19 Film Mounting and Radiographic Anatomy










213
19
Film Mounting and
Radiographic Anatomy
EDUCATIONAL OBJECTIVES
Upon completing this chapter, the student will be able to:
1. Dene the key terms listed at the beginning of the chapter.
2. Discuss the types of descriptive terminology used in
radiography, including how the density of a structure
determines its radiographic appearance.
3. Discuss the following related to mounting procedures:
• Statetheadvantageofmountingradiographs.
• Listthetwotechniquesinmountingconventionallms
and state which is the preferred method.
• Listthetwomodesofmountingtechniquesthatcanbe
employed when utilizing a digital radiographic system.
• Listvehelpfulhintsthatcanbeusedinmounting
radiographs.
4. Describe the following related to radiographic tooth
anatomy:
• Knowtheradiographicappearanceofthecomponents
of the tooth and surrounding bone and soft tissue
structures.
• Identifyanddescribetheanatomiclandmarksofthe
maxilla on radiographic images.
• Identifyanddescribetheanatomiclandmarksofthe
mandible on radiographic images.
5. Identifycommonrestorationsonradiographicimages.
6. Identifytheanatomiclandmarksonocclusal,panoramic,
and other extraoral images.
KEY TERMS
alveolar bone
alveolar crest
anterior nasal spine
antral or inverted Y
buccinator shadow
cancellous bone
cementum
concavity
coronoid process of the mandible
cortical bone
dentin
enamel
external oblique ridge
oor of the maxillary sinus
oor of the nasal cavity
oor of the nasal fossa
foramen
fossa
genial tubercle
hamular notch
hamular process (hamulus)
incisive canal
inferior border of the mandible
inferior nasal concha (turbinate)
internal oblique ridge (mylohyoid
ridge)
labial mounting
lamina dura
lateral fossa
lingual foramen
lingual mounting
mandibular canal (inferior alveolar
canal)
mandibular foramen
mandibular tori (torus mandibularis)
maxillary sinus
maxillary torus (torus palatinus)
maxillary tuberosity
median palatine suture
medullary spaces
mental foramen
mental ridge
mounts
mylohyoid ridge
nasal fossa (nasal cavity)
nasal septum
nasolabial fold
nasopalatine (incisive) foramen
nutrient canals
periodontal ligament (membrane)
pneumatization
pterygomaxillary ssure
pulp
pulp canal
pulp chamber
pulp horns
radiolucent (RL)
radiopaque (RO)
ridge
septa
sinus
submandibular fossa
trabeculae
tuberosity pad
viewbox
x-ray
zygoma
zygomatic arch
zygomatic process of the maxilla

214 CHAPTER 19 Film Mounting and Radiographic Anatomy
or opaque. e opaque mounts are preferred, because the
light is concentrated behind the radiographs and viewing
is easier and more accurate. If the number of radiographs
taken does not ll the mounts, the unused windows should
be covered to prevent the light from distracting the viewer.
e black opaque wrapper from the lm packet is ideal for
Introduction
e mounting of processed dental radiographs is another
important function of the dental professional. It is much
easier to view and interpret radiographs when the lms are
placed in mounts in their proper anatomic orientation.
Properly mounted lms make charting and examination
a more orderly procedure. e mounted lms are kept
with or in the patient’s chart. At each subsequent visit,
the radiographs are placed on the viewbox for the dentists
referral. Care should be taken not to handle the mounted
radiographs or the chart with contaminated gloves.
e nished radiographs are identied and oriented to
the position in the mouth by the raised portion of the dot,
teeth, and bony structures visible on each lm. A thorough
understanding of radiographic anatomy makes mounting
an interesting and challenging procedure.
is chapter discusses the basic concepts of lm mount-
ing and the appearance and signicance of radiographic
anatomy on periapical, bitewing, occlusal, panoramic, and
other extraoral projections.
Descriptive Terminology
Because this chapter deals with the processed radiograph in
mounting and interpretation, certain terms are needed to
describe the shades of black, white, and gray that appear.
e appearance of any area (e.g., tooth, bone) on a radio-
graph is determined by the density of that area, the quality
of the x-ray photons, and hence the penetration of the
x-ray beam that reaches the lm. With these terms, one
can more accurately describe the radiographic ndings. e
black areas, where there is greater penetration of x-rays that
reach the radiographs, are called radiolucent (RL). e
white areas, where there is little or no penetration, are called
radiopaque (RO). All structures are either RL or RO, but
each category includes gradations. For instance, metallic
llings are more RO than enamel, but both are still RO.
Caries appears RL, because the decay causes a lessening of
density when compared with enamel and dentin.
Mounts
Various types of dental lm mounts are available. Mounts
are made for both pediatric and adult surveys and come
with a full range of numbers of windows (Fig. 19.1). In
addition to full-survey mounts, single-lm, double-lm, and
bitewing survey mounts are also available (Fig. 19.2). Film
mounts usually are made of cardboard or a celluloid-like
material. e area around the lm windows may be clear
B
A
Figure 19.1 Full-mouth series mounted in clear celluloid (A) and
opaque (B) mounts.
HELPFUL HINT
A radiograph should never be referred to as an x-ray. One
may say “x-ray lm” or better still, “radiograph,” but the term
x-ray should only be used when referring to the beam of
energy that is aimed at the receptor in the patient’s mouth.
The lm is then processed to produce a radiograph.
Figure 19.2 Examples of various lm mounts. (Courtesy Dentsply
Rinn, York, PA.)

215CHAPTER 19 Film Mounting and Radiographic Anatomy
from another dental facility, the dental professional should
always establish which mounting technique was used by
the position of the orientation dot of the lm or lms
in the mount.
Procedure
e proper size and number of lm mounts is selected. e
patient’s name or identication number and the date
the lms were taken are entered on the mount. e patients
lms are laid out on the clean, dry tabletop, and the empty
mount is placed on the viewbox. e lms are placed so
that the dots are all one way, either facing toward or away
from the operator. e lms are then divided into three
groups: bitewings, anterior periapical, and posterior peri-
apical. e bitewing lms are easily identied, because
the crowns of both the upper and lower teeth are seen. e
anterior and posterior periapical lms are dierentiated
by the vertical orientation on the lm for anterior teeth and
the horizontal orientation for posterior teeth.
Dental professionals can dierentiate the maxillary ante-
rior lms from the mandibular anterior lms on the basis of
root and crown shape and anatomic landmarks, which are
discussed later in this chapter. To determine whether a lm
is from the patients right or left side, the lm is held up to
the mount, and one imagines that the mount is the patient’s
face. en, it is decided which is the mesial and which is
the distal side of the radiograph, and the lm is placed
accordingly. When the anterior lms have been placed in
their proper position in the mount, the same routine is
this, because it is the correct color and size and is easily
placed in the mount.
e patient’s name, chart number (if applicable), date,
and the number of lms taken should be recorded on each
mount.
Mounting
Placement of the radiographs in their correct position in
the mounts may seem challenging at rst. However, if one
develops a system based on understanding, this task can
be mastered in a short time. e operators must always
work on a clean, dry, light-colored tabletop so that they
can see the radiographs easily when they are laid out. e
radiographs are viewed on an illuminator, or viewbox,
placed on or in front of the surface where the mounting
is being done.
