 134 Fundamentals of Oral and Maxillofacial Radiologyas a thin radiopaque line extending posteriorly from the midline (i.e. bilaterally). It usually is located inferior to the teeth, but if excessive negative vertical angulation of the x‐ray beam occurs, the mental ridge will be superimposed over the mandibular anterior teeth. A synonym is mental process.External oblique ridge (Fig. U17) is the bony protuberance that extends off the anterolateral ABCFig.U13 Genial tubercles. A. The genial tubercles appear as a radiopaque circle. The small radiolucency within the genial tubercles is the lingual foramen. B. Increased vertical angulation of the PID results in the genial tubercles appearing as a spiny process. C. The genial tubercles appear as a spiny process in an axial view.http://dentalebooks.com U Radiographic Anatomy 135border of the ramus and runs diagonally towards the area of the first molar. It serves as an attachment site of the buccinator muscle. The external oblique ridge typically appears to run parallel and superior to the internal oblique ridge. It appears as a thin oblique radiopaque line that gradually disappears as it extends from the ramus to approximately the location of the first molar.Internal oblique ridge (Fig. U17) is the bony protuberance located on the lingual surface of mandible extending diagonally downward from the ramus and ending anteriorly near the apices of the premolars. Its function is to serve as an attachment site for the mylohyoid muscle of the floor of the mouth. The appearance of the internal oblique ridge can be quite variable. On periapical images, it may appear to be a well‐defined, thin radiopaque line located inferior to Fig.U14 Inferior border of the mandible (highlighted).Fig.U15 Lip line (highlighted).Fig.U16 Mental ridge (arrows).Fig.U17 External oblique ridge (a) and internal oblique ridge (b) (synonym: mylohyoid ridge).http://dentalebooks.com 136 Fundamentals of Oral and Maxillofacial Radiologythe external oblique ridge. It runs obliquely at the level of the apices of the molars and premo-lars from the ramus. In some individuals, the internal oblique ridge may be quite diffuse and indistinguishable from the surrounding alveo-lar bone. A synonym is mylohyoid ridge.Mandibular torus (pl. tori) (Fig.U18) is a bony protuberance located on the lingual side of the mandible, typically found bilaterally in the cuspid and premolar region. It occurs less commonly than the palatine torus (i.e. in approximately 8% versus 20% of the popula-tion). A mandibular torus typically appears as a rounded uniform radiopacity. The size of a torus is quite variable. Occasionally, bilateral tori together may fill the floor of the mouth. Placement of solid‐state receptors for intraoral images may be physically impossible due to space limitation. PSP plates, which are compar-atively thinner and more flexible, may be an alternative if available. Otherwise extraoral imaging (e.g. panoramic image) may be the only practical method to image the teeth. A syno-nym is torus mandibularis. Radiolucent landmarksLingual foramen (Fig.U13) is a small foramen that the lingual artery passes through. It is situated on the lingual side in the midline of the mandible. Typically on periapical images of the mandibular anterior region, the lingual foramen will appear as a pinpoint radiolucency surrounded by the radiopaque genial tuber-cles. The small size and location of the lingual foramen often make it difficult to visualize on x‐ray images.Mandibular canal (FigsU19 and U20) extends from the mandibular foramen to the mental foramen through the ramus and body of the mandible. The inferior alveolar nerve and artery travel within this canal. An extension of the mandibular canal can sometimes be seen ABFig.U18 Bilateral mandibular tori (highlighted in B).http://dentalebooks.com U Radiographic Anatomy 137Fig.U19 (a) Mandibular canal (highlighted in B): conventional x‐ray image.(b) Mandibular canal (highlighted in B): CBCT coronal view.AB(a)A(b)Bhttp://dentalebooks.com 138 Fundamentals of Oral and Maxillofacial Radiologycontinuing anteriorly beyond the mental fora-men. This is referred to as the anterior loop of the mandibular canal . The mandibular canal typically traverses the body of the mandible inferior to the apices of the molars and premo-lars. Excessive negative vertical angulation of the x‐ray beam may superimpose the mandibular canal over the apices of some teeth in periapical images. The mandibular canal typically is a uniform radiolucent channel bordered with thin parallel radiopaque lines. At times, the density of the mandibular canal may be indistinguish-able from the surrounding bone. This will be a particular concern when treatment planning mandibular implants. A dental implant that impinges on the mandibular canal may lead to long‐term paresthesia . On occasion, a second mandibular canal may be observed running parallel to the primary canal. The second canal contains smaller branches of the inferior alveo-lar nerve. It is referred to as a bifid canal and is more frequently visualized on extraoral images such as panoramic or CBCT views. A bifid canal may result in the inability of the practitioner to fully anaesthetize a patient while performing mandibular dental procedures. A synonym is the inferior alveolar canal.Mental foramen (Fig. U21) is the anterior opening of the mandibular canal allowing a branch of the inferior alveolar nerve and artery to exit into the facial soft tissue. It is bilaterally located on the buccal surface of the mandible in the premolar region. The mental foramen typically appears as a single round radiolu-cency in close proximity to the apices of the second premolar. However, its position on periapical images is very technique sensitive, being dependent upon both the vertical and horizontal angulation of the x‐ray beam. Occasionally the image of the mental foramen may be superimposed over the apex of one of the premolars. This could easily be misdiag-nosed as periapical pathology. Careful exami-nation of the image should reveal an intact lamina dura of a vital tooth beneath the mental foramen. To rule out pulpal pathology, the operator may expose an additional x‐ray image using a modified vertical or horizontal angulation of the x‐ray beam. If the apical radiolucency drifts off of the tooth, this would indicate that it was most likely the mental foramen. However, if the radiolucency remains attached to the apex after a significant modi-fication of the x‐ray beam angulation, it would seem to indicate that some periapical pathology is present and further evaluation is prudent. Clinical testing for pulp vitality should be done.Fig. U20 Anterior loop of the mandibular canal (high-lighted): CBCT coronal view.Fig.U21 Mental foramen (highlighted).http://dentalebooks.com U Radiographic Anatomy 139Mental fossa (Fig.U22) is an anatomic depres-sion in the midline of the mandible superior to the mental ridge. The definition of a depression presumes less bone thickness. Prominence or lack thereof of a patient’s mental protuberance will result in visibility or invisibility of the men-tal fossa on an x‐ray image. If there is sufficient difference in bony thickness between the mental fossa and the surrounding bone, the fossa will appear comparatively more radiolucent. If there is insufficient difference in bone thickness, the mental fossa will not be discernable.Nutrient canals (Fig.U23) are naturally occur-ring channels within bone that carry accessory blood vessels. They appear as thin radiolucent lines occurring in either the mandible or the maxilla. However, they are most commonly seen running vertically in the inter‐radicular spaces between mandibular anterior teeth. If a nutrient canal is orientated bucco‐lingually in the image, it will appear as a small round radiolucency.ABFig.U22 Mental fossa (highlighted in B).Fig.U23 Nutrient canals (highlighted).http://dentalebooks.com 140 Fundamentals of Oral and Maxillofacial RadiologySubmandibular gland fossa (Fig. U24) is a depression on the lingual side of the mandible body in the molar region and inferior to the internal oblique ridge (aka mylohyoid ridge). The submandibular salivary gland is situated in the fossa. Unlike the mental fossa, where there may not be an adequate difference in thickness of surrounding bone to distinguish it, the submandibular gland fossa usually is signifi-cantly thinner. Consequently the submandibular gland fossa is generally discernible on an x‐ray image. The clinician must be cognizant that the radiolucent region associated with the subman-dibular gland is not osseous pathology.A BFig.U24 Submandibular gland fossa (highlighted in B).http://dentalebooks.com Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology141Dental CariesVDental caries (aka dental cavity or tooth decay) is a disease process of the calcified tissues of teeth. Contributing etiologic factors include diet, oral hygiene, composition of tooth structure and saliva. Caries may be single or multiple in number and may occur in both the deciduous and permanent dentitions. There is no age, sex or racial predilection. The size of the lesion is variable, ranging from under a millimeter to total destruction of a tooth. Clinically, the appearance varies from a white chalky area onthe enamel to a large hollowed‐out, darkly stained cavity. Depending upon the location and stage of caries development, its appearance is extremely variable. It is important to state outright that both an x‐ray examination and a clinical oral examination are necessary to prop-erly diagnose dental caries.Limitations tovisualizing caries onx‐ray imagesDecalcification levelsX‐ray receptors require approximately a 40% decalcification of tooth structure prior to being able to detect a change. Consequently, early stages of caries development will not be visible on x‐ray images. Since minute levels of decalcifi-cation are not detected with an x‐ray receptor, lesions will automatically appear smaller on an x‐ray image than they are clinically. This becomes a concern when a caries is encroaching upon the pulp chamber. A thin dentin separation between the active caries and the pulp may be visible on the x‐ray image, but, in actuality, the caries may have already penetrated into the pulp.Incorrect angulation ofequipmentCaries detection may be impossible to visualize if incorrect angulation of the PID occurs. Incorrect horizontal angulation will superimpose adja-cent proximal contacts over one another, which will likely obscure incipient caries . Similarly, excessive vertical angulation will project caries through additional tooth structure and possibly behind radiopaque restorations making some caries undetectable on the x‐ray image(Fig.V1).AnatomyPhysical and anatomic factors may prevent an operator from positioning the x‐ray receptor anteriorly enough to capture the contact between http://dentalebooks.com 142 Fundamentals of Oral and Maxillofacial Radiologythe first premolar and cuspid. This may be the result of the patient’s mandibular and maxillary arch anatomy, which can restrict the placement of the receptor. Another impediment may be the sheer size and rigidity of the solid‐state image receptor. PSP plates, if available, would facilitate placement in this situation. Similarly, tooth crowding and tooth rotation may prevent the operator from positioning the PID properly to open the contacts for caries detection.ArtifactsArtifacts such as cervical burnout and the Mach band effect can lead to the misdiagnosis of x‐ray images. The Mach band effect is an illusionary radiolucent line sometimes seen along the borders of dentin and enamel or along the border of a radiopaque restoration and normal tooth structure.Cervical burnout is an illusionary radiolucency along the neck of the tooth caused by differential x‐ray absorption. More x rays penetrate through the cervical region, giving that area a more radiolucent appearance compared to the crown or the root. Cervical burnout can form a radiolucent band extending mesiodistally across the entire tooth or it can be localized to smaller areas in the mesial and/or distal surfaces along the neck of the tooth. None of these artifacts should be misdiagnosed as dental caries. Conversely, root surface caries should not be misdiagnosed as cervical burnout.Viewing conditionsViewing conditions can affect the quality of the x‐ray images. A high resolution x‐ray image that is viewed on a mediocre computer monitor will diminish the overall image quality. In addition, the viewing room itself, if brightly lit, can diminish the clinician’s ability to visualize fine details and may lead to missed diagnoses.ABCFig.V1 Effect of overangulation. A. The caries is unde-tected on no. 19 because of excessive vertical angula-tion of the PID. B. The caries still undetected on no. 19 with reduced vertical angulation. C. Zero vertical angu-lation reveals a large carious lesion previously hidden on no. 19.http://dentalebooks.com V Dental Caries 143Note: Caries detection can be enhanced by selecting lower kilovoltage settings for intra-oral imaging. A lower kilovoltage output produces an image with a more black–white contrast and fewer shades of gray.Classification ofcariesBuccal andlingual cariesBuccal and lingual caries typically appear asround or oval‐shaped radiolucencies with well‐defined margins, while cemental caries generally appear as well‐defined saucer‐shaped radiolucencies. Definitive diagnosis of buccal and lingual caries can be achieved by conducting a clinical exam. Clinically this type of caries is often associated with enamel