Lecture : 7
Radiographical interpretation
‫غسان علي‬.‫د‬
There are many anatomical structures can be seen from intraoral
radiographs and its necessary to know the radiographic appearance of these
anatomical landmarks and this will guide to determine the radiographic
appearance of abnormalities (diseases)
Objectives : we should be able to :


Name normal anatomic structures labeled on an intraoral radiograph,
and
Point out or trace on an intraoral radiograph the anatomic structures
named.
Several structures of the tooth and periodontium should be clearly identifiable
in any periapical radiograph. These structures, include the enamel, dentin,
pulp, periodontal membrane, and alveolar bone.
In a periapical radiograph : The enamel, which is the hardest substance in the human body, appears
as the most radiopaque ( lightest) part of the crown of the tooth.
 The dentin, a less mineralized area of the tooth between the enamel and
the pulp is not as radiopaque as the enamel.
 The pulp is the radiolucent area (dark) in the center of the root and
crown where the soft tissues which include the nerve and blood supply
are located.
 The periodontal membrane appears in a periapical radiograph as a space,
or radiolucent line adjacent to the tooth root.
 Lamina dura :- a thin radiopaque line next to the periodontal membrane
space which is the radiographic representation of the outer cortex of the
alveolar bone surrounding the tooth root.
Mandibular Anatomy
Mandibular anatomical landmarks :
1. The lower border of the mandible :
It is a thick cortical plate that forms the lower edge of the mandible. The solid
thickness of bone along the inferior border of the mandible is seen in the
radiograph as a uniform wide radiopaque band at the margin of the mandible.
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2. The mental ridges are elevated ridges of bone located along the anterior
aspect of the mandible. The ridges are also known as the mental tubercles
and fuse at the midline to form the mental protuberance, the anteriormost
aspect of the mandible. This periapical radiograph demonstrates the
radiopaque margin of the mental ridges. Study these and compare the
varying appearance of these landmarks.
3. The genial tubercles : are small bony spines found on the lingual aspect of
the mandible adjacent to the midline at the attachment of the geniohyoid
and genioglossus muscles. genial tubercles apper as a distinct circular
radiopacity, an area of dense bone, near the midline below the apices of the
teeth.
4. The lingual foramen : an opening in the lingual midline of the mandible for
a small vessel. The lingual foramen appears as a small circular radiolucent
area surrounded by the genial tubercles.
5. The soft tissues of the superior margin of the lower lip : will often be
projected onto the anterior periapical radiograph and are seen as a
horizontal step or change in the general radiopacity of crowns of the teeth.
The darker side of the step is toward the incisal edge of the crowns and
represents the air space above the lip.
Sometimes this lip line is projected lower and will be superimposed
over the free gingival margin or the crest of the alveolar ridge.
6. Nutrient canals, which hold blood vessels, run along the inner surface of the
bone cortex, where they lie in slight depressions. These are visible
radiographically because the bone is proportionately thinner where it is
displaced by a vessel and thus appears more radiolucent. Radiographically,
nutrient canals appear as uniform thin radiolucent lines. The margin of these
lines is often slightly more radiopaque than the adjacent bone. Sometimes
these canals can be seen running toward the apices of teeth as accessory
branches of the inferior alveolar canal. In this instance the canals contain
both blood vessel and nerve supplies to the tooth and are termed accessory
canals. Nutrient canals are most noticeable when they appear between roots
or within edentulous areas where they lie against the bony wall and reduce
the thickness of bone in the area of the vessel.
7. Mandibular tori, or singularly, a mandibular torus :
The rounded protuberances on the lingual surfaces of the alveolar process. This
fairly common feature is a hard, bony enlargement of the alveolar cortex.
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Radiographically, mandibular tori appear as large rounded radiopacities in the
area of the roots of the teeth, usually the canines and premolars. The tori are
quite distinct in these two anterior periapical projections.
8. Mental foramen :
is an opening in the facial aspect of the mandible in the premolar area near the
apex of the lower second premolar.