Every radiograph has an embossed or raised dot to help
decipher the lm orientation. e lm packet is placed
in the patient’s mouth so that the side with the dot is
always nearest the occlusal or incisal surfaces of the teeth.
Manufacturers position the lm in the packet so that the
raised portion of the dot faces the x-ray machine when
the exposure is made (Fig. 19.3). If the operator mounts the
radiographs so that the raised portion of the dot is toward
oneself, the operator is looking at the lm as if facing the
patient; the patient’s left side is on the operator’s right. is is
called labial mounting (Fig. 19.4A). If the lm is mounted
so that the depressed side of the dot is toward the operator,
the operator is looking at the lms as if viewing them from a
position on the patient’s tongue looking out; the patient’s left
side is on the operator’s left. is is called lingual mounting
(see Fig. 19.4B). Both mounting systems have been used in
dentistry, but the trend has been to adopt the labial mount-
ing system as the technique of choice. e American Dental
Association (ADA) recommends labial mounting for use
in dental facilities. When receiving mounted radiographs
Labial mounting view
Lingual mounting view
Figure 19.3 Raised dot on x-ray lm and its orientation in lm
mounts for labial or lingual viewing.
B
A
Figure 19.4 Periapical radiograph of right mandibular molar area.
A, Labial mounting. B, Lingual mounting.

216 CHAPTER 19 Film Mounting and Radiographic Anatomy
Mounting in Digital Imaging
In digital imaging, the arrangement of the images is either
performed by the radiographer after the images are captured
or set in the programs template during the radiographic
procedure. ere are some digital programs that enable the
operator to “click and drag” the captured images to their
appropriate window or frame on the template or mount
on the screen of the computers monitor after the images
are captured. Other digital programs allow the operator to
click” on the appropriate frame on the monitor’s template
for the planned exposure before capturing the image. is
“highlights” the corresponding window for the exposure
so that when the exposure is taken, the image automati-
cally appears in the respective window. For example, when
dental professionals are taking a maxillary central incisor
projection, they “click” on the frame for the maxillary
central incisor before capturing the image. After the image
is captured, it instantaneously appears in the respective
window. Once the images are accepted and approved, the
operator saves the images as a part of the patient’s electronic
health record (EHR).
Normal Radiographic Anatomy
To fully use and properly interpret radiographs, the dental
sta must be thoroughly familiar with normal radiographic
anatomy. is includes all of the structures seen on periapical,
bitewing, occlusal, panoramic, and extraoral projections. e
rst consideration in interpreting a suspected lesion should
be to dierentiate it from a normal structure. is may often
be challenging because of wide variations of normal gross
anatomy in regard to size, shape, and location that may be
further modied by age and use. Radiographically, these
variations may be exaggerated by the projection and angula-
tion used. Not all landmarks are always demonstrated on
every full-mouth survey or individual image. When a dental
professional is confronted with a suspicious lesion, the rst
things to consider are the anatomic landmarks normally seen
in that particular area. Normal anatomy should be ruled out
rst when making a dierential diagnosis.
In interpreting radiographic landmarks, dental profes-
sionals should keep in mind the gross conguration of the
repeated for the posterior lms. Be sure that the maxillary
radiographs are placed in the mount with the roots of
the teeth pointing up and the mandibular radiographs are
mounted with the roots of the teeth pointing down.
Bitewing radiographs show only the crowns of the
teeth; there are no root shapes and few surrounding bony
landmarks to aid in anatomic identication. However, the
bitewing lms can be mounted easily by orienting the curve
of Spee (also called von Spees curve or Spees curvature),
which is the curvature of the mandibular occlusal plane
beginning at the tip of the lower incisors and following
the buccal cusps of the posterior teeth, continuing to the
terminal molar. Another method is to mount the bitewings
rst, then the posterior periapical radiographs, using the
restorations on the bitewings to identify the posterior peri-
apical projections. With this method, the anterior periapical
radiographs are mounted last.
Some generalizations can be made about crown and root
shapes seen on radiographs. e following hints will aid the
dental professional in mounting lms:
• e crowns of the upper anterior central and lateral
incisors are wider and have longer roots than those of
the lower central and lateral incisors. Because they are
wider, the maxillary anteriors do not t on one lm like
the mandibular incisors.
• Maxillarypremolarsusuallyhavetworoots;mandibular
premolars have one root.
• Mandibular rst and second molars usually have two
divergent curved roots with bone clearly visible between
them. is is particularly true of the rst molar. Maxil-
lary molars have three roots: two buccal and one palatal.
e large palatal root obscures the interradicular bone.
• Mostrootscurvedistally.
• eocclusalplaneasitgoesdistallycurvesupinwhatis
called the curve of Spee. When looking at the bitewing,
one should imagine that the patient has a smile as the
curve rises and an unhappy look if the curve incorrectly
curves downward (Fig. 19.5).
ese aids, along with the anatomic landmarks that are
described next in this chapter, enable the dental professional
to properly orient radiographs in the x-ray lm mount.
HELPFUL HINT
Remember, even the unhappiest patient in the dental chair
will appear happy in the radiographic mount if the orientation
of the curve of Spee on the bitewing radiographs is correct.
All patients are smiling when their bitewing radiographs are
mounted properly. If they appear to be frowning, the bitewing
radiographs are incorrectly mounted and should be corrected.
NOTE
Knowing what structures are “within normal limits” on
radiographic images is critical in being able to recognize when
there is a radiographic sighting that is a cause for concern.
Figure 19.5 The “smile” appearance created by the curve of Spee.

217CHAPTER 19 Film Mounting and Radiographic Anatomy
B
A
Figure 19.6 Normal radiographic tooth anatomy, anterior (A) and
posterior (B) tooth: A, Enamel; B, dentin; C, periodontal membrane;
D, pulp chamber; E, cementum; F, lamina dura; G, alveolar bone.
wall of the tooth socket. As with the periodontal ligament,
it may not be seen on every surface because of angulation.
e alveolar bone is the bone that supports the tooth. It
is composed of cancellous and cortical-compact bone. e
cancellous bone is seen as a series of small RL compart-
ments called medullary spaces. ese spaces are separated
by a RO honeycomb pattern called trabeculae. e superior
part of the alveolar bone is referred to as the alveolar crest,
which is composed of cortical bone. It should be noted
that the mandible is a much denser bone than the maxilla;
hence, the medullary spaces are smaller, and there is greater
trabeculation in the mandible. e cortical bone is seen as
a dense radiopaque structure that comprises the buccal and
palatal plates of the maxilla, the buccal and lingual plates
of the mandible, the inferior border of the mandible, the
lamina dura, and the alveolar crest.
structure. A thick, bony structure such as a ridge or muscle
attachment appears more RO because of increased object
density. Any foramen, cavity, or concavity of bone produces
an area represented on the image as RL because of decreased
density. Radiographs, as two-dimensional representations
of three-dimensional objects, produce superimpositions of
many normal structures that can be misleading. Dental
professionals should remember this when interpreting
radiographic images.
