In the primary dentition, there are normally 20
teeth; in adult dentition there are 32.
Using one of two systems - Zsigmondy
system, which uses single digits for the
permanent dentition and letters for the primary
Federation Dentaire International (FDI)
notation, which assigns double digits for each
Part of a panoramic radiograph showing the permanent
dentition of a normal 18-year-old. The teeth in the upper left
quadrant have been numbered 1–8. The third molars are
unerupted, incompletely formed and impacted.
Part of a panoramic radiograph showing the dentition in a 6-year-old child. The
deciduous teeth in the upper left quadrant have been labelled A–E. The first permanent
molars (labelled 6) and the lower central incisors have erupted. All four primary first
molars and the primary lower second molars are carious.
All teeth consist of a crown and a root.
The crown is covered with a layer of enamel with a composition of
97 per cent mineral, thus being the most radio-opaque tissue in the
The bulk of the tooth consists of dentine, which is 70 per cent
The root is covered by a thin layer of cementum, which has a
similar radiodensity to dentine and so is indistinguishable from it.
Lying within the centre of the tooth is the radiolucent soft tissue
of the pulp, which runs from the pulp chamber in the crown along
each root canal to the root apex, through which enter the
The tooth is supported in the jaws by the periodontal ligament, as
a narrow radiolucent line. These fibres are inserted into a thin
layer of dense bone lining the tooth socket (lamina dura), which
appears as a linear radio-opaque structure, and is continuous with
the cortical bone of the alveolar crest.
Disorders of tooth eruption
The commonest cause for failure of full
eruption is insufficient room in the dental arch
to accommodate the erupting tooth.
Alternatively a tooth may be prevented from
erupting by, for example, a tumour, cyst or
Delayed eruption occurs in certain endocrine
disorders, e.g. hypothyroidism and some
genetic abnormalities, e.g. Down's syndrome.
Multiple failure of eruption of the permanent
dentition is found in cleidocranial dysplasia
Panoramic radiograph of cleidocranial dysplasia in
an adult. There are numerous unerupted teeth
including several supernumeraries.
It is seen in association with cleft lip and
palate, Ellis-van Creveld (chrondo-ectodermal
dysplasia) and facial-digital syndromes.
Marked absence of teeth is seen in hydrotic
Hyperdontia - presents as either supplemental
or supernumerary teeth.
Amelogenesis imperfecta is a developmental
disorder of enamel formation affecting all or
most of the teeth.
Varying degrees of hypoplasia from being
pitted to almost complete absence of enamel
when the crown appears angular.
Alternatively, the enamel may be of normal
thickness but be hypomineralized such that its
radiographic density is similar to that of
Intra-oral (bitewing) radiographs showing marked
hypoplasia and pitting of the enamel, whilst the
dentine appears normal. Several of the teeth are
Dentinogenesis imperfecta is a developmental
anomaly of collagen formation.
The teeth are discoloured, having a brown or
purple hue. The enamel chips away and the
teeth rapidly wear down.
The initial radiographic appearance shows
bulbous crowns and large pulp
chambers, which soon calcify with abnormal
dentine so that little or none of the root canal is
Although the teeth may appear sound, they
are prone to infection resulting in pulpal
necrosis and periapical radiolucencies.
associated with osteogensis imperfecta.
A panoramic radiograph of a young adult with
dentinogenesis imperfecta. The teeth have bulbous
crowns, short stumpy roots and sclerosis of the root canals.
Dental caries is caused by microbial action on sugar
with the formation of acid, which causes progressive
demineralization of the teeth, initially of the
enamel, and then the dentine with destruction of their
Radiographic detection of dental decay requires
images with good contrast and resolution. Despite its
limitations, intra-oral radiographs are valuable in the
detection and monitoring.
A carious lesion appears as a radiolucent zone, which
represents an area of demineralization. An approximal
lesion develops in the enamel just below the contact
point with an adjacent tooth and has a triangular shape
with the apex pointing towards the dentine.