Radiographically, the mental foramen appears as a rounded radiolucency in the
apical region distal to the canine and mesial to the first molar. Often it is not as
distinct as some other landmarks, but recognizing it is important. Sometimes
the mental foramen will be superimposed on the apex of a premolar, and will
give the appearance of pathology. The best way to differentiate periapical
disease from the mental foramen is to identify the periodontal membrane space
to see if it is confluent with the radiolucent opening. If the apical radiolucency
is due to periapical pathology, the periodontal membrane will appear to join the
radiolucency, but if the lucent area is due to the mental foramen, then the
periodontal membrane space will remain intact, and can be distinctly followed
around the tooth apex.
9. Mandibular canal :
The mandibular canal extends from the mandibular foramen, on the lingual
aspect of the ramus, through the body of the mandible under the roots of the
molar teeth. The canal terminates at the mental foramen, where the mental
nerve branches buccally through the cortex to innervate the soft tissues of the
lower lip and chin area. The rest of the inferior alveolar nerve extends mesially
to innervate the canines and incisors. This anterior extension of the inferior
alveolar canal is called the anterior loop.
The mandibular canal appears radiographically as two roughly parallel
radiopaque lines traversing the body of the mandible below the apicies of the
molar teeth.
The radiographic appearance of the mandibular canal ( which is tube-like
nature ) is due to the fact that the X-ray beam passes through the denser
cortices of the outer edges of the canal to produce radiopaque lines, while the
center, without so much superimposition of bone, retains a radiolucent
characteristic.
10. Internal oblique ridge (or mylohyoid line) :
It is an eminence of bone extending along the lingual aspect of the mandible. It
serves as the attachment point for the chief muscle of the mouth floor, the
mylohyoid muscle.
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Radiographically the internal oblique ridge appears as a radiopaque band
extending from the terminal molar region to the premolar area.
11. Submandibular fossa :
It is a depression in the lingual aspect of the mandible directly below the
internal oblique ridge. This concavity is visible radiographically since the
thickness of bone is substantially reduced in this area. The submandibular fossa
is the location of the submandibular salivary gland. It is important to recognize
this as normal anatomy because this is another feature which may resemble
pathology such as tumors or cysts.
12. External oblique ridge :
It is a ridge of bone located along the facial aspect of the mandible, which
extends from the superior aspect of the posterior body of the mandible down to
the necks of the molar teeth. It runs in the same direction as the internal oblique
ridge, but is located on the facial, or external surface of the mandible. The
external oblique ridge serves as the attachment point for the buccinator muscle
To distinguish radiographically between the internal and external oblique
ridges, note that the external ridge is always superior to the internal oblique
ridge.
Maxillary Anatomy :
Maxillary anatomical landmarks :
1. Nasal fossa (nasal antrum) :
It is two spaces, or fossae, one on either side of a thin septum at the midline.
The shapes of the fossae are determined in part by adjacent structures including
the nasal septum and the inferior conch.
2. Nasal septum :
It is the thin wall of bone in the midline of the face that separates the right and
left nasal fossae the nasal septum appear radiopaque band extends vertically at
the top, between the right and left nasal cavities.
3. Anterior nasal spine :
It is the triangular or dimond protuberance of bone that extends forward from
the inferior aspect of the nasal cavity at the midline. This bony feature serves as
an attachment point for the nasal cartilage.
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4. Mid-palatine suture :
It is the line down the center of the maxilla where embryonic palatal shelves
joined at the midline to form the hard palate. The mid-palatine suture appears
in this central incisor periapical projection as a dark, or radiolucent, line at the
midline.
5. Incisive foramen :
It is the opening in the midline of the palate just posterior to the central
incisors. Incisive foramen gives passage to the nasopalatine artery and nerve
which course through the incisive canal and foramen to innervate the anterior
palatal soft tissues.
Radiographically, it is almost always elliptical in shape and varies in size. Its
image varies in relation to the roots of central incisors and range from position
near to alveolar crest to one may be at level of the apex of root.
In the central incisor periapical projection may shown the appearance of the
incisive canal in addition to the incisive foramen.