Because radiographs are two-dimensional representa-
tions of a three-dimensional object, they do not portray
depth; teeth may be superimposed on anatomic structures
in the mandible, maxilla, or skull that may be millime-
ters in front of or in back of them. e best example is the
roots of the maxillary molars and the maxillary sinus. Max-
illary molar roots are rarely actually in the sinus, although
they may appear that way on almost all molar radiographs
(see Fig. 19.10).
Radiographic Tooth Anatomy
e component structures of the tooth and its supporting
structures are dened on the dental radiograph because of
their dierences in density (Fig. 19.6).
Enamel is the densest and thus the most RO of the
natural tooth structures. It is seen as a RO band that covers
the crown of the tooth and ends in a ne edge at the
cementoenamel junction.
Dentin is the next layer of tooth structure. It is not as
highly calcied as enamel and thus not as RO. It composes
the major part of the tooth structure and is seen in both the
crown and the root portions. On a radiograph with poor
contrast, it is dicult to see the border between the enamel
and dentin (the dentinoenamel junction).
Cementum is the thin, calcied covering on the surface
of the root of the tooth. It is dicult to distinguish cemen-
tum from dentin, because it is thin and its density is not
very dierent from that of dentin. Cementum, however,
is the outer covering of the root and dentin is the inner
layer of tooth structure just outside of the RL core of the
tooth known as the pulp. e pulp chamber and pulp
canal are seen as a continuous RL space in the center of
the crown and root of the tooth, respectively. e ngerlike
projections in the coronal portion are called pulp horns.
ey are seen most often in young patients, because the
pulp chambers of teeth become smaller with age and in
some cases may become totally obliterated by secondary
dentin.
e periodontal ligament (membrane) is seen as a RL
line approximately 0.5 mm wide between the cementum of
the root of the tooth and the lamina dura. ere is always
a periodontal ligament attaching the tooth to bone, but
the periodontal membrane may not always be seen clearly
on every root surface because of dierences in horizontal
angulation when the radiograph was taken.
e lamina dura is a RO line of cortical bone that
surrounds the periodontal ligament. It represents the bony
NOTE
The honeycomb pattern of the alveolar bone resembles the
3 × 3 grid used to play the game tic-tac-toe, with the
horizontal and vertical lines representing the trabeculae and
the spaces or boxes in between those lines representing the
medullary spaces.
Text continued on p. 225

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21319 Film Mounting and Radiographic AnatomyEDUCATIONAL OBJECTIVESUpon completing this chapter, the student will be able to:1. Dene the key terms listed at the beginning of the chapter.2. Discuss the types of descriptive terminology used in radiography, including how the density of a structure determines its radiographic appearance.3. Discuss the following related to mounting procedures:• Statetheadvantageofmountingradiographs.• Listthetwotechniquesinmountingconventionallmsand state which is the preferred method.• Listthetwomodesofmountingtechniquesthatcanbeemployed when utilizing a digital radiographic system.• Listvehelpfulhintsthatcanbeusedinmountingradiographs.4. Describe the following related to radiographic tooth anatomy:• Knowtheradiographicappearanceofthecomponentsof the tooth and surrounding bone and soft tissue structures.• Identifyanddescribetheanatomiclandmarksofthemaxilla on radiographic images.• Identifyanddescribetheanatomiclandmarksofthemandible on radiographic images.5. Identifycommonrestorationsonradiographicimages.6. Identifytheanatomiclandmarksonocclusal,panoramic,and other extraoral images.KEY TERMSalveolar bonealveolar crestanterior nasal spineantral or inverted Ybuccinator shadowcancellous bonecementumconcavitycoronoid process of the mandiblecortical bonedentinenamelexternal oblique ridgeoor of the maxillary sinusoor of the nasal cavityoor of the nasal fossaforamenfossagenial tuberclehamular notchhamular process (hamulus)incisive canalinferior border of the mandibleinferior nasal concha (turbinate)internal oblique ridge (mylohyoid ridge)labial mountinglamina duralateral fossalingual foramenlingual mountingmandibular canal (inferior alveolar canal)mandibular foramenmandibular tori (torus mandibularis)maxillary sinusmaxillary torus (torus palatinus)maxillary tuberositymedian palatine suturemedullary spacesmental foramenmental ridgemountsmylohyoid ridgenasal fossa (nasal cavity)nasal septumnasolabial foldnasopalatine (incisive) foramennutrient canalsperiodontal ligament (membrane)pneumatizationpterygomaxillary ssurepulppulp canalpulp chamberpulp hornsradiolucent (RL)radiopaque (RO)ridgeseptasinussubmandibular fossatrabeculaetuberosity padviewboxx-rayzygomazygomatic archzygomatic process of the maxilla 214 CHAPTER 19 Film Mounting and Radiographic Anatomyor opaque. e opaque mounts are preferred, because the light is concentrated behind the radiographs and viewing is easier and more accurate. If the number of radiographs taken does not ll the mounts, the unused windows should be covered to prevent the light from distracting the viewer. e black opaque wrapper from the lm packet is ideal for Introductione mounting of processed dental radiographs is another important function of the dental professional. It is much easier to view and interpret radiographs when the lms are placed in mounts in their proper anatomic orientation. Properly mounted lms make charting and examination a more orderly procedure. e mounted lms are kept with or in the patient’s chart. At each subsequent visit, the radiographs are placed on the viewbox for the dentist’s referral. Care should be taken not to handle the mounted radiographs or the chart with contaminated gloves.e nished radiographs are identied and oriented to the position in the mouth by the raised portion of the dot, teeth, and bony structures visible on each lm. A thorough understanding of radiographic anatomy makes mounting an interesting and challenging procedure.is chapter discusses the basic concepts of lm mount-ing and the appearance and signicance of radiographic anatomy on periapical, bitewing, occlusal, panoramic, and other extraoral projections.Descriptive TerminologyBecause this chapter deals with the processed radiograph in mounting and interpretation, certain terms are needed to describe the shades of black, white, and gray that appear. e appearance of any area (e.g., tooth, bone) on a radio-graph is determined by the density of that area, the quality of the x-ray photons, and hence the penetration of the x-ray beam that reaches the lm. With these terms, one can more accurately describe the radiographic ndings. e black areas, where there is greater penetration of x-rays that reach the radiographs, are called radiolucent (RL). e white areas, where there is little or no penetration, are called radiopaque (RO). All structures are either RL or RO, but each category includes gradations. For instance, metallic llings are more RO than enamel, but both are still RO. Caries appears RL, because the decay causes a lessening of density when compared with enamel and dentin.MountsVarious types of dental lm mounts are available. Mounts are made for both pediatric and adult surveys and come with a full range of numbers of windows (Fig. 19.1). In addition to full-survey mounts, single-lm, double-lm, and bitewing survey mounts are also available (Fig. 19.2). Film mounts usually are made of cardboard or a celluloid-like material. e area around the lm windows may be clear BA• Figure 19.1 Full-mouth series mounted in clear celluloid (A) and opaque (B) mounts. HELPFUL HINTA radiograph should never be referred to as an x-ray. One may say “x-ray lm” or better still, “radiograph,” but the term x-ray should only be used when referring to the beam of energy that is aimed at the receptor in the patient’s mouth. The lm is then processed to produce a radiograph.