1. THE DIAGNOSTIC IMAGING OF JAW LESIONS
Radiologists are often called upon to perform a variety of imaging studies on the
maxilla and mandible. Indications for these studies include evaluation of a known or
suspected jaw lesion, evaluation of a dental arch for dental implant placement, and the
assessment of the temporomandibular joint (TMJ) in a patient presenting with chronic facial
pain.
DIAGNOSTIC IMAGING OF JAW LESIONS:
Lesions occurring primarily in the jaws arise in either odontogenic or non-
odonotogenic tissues located within the jaw. Secondary involvement of the jaw may occur
on occasion via a number of different pathways. These include the direct extension of a
neoplastic or inflammatory process involving the soft tissues bordering the jaw, a blood-
borne metastatic process, or as a result of an underlying systemic process.
Jaw lesions are often classified according to their radiographic densities and
margination on plain film studies. Jaw lesions can be described as having either a
radiolucent radiopaque, or mixed appearance relative to the density of adjacent bone. The
majority of jaw lesions is radiolucent (> 80%), and includes a number of odontogenic and
nonodontogenic lesions. Lucent cystic lesions may exhibit internal septae resulting in a
multicystic or multiloculated appearance. Radiopaque lesions exhibit increased radiographic
density due to the presence of normal or dysplastic calcified odontogenic tissues (e.g.,
dentin or cementum), or the apposition of new bone on an existing osseous matrix. A
mixed appearance can result from the presence of two or more tissues of normally different
radiographic densities, variation in the degree of maturation of a single or multiple tissues
within the lesion.
Another important criterion used in evaluating a jaw lesion is its margination. Jaw
lesions can be either well circumscribed (defined) or poorly circumscribed. Well-
circumscribed lesions are usually benign, whereas poorly circumscribed lesions invariably
represent aggressive inflammatory or neoplastic processes. Involvement of a segment of a
jaw by a poorly circumscribed or infiltrating radiolucent lesions may result in a permeative
of “moth eaten” appearance.
Other important parameters that should be taken into account in arriving at a
diagnosis or in formulating a differential diagnosis include anatomic location, relationship to
the cortex, and associated periosteal and soft tissue changes. In assessing a jaw lesion, it
is important to note its precise anatomic location within the jaw, its relationship to the

2. dentition in general, and any specific relationship to a tooth or portion of a tooth. It is
important to remember that certain lesions occur exclusively in one area or site, whereas
other lesions have no specific predilection. In addition, a number of other lesions can occur
anywhere in the jaws but occur with greater frequency in a given site or area. Non-
odontogenic lesions usually have no specific relations to the dentition & can involve the
bone around two or more teeth, whereas odontogenic lesions typically involve only one
tooth or a specific part of a tooth. If a lesion involves only one tooth, it is important to note
the degree of tooth development present; the lesion’s location with respect to the tooth
(crown versus root versus entire tooth); and any signs of root resorption or displacement.
If assessing a lesion in an edentulous area, it is important to know if the lesion is associated
with the congenital or surgical absence of a tooth.
The lesion’s relationship to the cortex should also be noted. Signs of cortical
expansion, destruction, or breakthrough should be looked for as well as evidence of
periosteal or soft tissue involvement. Slow growing lesions often cause cortical bowing and
pressure resorption with minimal if any periosteal or soft tissue involvement. Aggressive
inflammatory and neoplastic lesions often cause cortical destruction or breakthrough, which
may be accompanied by periosteal reactions or soft tissue masses.
In general, jaw lesions exhibit one of the following radiographic patterns.
1. Well – circumscribed radiolucent lesions
2. Poorly circumscribed radiolucent lesions.
3. Mixed lesions.
4. Radiopaque lesions.
Included in each of these groups are a number of odontogenic and nonodontogenic
lesions. The following sections examine a number of commonly encountered jaw lesions
presenting with each of these patterns.
Well – Circumscribed Radiolucent Lesions:
A number of odontogenic and nonodontogenic lesions can present as well
circumscribed radiolucent lesions. Odontogenic lesions include periapical lesions,
dentigerous cysts, odontogenic keratocysts, cysts of the globullomaxillary region, and
ameloblalstomas. Nonodonstogenic lesions include nasopalatine duct cysts, traumatic cysts,
aneurismal bone cyst, and central giant cell granuloma.
Odontogenic Lesions:
Odontogenic cysts are derived directly or indirectly from remnants of the dental
lamina or cells of the periodontal membrane. Odontogenic lesions presenting as well-