6. Border of the nose :
A well-defined density difference step. The delineation of the border of the
nose produces a symmetrical bow-like shape on the central incisor periapical
image. The alar cartilage of the nose is seen as a rounded soft tissue radiopacity
in the canine - lateral projection.
7. Lip line :
The border of the lip will occasionally project across the crowns of the teeth as
a linear density step. If the lip line is projected across the contact area of a
crown, the radiolucent / radiopaque step may simulate a carious lesion.
8. Nasolabial fold :
This fold marks the anterior border of the thicker soft tissues of the cheek
including the buccal fat pad. The fold produces a linear step density that
courses from the region above the apicies of the canine or lateral incisor to the
occlusal plane in the premolar region.
9. Maxillary sinuses :
M.S. are pyramid-shaped radiolucent cavities in the mid-facial aspect of the
skull. the maxillary sinuses are bilateral structures, located beside each nasal
fossa. the sinus extends posteriorly near the roots of the maxillary premolar and
molar teeth and the lower border of M.S. may extend between the apices of
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maxillary 1st molar but this does not indicate perforation of sinus. floor of M.S.
appear radiopaque line. Parts of the maxillary sinus may appear in many of the
maxillary periapical projections.
The tendency for the maxillary sinus to pneumatize and form multiple lobes
may give rise to the appearance of radiopaque lines extending from the floor of
the sinus.
View of the canine region demonstrates an important landmark: the antral
Y or inverted Y formation. This landmark is formed by the intersection of the
floor of the nasal cavity and the anterior wall of the maxillary sinus. Because
the inverted Y represents the superimposition of two features projected
radiographically over each other the formation may appear different in different
projections.
10. Incisive fossa and the canine fossa :
These are indentations in the maxillary alveolar process, shown in shadow in
this skull view, which may result in a radiolucent region on the film. The
incisive fossa is the indentation between the roots of the central and lateral
incisors, and the canine fossa is between the roots of the lateral incisor and
canine. appear radiographically as teardrop-shaped areas of less radiopaque
alveolar bone, located between and a little above the roots of the incisors
(incisive fossa), or between the roots of the lateral incisor and canine (canine
fossa).
11. Malar process (zygomatic process) :
The malar process is the portion of the maxilla that protrudes to meet the
zygomatic bone, or cheekbone.
Radiographically it is show as characteristic curved radiopaque shape (Ushaped or J- shaped).
12. Maxillary tuberosity :
It is the rounded bony eminence just posterior to the most distal molar, at the
distal end of the maxillary alveolar ridge.
13. Lateral pterygoid plate :
it is a thin, bony extension of the sphenoid bone, to which are attached the
lateral pterygoid muscle as well as muscles of the throat.
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14. Hamulus : is a small bony spine extending downward below the lateral
pterygoid plate and lie posterior to the maxillary tuberosity. The
radiographic appearance of these features is occasionally visible in
periapical views of the posterior area showen as a hook- like radiopaque
projection, varies in length, width and shape.
15. Inferior conch or inferior nasal turbinate :
There are actually three turbinates on each side of the nasal antrum; however,
only the most inferior of these is routinely projected onto the periapical view of
the incisor region. Appears slightly more radiopaque than the alar cartilage of
the nose. Also the conch lies within the more radiolucent nasal fossa and is
circumscribed by the border of the fossa and the nasal septum whereas the
torus palatinus crosses the nasal midline and may appear to extend below the
floor of the nasal fossa.
16. coronoid process of the mandible :
This is the thin triangular radiopaque prominence of the upper part of the
mandible. You can see how the tip of the coronoid process may appear in some
maxillary molar projections. The coronoid process of the mandible serves as an
attachment for certain muscles of mastication,
The tip of the coronoid process is also a homogenous radiopacity that may
project on the posterior sinus region. Because the mouth is partially opened to
accommodate the image receptor holder, the coronoid process rotates forward
and downward. The resulting position allows the tip of the coronoid to be
projected onto the tuberosity of the maxilla. Occasionally this geometry
produces an image where the conical form of the coronoid resembles a third
molar root.
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