pits and fissures.Interproximal cariesAn interproximal caries is first evident as a triangular radiolucency in the enamel with the base of the triangle along the outer surface of the tooth and the apex of the triangle pointing toward the dentin (Fig. V2b). At the dentin–enamel junction, a second similarly orientated AB(a)(b)Fig.V2 (a) Interproximal caries (highlighted in B). (Source: Courtesy of Adam Chen, XDR Radiology.) (b) An early inter-proximal caries forms a triangle in the enamel with the broad base of the triangle located at the outer surface and the apex directed towards the dento‐enamel junction. Progression of caries in the dentin similarly forms a broad base at the dento‐enamel junction with the apex pointing toward the pulp.http://dentalebooks.com 144 Fundamentals of Oral and Maxillofacial Radiologyradiolucent triangle will form (i.e. the base located at the dentin–enamel junction and the apex pointing toward the pulp chamber). As it progressively enlarges and begins to encroach upon the pulp chamber, it will lose its triangular shape and become irregular in outline (FigsV3 and V4). Bitewing images are ideally suited for diagnosing interproximal caries.Occlusal cariesAn occlusal caries classically forms a triangular‐shaped radiolucency in the enamel with the tri-angle’s apex at the outer surface of the crown and its base located along the dentin–enamel junc-tion. As it progresses into the dentin, it forms an additional opposing triangle with the base also located at the dentin–enamel junction. Identical ABFig.V3 Interproximal caries (highlighted in B).ABFig.V4 Interproximal caries (highlighted in B). V Dental Caries 145to interproximal caries, the triangle’s apex points inward towards the pulp chamber (Fig. V6b). These caries will continue to spread laterally in the dentin, undermining the enamel and will transform it into a large, irregular‐shaped radio-lucent lesion (FigsV6 and V7). At some juncture the undermined enamel will break away, clini-cally revealing a large open cavity (Fig.V8).Radiation cariesMedical radiotherapy for the treatment of head and neck cancer can result in loss of function of the salivary glands causing dry mouth (aka xerostomia). Reduced salivary flow increases the risk for dental caries. The phenomenon is referred to as radiation caries, where the caries are indirectly the result of the radiation treat-ment and not directly due to the radiation itself. The result can be rampant caries with total destruction of the coronal portions of the teeth. There are limited options to protect the teeth in patients undergoing therapeutic radiation for head and neck cancer. Teeth will require metic-ulous oral hygiene care and may be treated with topical fluorides and artificial saliva.Recurrent cariesRecurrent caries (aka secondary caries) refers to active caries associated with an existing dental res-toration. A radiolucency particularly associated with the proximal surface of an existing restora-tion may be a new carious lesion that requires retreatment. However, not all radiolucencies asso-ciated with restorations are active caries. The radiolucency can possibly be a liner that was intentionally placed at the time underneath the restoration. If the depth of the caries was close to the pulp chamber, the restoring clinician may have intentionally left some caries behind and lined it with the medicament. Without an x‐ray image and clinical history of an existing restora-tion, a new dentist cannot determine if the radio-lucency associated with the restoration is an active caries. An active caries requires proper treatment.ABFig.V5 Interproximal caries (highlighted in B). 146 Fundamentals of Oral and Maxillofacial RadiologyRoot surface cariesRoot surface caries (synonym: cemental caries) is associated with gingival recession and crestal alveolar bone loss. It affects the dentin and cementum together and it should be evident clinically. X‐ray images should not even be required for its diagnosis. When x‐ray images are available, a root surface caries has a diffuse periphery and may have a saucer shape (Fig.V9). Root surface caries should not be mis-diagnosed as cervical burnout (Fig.V10).BA(a)(b)Fig.V6 (a) Occlusal caries (highlighted in B). (Source: Courtesy of Adam Chen, XDR Radiology.) (b) An early occlusal caries forms a triangle in the enamel with the apex of the triangle located at the outer surface and the broad base directed towards the dento‐enamel junction. Progression of the caries in the dentin forms a broad base at the dento‐enamel junction with the apex pointing toward the pulp. V Dental Caries 147ABFig.V7 Occlusal caries (highlighted in B).ABFig.V8 Severe caries (highlighted in B).ABFig.V9 Root caries (highlighted in B). 148 Fundamentals of Oral and Maxillofacial RadiologyA(b)BFig.V10 (a) Root caries (highlighted in B). (b) Cervical burnout (highlighted in B). This must not be misdiagnosed as root caries.AB(a) Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology149Dental AnomaliesWNumberAnodontia (Fig.W1)Anodontia is the congenital absence of all deciduous and/or permanent teeth. It is a rare condition, often associated with other disorders such as ectodermal dysplasia , progeria or Down’s syndrome. Females are more often affected, but there is no racial predilection. Synonyms include hypodontia and agenesis of teeth.Oligodontia (Fig.W2)Oligodontia is the congenital absence of one or more deciduous or permanent teeth. The maxil-lary and mandibular third molars, the maxillary lateral incisors and the mandibular second pre-molars are the most frequent congenitally absent permanent teeth, while the maxillary and man-dibular lateral incisors and the mandibular cus-pids are the most frequently absent deciduous teeth. Oligodontia is often associated with other disorders such as anhidrotic ectodermal dyspla-sia, chondro‐ectodermal dysplasia, oro‐digitofacial dysostosis and Down’s syndrome. Synonyms include partial anodontia and hypodontia.Supernumerary tooth (Fig.W3)Supernumerary tooth/teeth refer to the presence of one or more teeth in excess of the normal com-plement. Although supernumerary teeth are more prevalent in males, there is no age or racial predilection. They are often small rudi-mentary teeth, single or multiple and may be found in any of the tooth‐bearing areas of the jaws. However, the area between the maxillary central incisors, the area distal to the third molars and the mandibular bicuspid regions are the most common sites for supernumerary teeth. Clinically, the patient may present with malocclusion. Synonyms include mesiodens, peridens, hyperdontia and supplemental teeth.SizeMacrodontia (Fig.W4)Macrodontia is a term used to describe one or more deciduous or permanent teeth that appear normal in every respect, except for their large size. They may be found in any of the tooth‐bearing areas of the maxilla and mandi-ble and in individuals of all ages. They are often associated with giantism and unilateral 150 Fundamentals of Oral and Maxillofacial RadiologyFig.W1 Anodontia.Fig.W2 Oligodontia.ABFig.W3 Supernumerary teeth. A. Mandibular bicuspid. B. Mesiodens (e.g. microdont). W Dental Anomalies 151hypertrophy of the face. Synonyms include megalodontia and megadontia.Microdontia (Fig.W5)Microdontia is a term used to describe one or more deciduous or permanent teeth that appear normal in every respect, except for their small size. They can be found in any of the tooth‐bearing areas of the jaws and in individuals of all ages. Particularly affected are the maxillary lateral incisors and maxillary third molars in the permanent denti-tions. In addition, they are often associated with osteogenesis imperfecta and Down’s syndrome. Synonyms include dwarf teeth and peg laterals.ShapeConcrescence (Fig.W6)Concrescence is the union of either two deciduous or two permanent teeth by cementum alone. There are occasional reports of cases in which Fig.W4 Macrodontia (e.g. fusion).Fig.W5 Microdontia.ABFig. W6 Concrescence. (Source: Courtesy of Dr. K. Thunthy.) 152 Fundamentals of Oral and Maxillofacial Radiologythree teeth are joined together by cementum. The maxillary molars are the most frequently affected teeth and, although the etiology is unknown, there is often a history of trauma to the area or severe crowding of the dentition. There is no age, sex or racial predilection. Concrescence appears as two fused teeth having amorphous roots, and often one of those teeth is unerupted. It is notable that the diagnosis of concrescence using x‐ray images alone is often impossible.Dens invaginatus (Fig.W7)Dens invaginatus is a developmental anomaly believed to arise from an invagination in the surface of the crown of a permanent tooth before calcification has occurred. The maxillary lateral incisors are most frequently affected. Dens invaginatus often appears as a “pear‐shaped” radiolucent invagination lined with a thin layer of enamel and dentin that projects into the pulp. There is no age, sex or racial predilection. Clinically, the patient often presents with pain and/or a periapical abscess. Synonyms include dens in dente, dilated composite odontome and gestant odontome.Denticle (Fig.W8)A denticle is a round or oval‐shaped calcified body within a pulp chamber of either a perma-nent or deciduous tooth. It appears as a uniform, dense, radiopaque mass with well‐defined borders. Its size can range from 1 mm in diameter to total obliteration of the pulp chamber. Clini-cally, there is no age or racial predilection and it is usually asymptomatic. Synonyms include pulp stone, pulp nodule and endolith.ABFig.W7 Dens invaginatus. A. Lateral incisor. B. Holar. (Source: Courtesy of Dr. K. Thunthy.) W Dental Anomalies 153Dentinal bridge (Fig.W9)A dentinal bridge is a partial obliteration of apulp chamber of either a deciduous or per-manent tooth. Typically only a single tooth is involved. There is no racial or sexual predilec-tion and it may be diagnosed in any age group. It appears as a narrow radiopaque band span-ning horizontally across the pulp chamber. The thickness of the band is variable, ranging from one to several millimeters in width. Clinically, the affected tooth is asymptomatic.Dilaceration (Fig.W10)Dilaceration refers to an abnormal distortion either in the root of a tooth or at a junction of the crown and root of a tooth. The etiology is believed to be trauma during tooth develop-ment. It may occur in either the permanent or the deciduous dentition, but it is more frequently found in permanent teeth. There is no sexual or racial predilection and it may be diagnosed in any age group. The tooth appears normal except that its shape is bent or twisted. Clinically, dilaceration is asymptomatic.Enamel pearl (Fig.W11)An enamel pearl is a small hemispherical massof enamel attached to the surface of a permanent tooth. Typically, it is a single globular mass found at the cemento‐enamel Fig.W8 Denticle.Fig.W9 Dentinal bridge.Fig.W10 Dilaceration. 154 Fundamentals of Oral and Maxillofacial Radiologyjunction in or near the bifurcation or trifurca-tion of the roots of the posterior teeth, par-ticularly the maxillary first molar. The average size of the enamel pearl varies from 1 to 5 mm. There is no sex predilection. The enamel pearl appears as a well‐defined, round or ovoid, dense radiopacity with or without a normal lamina dura and a perio-dontal ligament‐like space present. Clinically, it is usually asymptomatic. Synonyms include enameloma, enamel nodule and enamel drop.Fusion (Fig.W4)Fusion is either the partial or complete union of two deciduous or permanent teeth. Although its etiology is uncertain, fusion is believed to be hereditary. The mandibular and maxillary anterior deciduous teeth are most frequently affected, but there is no age, sex or racial predilection. In addition to affecting two normal teeth, fusion may occur between a supernumerary tooth and a normal tooth. It resembles a macrodont tooth, except that fused teeth often have two pulp chambers. Clinically, there is at least one tooth missing from the normal complement of teeth. A syno-nym is synodontia.Gemination (Fig.W12)Gemination is a developmental anomaly in which a single tooth bud attempts to divide by invagination, resulting in incomplete formation of two teeth. There is a predilection for the maxillary and mandibular anterior deciduous dentition, with rare reports of occurrence in the permanent dentition. Consequently, geminated teeth may be found in any age group but occur more frequently in children under 12 years of age; there is no sexual or racial predilection. The teeth appear normal except for atypically large crowns. Unlike fusion, there is often a full complement of teeth present.ABFig.W11 Enamel pearl. (B. Source: Courtesy of Dr. K. Thunthy.) W Dental Anomalies 155Hutchinson’s incisor (Fig.W13)A Hutchinson’s incisor refers to a characteristic screwdriver shape and/or notching of the incisal edges of permanent maxillary and man-dibular incisors. Hutchinson’s incisors appear normal except for an irregular border of the incisal edges. Clinically, there is no racial or sexual predilection, and it is rarely diagnosed in children below 6 years of age. Hutchinson’s incisors are associated with congenital syphilis, interstitial keratitis and deafness. A synonym is screwdriver tooth.Hypercementosis (Fig.W14)Hypercementosis is an alteration in the shape of a root of a permanent tooth as a result of the deposition of excessive amounts of secondary cementum. It is often described as "club‐shaped." Regardless of the shape of the altered root, it always maintains the normal width of Fig.W12 Gemination. (Source: Courtesy of Dr. K. Thunthy.)Fig.W13 Hutchinson’s incisors. (Source: Courtesy of T. Putkonen.)Fig.W14 Hypercementosis. 