• Figure 19.2 Examples of various lm mounts. (Courtesy Dentsply Rinn, York, PA.) 215CHAPTER 19 Film Mounting and Radiographic Anatomyfrom another dental facility, the dental professional should always establish which mounting technique was used by the position of the orientation dot of the lm or lms in the mount.Proceduree proper size and number of lm mounts is selected. e patient’s name or identication number and the date the lms were taken are entered on the mount. e patient’s lms are laid out on the clean, dry tabletop, and the empty mount is placed on the viewbox. e lms are placed so that the dots are all one way, either facing toward or away from the operator. e lms are then divided into three groups: bitewings, anterior periapical, and posterior peri-apical. e bitewing lms are easily identied, because the crowns of both the upper and lower teeth are seen. e anterior and posterior periapical lms are dierentiated by the vertical orientation on the lm for anterior teeth and the horizontal orientation for posterior teeth.Dental professionals can dierentiate the maxillary ante-rior lms from the mandibular anterior lms on the basis of root and crown shape and anatomic landmarks, which are discussed later in this chapter. To determine whether a lm is from the patient’s right or left side, the lm is held up to the mount, and one imagines that the mount is the patient’s face. en, it is decided which is the mesial and which is the distal side of the radiograph, and the lm is placed accordingly. When the anterior lms have been placed in their proper position in the mount, the same routine is this, because it is the correct color and size and is easily placed in the mount.e patient’s name, chart number (if applicable), date, and the number of lms taken should be recorded on each mount.MountingPlacement of the radiographs in their correct position in the mounts may seem challenging at rst. However, if one develops a system based on understanding, this task can be mastered in a short time. e operators must always work on a clean, dry, light-colored tabletop so that they can see the radiographs easily when they are laid out. e radiographs are viewed on an illuminator, or viewbox, placed on or in front of the surface where the mounting is being done.Every radiograph has an embossed or raised dot to help decipher the lm orientation. e lm packet is placed in the patient’s mouth so that the side with the dot is always nearest the occlusal or incisal surfaces of the teeth. Manufacturers position the lm in the packet so that the raised portion of the dot faces the x-ray machine when the exposure is made (Fig. 19.3). If the operator mounts the radiographs so that the raised portion of the dot is toward oneself, the operator is looking at the lm as if facing the patient; the patient’s left side is on the operator’s right. is is called labial mounting (Fig. 19.4A). If the lm is mounted so that the depressed side of the dot is toward the operator, the operator is looking at the lms as if viewing them from a position on the patient’s tongue looking out; the patient’s left side is on the operator’s left. is is called lingual mounting (see Fig. 19.4B). Both mounting systems have been used in dentistry, but the trend has been to adopt the labial mount-ing system as the technique of choice. e American Dental Association (ADA) recommends labial mounting for use in dental facilities. When receiving mounted radiographs Labial mounting viewLingual mounting view• Figure 19.3 Raised dot on x-ray lm and its orientation in lm mounts for labial or lingual viewing. BA• Figure 19.4 Periapical radiograph of right mandibular molar area. A, Labial mounting. B, Lingual mounting. 216 CHAPTER 19 Film Mounting and Radiographic AnatomyMounting in Digital ImagingIn digital imaging, the arrangement of the images is either performed by the radiographer after the images are captured or set in the program’s template during the radiographic procedure. ere are some digital programs that enable the operator to “click and drag” the captured images to their appropriate window or frame on the template or mount on the screen of the computer’s monitor after the images are captured. Other digital programs allow the operator to “click” on the appropriate frame on the monitor’s template for the planned exposure before capturing the image. is “highlights” the corresponding window for the exposure so that when the exposure is taken, the image automati-cally appears in the respective window. For example, when dental professionals are taking a maxillary central incisor projection, they “click” on the frame for the maxillary central incisor before capturing the image. After the image is captured, it instantaneously appears in the respective window. Once the images are accepted and approved, the operator saves the images as a part of the patient’s electronic health record (EHR).Normal Radiographic AnatomyTo fully use and properly interpret radiographs, the dental sta must be thoroughly familiar with normal radiographic anatomy. is includes all of the structures seen on periapical, bitewing, occlusal, panoramic, and extraoral projections. e rst consideration in interpreting a suspected lesion should be to dierentiate it from a normal structure. is may often be challenging because of wide variations of normal gross anatomy in regard to size, shape, and location that may be further modied by age and use. Radiographically, these variations may be exaggerated by the projection and angula-tion used. Not all landmarks are always demonstrated on every full-mouth survey or individual image. When a dental professional is confronted with a suspicious lesion, the rst things to consider are the anatomic landmarks normally seen in that particular area. Normal anatomy should be ruled out rst when making a dierential diagnosis.In interpreting radiographic landmarks, dental profes-sionals should keep in mind the gross conguration of the repeated for the posterior lms. Be sure that the maxillary radiographs are placed in the mount with the roots of the teeth pointing up and the mandibular radiographs are mounted with the roots of the teeth pointing down.Bitewing radiographs show only the crowns of the teeth; there are no root shapes and few surrounding bony landmarks to aid in anatomic identication. However, the bitewing lms can be mounted easily by orienting the curve of Spee (also called von Spee’s curve or Spee’s curvature), which is the curvature of the mandibular occlusal plane beginning at the tip of the lower incisors and following the buccal cusps of the posterior teeth, continuing to the terminal molar. Another method is to mount the bitewings rst, then the posterior periapical radiographs, using the restorations on the bitewings to identify the posterior peri-apical projections. With this method, the anterior periapical radiographs are mounted last.Some generalizations can be made about crown and root shapes seen on radiographs. e following hints will aid the dental professional in mounting lms:• e crowns of the upper anterior central and lateralincisors are wider and have longer roots than those of the lower central and lateral incisors. Because they are wider, the maxillary anteriors do not t on one lm like the mandibular incisors.• Maxillarypremolarsusuallyhavetworoots;mandibularpremolars have one root.• Mandibular rst and second molars usually have twodivergent curved roots with bone clearly visible between them. is is particularly true of the rst molar. Maxil-lary molars have three roots: two buccal and one palatal. e large palatal root obscures the interradicular bone.• Mostrootscurvedistally.