If left untreated, the caries reaches the pulp chamber
and the weakened crown eventually crumbles away.
granuloma at the
apex of the grossly
well defined, its
margins are not
the loss of the
lamina dura at the
tooth apex. There
is a similar but
smaller lesion at
the apex of the
premolar root and
the upper right
central incisor is
Odontogenic and non-odontogenic cysts
Common findings - slow-growing lesions, i.e.
they are radiolucent, well defined and often
have a cortical margin.
they have raised intracystic pressure and
expand by tissue fluid transudation, and so
appear as circular or oval in shape.
Jaw cysts tend to displace structures
Radicular cysts are the most common of the
They are derived from the cell rests of Malassez.
develop at the apex of a nonvital tooth
Any tooth can be affected but the majority are
found on the permanent anterior teeth or first
When small (less than 15 mm in diameter) they
resemble periapical granulomas but, unlike
granulomas, can enlarge well beyond this size.
In many cases extraction of the causative tooth
brings about resolution, but when this does not
happen, the cyst is then termed a ‘residual cyst’.
Thus a residual cyst found in an edentulous part of
the jaw, has a well-defined, circular radiolucency
usually with a cortical margin.
Part of a panoramic radiograph showing a corticated radiolucent lesion
associated with the carious root of the upper left second
premolar, extending into the maxillary antrum above the hard
palate, consistent with a radicular cyst. Note the periapical radiolucency
(granuloma/abscess) on the upper left second molar.
Dentigerous cyst (follicular cyst) - arises from
the reduced enamel epithelium, the tissue
which surrounds the crown of an unerupted
It is thus found only on teeth that are
buried, particularly mandibular third molars
and maxillary canines.
Cystic enlargement of the tooth follicle
produces a pericoronal radiolucency, which is
attached to the tooth at its neck, with the crown
appearing to lie within the cyst lumen;
however with large cysts this relationship may
not be apparent.
Part of a panoramic radiograph of a dentigerous cyst arising on a lower
left wisdom tooth, which is unerupted and lying horizontally. It appears
as a well-defined, circular radiolucency attached to the tooth at its neck.
The inferior alveolar canal has been displaced inferiorly.
Odontogenic keratocysts arise from remnants of the dental
lamina, the precursor of the tooth germ.
The cyst lining has a higher mitotic activity and is thought to
enlarge by mural growth and so behaves more like a benign
neoplasm and is now classified as such.
It appears as a unilocular or
multiloculated, elongated, irregularly shaped radiolucency
with a scalloped, well-defined margin.
It lacks the more ballooning characteristics of the other
odontogenic cysts, which is an important diagnostic feature.
Keratocysts occur most often in the lower third
molar/ramus region, where they may displace, or
occasionally replace an unerupted wisdom tooth.
Recurrence is common (15–20 per cent) so radiographic
follow-up is necessary for several years.
On CT, attenuation values of cyst fluid are higher than most
other jaws cysts due to its high protein (keratin)
content, ranging from 30–200 Hounsfield Units, with
longstanding, multilocular cysts having the higher value.
Part of a panoramic
radiograph of an
which appears as a
extending from the
condylar neck to the
lower first molar
region. There is
thinning of the bony
cortices but no jaw
expansion, a feature
keratocysts. Note the
displaced lower right
Multiple odontogenic keratocysts are a feature
of Gorlin-Goltz syndrome which also
includes multiple basal cell naevi, calcification
of the falx, bifid ribs, synostosis of the
ribs, kyphoscoliosis, temporal and parietal
bossing, hyperptelorism, and shortening of the
Part of a panoramic radiograph showing multiple odontogenic keratocysts consistent withGorlinGoltz syndrome. All four third molars have been extensively displaced and a lateral facial view
showed the upper right one to lie posteriorly close to the orbit.
OKC in a 41-year-old man with basal cell nevus syndrome (Gorlin-Goltz syndrome).