3. circumscribed radiolucent lesions include periapical lesions, dentigerous cysts, odoontogenic
keratocysts, cysts of the globullomaxillary region, and ameloblastomas.
Periapical Lesion: Periapical lesions include both the dental granuloma and the periapical
cyst.
The earliest radiographic sign of a developing periapical lesion is widening of the
periodontal space around the apex of the tooth. As the lesion evolves and enlarges,
osteolysis occurs resulting in a well – circumscribed, unilocular, radiolucent lesion around
the root apex. Lesions less than 1 cm in diameter is usually granuloma, whereas lesions
greater than 1 cm are usually periapical cysts. Infected periapical lesions initially are
radiographically indistinguishable from sterile lesions. Advanced lesions, however, may
demonstrate loss of smooth margination and osseous destruction.
Residual cysts are radiographically indistinguishable from a number of other well-
circumscribed radiolucent lesions. Therefore a clinical history of the extraction of a tooth
associated with periapical lesion is a key in making the diagnosis.
On CT studies, a sterile periapical lesion presents as a well-defined low-density area
around the apex (ices) of an involved tooth. Infected cysts may exhibit cortical
breakthrough and extension of the inflammatory process into the adjacent soft tissues.
Radionuclide bone scans demonstrate discrete foci of increased uptake around the roots of
involved teeth. Uncomplicated periapical cysts on MR imaging studies demonstrate low to
intermediate signal intensity on T1-weighted, intermediate signal intensity on proton density
on T2-weighted images.
Dentigerous (Follicular Cyst.) The dentigerous or follicular cyst is the second most
common odontogenic cyst, resulting from the cystic degeneration of the enamel organ after
full or partial completion of the crown (an unerupted tooth).
Radiographically, dentigerous cysts present as well-circumscribed, expansible,
radiolucent lesions, associated with a partially or completely formed, unerupted crown
Opacification and bowing of the walls of maxillary sinus can be seen in lesions involving the
maxillary sinus.
On CT studies and reformatted three-dimensional images, dentigerous cysts present
as expansile, low-density lesions associated with a full or partially formed unerupted crown
or tooth. Cortical bowing and pressure resorption are well demonstrated on CT Associated
periosteal and soft tissue reactions are absent. Direct coronal CT images are important in
assessing possible ostium obstruction by a displaced crown in the case of lesions involving

4. the maxillary sinus. On MR imaging studies, the cystic fluid usually exhibits low to
intermediate signal intensity on T1and high signal intensity on T2- weighted images,
whereas the crown appears devoid of signal intensity on all sequences.
Dentigerous cyst
Odontogenic Keratocyst: Odontogenic Keratocyst is a relatively common developmental
odontogenic cyst constituting approximately 10% to 12% of all developmental odontogenic
cysts.
Approximately three quarters of all odontogenic keratocysts occur in the mandible,
usually in the posterior body and ramus. Maxillary odontogenic keratocysts occur primarily
in the cuspid region. Odontogenic keratocysts can present as either single or multiple
lesions. Multiple lesions are associated with the nevoid basal cell carcinoma syndrome
(Gorlin’s syndrome). Components of this syndrome include multiple odontogenic
keratocysts, early appearing basal cell carcinomas of the skin, skeletal developmental
anomalies, dyskeratotic pitting of the hands and feet, dural calcification, and ectopic soft
tissue calcification.
Odontogenic keratocysts present on plain films as well circumscirbed and often well
corticated radiolucent. Smaller odontogenic keratocysts, typically present as unilocular
lesions, whereas larger lesions often exhibit a multilocular appearance. They can have
additional radiographic or clinical features that may simulate or suggest other odontogenic
lesions. These include small, well-corticated, radiolucent lesions associated with the absence
of a tooth (primodial cyst); radiolucent lesions associated with a tooth and indistinguishable
from a dentigerous cyst (25% to 40% of cases); or as radiolucent lesions indistinguishable
from either unicystic or multicystic ameloblastoma. A feature of many odontogenic
keratocysts that can be useful in differentiating them from other lesions is the tendency for
them to grow within the medulary space in a predominantly anteroposterior direction while

5. causing minimal if any cortical expansion. Maxillary odontogenic keratocysts can extend into
the maxillary sinus, and present as a soft tissue density indistinguishable from a mucus
retention cyst on plain film studies. CT can be helpful in assessing these intra sinus lesions
from uncomplicated mucus retention cysts. On CT examination, we have found odontogenic
keratocysts to have higher CT numbers than uncomplicated retention cysts, and to cause
localized bowing of the sinus wall. On MR imaging studies, odontogenic keratocysts typically
demonstrate low to intermediate signal intensity on T1 sequences, intermediate signal
intensity on proton density sequences, and high signal intensity on T 2 sequences As a result
of the different radiographic appearances an odontogenic keratocyst can have, they should
always be considered in the differential diagnosis of cystic lesions of the jaw.
Odontogenic keratocyst
Cysts of the Globulomaxillary Region: The term globulomaxillary is used to denote the
area of fusion between the embryonic globular process of the median nasal process and the
maxillary process. This region corresponds to the area between the maxillary lateral incisor
and cuspid.
Odontogenic cysts that can present with radiographic findings suggestive of the
classic globulomaxillary cyst include periapical cysts, odontogenic keratocysts, and lateral
periodontal cysts. In light of the histologic diversity of lesions presenting with similar
radiographic findings in this area, it is more appropriate to refer to these lesions as cysts of
the globulomaxillary region.