• eocclusalplaneasitgoesdistallycurvesupinwhatiscalled the curve of Spee. When looking at the bitewing, one should imagine that the patient has a smile as the curve rises and an unhappy look if the curve incorrectly curves downward (Fig. 19.5).ese aids, along with the anatomic landmarks that are described next in this chapter, enable the dental professional to properly orient radiographs in the x-ray lm mount.HELPFUL HINTRemember, even the unhappiest patient in the dental chair will appear happy in the radiographic mount if the orientation of the curve of Spee on the bitewing radiographs is correct. All patients are smiling when their bitewing radiographs are mounted properly. If they appear to be frowning, the bitewing radiographs are incorrectly mounted and should be corrected.NOTEKnowing what structures are “within normal limits” on radiographic images is critical in being able to recognize when there is a radiographic sighting that is a cause for concern.• Figure 19.5 The “smile” appearance created by the curve of Spee. 217CHAPTER 19 Film Mounting and Radiographic AnatomyBA• Figure 19.6 Normal radiographic tooth anatomy, anterior (A) and posterior (B) tooth: A, Enamel; B, dentin; C, periodontal membrane; D, pulp chamber; E, cementum; F, lamina dura; G, alveolar bone. wall of the tooth socket. As with the periodontal ligament, it may not be seen on every surface because of angulation.e alveolar bone is the bone that supports the tooth. It is composed of cancellous and cortical-compact bone. e cancellous bone is seen as a series of small RL compart-ments called medullary spaces. ese spaces are separated by a RO honeycomb pattern called trabeculae. e superior part of the alveolar bone is referred to as the alveolar crest, which is composed of cortical bone. It should be noted that the mandible is a much denser bone than the maxilla; hence, the medullary spaces are smaller, and there is greater trabeculation in the mandible. e cortical bone is seen as a dense radiopaque structure that comprises the buccal and palatal plates of the maxilla, the buccal and lingual plates of the mandible, the inferior border of the mandible, the lamina dura, and the alveolar crest.structure. A thick, bony structure such as a ridge or muscle attachment appears more RO because of increased object density. Any foramen, cavity, or concavity of bone produces an area represented on the image as RL because of decreased density. Radiographs, as two-dimensional representations of three-dimensional objects, produce superimpositions of many normal structures that can be misleading. Dental professionals should remember this when interpreting radiographic images.Because radiographs are two-dimensional representa-tions of a three-dimensional object, they do not portray depth; teeth may be superimposed on anatomic structures in the mandible, maxilla, or skull that may be millime-ters in front of or in back of them. e best example is the roots of the maxillary molars and the maxillary sinus. Max-illary molar roots are rarely actually in the sinus, although they may appear that way on almost all molar radiographs (see Fig. 19.10).Radiographic Tooth Anatomye component structures of the tooth and its supporting structures are dened on the dental radiograph because of their dierences in density (Fig. 19.6).Enamel is the densest and thus the most RO of the natural tooth structures. It is seen as a RO band that covers the crown of the tooth and ends in a ne edge at the cementoenamel junction.Dentin is the next layer of tooth structure. It is not as highly calcied as enamel and thus not as RO. It composes the major part of the tooth structure and is seen in both the crown and the root portions. On a radiograph with poor contrast, it is dicult to see the border between the enamel and dentin (the dentinoenamel junction).Cementum is the thin, calcied covering on the surface of the root of the tooth. It is dicult to distinguish cemen-tum from dentin, because it is thin and its density is not very dierent from that of dentin. Cementum, however, is the outer covering of the root and dentin is the inner layer of tooth structure just outside of the RL core of the tooth known as the pulp. e pulp chamber and pulp canal are seen as a continuous RL space in the center of the crown and root of the tooth, respectively. e ngerlike projections in the coronal portion are called pulp horns. ey are seen most often in young patients, because the pulp chambers of teeth become smaller with age and in some cases may become totally obliterated by secondary dentin.e periodontal ligament (membrane) is seen as a RL line approximately 0.5 mm wide between the cementum of the root of the tooth and the lamina dura. ere is always a periodontal ligament attaching the tooth to bone, but the periodontal membrane may not always be seen clearly on every root surface because of dierences in horizontal angulation when the radiograph was taken.e lamina dura is a RO line of cortical bone that surrounds the periodontal ligament. It represents the bony NOTEThe honeycomb pattern of the alveolar bone resembles the 3 × 3 grid used to play the game tic-tac-toe, with the horizontal and vertical lines representing the trabeculae and the spaces or boxes in between those lines representing the medullary spaces.Text continued on p. 225 218 CHAPTER 19 Film Mounting and Radiographic AnatomyPROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLEMaxillaMaxillary Incisor Area (Fig. 19.7)The nasopalatine (incisive) foramen is seen as an oval radiolucency between the roots of the maxillary central incisors. In some radiographs, the incisive canal can be seen leading to the foramen. The foramen (an opening, hole, or passage in a bone) is actually in the anterior portion of the palate, but superimposition makes it appear to be located between the roots of the central incisors. The position of the nasopalatine (incisive) foramen on the radiograph may vary from just above the crest of the alveolar ridge to the level of the apices of the teeth because of anatomic variations and vertical angulation. In some cases, the shadow of the foramen may be superimposed on the apex of a central incisor and must be differentiated from periapical disease. This is done by tracing the lamina dura and periodontal ligament space. These structures will be completely intact if it is a foramen and interrupted if an actual periapical pathologic condition is present.The median palatine suture is seen as a thin radiolucent (RL) line running vertically between the roots of the maxillary central incisors. It must be differentiated from a fracture line, nutrient canal, and stulous tract.The nasal fossa (nasal cavity) is the paired RL structure superior to the apices of the maxillary incisor teeth. The fossa is also seen on the canine projection, where it may overlap or appear to adjoin the maxillary sinus. The radiopaque (RO) band that separates the left and right nasal fossa is called the median nasal septum. The septum ends inferiorly in the V-shaped RO anterior nasal spine.The RO anterior nasal spine is near or superimposed on the nasopalatine (incisive) foramen. The radiopacity that sometimes projects into the nasal fossa from its lateral wall is the inferior nasal concha (turbinate). When the concha is very large, the thickness of the soft tissue may make it look RO.The soft tissue and cartilaginous shadow of the tip of the nose and the soft tissue outline of the lip may be superimposed from the crest of the ridge to the crowns of the teeth. These soft tissue shadows are seen most clearly on • Figure 19.7 Maxillary central incisor area. A and B, Skull. C, Radiographs: A, Nasopalatine foramen; B, median palatine suture; C, nasal fossa; D, median nasal septum; E, oor of nasal cavity; F, anterior nasal spine; G, columella of nose; H, lip line; I, lateral fossa; J, inferior concha. HELPFUL HINTIt is important to remember when visualizing the anatomic landmarks of the head and neck regions that radiographs of these structures are two-dimensional representations of three-dimensional objects. Therefore, these anatomic landmarks appear differently when comparing an actual skull view with the radiographic depiction of these structures. 