Contrast material–enhanced CT scan shows multiple cysts (arrows) in the mandible.
Cystic lesions (arrowheads) are also identified within the maxilla. CT also demonstrated
a calcified falx and large frontal sinuses, findings that helped establish the diagnosis.
The nasopalatine cyst is probably the
commonest non-odon-togenic cyst.
believed to arise from epithelial residues in the
It appears as a round, well-defined, midline
radiolucency between, but not associated
with, the upper central incisor teeth.
Three lesions that may resemble jaw cysts but have
no epithelial lining are sometimes considered with
Solitary bone cyst occurs during the first 2
decades of life, mainly in the premolar/molar
regions of the mandible.
Its margin is less well defined than those of
odontogenic cysts and its superior border arches
up between the roots of the adjacent teeth.
Tooth displacement and root resorption is
uncommon. At surgery an empty cavity is
found, which subsequently heals after bleeding has
Part of a panoramic radiograph showing a partially corticated radiolucency in the right
mandible involving the apices of the second premolar and first and second molars
diagnosed as a solitary bone cyst. Note the characteristic scalloping between the roots of
the first and second molars.
Aneurysmal bone cyst is considered to be a
reactive lesion of bone and is characterized by a
fibrous connective tissue stroma containing many
cavernous blood-filled spaces.
It is rare and occurs mainly in the young, with over
90 per cent occurring before 30 years of age.
It is typically found in the posterior region of the
mandible as a well-defined, multilocular, often
septated, circular radiolucency. It has a tendency
to produce marked cortical expansion.
Computed tomography (CT) or magnetic
resonance imaging (MRI) shows the presence of
fluid levels due to the presence of blood-filled
Stafne's bone cavity is asymptomatic and typically
found in men over the age of 35 years.
It forms a depression in the lingual cortex of the
mandible just in front of the angle and below the
inferior dental canal.
Its origin is controversial and it has been postulated
that it arises from pressure from the submandibular
salivary gland, however whilst some may contain
salivary gland tissue a number develop anterior to the
On plain radiographs, it appears as a well
defined, punched out, dense radiolucency, which
rarely exceeds 2 cm in diameter. Its appearance is
characteristic and so does not require further imaging
or biopsy. However, if CT or MRI is performed, the
cavity is often found to contain fat.
Part of a panoramic
radiograph showing a
the inferior alveolar
canal and the lower
border of the
mandible due to the
presence of a Stafne
bone cavity. The 3D
CT (B) shows the
depression on the
lingual aspect of the
Static bone cavity (Stafne cyst) in a 35-year-old man. CT scan
reveals a cortical defect (arrow) in the lingual surface of the right
mandibular angle, a finding that does not represent a true cyst.
Odontomes are developmental malformations or
hamartomas consisting of dental hard tissues or toothlike structures.
Most are diagnosed in the second decade of life and
frequently impede tooth eruption.
There are two main types. The compound odontome
consists of a collection of small discrete teeth called
denticles and is found typically in the anterior region of
Complex odontome consists of a randomly arranged
mass of enamel, dentine and cementum found
predominantly in the lower premolar/molar region.
Both types are densely radiopaque due to the presence of
tooth enamel and are surrounded by a thin radiolucent
Cystic odontoma in a 17-year-old boy with painful third molars
Odontogenic tumours are uncommon, mostly
benign and arise from either the odontogenic
epithelium, odontogenic epithelium and
ectomesenchyme, or primarily ectomesenchyme.
The commonest is the ameloblastoma, which
accounts for 11%.
It occurs mainly in patients between 30–50 years of
age with most (80 per cent) forming in the
molar/ramus region of the mandible.
When the maxilla is involved, it has the potential
to spread insidiously to involve the infratemporal
fossa, orbit and skull base, thus a thorough
assessment is essential.
Part of a panoramic radiograph showing an
ameloblastoma, which appears as an
expansile, multilocularradiolucency involving the left body
of the mandible.