156 Fundamentals of Oral and Maxillofacial Radiologythe lamina dura and periodontal membrane around it. Secondary cementum may form over the entire root surface or focally in one area. Because cementum is less radiopaque than dentin, the border between the two is distinguishable. Hypercementosis primarily affects the premolar and molar teeth. There is a higher incidence of occurrence in the mandible. There is no racial or sexual predilection and it is rarely diagnosed in individuals younger than 6 years of age. Clinically, the involved tooth is vital and asymptomatic. However, it is notable that there often is a history of trauma to the tooth. Hypercementosis is frequently associated with systemic disorders such as giantism, acromegaly or Paget’s disease. A synonym is cementum hyperplasia.Taurodont tooth (Fig.W15)Taurodont tooth describes any tooth that con-genitally develops a large body and pulp chamber, with very little root formation and an overall tooth size that is normal. Children under 6 years of age are rarely affected. The pulp chamber of a taurodont tooth is gradually obliterated as the patient’s age increases. A syn-onym includes bull‐like tooth.Turner’s tooth (Fig.W16)A Turner’s tooth refers to an enamel hypo-plasia of a permanent tooth that is believed tooriginate from a precursory, periapically involved, deciduous tooth. This typically occurs in the anterior regions of the maxilla and the mandible. Clinically, Turner’s tooth manifests in varying degrees of severity. The tooth may vary from simply being stained to, in severe cases, only a shell of a tooth being present. There is no racial or sexual predilection. The appearance of the affected tooth varies according to the sever-ity of the lesion. Typically, the crown of a Turner’s tooth has irregular contours, and its root occasionally has an irregular out-line. Its size is also quite variable, depend-ing upon the severity of the lesion. A synonym is localized hypoplasia.Fig.W15 Taurodontism. Fig.W16 Turner’s tooth. (Source: Courtesy of P. R. Ritwick.) W Dental Anomalies 157Developmental factorsAmelogenesis imperfecta (Fig.W17)Amelogenesis imperfecta represents a develop-mental anomaly of enamel. Two basic types of amelogenesis imperfecta exist: enamel hypo-plasia and enamel hypocalcification. Neither type shows any racial or sexual predilection. It may be present in either the deciduous or the permanent dentitions. In the hypoplastic type, there is a reduction in the thickness of enamel. The crowns of teeth often appear square because they are devoid of normal mesial and distal contours. However, the radiologic den-sity of a hypoplastic tooth appears normal. In the hypocalcified type, the enamel is of proper thickness but it is not properly calcified. The resultant appearance is a tooth with proper contours and an enamel layer that is more radi-olucent than normal. This is made apparent by the lack of image contrast between the enamel and dentin. Clinically, both types often show a discoloration of the crowns, ranging from yel-low to brown, and there frequently is marked attrition of the involved teeth. Synonyms include hereditary enamel dysplasia, hereditary brown enamel, hereditary brown opalescent teeth, hereditary enamel hypoplasia, hereditary enamel hypocalcification and enamel dysplasia.Dentinal dysplasia (Fig.W18)Dentinal dysplasia is a disturbance in dentin for-mation of one or more teeth, characterized by little or no pulp chambers and very little root formation. Both the deciduous and permanent dentitions may be affected. Clinically, the teeth appear normal in morphology and color, but they often become loose and are exfoliated prematurely. There is no age, sex or racial pre-dilection. A synonym is rootless teeth.Dentinogenesis imperfecta (Fig.W19)Dentinogenesis imperfecta refers to a developmen-tal anomaly of dentin formation found in both the deciduous and permanent dentitions. There is no sexual or racial predilection and it may be diagnosed in any age group. The teeth are frequently described as “tulip teeth,” because they often have thin, short roots and constricted Fig.W17 Amelogenesis imperfecta (e.g. enamel hypoplasia). 158 Fundamentals of Oral and Maxillofacial Radiologynecks, which gives the crowns a bulbous shape. Initially, the pulp chambers are wide, but gradu-ally there is a partial or total precocious oblitera-tion of the pulp chambers as a result of continued dentin formation. Clinically, the teeth often have a translucent or opalescent hue and marked attrition. Synonyms include hereditary opalescent dentin and opalescent dentin.Hypoplasia, enamelEnamel hypoplasia is the incomplete or defective formation of the enamel matrix of teeth. Its etiology may be either hereditary or environ-mental and one or more deciduous or perma-nent teeth may be affected. The patient’s dental and medical histories may indicate possible ABFig.W18 Dentinal dysplasia.Fig.W19 Dentinogenesis imperfecta. (Source: Courtesy of Dr. J. Townsend.) W Dental Anomalies 159etiologic factors such as a nutritional deficiency, metabolic disorders, childhood diseases or excessive fluoride intake. There is no sexual or racial predilection and it may be diagnosed inany age group. The clinical appearance of hypoplasia may vary from a slight discolora-tion to severe pitting and irregularity in the shape of a crown. The tooth appears normal except for a reduced thickness and, possibly, an irregular outline of its crown. (see Amelogenesis imperfecta). Synonyms include mottled tooth, enamel dysplasia, hereditary enamel hypoplasia and brown teeth.Odontoma, complex (Fig.W20)A complex odontoma is an odontogenic tumor composed of an irregular conglomerate mass of dental tissues which bears no resemblance to a tooth. Typically it is a slow‐growing lesion, varying in size from a few millimeters to several centimeters in diameter. Any tooth‐bearing areas of the maxilla or mandible may be affected. However, it is most often located in the mandibular molar regions. Controversy, similar to that surrounding the compound odontoma, still exists regarding the etiology ofthis lesion. The average patient is between 5 and 30 years of age, but it may be evident inany age group. Also, there is no racial or sexual predilection. The complex odontoma appears typically as a unilocular radiolucency with smooth contours, within which are numerous patternless radiopacities. This often gives it the appearance of being surrounded by a radiolucent capsule. In addition, the borders of the lesion are usually scalloped and radiopaque. The patient often presents with a painless swelling. A synonym is complex composite odontome.Odontoma, compound (Fig.W21)A compound odontoma is an odontogenic tumor composed of one or more supernumerary denticles of different sizes and shapes. ABFig.W20 Complex odontoma. A. Sagittal view. B. Coronal cross‐sectional view of the same tooth as A. 160 Fundamentals of Oral and Maxillofacial RadiologyTypically, it is a single, slow‐growing lesion, varying in size from a few millimeters to several centimeters in diameter. Any tooth‐bearing areas of the maxilla or mandible may be affected. However, it is most often located in the maxillary central incisor region, followed by the mandibular molar region. Interestingly, these are areas that show a predisposition for supernumerary teeth. However, controversy still exists concerning the etiology of the lesion, with suggestions that local trauma, infection or excessive budding of the dental lamina may lead to development of the odontoma. The average patient is between 5 and 30 years of age, but it may be diagnosed in all age groups. Also, there is no racial or sexual predilection. The compound odontoma typically appears as a unilocular radiolucency, within which are well‐defined tooth‐like radiopacities. This gives the lesion the impression of being sur-rounded by a radiolucent capsule. In addition, the borders of the lesion are often scalloped and radiopaque. Clinically, the patient often presents with a painless swelling. Synonyms include compound composite odontome and cystic compound composite odontome.Odontodysplasia, regional (Fig.W22)Regional odontodysplasia is a developmental anomaly in which one or more teeth in a local-ized area of the maxilla and/or the mandible have exceedingly large pulp chambers and very thin layers of enamel and dentin. Both the enamel and dentin show a marked reduction in ABFig.W21 Compound odontoma.Fig.W22 Regional odontodysplasia. W Dental Anomalies 161density. As well, the trabeculae in the affected region appear very fine. It is notable that the size of the affected teeth is either normal or slightly smaller than average. The maxillary teeth are more commonly involved than those in the mandible and the most frequently affected teeth are those in the anterior region. There is no racial or sexual predilection and it may be diagnosed in all age categories. Clinically, the patient may present with delayed or unerupted teeth. Synonyms include odontogenesis imperfecta, odontodysplasia, odontogenic dysplasia and ghost teeth.Osteogenesis imperfectaOsteogenesis imperfecta is a disease of bone char-acterized by extreme fragility and porosity of the bones, blue sclera, deafness and an unu-sual shape of the skull. It usually is present at birth or manifests itself shortly afterwards. There is no racial or sexual predilection. The oral manifestations are identical to dentino-genesis imperfecta, although there are cases in which the teeth appear normal. It is notable that osteogenesis imperfecta is usually diagnosed by a medical doctor, prior to the patient’s first dental appointment. Synonyms include brittle bones, fragilitas ossium, osteopsathyrosis and Lobstein’s disease.Pulpal obliteration (Fig.W23)Pulpal obliteration refers to the partial or total constriction of the pulp chamber and/or root canal of a tooth. Any number of permanent or deciduous teeth may be affected and there is no age, sex or racial predilection. It appears as a generalized pacification of the pulp. Clinically, the patient is often asymptomatic, but pulpal obliteration is often associated with trauma or developmental disorders such as dentinogene-sis imperfecta.Environmental factorsAbrasion (Fig.W24)Abrasion is the pathologic wearing down of a tooth structure by mechanical means. The amount of wear is variable, ranging from under a millimeter to total destruction of the crown of a tooth. The area of abrasion appears more radiolucent than the remainder of the crown and it often has irregular borders. Abrasion may be associated with any deciduous or per-manent teeth, and there is no age, sex or racial predilection. Various etiologic factors include improper toothbrushing technique, abrasive dentifrice, ill‐fitting partial dentures, personal habits or occupational hazards. The patient is often asymptomatic.Ankylosis (Fig.W25)Ankylosis of a tooth is the proliferation of bone between the alveolar bone and the cementum or dentin of a tooth, with the elimination of any Fig.W23 Pulpal obliteration. 162 Fundamentals of Oral and Maxillofacial Radiologyintervening soft tissue. Its etiology is uncertain, but there often is a history of trauma to or infec-tion in the tooth. There is no racial or sexual predi-lection and it may be diagnosed in all age groups. Although the deciduous molars are primarily affected, it may involve any deciduous or perma-nent teeth. The normal radiolucent periodontal ligament space is transformed into a radiopaque region confluent with the surrounding bone. Occasionally, the root may have an irregular out-line and a moth‐eaten appearance . As a result, there may also be a reduction in the overall size of the tooth. Clinically, the affected tooth is generally asymptomatic.Attrition (Fig.W26)Attrition is the physiologic or pathologic wear-ing down of a tooth structure as a result of tooth to tooth contact. The amount of tooth reduction is variable, ranging from under a millimeter tototal destruction of the crown of the tooth. Typically, the pattern of wear is irregular. In addition to the reduction in the size of the tooth, pulpal obliteration may also be apparent. Attrition may be associated with any deciduous or permanent teeth and there is no age, sex or racial predilection. Etiologic factors associated with pathologic attrition include occupations where a patient is exposed to abrasive airborne materials, malpositioned teeth or a coarse diet. The patient is often asymptomatic.Calculus (Fig.W27)Calculus is a hard mineralized deposit found only above the bone level around one or more Fig.W24 Tooth abrasion: caused by a partial denture clasp.Fig.W25 Ankylosis of unerupted premolar.Fig.W26 Attrition. (Source: Courtesy of R. Saeves.) W Dental Anomalies 163deciduous or permanent teeth. There is no sexual or racial predilection and it is found in all age groups. Calculus usually appears as a spur‐like projection near the cervical aspect of a tooth or as a linear radiopaque line running from the mesial to distal aspects of a tooth. However, in the case of a heavy build‐up of calculus, it may appear as a wide continuous radiopaque band adjoining several teeth. Clinically, calculus varies in color from yellow to dark brown or black, depending upon the amount of stain present. The patient may com-plain of bad breath, loose teeth and bleeding gums. As well, the patient often claims that his or her teeth are chipping or breaking. Synonyms include tartar and calcareous deposit.Caries, dentalSee Section V.Erosion (Fig.W28)Erosion is the pathologic wearing down of a tooth structure by chemical means. The amount of wear is variable, ranging from under a mil-limeter to total destruction of the crown. The area of erosion appears more radiolucent than the remainder of the crown and it often has well‐defined borders. Erosion may affect any deciduous or permanent teeth and there is no age, sex or racial predilection. It is notable that the mesial and distal surfaces of teeth are rarely affected. Clinically, the affected area often appears as either a smoothly polished, disc‐shaped cavity or as a pitted tooth surface. Various etiologic factors include occupational hazards, diet, medications or a low salivary pH value.Foreign body (Fig.W29)A foreign body is any object or particle of material that is not indigenous to the area in ABFig.W27 Calculus.Fig.W28 Erosion. 