219CHAPTER 19 Film Mounting and Radiographic Anatomyedentulous images in which even the nares (openings) of the nose and the columella (separating column) are seen.The lateral fossa is a depression in the labial plate in the lateral incisor region. It appears as a radiolucency between the lateral incisor and canine because it represents an area of thin bone.Maxillary Canine Area (Fig. 19.8)In the maxillary canine region, two large RL areas are seen. The more mesial area is the lateral aspect of the nasal fossa, and the more distal is the anterior extent of the maxillary sinus. In edentulous images, the RO Y, known as the antral or inverted Y, formed by the anterior and inferior border of the maxillary sinus as the arms and the oor of the nasal cavity as the stem, is useful in the mounting orientation of maxillary canine projections.The RO soft tissue shadow of the nose may also show on canine area radiographs. In some projections, a RL area is seen distal to the canine and represents the nasolabial fold.Maxillary Premolar Area (Fig. 19.9)In the maxillary premolar area, the RL maxillary sinus may be seen either superimposed on, between, or above the apices of the teeth. It is not always visible because of vertical angulation of the x-ray beam and because the size and position of the maxillary sinus may vary from patient to patient. The oor of the maxillary sinus appears as a RO line running horizontally along its lower border.The oor of the nasal fossa may be seen as a RO line running horizontally at the superior portion of the maxillary sinus. Nutrient canals may be seen in the alveolar bone along with grooves for vessels in the walls of the maxillary sinus. Bony septum also may be seen in the maxillary sinus.The edentulous premolar radiograph is identied by the presence of the maxillary sinus. It differs from the molar radiograph in the absence of the maxillary sinus in the mesial part of the image and the start of the RO zygomatic arch band at the distal portion of the image.In some edentulous images, the shadow of the buccinator muscle is seen. The buccinator shadow makes part of the normally RL area below the ridge appear RO because of the increased density of the muscle.Maxillary Molar Area (Fig. 19.10)The maxillary sinus is a RL area that appears on periapical projections of the maxillary molar region. The sinus may be unilocular or compartmentalized by bony septa. RO spurs or ridges may project into the sinus; RL tracts or grooves, representing blood vessel positions, may be seen in the walls of the sinus. The size of the maxillary sinus varies greatly because of age, morphology, radiographic projection, • Figure 19.8 Maxillary canine area. A, Skull. B, Radiographs: A, Nasal fossa; B, maxillary sinus; C, septum of bone separating maxillary sinus and nasal septum; D, oor of nasal cavity; E, shadow of the nose; F, nasolabial fold; G, oor of maxillary sinus; H, lateral fossa. PROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLE—cont’dContinued 220 CHAPTER 19 Film Mounting and Radiographic AnatomyPROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLE—cont’dand vertical angulation used. A patient’s sinuses may be asymmetric and may tend to enlarge or grow into areas of the alveolar ridge where teeth have been extracted. This process is called pneumatization. Just distal to the third molar ridge area is the maxillary tuberosity. This area of cancellous bone also may contain the posterior extension of the maxillary sinus. The large, brous buildup of soft tissue over the tuberosity may cause a slightly RO shadow on the radiograph and is called the tuberosity pad.The zygomatic process of the maxilla is seen as a U-shaped radiopacity superimposed on the roots of the rst and second molars and the maxillary sinus. The malar bone (zygoma), which is a continuation of the zygomatic process, appears as a broad, uniform RO band that extends posteriorly. Together with the zygomatic process of the temporal bone, they make up the zygomatic arch.The hamular process (hamulus) is the RO projection that extends downward and distal to the posterior surface of the maxillary tuberosity. It is the inferior end of the medial pterygoid plate of the sphenoid bone. The RL area between the tuberosity and the hamular process is referred to as the hamular notch (Fig. 19.11).In the distal inferior portion of maxillary molar radiographs, a large RO structure may be seen. This is the coronoid process of the mandible. When an edentulous series is mounted, this landmark is helpful in determining which is the most distal of the maxillary radiographs.The maxillary torus (torus palatinus) is a lobulated bony growth in the midline of the palate. It is considered an anomaly and not anatomic landmark, because it does not exist in the anatomy of all patients. On a periapical radiograph, it appears as a dense, well-demarcated, RO area (Fig. 19.12).• Figure 19.9 Maxillary premolar area. A, Skull. B, Radiographs: A, Floor of nasal fossa; B, nutrient canals in sinus wall; C, maxillary sinus; D, sinus septum; E, buccinator shadow; F, extraction socket; G, oral-antral communication; H, oor of maxillary sinus; I, zygomatic process of maxilla; J, zygomatic arch; K, pneumatization. 221CHAPTER 19 Film Mounting and Radiographic AnatomyPROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLE—cont’dMandibleMandibular Incisor Area (Fig. 19.13)In the mandibular central incisor area, just below the apices of the central incisors in the midline, there is often a somewhat circular radiopacity. This is the genial tubercle, which represents a bony growth on the lingual surface of the mandible to which the genioglossus and the geniohyoid muscles are attached. In the middle of the genial tubercle, a small circular radiolucency may be seen. This is the lingual foramen, which is the exit point from the mandible for the lingual branches of the incisive vessels. Nutrient canals, although found in all areas of the mandible and maxilla, are seen most easily in this area, because the mandibular bone is thin in this location and must be differentiated from stulous tracts or fracture lines. They appear as RL lines that run vertically in the alveolar bone and terminate in small, circular, • Figure 19.10 Maxillary molar area. A, Floor of sinus; B, zygomatic arch; C, zygomatic process of maxilla; D, coronoid process of mandible; E, maxillary sinus; F, septum in sinus. • Figure 19.11 Posterior part of maxillary molar region. In the circle are maxillary tuberosity, hamular notch, and hamular process. • Figure 19.12 Maxillary torus. A, Anterior periapical. B, Posterior periapical. Continued 222 CHAPTER 19 Film Mounting and Radiographic AnatomyPROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLE—cont’dRL nutrient foramina. The nutrient canals are pathways for blood vessels and nerves.The mental ridge is a broad V-shaped RO band that represents a ridge of bone on the labial aspect of the mandible. It arises bilaterally below the apical area of the canine and incisors and runs medially and upward toward the mandibular symphysis. The ridge, if superimposed on the apices of the teeth, may hinder diagnosis. The mental ridge should be differentiated from the internal oblique ridge (mylohyoid ridge).The shadow of the lip is seen on anterior radiographs. That portion of the image not covered by the lip appears darker than the rest of the image, because there is no soft tissue attenuation in the area. The lip line, unless identied as such, can hinder radiographic interpretation.The inferior border of the mandible is seen as a broad RO band that represents the thick cortical bone of this area. The inferior border of the mandible can be seen in all of the intraoral mandibular projections.Mandibular Canine Area (Fig. 19.14)The anterior extension of the internal oblique ridge and submandibular fossa can be seen in the canine area.The edentulous mandibular canine may be difcult to orient in the mount. One should look for the genial tubercle on the mesial part of the image and possibly the mental foramen in the distal part. The edentulous alveolar ridge crest slopes downward as it goes distally.Mandibular Premolar Area (Fig. 19.15)The mental foramen is seen as a round or oval radiolucency near the apices of the premolars. The mental foramen may be found between, below, or even superimposed on the apices of the premolars. The mental foramen may not be seen on all premolar periapicals because of