Unilocular or multilocular radiolucency, but typically contains
septa or locules of variable size to produce a honeycombed
The margin is well defined, often corticated but when
large, produces jaw expansion with perforation of the bony cortex.
A useful diagnostic feature is knife-edge resorption of the tooth
roots by the tumour, which can be quite marked.
The lesion is locally aggressive and requires a wide excision
Multislice CT can be used to differentiate ameloblastoma from
odontogenic keratocysts because of higher density increase during
the arterial phase.
On T1-W images with gadolinium enhancement and T2-W
images, there is good conspicuity of the tumour margin with the
soft tissues, the lesion having a moderate to high signal.
Very rarely undergoes malignant transformation with metastases
occurring in the lungs.
An axial CT on bone window settings of a large cystic ameloblastoma of
the right side of the mandible showing marked thinning and expansion of
the bone. Note the presence of root resorption.
Odontogenic myxoma is a benign but locally
aggressive tumour of odontogenic
mesenchyme occurring mainly in those
younger than 45 years of age.
Most occur in the mandible in the premolar
The lesion is usually well defined, unilocular
and contains a variable number of internal
coarse trabeculations to produce a reticular
Panoramic radiograph shows an expan-sile, ellipsoid, partially
corticated, lucent lesion with heterogeneous internal
mineralization in the right posterior aspect of the mandibular
body and extending into the lower ascending ramus (arrows).
Calcifying epithelial odontogenic tumour - well
defined and contain variable amounts of focal
more common in men, occurs in middle life and is
found mainly in the premolar/molar region of the
Adenomatoid odontogenic tumour - affects
females in the second decade of life and typically
occurs anteriorly, especially in the maxilla and is
associated with an unerupted tooth.
well defined and contain variable amounts of focal
Fibrous dysplasia is a localized abnormality in which
cancellous bone is replaced by fibrous tissue containing
varying amounts of calcified tissue.
When the jaws are affected, the maxilla is involved
twice as frequently as the mandible.
An immature lesion is largely radiolucent and may
mimic a dental cyst, typically having an orange peel or
On radiographs the margins are usually
indistinct, blending in with the normal adjacent bone.
It may displace teeth or prevent their eruption.
Large lesions produce jaw expansion, with
thinning of the bony cortices and displacement
of the antral floor.
It can resemble both a cemento-ossifying
fibroma, which is better defined, and an
osteosarcoma, which produces destructive
CHAPTER 63 -Dental and Maxillofacial Radiology from Adam: Grainger & Allison's ...
Figure 63.22 Axial CT on bone window setting of fibrous dysplasia of the anterior aspect of the mandible. Ther
Axial CT on bone window setting of fibrous dysplasia of the
anterior aspect of the mandible. There is thinning and expansion
of the bony cortical plates. The lesion shows areas of low
attenuation, lingual to the teeth, due to the presence of fibrous
Cherubism is a rare dysplasia of bone that
develops during the first decade of life.
It occurs bilaterally in both jaws, but more
commonly affects just the mandible.
It develops in the posterior aspects of the jaws
as a multilocular, honeycombed, expansile
Tooth displacement is common. It regresses
spontaneously after skeletal growth ceases.
Periapical cemento-osseous dysplasia and florid
cemento-osseous dysplasia are similar
conditions, with the latter being a more extravagant
version of the former.
Women, particularly of Afro-Caribbean origin, after 25
years of age.
Characterized by the formation of multiple deposits
around the tooth roots and the mandible is more
frequently involved than the maxilla.
Teeth are clinically sound, radiolucent lesions form at
the apices of the teeth, which resemble periapical
Gradually cemental-like tissue is deposited within so
that it become increasingly radiopaque but is
surrounded by a thin, peripheral radiolucent
zone, which helps distinguish it from sclerosing
The appearance of florid cemento-osseous
dysplasia is similar to periapical cemental
dysplasia but the lesions are larger, may
produce jaw expansion, are more
numerous, and often in both the maxilla and
mandible. May resemble Paget's disease of
Osteomyelitis of the jaws is uncommon.