164 Fundamentals of Oral and Maxillofacial Radiologywhich it is located. Foreign bodies may be any shape and size, but they must be radiopaque. They may occur anywhere within an x‐ray image and there is no age, sex or racial predilection. Clinically, the patient may present with pain and swelling in the affected area and its etiology may be ascertained from a history of previous trauma or dental treatment.Fracture (Fig.W30)Fracture of a crown or root of a tooth is a com-mon injury, often a result of a sudden severe trauma. Other etiologic factors include large dental restorations, internal resorption and endodontic treatment. One or more deciduous and/or permanent teeth in either the maxilla or mandible may be fractured. There is no racial predilection, but fractures occur more frequently in the anterior teeth of children because of the greater incidence of trauma in such individuals. A fracture is evident when there is a discontinuity in the outline of a tooth, but there may or may not be displacement of any part of the fractured tooth. A root fracture often appears as a regular or irregular radiolu-cent line. However, depending on the angle of a fracture, it may or may not be visible on every x‐ray image. A crown fracture also may not be visible on an x‐ray image. The border outline Fig.W29 Bullet fragments.ABFig.W30 Root fractures. (B. Source: Courtesy of Drs M. Beilman, M. Burns and G. Klasser.) W Dental Anomalies 165may be regular or irregular. Clinically, the tooth may be sensitive to temperature changes, pain-ful to percussion or loose. A CBCT may reveal a fracture line.Impaction (Fig.W31)An impacted tooth is any partially or totally unerupted tooth that is prevented from normal eruption by an obstruction. Clinically, there is no age, sex or racial predilection. However, the patient may experience pericoronitis .Resorption, external (Fig.W32)External resorption is the destruction of a crown and/or root of a deciduous or permanent tooth originating at the outer surface and continuing pulpally. This results in either a smooth or an irregular periphery. There is a reduction in its size that can vary from a millimeter to total destruction of the tooth. Its etiology may reflect normal physiologic resorption, previous ortho-dontic treatment, trauma, an apicoectomy, an artifact or a congenital defect. There is no sexual or racial predilection and it may be diag-nosed in any age group.Resorption, internal (Fig.W33)Internal resorption is the destruction of dentin commencing from the pulp chamber and con-tinuing outwards. Although it may affect either the deciduous or permanent denti tion, it pri-marily is found within permanent teeth. Internal resorption generally results in a well‐defined round or oval radiolucent area in the central portion of a tooth, associated with the pulp chamber and occasionally extending to the external surface of the root. However, the resorbed area may assume any shape and its size may range from a millimeter to total destruction of the tooth. There is no racial or sexual predilection and it may be diagnosed in any age group. It is noteworthy that there often is a history of a pulpotomy or other trauma to Fig.W31 Impaction: molars.Fig.W32 External resorption. 166 Fundamentals of Oral and Maxillofacial Radiologythe affected tooth. Clinically, the tooth charac-teristically has a pink color. Synonyms include pink spot, internal granuloma, chronic perforation and hyperplasia of pulp.Restorations, dentalDental restorations encompass a diverse range of clinical and radiological appearances. There is no characteristic location, number or shape, and there is no age, sex or racial predi-lection. As well, the size of a restoration is quite variable, ranging from a couple of millimeters in diameter to total involvement of a crown. Composite restorations often match the natural shade of tooth structure and may be overlooked in a clinical examina-tion. A composite restoration appears as either a well‐defined radiopaque or radiolucent area within the coronal portion of a tooth (Figs W34, W35, W36 and W37). Porcelain restorations are similar to compos-ites (Fig.W38). Metallic restorations, such as amalgam and gold appear as well‐defined radiopaque areas and they are primarily located within posterior teeth (FigsW39 and W40). Gutta percha (Fig. W38) is a radiopaque filling material found within a root canal. Typically, it will appear as a conical shape in the pulpal portion of a tooth, extending from the coronal portion of a tooth to its apex. Figures W41, W42, W43 and W44 illustrate other restoration features.Fig. W33 Internal resorption. (Source: Courtesy of M.Fernandes.)Fig.W34 Restorations: a, composite restorations; b, amal-gam restorations; c, onlay restoration .Fig.W35 Pin associated with restoration. W Dental Anomalies 167Fig.W37 Composite restorations: red circles, composite material without radiopaque filler; yellow circles, com-posite with radiopaque filler.Fig.W38 Restorations: a, porcelain fused to metal crowns; b, prefabricated post; c, pin; d. gutta percha.ABFig.W36 Class III composite restorations. A. Composite material with radiopaque filler and those without radiopaque filler that appear radiolucent. B. Highlighted cervical composite on the mandibular first molar and mesio‐occlusal com-posite on the maxillary second molar. 168 Fundamentals of Oral and Maxillofacial RadiologyFig.W39 Crowns: a, full gold crown on the mandibular first molar; b, porcelain bonded to metal crown on the mandibular second molar.Fig. W40 Stainless steel crowns on the maxillary and mandibular first molars.Fig.W41 Implants.Fig.W42 Cast of a removable partial denture (circled). W Dental Anomalies 169Fig.W44 Orthodontic hardware.Fig.W43 Open margin with the crown, recurrent decay or radiolucent cement? A clinical assessment would be necessary to determine. Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology170Osseous Pathology (Alphabetic)XExplanatory note: First of all, this book is not intended to be a comprehensive atlas of oral pathology. As mentioned earlier, most dental textbooks only show dental images of osseous pathology during a classic late stage of develop-ment which often stereotypes their appearances. The problem is that an osseous lesion will often appear dramatically different in earlier stages of development when most patients may be una-ware of any problem and something is inciden-tally observed on a dental x‐ray image. Unlike most dental anomalies, the size, shape, borders, loculations and even density of an osseous lesion may be dramatically different dependent upon the time of discovery. A large soap bubble radiolucency initially began as a pinpoint, uni-locular radiolucency. A radiopaque lesion may have transitioned from a radiolucency through a mixed phase until it progressed into a radiopacity. This is analogous to comparing photographs of an adult person and assuming that the individual appeared physically similar as a newborn and throughout childhood. Conse-quently, only written descriptions of the osseous entities will be found here. A review of the terminology used to describe osseous pathology will be found in Appendix 4.Abscess, periapicalA periapical abscess is an acute or chronic sup-purative lesion affecting either the deciduous or permanent dentition. It may be single or multiple in number and the size of the lesion varies from a few millimeters to a couple of centimeters in diameter. The periapical abscess occurs in all age groups and there is no racial or sexual predilection. Typically, there is a history of caries or trauma to the affected tooth and the duration may be years before the abscess is diagnosed. It appears as a unilocular, diffuse or well‐circumscribed radiolucent area at the apex of a tooth. It is notable, however, that there is no radiopaque border around the lesion. During the acute stage, the patient often complains of pain, swelling, tenderness to percussion, a slight extrusion of the affected tooth from the tooth socket and, occasionally, a fever. During the chronic stage, the affected tooth is often asymptomatic, but there usually is suppuration from an opening of a fistulous tract to the oral cavity. In both stages, the affected tooth is non‐vital. Synonyms include acute alveolar abscess, dento‐alveolar abscess, alveolar abscess and acute rarefying osteitis. X Osseous Pathology (Alphabetic) 171AmeloblastomaAn ameloblastoma is a benign odontogenic neo-plasm of epithelial origin. The average patient is between 30 and 50 years of age when the tumor is diagnosed, but it may occur in patients of all ages. It has been generally accepted that there is no racial or sexual predilection. Trauma, infection or previous dental extractions have been cited in numerous cases. On average, the duration of time between the patient’s first awareness of the lesion and the diagnosis of the ameloblastoma is over 2 years. Ameloblastomas typically are single in number and found in the posterior (i.e. molar–ramus) regions of the mandible. The size of the lesion is quite varia-ble, ranging from a 0.5 cm to over 18 cm in diameter. However, the average size is from 3 to 5 cm in diameter. A larger ameloblastoma often will appear as a multilocular radiolucent lesion with a soap bubble appearance (Fig.X1). Regardless of size, it still may be aunilocular radiolucency. The border is also quite variable depending upon the stage of development at the time of the diagnosis. Early in its develop-ment, the ameloblastoma displays well‐defined borders without any expansion of the cortical plate. Later stages reveal a lesion with a notch-ing and/or undulating expansion of the cortical plate and ill‐defined borders. Careful histologic examination is required as an ameloblastoma frequently may arise in the wall of a dentiger-ous cyst. The ameloblastoma has also been found to develop in association with a fibroma and/or an odontoma. Clinically, the amelo-blastoma is often observed as a painless swell-ing of the mandible. Synonyms include adamantinoma and central epithelioma.AntrolithAn antrolith is a mass that arises from the depo-sition of calcific salts around the nuclei of blood, mucous or foreign bodies. The antrolith is a generalized term simply used to indicate that the mass is found within an antrum. It may be single or multiple in number and they may vary from a few millimeters to a few centime-ters in size. They are most commonly found in individuals younger than 40 years of age, but they may occur in any age group. Also, there is no sexual or racial predilection. Antroliths appear as regular or irregular radiopacities with well‐defined margins. The patient’s past medical and dental histories often reveal an incident of an earlier traumatic extraction or an instance during childhood when a small object (e.g. cherry pit) was inserted into the patient’s nose. Antroliths are slow‐growing lesions and the individual may not be cognizant of any unusual symptoms for years. Some patients may complain of headaches, nasal obstruction ABFig.X1 A. Multilocular. B. Soap bubble appearance. 