horizontal angulation of either the central ray or the position of the foramen itself. It is through this foramen that the mental nerves and blood vessels emerge. In some cases, the RL mandibular canal may be seen leading directly to the foramen. The mental foramen, in many cases because of its superimposition on the apices of the premolar, must be differentiated from a periapical pathologic condition. Tracing the lamina dura and periodontal ligament space will again be helpful in distinguishing normal anatomy from a pathologic condition.The termination of the external oblique ridge can be seen in this area, along with the internal oblique ridge, submandibular fossa, and inferior border of the mandible.The mandibular tori (torus mandibularis), although not considered normal landmarks but rather considered anomalies, are included in this section because of their frequency in appearance. They are seen singularly or multiply, usually bilaterally on the lingual aspects of the mandible in or near the • Figure 19.13 Mandibular incisor area. A and B, Skull. C, Radiographs: A, Alveolar ridge; B, genial tubercles; C, lingual foramen; D, nutrient canals; E, mental ridge; F, mylohyoid ridge; G, inferior border of mandible. 223CHAPTER 19 Film Mounting and Radiographic AnatomyPROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLE—cont’dpremolar region. They appear as clearly outlined radiopacities (Fig. 19.16).The edentulous premolar image is identied and oriented for mounting by the presence of the mental foramen and the ending of the external oblique ridge. The crest of the edentulous alveolar ridge tends to rise as it goes mesially.Mandibular Molar Area (Fig. 19.17)The mandibular canal (inferior alveolar canal) is seen as a RL band below the apices of the posterior teeth. It originates at the mandibular foramen and runs downward and forward to end at the mental foramen. It is bordered by thin RO lines.The oblique ridges refer to the internal oblique ridge and the external oblique ridge. The external ridge, a continuation of the anterior border of the ramus, is seen as a RO line that passes diagonally down and forward across the molar region. The internal oblique or mylohyoid ridge is a RO line that runs from the medial and anterior aspect of the ramus downward and forward to end at the lower border of the symphysis. When these two ridges are seen together, the internal oblique ridge is the lower of the two RO lines.The submandibular fossa is seen as a RL area below the internal oblique (mylohyoid) ridge. It represents an area of reduced thickness of bone caused by a depression on the medial surface of the mandible. This radiolucency may be accentuated by a prominent mylohyoid ridge and a thick, opaque, inferior border of the mandible.Nutrient canals are seen commonly in the molar region, especially when it is edentulous.• Figure 19.14 Mandibular canine area. A, Alveolar ridge; B, infe-rior border of mandible; C, internal oblique ridge; D, submandibular fossa; E, mental foramen; F, mental ridge; G, periapical pathologic condition. • Figure 19.15 Mandibular premolar area. A, Skull. B, Radiographs: A, Mental foramen; B, mandibular canal; C, inferior border of the mandible; D, submandibular fossa; E, internal oblique ridge; F, external oblique ridge. ContinuedNOTEThe external oblique ridge is higher and shorter, whereas the internal oblique ridge (mylohyoid ridge) is lower and longer. 224 CHAPTER 19 Film Mounting and Radiographic AnatomyPROCEDURE 19.1 RECOGNIZING AND UNDERSTANDING RADIOGRAPHIC ANATOMY OF THE MAXILLA AND THE MANDIBLE—cont’d • Figure 19.16 Mandibular tori. A, Premolar projection. B, Canine projection. • Figure 19.17 Mandibular molar area. A, Skull. B, Radiographs: a, Mandibular canal; b, external oblique ridge; c, internal oblique ridge; d, submandibular fossa; e, inferior border of mandible. 225CHAPTER 19 Film Mounting and Radiographic AnatomyRestorationsAs with tooth and bone structure, the density of the restora-tion determines its appearance on radiographs. Metallic res-torations (such as, gold inlays, crowns, foils, posts, pins, or silver amalgam) are the most RO areas seen on radiographs (Figs. 19.18 and 19.19). One can identify them only on the basis of size and shape, not on the degree of radiopac-ity. e synthetic restorations used in anterior teeth (e.g., glass ionomers, laminates, composites, and acrylics) appear RL and may be mistaken radiographically for caries (Fig. 19.20). Some manufacturers of synthetic restorations now incorporate RO particles in their preparations to distin-guish the restorations from caries (Fig. 19.21). Temporary or sedative llings and cavity liners (such as, zinc oxide, calcium hydroxide, and zinc oxyphosphate cement) appear RO, because they contain some metallic elements (see Figs. 19.20 and 19.21). Porcelain jackets appear slightly RO, because the silicate from which they are made is a metal, with the RO cement being more apparent (Fig. 19.22A). Porcelain-fused-to-metal (PFM) crowns appear with dis-tinct outlines of the metal, with the porcelain seen poorly or not at all (see Fig. 19.22). Endodontic llings appear as radiopacities in the pulp and root canal chambers. Of the two types of endodontic llings most commonly used, the silver cones appear more RO than the gutta-percha points. However, silver cones are not commonly used in contem-porary dentistry. Compare the endodontic lling in Fig. 19.19A with the lling in Fig. 19.23. Other materials that can be seen are fracture wires (Fig. 19.24) and orthodontic bands and wires (Fig. 19.25).Radiographic Anatomy for Panoramic Filmse normal radiographic anatomy for panoramic images is shown in Fig. 19.26. Some of the anatomic landmarks listed were described in the preceding section on periapi-cal radiographs. ose landmarks commonly seen on • Figure 19.18 Fixed bridge and amalgam restoration. Note that the acrylic facing of the pontic does not appear on radiograph. Also note the difference in radiopacities between the amalgam and the cement base in the premolar. BA• Figure 19.19 A, Gold post and core under porcelain jacket. B, Metallic pins under synthetic restoration. • Figure 19.20 Radiolucent (RL) anterior synthetic restorations with cement bases. 226 CHAPTER 19 Film Mounting and Radiographic Anatomy• Figure 19.21 Radiopaque (RO) anterior synthetic restoration mesial to the canine. Mesial to the lateral incisor is a radiolucent (RL) synthetic restoration. BA• Figure 19.22 Porcelain-fused-to-metal (PFM) crown on an anterior tooth (A) and on a posterior tooth (B). Note the different densities of the metal and porcelain components. • Figure 19.23 Silver cones used as endodontic lling material in the rst premolar. panoramic projections that are diagnostically important are also discussed here.Mandibular Foramene mandibular foramen appears as an oval radiolucency at the origin of the mandibular canal at the midpoint of the ramus of the mandible.Pharyngeal Airspacee pharyngeal airspace appears as a bilateral, symmetric, RL band between the RO palatal line and the apices of the maxillary posterior teeth. It runs posteriorly and downward across the ramus and into the soft tissues of the neck. e appearance of the airspace on radiographs varies depending on the position of the tongue and thus the air above it and the state of contraction of the pharyngeal muscles. e diagnostic key for the airspace is the bilateral and symmetric appearance that can be followed running distally o the bone into the soft tissue.Styloid Processe styloid process is a RO projection that may be seen bilaterally projecting downward just posterior to the ramus of the mandible. e styloid ligaments attached to the process may calcify and give the appearance of an abnor-mally long styloid process. e calcication of the ligament may not be continuous or may start at the attachment of the ligament to the styloid process, giving the appearance of a fracture of the styloid process (Fig. 19.27).Mandibular Condylee condyle, condylar neck, sigmoid notch, and coronoid process of the mandible are seen on panoramic lms. Unless the unit has a variable focal plane, this is not the best way to view the condyle, because it does not lie within the usual focal trough. At best, the panoramic image can be considered a “scout lm” to enable looking for gross changes in the maxilla or mandible.Pterygomaxillary Fissuree pterygomaxillary ssure is a ssure of the human skull. It is vertical and descends at right angles from the 227CHAPTER 19 Film Mounting and Radiographic Anatomy• Figure 19.25 Orthodontic brackets and wires. • Figure 19.24 Healing mandibular fracture with intraosseous wires in place. • Figure 19.26 Panoramic lm. a, Mandibular foramen; b, pharyngeal airspace; c, styloid process; d, maxillary sinus; e, coronoid process; f, articular eminence; g, glenoid fossa; h, hard palate; i, sigmoid notch; j, mandibular condyle; k, mandibular canal; l, mental foramen; m, nasal fossa; n, nasal septum; o, cervical vertebra; p, zygoma; q, inferior turbinate; r, external auditory meatus; s, Orbit. 