It may develop from a dental abscess or complicate
In acute osteomyelitis, there is thinning and
discontinuity of the bony trabeculae to produce illdefined, patchy areas of radiolucency within the
cancellous and cortical bone.
With time bony sequestrae form and are
recognized as irregularly shaped islands of bone
set against a region of radiolucency.
The features of osteomyelitis are more readily
visualized on CT, which also is useful to show
periosteal bone formation.
On MRI, the marrow usually shows a low signal
intensity on T1 and a high signal on T2 weighted
If the disease becomes chronic, the bone becomes
diffusely affected and extensively involved with
sclerosis of the marrow spaces. CT will
demonstrate the internal structure and the
presence of sequestration.
Part of a panoramic radiograph of the right mandible of a patient
who developed acute osteomyelitis following the extraction of a
premolar root 3 weeks previously. There are three sequestra in the
alveolar portion of the mandible.
Hyperparathyroidism of the jaws results in a
general demineralization of the bone, creating a
‘ground glass’appearance, loss of the lamina
dura, formation of brown tumours, and
subperiosteal erosions at the angle.
Haematological replacement disorders may affect
the jaws. In moderate to severe thalassaemia, the
jaws become radio-lucent with the presence of
coarse trabeculations due to marrow hyperplasia
and the maxillary antrum is reduced in size. The
skull takes on a granular appearance, with
thickening of the diploic spaces and occasionally a
‘hair on end’appearance.
Panoramic radiograph of a case of thalassaemia. There is marked
increase in the height of the mandible, which is composed of
coarse trabeculae enclosing large marrow spaces and the small
maxillary sinuses. Note the generalized loss of the lamina dura
and the periodontal abscess on the distal root of the lower right
Cemento-ossifying fibroma - Its behaviour varies
from those showing slow growth to others being
Occurs mainly in young adults, mostly in the body
of the mandible.
The radiographic appearance depends on its
degree of mineralization, and typically contains a
wispy or tufted bony trabecular pattern. The lesion
is encapsulated and so appears well
defined, helping to distinguish it from fibrous
Bone window setting of an axial CT of a cemento-ossifying fibroma of
the mandible showing mainly buccal expansion and thinning of both
cortical plates, which remain intact. The lesion is of mixed attenuation as
it contains areas of fibrosis, mineralization, and coarse bony
Osteomas of the maxillofacial bones and jaws are
usually slow-growing, painless and thus
discovered by chance.
In the jaws, osteomas more commonly affect the
mandible than the maxilla and, whilst any site can
be involved, they tend to be found posteriorly on
its medial aspect.
CT assists in showing the site of origin and
provides three-dimensional (3D) topographic
Multiple osteomas are a feature of Gardner's
syndrome (familial adenomatous polyposis) and
precede the formation of intestinal colonic
Osteosarcoma is uncommon in the jaws(7 %)
It tends to be slower growing and occurs about 10
years later than osteosarcoma of the long bones.
The mandible is more commonly affected than the
maxilla. Maxillary lesions tend to arise from the
alveolar ridge, and mandibular ones in the body.
It has a destructive appearance and its density varies
from being radiolucent, to patchily radio-opaque or
An important early dental radiographic sign is
widening of the periodontal ligament space due to
tumour spread along the periodontal
ligament, however this feature is also seen in other
sarcomas (e.g. fibrosarcoma Ewing's sarcoma).
When the periosteum is elevated a ‘hair-onend’, sunray or onion skin appearance may be
visible. CT is required to demonstrate
accurately tumour calcification, bone
destruction, and bone reaction ( Fig. 63.28
), whilst MRI (T1- and T2-weighted images)
will provide better information on the
intramedullary and extraosseous components
of the tumour.
setting of an
axial CT of
sarcoma of the
ramus. There is
the region of
y to the styloid
shown on a
CT at the
level of the
few areas of
the lesion are
with loss of
much of the