172 Fundamentals of Oral and Maxillofacial Radiologyand/or discharge, laryngitis or epistaxis, while other individuals may be totally asymptomatic. Of note, similar calcifications located within the nose are called rhinoliths or nasal calculi.Bone marrow defectA bone marrow defect develops when foci of hematopoietic or fibro‐fatty marrow form a localized collection of large marrow spaces. The etiology remains unknown, but it is often asso-ciated with chronic anemia. The condyle, the angle of the mandible and the maxillary tuber-osity are the most frequently affected sites. The typical patient is white, female and 30–50 years of age at the time of diagnosis. However, it may be found in either sex and in any race. The bone marrow defect may be single or multiple in number and it ranges from a few millimeters to several centimeters in diameter. It is quite variable in appearance, often appearing as a poorly defined radiolucency with irregular borders. Occasionally, it may appear as a sharply defined radiolucency. The bone marrow defect is usually asymptomatic and it is often discovered inadvertently during routine radio-logic examination.Calcifying epithelial odontogenic tumorA calcifying epithelial odontogenic tumor (CEOT) is a slow‐growing benign neoplasm found only within the maxilla and mandible. The tumor is predominantly located within the premolar–molar regions, with the mandible being more frequently affected than the maxilla. Typically it is a single lesion, varying from 2 to 5 cm in size. There is no racial or sexual predilection and while the average patient is 30–60 years of age at the time of diagnosis, it may be found in all age groups. The calcifying epithelial odon-togenic tumor is quite variable. Initially, it may appear as a well‐defined or diffuse unilocular or multilocular radiolucency often around the coronal aspect of a fully embedded tooth. The late stage of a CEOT is characterized by the formation of multiple, small, radiopaque foci within the radiolucency. Clinically it presents as a painless swelling of long duration, varying from weeks to several years prior to the patient seeking dental care. A synonym is Pindborg tumor.CementoblastomaA cementoblastoma is a benign neoplasm consisting of sheets of cementum‐like tissue, which may not be mineralized at the periphery of the mass or in the more active growth areas. However, there is a paucity of precise informa-tion available to distinguish this lesion clearly from periapical osseous dysplasia. Typically, the cementoblastoma is a single, slow‐growing lesion found only in the tooth‐bearing areas of the maxilla and mandible. Classically, it is attached to the root of the mandibular first molar and the average size of the lesion is 1 cm in diameter. There is a predilection for males, whose average age is 25 years, but it may be found in any age group and there is no racial predilection. The cementoblastoma appears as a mottled, dense radiopaque mass bordered by a well‐demarcated peripheral radiolucent zone, confluent with one or more roots that may show evidence of root resorption. Clinically, the cementoblastoma often presents as an expansion of the bone and there may or may not be pain associated with it. Synonyms include true cementoblastoma and benign cementoblastoma.CherubismCherubism is a rare fibrous proliferating disease found only within the maxilla and/or the man-dible. There is no racial predilection, but males are more frequently affected. It is notable that the majority of cases occur in childhood, with the average patient being between 2 and 5 years X Osseous Pathology (Alphabetic) 173of age. Also, a natural regression of the lesion occurs as the patient approaches puberty, often leading to a near normal appearance by the time the patient is 20 years of age. Cherubism is generally accepted to be a hereditary disorder and examination of the parents’ past medical histories will often confirm a familial history ofthe disease. Cherubism usually appears as a well‐defined, multiloculated radiolucency having a soap bubble appearance. Occasionally, it appears as a unilocular radiolucency. In addition, it typically occurs bilaterally in the posterior regions of the mandible and results in osseous expansion and thinning of the cortical plate. While in the maxilla, the lesions may be found predominantly in the tuberosity areas. The healed bone generally appears to be abnormally calcified or sclerotic. Clinically, the patient presents with a painless, symmetric, bony hard enlargement of the mandible and/or the maxilla, giving rise to the chubby face sug-gestive of a cherub. Synonyms include familial fibrous dysplasia of the jaws, disseminated juvenile fibrous dysplasia, familial multilocular cystic disease of the jaws and familial fibrous swelling of the jaws.Condensing osteitisCondensing osteitis is a chronic inflammatory process within the tooth‐bearing areas of the maxilla and mandible that results in a localized area of bone formation. Typically, it is a single lesion occurring in the premolar–molar regions of the mandible. The associated tooth is carious or has a large restoration. It is most frequently found in young adults, but it can also be diag-nosed in older individuals. The average size of the lesion is from 0.5 to 1.5 cm in diameter. Because the lesion is slow growing and usually asymptomatic, the patient may not be cogni-zant of the condition. The lesion can be classi-fied into early and late stages. The early stage is characterized by a region of dense osteosclero-sis having rounded and lobulated margins with either well‐defined or diffuse borders. The late stage shows the same lesion with a radiolucent rim and often there is expansion of the alveolar bone. It is notable that the lesion appears outside of the lamina dura. Synonyms include focal sclerosing osteomyelitis, enostosis, sclerosing osteitis, bone whorl and osseous dysplasia.CystsAneurysmal bone cystAn aneurysmal bone cyst is a controversial lesion of bone, which has been considered to be a vari-ant of the giant cell tumor. Essentially, the aneu-rysmal bone cyst is a solitary, localized and expanded fibrous lesion honeycombed by an enormously plexiform vascular bed. The typical patient is under 20 years of age at the time of diagnosis, yet it may be present in any age group. Males are more frequently affected, but there is no apparent racial predilection. Characteristically, it is a rapidly growing lesion located within the long bones and vertebrae with rare cases found in the posterior regions of the mandible and maxilla. While the etiology is uncertain, there often is a history of trauma to the area. It typically appears as a unilocular radiolucency (Fig. X2). However, it may be a multiloculated radiolu-cency with a soap bubble appearance (Fig.X1). In either situation, the margins may or may not be well‐defined and the cortical plate often is expanded and perforated. Clinically, the aneu-rysmal bone cyst presents as a swelling with or without pain, paresthesia and tooth displace-ment. Synonyms include ossifying hematoma, aneurysmal giant cell tumor, subperiosteal giant cell tumor and periosteal benign giant cell tumor.Botryoid odontogenic cystThe botryoid odontogenic cyst (BOC) is a poly-cystic variant of the lateral periodontal cyst. The age group ranges from 23 to 85 years. ABOC is typically multilocular (Fig.X1) and is larger than a lateral periodontal cyst, ranging 174 Fundamentals of Oral and Maxillofacial Radiologybetween 0.5 and 4.5 cm in diameter. The BOC often extends into the periapical region of involved teeth. It can be asymptomatic or very painful. Paresthesia and tumefaction have also been reported. Although the histopathologic features of BOCs are similar to lateral perio-dontal cysts, the BOC recurrence rate is higher.Calcifying odontogenic cystA calcifying odontogenic cyst (COC) is an unu-sual lesion, manifesting some features of both cysts and solid neoplasms. It presents as a slow‐growing, single lesion that ranges from 1 to 10 cm in diameter. Predominantly, it is located within the posterior regions of the mandible and, less frequently, it is found within the maxilla. There is no racial or sexual predi-lection, although the majority of cases occur in adulthood. The COC is quite variable. It may be a well‐defined or ill‐defined, unilocular or mul-tilocular radiolucency (Figs X1 and X2) There will be varying numbers of small radiopaque masses within the radiolucency. As well, it is often associated with an unerupted tooth. Clinically, the patient often presents with a painless swelling. Synonyms include calcifying cystic odontogenic tumor and Gorlin cyst.Dentigerous cystA dentigerous cyst is odontogenic in origin, arising from the enamel organ after partial completion of the crown of the tooth. The inci-dence is primarily in the posterior region of the mandible around the third molar. Occasionally they have been diagnosed in the maxilla, around which the cuspid and bicuspids are most frequently involved. A dentigerous cyst may be located either on the coronal or lateral aspect of an unerupted tooth. Typically, it is slow‐growing lesion ranging from a couple of millimeters to several centimeters in diameter. There does not appear to be any racial or sexual predilection. The average patient is between 10 and 20 years of age at the time of diagnosis, but it may found in any age group. A dentiger-ous cyst predominantly appears as a single, oval or round, unilocular radiolucency with well‐defined margins (Fig.X2). It may or may not have a radiopaque rim. The radiolucency is devoid of any internal trabeculation or calcifications. Occasionally, it may appear as a multiloculated radiolucency (Fig. X1) and display an aggressive behavior leading to bony expansion, root resorption and displacement of teeth. Clinically, the patient is often asympto-matic, but may be cognizant of a missing tooth or delayed tooth eruption. A synonym is the follicular cyst.Incisive canal cystAn incisive canal cyst is a non‐odontogenic cyst that originates from the proliferation of the epithelial remnants of the nasopalatine duct. Its etiology is unknown, but various factors, such as trauma and bacterial infection, have been proposed to explain its development. It is a single entity found only in the area of the incisive canal or the anterior palatine papilla. Although Fig.X2 Unilocular appearance. X Osseous Pathology (Alphabetic) 175it may be found in all age categories, there is prevalence for individuals between 30 and 50 years of age. There is no racial predilection, but males are primarily affected. The incisive canal cyst appears as a well‐defined, round, ovoid or heart‐shaped radiolucency (Fig. X2). The average size of the lesion ranges from under 0.5 to 1 cm in diameter. The incisive canal cyst is usually asymptomatic, but it occasionally pre-sents as a painful fluctuant swelling. Synonyms include median anterior maxillary cyst, anterior palatine foramen cyst and nasopalatine duct cyst.Keratocystic odontogenic tumorKeratocystic odontogenic tumor is an all‐encom-passing term used to describe any cyst that is derived from epithelium associated with the development of the dental structures. Typically, an odontogenic cyst is a single lesion, with less than 10% of the patients presenting with multi-ple cysts. A preponderance of the cases involves the posterior regions of the mandible, but it may be located anywhere within either the maxilla or the mandible. The size of the cyst is quite variable, ranging from 1 cm to over 7 cm in diameter. While there is a predilection for males, particularly in those under 30 years of age, it may occur in all age groups of either sex. The patient’s dental records often reveal the eti-ology of the cyst, as it is usually associated with a history of tooth extraction, an inadequately treated cyst or missing and unerupted teeth. Characteristically, the appearance of an odonto-genic cyst is a well‐defined round or oval uni-locular radiolucency with smooth borders (Fig. X2). Other features may include a multi-loculated appearance (Fig. X1), scalloped bor-ders, thinning and expansion of the cortical plate and root displacement with or without root resorption. It may or may not have a corti-cated (i.e. radiopaque) border. Clini cally, the odontogenic cyst is usually asymptomatic. However, a cyst of long duration may cause pain and swelling of the jaw. A synonym is an odontogenic keratocyst.Lateral periodontal cystA lateral periodontal cyst (LPC) is a non‐inflam-matory and non‐keratinized developmental cyst located lateral to the root of a vital tooth. They arise either between the roots or along the lateral periodontium of vital erupted teeth. A LPC typically appears as a well‐defined round or ovoid unilocular radiolucency located along the root between the alveolar crest and apex of the tooth. The average size is less than 1 cm in diam-eter. Occasionally, there may be a divergence of adjacent roots and loss of the lamina dura. Histopathologic examination is necessary to dif-ferentiate a LPC from other odontogenic cysts (see Botryoid odontogenic cyst).Median palatine cystA median palatine cyst is a fissural cyst that arises from epithelium trapped along the line of fusion of the palatal processes. The cyst is a single lesion found posterior to the anterior palatine papilla, in the midline of the hard palate. There is no racial or sexual predilection and it may be found in all age categories. However, there is prevalence for persons aged 30–50 years. It appears as a well‐defined unilocular, round or oval radiolucency with or without a radiopaque periphery (Fig. X2). The average size of the lesion is 2 cm in diameter. Clinically, the median palatine cyst usually presents as a painless swelling, but it occasionally causes discomfort.Periapical cystA periapical cyst arises from a non‐vital tooth. It is the most common variety of cyst found in the mandible and maxilla. Similar to the peria-pical abscess, it may be single or multiple in number. The size of the cyst varies from a centimeter to multiple centimeters in diameter. The periapical cyst occurs in all age groups but is more commonly found in the third to sixth decades of life. It can be found in both sexes, but is slightly more common in males. Typically, 176 Fundamentals of Oral and Maxillofacial Radiologythere is a history of deep caries or trauma to the affected tooth that results in necrosis of the pulp. It often is non‐symptomatic and found incidentally on x‐ray images. A periapical cyst typically appears as a single, uniform, well‐defined radiolucency with or without a cortical border (Fig.X2). Unless it is affected by surround-ing structures, it typically appears round. Large cysts may cause expansion of the surrounding cortical plates, displace adjacent teeth and cause root resorption. Treatment often entails endo-dontic therapy, apical surgery or extraction of the offending tooth with enucleation of the cyst. If there was incomplete removal of the cyst when the tooth was extracted, the resultant lesion is now referred to as a residual cyst . Synonyms include radicular cyst, dental cyst and periapical periodontal cyst.Stafne bone