228 CHAPTER 19 Film Mounting and Radiographic Anatomymedial end of the inferior orbital ssure; it is a triangular interval formed by the divergence of the maxilla from the pterygoid process of the sphenoid. It appears as an inverted teardrop on extraoral radiographs.Occlusal RadiographsWhen interpreting occlusal lms, dental professionals must remember that the projection is in the superoinferior plane (“axial”) and shows the third dimension not seen in periapical, bitewing, and panoramic lms (Figs. 19.28 and 19.29). e type of occlusal projection used, right-angle • Figure 19.27 Calcied styloid ligament (arrows). caefdb• Figure 19.28 Maxillary occlusal lm. a, Nasolacrimal duct; b, ante-rior palatine foramen; c, maxillary sinus; d, nasal fossa; e, lateral wall of nasal fossa; f, lateral wall of maxillary sinus. CABDE• Figure 19.29 Mandibular occlusal lm. A, Genial tubercles; B, interior border; C, buccal cortical plate; D, lingual cortical plate; E, shadow of tongue. or topographic (65 degrees), also should be considered, because the position of the landmarks varies depending on the angulation used.Extraoral Projectionse most commonly seen and important landmarks for the extraoral techniques described in Chapter 13 are illustrated in Figs. 19.30 to 19.34.• Figure 19.30 Lateral oblique projection of mandible. A, Coronoid process; B, sigmoid notch; C, condyle; D, pharyngeal airspace; E, mandibular foramen; F, mandibular canal; G, mental foramen. 229CHAPTER 19 Film Mounting and Radiographic Anatomy• Figure 19.31 Lateral skull projection. A, Inner and outer table; B, vascular markings; C, lateral venous sinus; D, mastoid air cells; E, sphenoid sinus; F, anterior and posterior clinoid processes and sella turcica. • Figure 19.32 Posteroanterior view. A, Frontal sinus; B, ethmoid sinus; C, petrous ridge; D, base of skull; E, maxillary sinus; F, fronto-zygomatic suture; G, orbit. • Figure 19.33 Posteroanterior view of sinuses (Waters view). A, Orbit; B, maxillary sinus; C, coronoid process; D, foramen magnum and vertebra; E, lateral wall of maxillary sinus; F, zygomatic arch; G, malar bone; H, frontozygomatic suture; I, ethmoid sinus; J, frontal sinus. • Figure 19.34 Normal temporomandibular joint (TMJ). A, External auditory meatus; B, condyle; C, articular fossae; D, articular eminence. 230 CHAPTER 19 Film Mounting and Radiographic AnatomyChapter Summary• Itis easiertoviewandinterpretradiographs whenthelms are placed in the mount in the same anatomic order as the teeth and anatomic structures appear in the patient’s oral cavity. Properly mounted lms make charting and examination a more orderly procedure. Digital radiographic techniques do not usually require a separate procedure for mounting the exposed images.• edensityofastructuredirectlyaectsitsradiographicappearance. Structures that have considerable density appear RO, and areas with little or no density appear RL.• e accurate mounting and interpretation of dentalimages is enhanced by the dental professional’s knowl-edge regarding the radiographic appearance of the tooth structures and anatomic landmarks as they appear on periapical, bitewing, occlusal, panoramic, and other extraoral images.• Knowledge of the normal anatomy on intraoral andextraoral radiographs is vital before the dental profes-sional is capable of recognizing dental abnormalities.Chapter Review QuestionsMultiple Choice1. Which of the following anatomic structures is better demonstrated on panoramic radiographs? a. Mandibular foramen b. Mental foramen c. Mylohyoid ridge d. Median palatine suture e. Coronoid process of the mandible2. e radiolucent (RL) anatomic landmark represented by the letter C in the accompanying radiograph depicts the: a. Mental ridge b. Lingual foramen c. Genial tubercle d. Mental foramen e. External oblique ridge3. e radiopaque (RO) structure distal to the hamular notch in this maxillary right posterior radiograph is known as the: a. Zygoma or malar bone b. Floor of the maxillary sinus c. Coronoid process of the mandible d. Hamular process e. Zygomatic arch4. e RO structure seen superimposed over the roots of these maxillary posterior teeth represents: a. Maxillary tori b. Bone trabeculation c. e internal oblique ridge d. Mandibular tori e. e inferior border of the mandible 231CHAPTER 19 Film Mounting and Radiographic Anatomy5. e RL anatomic landmark represented by the letter C is the: a. Floor of the nasal cavity b. Median palatine suture c. Inferior nasal concha d. Nasal spine e. Nasal fossa6. e most RO tooth structure is: a. Dentin b. Enamel c. Cementum d. Pulp chamber e. Pulp canal7. e RL area lying below the internal oblique ridge in the mandible that represents an area of a reduced thickness of bone is called the: a. Mandibular canal b. Submandibular fossa c. External oblique ridge d. Mandibular tori e. Mental foramen8. e U-shaped radiopacity superimposed over the roots of the rst and second molars and the maxillary sinus is known as the: a. Hamular process b. Maxillary tuberosity c. Maxillary tori d. Zygomatic process of the maxilla e. Coronoid process of the mandible9. e thin RO line of cortical bone that radiographically surrounds the periodontal ligament is known as the: a. Medullary space b. Nutrient canals c. Pulp canal d. Lamina dura e. Mental ridge10. If the raised portion of the orientation dot is toward the operator when mounting radiographs, the mounting technique that is being employed is known as the: a. Curve of Spee mounting technique b. Lingual mounting technique c. Labial mounting technique d. Paralleling mounting technique e. Bisecting mounting techniqueRadiographic Appearance of Common Anatomic LandmarksIndicate whether the following anatomic landmarks appear RO or RL on radiographic images by circling the correct answer:Maxillary Anterior RegionNasal septum: RO or RLNasal fossa (nasal cavity): RO or RLFloor and walls of the nasal fossa (nasal cavity): RO or RLMedian palatine suture: RO or RLAnterior nasal spine: RO or RLIncisive foramen (nasopalatine foramen): RO or RLNasal concha: RO or RLMaxillary Canine RegionInverted/antral Y: RO or RLMaxillary Posterior RegionMaxillary sinus: RO or RLFloor/walls/septa of the maxillary sinus: RO or RLZygoma (of the maxilla): RO or RLZygomatic arch (of the temporal bone): RO or RLMaxillary tuberosity: RO or RLHamular notch: RO or RLHamular process: RO or RLCoronoid process of the mandible: RO or RLMandibular Anterior (and Canine) RegionGenial tubercles: RO or RLLingual foramen: RO or RLMental ridges: RO or RLInferior border of the mandible: RO or RLNutrient canals: RO or RLMandibular Premolar RegionMental foramen: RO or RLInferior border of the mandible: RO or RLMandibular Molar RegionMandibular canal: RO or RLSubmandibular (gland) fossa: RO or RLExternal oblique ridge: RO or RLInternal oblique ridge (mylohyoid ridge): RO or RLInferior border of the mandible: RO or RLBibliographyIannucci JM, Howerton LJ: Dental radiography: Principles and tech-niques, ed 5, St Louis, MO, 2016, Elsevier Saunders.White SC, Pharoah MJ: Oral radiology: Principles and interpretation, ed 7, St Louis, MO, 2013, Mosby.

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