cystA Stafne bone cyst is generally accepted to be a salivary gland tissue inclusion defect that occurs during the development and growth of the mandible. It often is an incidental finding on panoramic images. The lesion is always situated between the mandibular canal and the cortical plate and, typically, in the region of the first molar and angle of the mandible. Occasionally, it may be located in the central incisor and bicuspid region. As well, there is a growing consensus of opinion that the lesion connects to the surrounding soft tissues. Males are primarily affected, but there is no racial pre-dilection. It often appears as a single, round or oval unilocular radiolucency with either well‐defined or ill‐defined borders (see Fig. Y16). The size of the lesion averages from 1 to 3 cm in diameter. On occasion, it has been reported to occur bilaterally. Clinically, the lesion is usually asymptomatic and, therefore, tends to be dis-covered inadvertently during routine radiologic examination. To rule out any pathology, a CBCT scan is best for diagnosing this defect. Synonyms include Stafne bone cavity, developmental lingual mandibular salivary gland depression, static bone cavity, static bone cyst, idiopathic bone cavity, lingual mandibular bone cavity and latent bone cyst.Traumatic bone cystA traumatic bone cyst is a controversial lesion. The general consensus is that this lesion lacks an epithelial lining and therefore the term “cyst” is a misnomer. It is most frequently located in the long bones and in the posterior regions of the mandible, lying above the mandibular canal. Although it can occur in any bone, it rarely is found in the maxilla. The typical patient is male and between 10 and 20 years of age at the time of diagnosis. However, it can be found in any age group of either sex and there is no racial predilection. While the etiology of this lesion remains unknown, there is often a history of trauma to the involved area. The traumatic bone cyst is a slow‐growing lesion. Consequently, the patient may not be cognizant of the lesion exist-ing, sometimes for several years. A traumatic bone cyst frequently appears as a lobulated, fairly well‐demarcated unilocular radiolucency (Fig.X2) extending high up between the roots of teeth. Typically, there will be trabeculae found within the radiolucency and the teeth in the area will be vital. Clinically, the traumatic bone cyst often presents as a painful swelling, but occasionally it may be totally asymptomatic. Synonyms include intraosseous hematoma, blood cyst, hemorrhagic cyst, solitary bone cyst, simple bone cyst, progressive bone cavity, extravasation cyst and unicameral cyst.ExostosisAn exostosis is a benign osseous growth charac-terized as a bony excrescence on the outer sur-face of a bone. Intraorally, the exostosis predominantly occurs in the posterior regions of either the maxilla or the mandible. Typically, it averages from 1 to 2 cm in size and it may be either single or multiple in number. Although the exostosis may arise at any age, it seems to X Osseous Pathology (Alphabetic) 177be somewhat more common in young adults. There is no sexual predilection. The exostosis generally appears as a rounded radiopaque mass with a well‐circumscribed lamina dura‐like border, and it is often surrounded by a radiolucent capsule. Clinically, the patient is asymptomatic, but presents with one or more bony hard nodular, pedunculated or flat protu-berances on the surface of the maxilla and/or the mandible. A synonym is the osteoma.FibrosarcomaA fibrosarcoma is a malignant fibroblastic tumor that is characterized by varying amounts of collagen formation and the absence of bone pro-duction. Typically, it is a single lesion showing a predilection for the long bones, with only rare cases located in either the maxilla or the mandi-ble. However, within the jaws, there is a predilec-tion for the posterior regions (e.g. molar–ramus) of the mandible. The average patient is between 20 and 40 years of age at the time of diagnosis, but a fibrosarcoma may occur at any age and there is no sexual or racial predilection. A fibro-sarcoma often appears as an irregular radio-lucent lesion with ill‐defined borders. It is an aggressive, fast‐growing lesion that causes dif-fuse bone destruction, often in less than 6 months. As the lesion does not have any distinct borders, it consequently blends into the surrounding bone. Within the radiolucent lesion, there are often nodular or diffuse calcifications that repre-sent remnants of bone that the fibrosarcoma did not fully destroy. This is indicative of the rapidity with which the tumor spreads throughout the bone. There is also a characteristic thinning and perforation of the cortical plate. Once the fibro-sarcoma pervades the cortical plate, the cortical plate resembles a grate or a mesh because of the numerous perforations through it. It is notable that a sunburst appearance is not produced as in an osteosarcoma. Clinically, the patient often pre-sents with pain, swelling, loosening of the teeth, paresthesia and hyperplastic gingiva.Fibrous dysplasiaFibrous dysplasia is a slow‐growing, benign, fibro‐osseous lesion of unknown etiology, characterized by the formation of fibrous connective tissue within the affected bone(s). Various theories concerning the pathogenesis, such as trauma or congenital development, have been proposed, but a unanimous consen-sus still does not exist. This lesion is classified into three categories: monostotic fibrous dysplasia, polyostotic fibrous dysplasia and Albright’s syndrome. Monostotic fibrous dys-plasia characteristically affects only a portion of a single bone. Polyostotic fibrous dysplasia affects more than one bone and is associated with café‐au‐Iait spots . Albright’s syndrome is characterized by polyostotic bone involvement, café‐au‐lait spots and endocrine involvement (e.g. precocious puberty). All three classifica-tions may affect any bone. Within the maxilla and the mandible, fibrous dysplasia is predom-inantly found in the posterior regions of the maxilla and less frequently it is located in the posterior regions of the mandible. The size of the lesion is quite variable, ranging from 1cm to total involvement of the bone(s). There is a predilection for females under 30 years of age, but it can occur in either sex, in any age group and develop in all races. Fibrous dysplasia is quite variable. Initially, it appears as a small, unilocular or multilocular radiolucency with well‐defined borders (Figs X1 and X2). The lesion develops into an ill‐defined radiolucent area (i.e. lacking a radiopaque rim), with zones of sclerotic bone within it. This stage is often described as having a mottled appearance. The late stage is characterized by thinning and expansion of the cortical plate and an increas-ing amount of sclerotic bone within the lesion, giving it a ground glass appearance (Fig.X3). It is important to note that outside of the lesion, there are not any sclerotic changes occurring within the bone. Also, the lamina dura is destroyed when the lesion involves a tooth. Clinically, the patient often presents 178 Fundamentals of Oral and Maxillofacial Radiologywith a painless swelling, while less frequently nasal obstruction and tooth displacement may be observed. Synonyms include osteitic fibrosa, osteofibroma, localized osteodystrophia and Jaffe’s type fibrous dysplasia.Foreign bodyAny substance introduced into an individual either voluntarily or involuntarily must be properly interpreted by the clinician. Invol-untary inclusion refers to iatrogenic causes related to a medical or dental procedure (e.g. broken instrument) or during an unrelated accident (e.g. gunshot wound, auto incident). The shape, size, location, density and number of foreign bodies are variable. Dental artifacts may include restorative materials, cements, broken endodontic files, broken surgical burs, etc. In addition, radiopacities located in eden-tulous areas on x‐ray images may have been introduced into the socket during a dental extraction procedure (e.g. remnant of an occlusal restoration). A thorough review of a patient’s clinical history will often reveal the source of the foreign material.Giant cell granuloma, centralA giant cell granuloma is a term that was first used in the 1950s to describe and to categorize giant cell tumors of the maxilla and mandible. Controversy still exists as to whether the giant cell tumor of bone and the central giant cell granuloma are actually separate entities. The central giant cell granuloma is a slow‐growing lesion rarely found outside of the maxilla and mandible. Typically, the anterior region of the mandible is affected and less frequently the anterior region of the maxilla. The lesion will average from 1 to 3 cm in diameter, but it could involve the entire bone. The central giant cell granuloma is rarely found in individuals over 21 years of age and females are most often affected with this lesion. The patient’s past medical and dental history frequently indicates prior trauma to the area. Typically it appears as a single, multiloculated radiolucency, having a soap bubble appearance (Fig. X1) with smooth, well‐defined margins. Often thinning, expan-sion and perforation of the cortical plate ensue. However it may appear as a unilocular radiolu-cency and the margins may be ragged. The patient often presents with a painless swelling ABFig.X3 Ground glass appearance. (Source: Shumway BS, Foster TS (2011) Pathology of the jaw: the importance of radio-graphs. J Can Dent Assoc 77: b132. Reproduced with permission of the Canadian Dental Association.) X Osseous Pathology (Alphabetic) 179and displaced teeth. Pain and root resorption occur less frequently. The giant cell granuloma is a self‐limiting lesion that occasionally sub-sides spontaneously and seldom recurs.Giant cell tumorA giant cell tumor is a benign, yet aggressive, lesion, classically located within the long bones, particularly about the knee. Few cases have been located within the maxilla and mandible. The mandible is more frequently involved than the maxilla, with both showing a predilection for the anterior region. Typically, the giant cell tumor is a single lesion, averaging from 1 to 3 cm in diameter. The average patient is between 21 and 40 years of age at the time of diagnosis, but the tumor may be found in any age group. There is a slight predilection for occurrence in females. Because the lesion is slow growing, it may be years before the patient is cognizant of any unusual symptoms. Radiologically, the giant cell tumor is quite variable. Frequently, the tumor appears as a multiloculated radiolu-cency with smooth, well‐defined borders and with thinning and expansion of the cortical plate (Fig. X1). However, the giant cell tumor may perforate the cortical plate. The patient often complains of pain, swelling, paresthesia and loosening of the teeth. Inadequate enuclea-tion of the tumor often results in recurrence of the lesion. Synonyms include chronic hemorrhagic osteomyelitis, osteoclastoma, myeloid sarcoma and giant cell sarcoma.Granuloma, periapicalA periapical granuloma is a localized mass of chronic granulation tissue formed in response to pulpal infection. Any tooth in either the maxilla or the mandible may be affected. It may either be single or multiple in number and the size of the lesion may vary from a few millimeters to over a centimeter in diameter. The periapical granuloma has reportedly occurred in all age groups, but it is most frequently found in patients aged 20–30 years. It has generally been accepted that there is no sexual or racial predi-lection. The periapical granuloma appears as a round or oval‐shaped radiolucency and it may or may not have well‐defined borders. Also, there is a partial loss of the lamina dura in the affected region. A patient’s past dental history will often indicate a record of pulpitis as a result of caries or, less frequently, an incident of trauma to the affected tooth. Typically, the duration of time between the pulpitis or the  trauma to the tooth and the diagnosis of the periapical granuloma is less than 1 year. Histologic examination is necessary to differ-entiate the granuloma from a cyst or an abscess. Clinically, the patient often is asymp-tomatic. However, if the etiology is caries, then the patient may experience discomfort from percussion and chewing. The affected tooth is non‐vital and it may appear darker in color than the surrounding normal teeth. Synonyms include apical granuloma and periapical rarefying osteitis.HemangiomaA hemangioma of bone is a benign neoplasm characterized by a proliferation of blood vessels. Typically, the hemangioma is a single lesion, but it can be multiple in numbers. The average patient is between 10 and 30 years of age at the time of diagnosis but it may occur in patients of all ages. There does not appear to be any racial or sexual predilection present. The etiology of a hemangioma remains uncertain, but often there is a history of other vascular disorders or tooth extraction in the affected area. It is a slow‐growing lesion with duration of time varying from weeks to years. The hemangioma is pre-dominantly located in the spinal vertebrae. Less frequently, it is found in the posterior regions of the maxilla and the mandible, particularly in the mandible. The size of the lesion is quite var-iable ranging from 1 cm to total involvement of 180 Fundamentals of Oral and Maxillofacial Radiologythe bone(s). The hemangioma is quite variable in appearance. It ranges from a well‐defined multilocular radiolucency with well‐defined margins having a soap bubble appearance (Fig.X1) to a diffuse, oval or round unilocular radiolucency with irregular, indistinct margins. Occasionally the hemangioma has been reported to have a sun‐ray appearance inside the radiolucency as a result of bone proliferation from within the lesion. On average, the hemangioma is 1–2 cm in diameter. In addition, there frequently is erosion of the lamina dura, root resorption and phleboliths (Fig. X4) within the lesion. Clinically, the hemangioma pre-sents as a painless swelling, with loosening of the teeth and bleeding around the necks of the teeth.HyperparathyroidismHyperparathyroidism is a metabolic bone disease resulting from an increased secretion of parathy-roid hormone. This increased hormone secretion results in a generalized decrease in image density of the skeletal bones including the maxilla and mandible, giving them a ground glass appearance. Also, hyperparathyroidism leads to the partial or total loss of the lamina dura around all of the teeth and a fading or a disappearance of the radi-opaque lines bordering the maxillary sinus and the nasal cavity. Inassociation with it, there are often brown tumors, which are vascular intraos-seous soft tissue masses. The brown tumor appears as a well‐circumscribed radiolucent area identical to the giant cell granuloma and it is most often observed in the mandible, clavicle, ribs and pelvis. Females over 30 years of age are most often affected, but there is no racial pre-dilection. Clinically, the patient presents with loosening of the teeth, nausea, a history of bone fractures, hypercalcemia and hypophos-phatemia. It is notable that after treatment of hyperparathyroidism, the healed bone is often very dense and never appears quite normal. Asynonym is osteitis fibrosa.Metastatic tumorA characteristic of malignant tumors is their ability to metastasize at some stage of develop-ment to sites distant from their origin. Metastatic tumors to the maxilla and/or the mandible are quite rare. However, the paucity of cases reported in the literature indicates that the most prevalent metastatic sites of origin are the breast, lung, kidney and prostate gland. Typically, the posterior regions of the mandible are affected. Should the condyle be involved, almost a definitive diagnosis of a metastatic tumor is possible, as a result of the rarity of lesions that affect it. The average patient is over 50 years of age at the time of the diagnosis and there is no apparent sexual or racial predilec-tion. There are not any characteristic clinical or radiologic findings associated with a metastatic tumor. It may be single or multiple in number, range from one to several centimeters in size, appear unilocular or multilocular, have well‐defined or ill‐defined borders, be regular or Fig.X4 Phleboliths. X Osseous Pathology (Alphabetic) 181irregular in outline and can be radiolucent orradiopaque in density. Typically, however, it appears as an ill‐defined radiolucent lesion. The patient may present with pain, swelling, paresthesia, trismus, mobile teeth and a poor healing tooth socket from an earlier extraction. It may also present as a single extruded tooth in an otherwise normal appearing dentition.Multiple myelomaMultiple myeloma is a malignant tumor of plasma cells, primarily characterized by widespread bone destruction. Typically, it is found in patients over 60 years of age, rarely being found in any-one below 50 years of age. There is a predilection for black males. Bones containing hematopoietic marrow such as the vertebrae, ribs, pelvis and skull are most frequently affected. When the bones of the oral cavity are involved, it predomi-nantly occurs in the posterior regions of the mandible. Compared to histiocytosis‐X, the size of a myelomatous lesion is quite small, averag-ing from 1 to 2 cm in diameter. Also, there are greater numbers of lesions (unless the lesions coalesce) present in the individual with multiple myeloma than in patients with histiocytosis‐X. On rare occasions, the myeloma has been reported to occur as a single lesion, but contro-versy exists as to whether it is a separate entity or simply an early developmental stage of the multiple myeloma. Classically, multiple myelo-mas appear as punched‐out radiolucent areas of bone destruction which do not show trabecu-lae within them, nor any sclerotic zones around their periphery. Within the mandible, there is often expansion, thinning and perforation of the cortical plate. The patient’s past medical and/or dental history often indicates anemia, renal dys-function, weight loss, a history of multiple bone fractures and numerous extractions of loose teeth. Clinically, the patient often presents with pain, swelling, weakness and mobile teeth. Synonyms include plasma cell myeloma, plasma-cytic myeloma and myelomatosis.MyxomaMyxoma is a benign odontogenic tumor that is believed to originate from the mesenchymal por-tion of the tooth germ. The tumor is very rarely located outside of the maxilla and the mandible. It shows a slight predilection for the mandible over the maxilla, with the posterior regions primarily being affected. The average patient is between 10 and 50 years of age, but reports exist of the tumor occurring in patients of all ages. Past dentalhisto-ries often reveal the occurrence of congenitally absent or unerupted teeth. However, there does not appear to be any racial or sexual predilection. The myxoma is quite variable in appearance, ranging from asingle, multiloculated radiolucent lesion with well‐defined borders having a honey-comb appearance (Fig.X5) to a unilocular, cyst‐like radiolucency with ill‐defined borders. The margins often appear scalloped and there fre-quently is bony destruction of the cortical plate. Occasionally, there may be root resorption. The size of the lesion is also quite variable, ranging from 1 to 10 cm in diameter. Clinically, the patient presents with a painless swelling and possibly loosened or displaced teeth. The myxoma hasalso been found to recur frequently. Synonyms include odontogenic myxoma, myxofibroma and odontogenic fibromyxoma.Fig.X5 Honeycomb appearance. 182 Fundamentals of Oral and Maxillofacial RadiologyOdontoma, complexSee Section W.Odontoma, compoundSee Section W.Osseous dysplasiaOsseous dysplasia is a benign fibro‐osseous lesion of unknown etiology. Typically, it is asymptomatic and as a result it is often found incidentally on intraoral x‐ray images during routine examinations. Three clinical presenta-tions of osseous dysplasia exist: periapical osseous dysplasia, focal osseous dysplasia and florid osseous dysplasia. Periapical and focal osseous dysplasia share the same clinical, radiologic and histologic features, only differ-ing on the basis of location. Periapical osseous dysplasia is typically diffusely located in the mandibular incisor region, while focal osseous dysplasia is typically a well‐defined lesion located in the posterior region of the mandible. Because periapical osseous dysplasia frequently is associated with the apices of several teeth, it may be misdiagnosed as being multiple lesions. The location of florid osseous dysplasia is more generalized and it is found in at least two quad-rants. Osseous dysplasia is quite variable and can be classified into early, mixed and late stages of development. The early stage is characterized as a small periapical radiolucent defect. Note that if multiple neighboring teeth are involved, then a fusion of these radiolucencies may give rise to a single, large, less clearly defined radio-lucent lesion. The mixed stage is characterized by the formation of minute radiopacities within the radiolucent lesion. The late stage is charac-terized by the coalescing of the calcified struc-tures within the radiolucent area, resulting in a dense radiopacity. The average size of a lesion is 1–2 cm in diameter. Florid osseous dysplasia appears as multiple, irregularly‐shaped radi-opacities surrounded by thin, radiolucent borders located in multiple quadrants. Osseous dysplasia shows a predilection for middle‐aged black females. Clinical examination will reveal that the involved tooth or teeth are vital. Osseous dysplasia is self‐limiting and typically does not require treatment. Clinical and radio-logic follow‐up is recommended. Synonyms include cemento‐osseous dysplasia, cementoma, true attached cementoma, periapical cemental dyspla-sia, sclerosing cementum, periapical fibrous dysplasia and periapical fibro‐osteoma.Ossifying fibromaAn ossifying fibroma is a central fibro‐osseous lesion. It is a single lesion located predominantly in the posterior regions of the mandible and, less frequently, in the anterior regions of the maxilla. The lesion develops close to the roots of teeth and often results in tooth displacement. Typically, the average patient is aged 20–40 years at the time of the diagnosis, but the tumor may be found in any age group. It is notable that there is a slight predi-lection for females. While the etiology remains unknown, there is often a history of trauma to the affected area. Radiologically, the cementifying–ossifying fibroma is quite variable. Initially, it may appear as a unilocular or multilocular radio-lucency with well‐defined borders. During the intermediary stage, it is transformed into a mixed radiolucent–radiopaque lesion having a ground glass or a cotton wool appearance (Figs X3 and X6). The late stage of the tumor is charac-terized by a well‐circumscribed radiopaque lesion surrounded by a uniform radiolucent rim. In addition, there may be expansion of the cortical plate. Clinically, the ossifying fibroma is a slow‐growing, painless lesion. As a result, the patient is often not cognizant of any unusual symptoms for years. Synonyms include cemen-tifying fibroma, ossifying fibroma, osteofibroma, fibrous osteoma, fibro‐osseous lesion of bone and benign non‐odontogenic tumor of the jaw. X Osseous Pathology (Alphabetic) 183OsteomyelitisOsteomyelitis is an inflammation of bone com-monly initiated by either an abscessed tooth or the result of a post‐surgical infection. There are many different forms of osteomyelitis. However, they can be categorized into acute and chronic phases. Occasionally the source of infection may not be known. Inflammation can involve all of the bony components: cortical and cancellous bone and the periosteum. The mandible is more commonly affected than the maxilla because of its comparatively poorer blood supply, although either may be affected. CBCT imaging is the modality of choice. Acute osteomyelitis occurs in all age groups, with males being affected more commonly. It often has a rapid onset, with pain, swelling and a purulent discharge in the affected area. Teeth in the affected area may be mobile and sensitive to percussion. In the early stage of acute osteo-myelitis there may not be any changes seen radiologically. Gradually, however, there will be a decrease in bone density that may be iso-lated locally or widespread. Additionally, there may be the appearance of sclerotic patches and the formation of bone sequestrae. Should the acute phase of osteomyelitis be inade-quately resolved, a chronic diffuse sclerosing form of osteomyelitis may develop. Chronic osteomyelitis predominantly occurs in the pos-terior aspect of the mandible and is associated with an increase in bone deposition. Gradually the appearance will change from a mixed radio-lucent–radiopaque area to a dense radiopacity. Patient’s signs and symptoms may include recurring episodes of swelling, pain, fever and lymphadenopathy. Synonyms for osteomyelitis include acute suppurative osteomyelitis, pyogenic osteomyelitis, subacute suppurative osteomyelitis, Garre’s osteomyelitis, proliferative osteomyelitis, periostitis ossificans, chronic osteomyelitis, chronic diffuse suppurative osteomyelitis, chronic non‐sup-purative osteomyelitis, chronic osteomyelitis prolif-erative osteomyelitis and Garre’s non‐suppurative osteomyelitis.OsteopetrosisOsteopetrosis is a disease of unknown etiology characterized by a generalized thickening and sclerosis of bone . Two forms of osteopetrosis exist. Osteopetrosis congenita is a malignant form, commonly seen in infants or young chil-dren and it is typically fatal as a result of anemia, massive hemorrhage or rampant bone infection. Osteopetrosis tarda is a benign form and it may be diagnosed during childhood or during any stage of adult life. This latter type ABFig.X6 Cotton wool appearance. 184 Fundamentals of Oral and Maxillofacial Radiologymay be asymptomatic and the patient’s lifespan does not seem to be shortened. There is no sexual or racial predilection in either form. Both forms show an increase in the density and thickness of the bones of the entire skeleton. As a result, the bones have a homogeneous, symmetrically sclerotic appearance. The cortex and the medullary cavity of each of the bones become indistinguishable. There is loss of the lamina dura and, in severe cases, the paranasal sinuses become opacified. Clinically, during the early stages of the disease, the patient may be asymptomatic and consequently osteopetrosis may be diagnosed inadvertently during routine radiologic examination. However, during the later stages of the disease, the patient often presents with a thickening of the skull, deaf-ness, blindness, facial paralysis, poor healing capabilities, a history of repeated fractures and anemia. Synonyms include Albers–Schonberg disease, marble bone disease and osteosclerosis fragilis generalsata.OsteoporosisOsteoporosis is a common bone disease in which the density of bone is diminished. There are no symptoms in the early stages. Patients are often unaware of their condition until a fracture occurs. Ostoeporosis of the maxilla and mandible will appear as a generalized rarefaction. Generalized thinning of the corti-cal plates and thinning or loss of trabeculae will be evident. It is more commonly found in post‐menopausal white and Asian females. Risk factors include small stature, taking med-ications (e.g. for treatment of lupus, asthma, thyroid deficiencies and prostate cancer), low calcium intake, inactive lifestyle, smoking and drinking excessive alcohol. With increasing age, both women and men frequently will suffer a fracture of a hip, wrist or vertebra as a result of osteoporosis. Antiresorptive media-tions such as bisphosphonates are commonly used to treat post‐menopausal osteoporosis. Bisphosphonates have been associated with unusual fractures in the femur.OsteosarcomaOsteosarcoma is a malignant neoplasm in which the tumor cells produce immature bone. Typically, it involves one or more bones, show-ing a predilection for occurrence in the long bones and the knee, with fewer than 10% of the cases reported in the maxilla or mandible. The average patient is aged 30–40 years at the time of diagnosis. Cases involving the maxilla and/or the mandible often develop in patients who are 10 years older than those individuals with tumors found in the long bones. There is no racial predilection, but males are more fre-quently affected. While the etiology remains unknown, there often is a history of trauma to the area. It is a fast‐growing, aggressive lesion with a duration varying from weeks to years. The mandible is involved approximately twice as often as the maxilla and it predominantly occurs in the anterior region of either bone. The osteosarcoma can be classified into early (osteolytic), intermediate (osteolytic and oste-oblastic) and late (sclerotic) stages. The early stage is characterized by a generalized widen-ing of the periodontal ligament spaces and an ill‐defined pear‐ or oval‐shaped radiolucency. The intermediate stage reveals a concurrent process of resorption and deposition of bone, giving rise to an ill‐defined mixed radio-lucent–radiopaque region. The late stage is characterized by a dense radiopaque lesion, often displaying the classic sunburst or sun‐ray appearance (Fig. X7), with or without the partial destruction of the cortical plate. The size of the lesion is quite variable, ranging from one to several centimeters in diameter. Clinically, the symptoms include pain, maloc-clusion, swelling, paresthesia and loosening of the teeth; also, the osteosarcoma is often associated with Paget’s disease. A synonym is osteogenic sarcoma. X Osseous Pathology (Alphabetic) 185Paget’s diseasePaget’s disease is a disease of unknown etiology that is characterized by concurrent destruction and formation of bone. This condition appears on average in patients over 40 years of age and it rarely appears in patients younger than 30 years of age. There is a predilection for occurrence in males (the male : female ratio being approximately 2 : 1), and approximately 50% of the cases demonstrate a hereditary pat-tern. Patients are not cognizant of any unusual symptoms until the disease is of several years’ duration. However, in the later stages, patients often complain of pain, deafness, visual loss, ill‐fitting dentures and hats that have become too small. Typically, Paget’s disease involves more than one bone, mainly affecting the bones of the lower extremities, the neck and the skull. This often results in a bowing of the lower extremities, scoliosis, kyphosis and an enlarge-ment of the affected bone. Paget’s disease is also associated with osteosarcoma. The size of the lesion is quite variable, ranging from a few centimeters to total involvement of the affected bone(s). Its appearance can be classified into the early (osteolytic), intermediate (mixed) and late (osteoblastic) stages. The early stage is characterized by radiolucencies of variable size, often becoming confluent with sharp, somewhat jagged contours and also potentially having a ground glass appearance. The intermediate stage reflects the concurrent process of resorp-tion and deposition of bone. This results in an ill‐defined lesion with widening of the cortex, enlargement of the bone and a cotton wool appearance (Fig.X6). The late stage is character-ized by a coalescing of the radiopacities, result-ing in dense, irregular areas of calcification, a loss of the lamina dura and frequent bone fractures. A synonym is osteitis deformans.Phlebolith, intraoralIntraoral phleboliths are calcified thrombi found within the soft tissues. They are characteristically associated with cases of cavernous hemangiomas. Consequently, phleboliths appear predominantly in individuals under 30 years of age, but they may arise in any age group. There is no racial or sexual predilection. Phleboliths typically appear as multiple, small, rounded radiopacities having concentric structures, with radiolucent centers (Fig. X4). The average size of each phlebolith is from 1 to 3 mm in diameter. Sometimes, they are referred to as having a buckshot appearance. Clinically, the patient often presents with a pain-less swelling. It is notable that this swelling is not affected by eating, as with sialoliths. Phleboliths are frequently associated with hemangiomas.RhinolithA rhinolith is a mass that arises from the depo-sition of calcific salts around the nuclei of blood, mucous or foreign bodies. The rhinolith is specifically located within the nasal fossa. Arhinolith may be single or multiple in num-ber and it may vary from a few millimeters to a Fig.X7 Sunburst appearance. 186 Fundamentals of Oral and Maxillofacial Radiologyfew centimeters in size. It is most commonly found in individuals younger than 40 years of age, but it may occur in any age group. Also, there is no sexual or racial predilection. A rhino-lith appears as a regular or irregular radiopacity with well‐defined margins. The patient’s past medical and dental histories often reveal an incident of an earlier traumatic extraction oran instance during childhood when a small object (e.g. cherry pit) was inserted into the patient’s nose. A rhinolith is a slow‐growing mass and the individual may not be cognizant of any unusual symptoms for years. Some patients may complain of headaches, nasal obstruction and/or discharge, laryngitis or epistaxis, while other individuals may be totally asymptomatic. A synonym for a rhinolith is nasal calculus.Salivary gland tumors, benign andmalignantBenign and malignant tumors of the salivary glands rarely manifest themselves in the jaws. Typically, both types of tumors present as sin-gle lesions occurring predominantly in the pos-terior aspects of either the maxilla and/or the mandible. There is no sexual or racial predilec-tion; however the benign and malignant sali-vary gland tumors typically occur in individuals more than 30 years of age. Malignant tumors are particularly prevalent in the older age cate-gories. It is notable that while a benign tumor has a duration varying from months to years prior to its diagnosis, a malignant lesion gener-ally only has a duration of weeks to months prior to its diagnosis. The benign salivary gland tumor usually appears as a well‐defined, round or oval‐shaped radiolucent lesion having a radiopaque periphery. The malignant salivary gland tumor often appears as an ill‐defined, irregular‐shaped radiolucency that lacks a radi-opaque periphery. The size of both of the lesions averages from 1 to 5 cm in diameter. Clinically, the benign salivary gland tumor presents as a painless swelling, while the malignant salivary gland tumor may present with or without pain and/or swelling. Synonyms for benign salivary gland tumors include benign adenoma and adenoma, while a synonym for a malignant salivary gland tumor is adenocarcinoma.Scar, periapicalA periapical scar is a well‐defined or an ill‐defined radiolucent lesion found at the apex of a tooth that has a history of periapical involve-ment and endodontic treatment. It represents an area where the healing process terminated in the formation of collagen rather than bone. The size of the periapical scar is variable, ranging from less than 1 cm to several centimeters in diameter. It may be located in any of the tooth‐bearing areas of the maxilla and mandible. There is no sexual or racial predilection and it may be found in any age group. Clinically the tooth is asymptomatic and the periapical scar is often incidentally discovered during routine intraoral imaging. A synonym is apical scar.SialolithSialoliths are calcareous concretions that slowly develop within a salivary duct or a salivary gland. They form by the deposition of calcium salts around a central nidus, which may be a foreign body, desquamated epithelial cells or bacteria. Sialoliths may be single or multiple in number, and they may vary from less than 1 cm to over 12 cm in size. They are most commonly found in middle‐aged adults, but they occur in all age groups. There is no sexual or racial pre-dilection. The submandibular gland and duct are most frequently involved with sialolithiasis, followed by the parotid gland and duct and the sublingual gland and duct. On extremely rare occasions, sialoliths have involved the minor salivary glands and ducts. The sialolith usually appears as a round or oval, uniformly dense radiopacity, with either regular or irregular X Osseous Pathology (Alphabetic) 187margins (see Fig. Y15). Clinically, the patient often complains of a painful swelling, parti-cularly during eating. It is also notable that the sialoliths are not attached to any bones. Synonyms include salivary duct calculus, salivary duct stone and salivary calculi.TorusA torus is a slow‐growing bony excrescence of unknown etiology that may be found either singly or multiple in number. It is either located on the lateral aspect of the lingual surface of the mandible, particularly in the premolar–molar region, and is referred to as a torus mandibularis or it is located in the midline of the palate and is referred to as a torus palatinus. The shape and size of any torus is quite variable. It may appear flat, lobular or oval and it may range from a few millimeters to several centimeters in length (see Figs M25 and U18). There is no sexual pre-dilection. The average patient is under 30 years of age when the lesion is first diagnosed and it stops increasing in size by middle‐age. A torus appears as an oval‐shaped radiopacity, usually with well‐defined borders. Clinically, the lesion is asymptomatic. Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology188Lagniappe (Miscellaneous Oddities)YABFig.Y1 A. Poorly filled interproximal composite restora-tions on distal of no. 13 and mesial no. 14. B. Re‐treated nos 13 and 14 with good composite restorations. Note that recurrent decay was not the cause of the radiolucency in this instance.ABFig.Y2 A. Carious lesion in distal no.14. B. Progression ofthe untreated carious lesion 6 years later. Y Lagniappe (Miscellaneous Oddities) 189A BFig.Y3 Measurements of a tooth imaged twice (consecutively) with altered vertical angulation. The results show significant differences in tooth measurements. Conclusion: measurements taken on conventional images often are inaccurate because software measuring tools cannot compensate for image distortion (e.g. elongation or foreshortening).ABFig.Y4 Misdirected anchoring device for sleep apnea device resulting in root fractures (highlighted in B). The anchoring device was intended to be inserted into bone inferior to the root. 190 Fundamentals of Oral and Maxillofacial RadiologyFig.Y5 Mucosal antral cyst: dome‐shaped radiopacity. Do not confuse this with a sinus lift procedure as shown in Fig. Y14.Fig. Y6 Carotid artery calcification: irregular‐shaped radiopacity.Fig.Y7 Internal radiotherapy involves surgically implanting tiny pellets or rods (multiple small radiopacities) containing radioactive materials in or near a tumor. Y Lagniappe (Miscellaneous Oddities) 191Fig. Y8 Calcification of the stylohyoid ligament: elon-gated, segmented radiopacity.Fig. Y9 Colorized x‐ray image highlighting localized angular periodontal bone loss.Fig.Y10 Nose piercing: barbell‐shaped radiopacity. 192 Fundamentals of Oral and Maxillofacial RadiologyFig.Y11 Example of multiple exposures taken in the hope of obtaining one perfect image. Biologic effects of radiation are cumulative. Follow the ALADA principle.ABFig.Y12 Tongue depressor. Y Lagniappe (Miscellaneous Oddities) 193A BFig. Y13 Patient holding the receptor in position. A tongue depressor works well beneath a rubber dam when a conventional receptor holder may not work.ABFig.Y14 Post‐sinus lift surgery: radiopaque mass in the maxillary right sinus (arrows). A. CBCT panoramic view. B. CBCT coronal view. This radiopacity should not be misinterpreted as sinusitis. 194 Fundamentals of Oral and Maxillofacial RadiologyA BFig.Y15 A. Sagittal view of a sialolith. B. Coronal view of a sialolith, showing it located on the lingual aspect of the mandible.ABFig.Y16 A. Sagittal view of a Stafne bone cyst. B. Coronal view revealing the radiolucent concavity attributed to the Stafne bone cyst. Part Three Appendices Fundamentals of Oral and Maxillofacial Radiology, First Edition. J. Sean Hubar. © 2017 John Wiley & Sons, Inc. Published 2017 by John Wiley & Sons, Inc. Companion website: www.wiley.com/go/hubar/radiology197Appendix 1FDA Recommendations forPrescribing Dental X‐ray Images

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