6. Radiographically, these lesions present as well circumscribed, often inverted pear-
shaped, radiolucencies between the maxillary lateral incisor and cuspid. Large lesions can
have significant palatal extensions and are best appreciated on intraoral dental occlusal
plain film or on CT studies. On axial CT and reformatted panoramic images of the maxilla,
cysts of the globulomaxillary region appear as well-circumscribed low-density lesions
between the lateral incisor and cuspid.
Ameloblastoma: The ameloblastoma is the most common clinically significant odontogenic
tumor, constituting 1% of all tumors and cysts of the jaws, and approximately 11% of all
odontogenic tumors Ameloblastomas arise from either the surface epithelium or remnants of
the dental lamina, or from pluripotential epithelial cells lining dentigerous cysts.
Approximately 80% of all ameloblalstomas occur in the mandible, with the ascending
ramus and proximal body being the most common sites. Maxillary ameloblastomas occur
most often in molar premolar region.
Grossly and radiographically ameloblalstomas are divided into two subtypes: (1)
multicystic and (2) unicystic .The multicystic ameloblastoma constitutes approximately 85%
of all ameloblastomas and contains both solid and cystic elements. The majority of
multicystic ameloblastomas occur in the distal ramus and proximal body of the mandible
(85%). Occasionally, a multicystic ameloblastoma may occur in the posterior maxilla.
The multicystic ameloblastoma is often described as having a “soap bubbly”
appearance on various plain film examinations; this appearance results from its usually
pronounced buccal-lingual cortical expansion as well as the presence of internal osseous
septae between the low-density solid and cystic elements on plain film studies it is
impossible to differentiate between the solid and cystic elements of the tumor.
Unicystic ameloblastomas are grossly cystic, and account for approximately 15% to
20% of all ameloblalstomas.
Radiographically, the unicystic ameloblalstoma presents as a well-circumscribed,
unicystic, radiolulcent lesion, occurring most often in the mandibular molar region. On CT
studies both the unicystic and multicystic ameloblastomas present as well-circumscribed
low-density lesions. Cortical expansion with cortical pressure resorption is usually present in
larger lesions Associated periosteal and soft tissue reactions are absent. Multicystic lesions
also demonstrate the presence of internal osseous septae.
MR imaging, as a result of its greater soft tissue resolution, can provide important
preoperative evaluation of a multicystic ameloblastoma. This information includes
differentiating between solid and cystic elements, and the demonstration of soft tissues

7. lining cyst walls. This information is important for the surgeon in planning the level of
surgical resection. On T1-weighted images both solid and cystic components are usually of
low signal intensity. Areas of high signal intensity on T1 sequences usually denote the
presence of highly proteinaceous cystic fluids. Solid components, including soft tissues
lining cyst walls, exhibit a homogeneous appearance on T1 sequences and significant
enhancement following gadolinium administration. On T2 sequences solid tissues
demonstrate low signal intensity, where as cystic areas demonstrate high signal intensity
Postoperatively, MR imaging can demonstrate the presence of early recurrences, which
typically exhibit high signal intensity on T2-weighted images.
Ameloblastoma of the mandible
Nonodontogenic Lesions
Nasopalatine Duct (Incisive Canal) Cyst. The incisive canal is located in the anterior
palatal midline, extending between the nasal fossa and incisive foramen. Located within the
incisive canal are remnants of the embryonic nasopalatine duct. The nasopalatine duct cyst
is the most common non-dental developmental lesion of the maxilla, and is believed to
result from the spontaneous degeneration and proliferation of remnants of the nasopalatine
duct or mucous cells located within the incisive canal. On panoramic studies, nasopalatine

8. duct cysts often appear as avoid or “heart-shaped” radiolucencies between the roots of the
maxillary central incisors. Nasopalatine duct cysts are often incidental findings on CT and
MR imaging studies performed for other reasons.
On CT studies, there is focal or diffuse enlargement of the nasopalatine canal. On
MR imaging studies nasopalatine duct cysts demonstrate low signal intensity on T1- and
high signal intensity on T2 weighted sequences.
Traumatic Bone Cyst: The traumatic bone cyst is a pseudocyst, lacking a true epithelial
lining. Although it is widely held that traumatic bone cysts result from the breakdown of an
intramedullary hematoma following trauma, conclusive evidence in support of this or any
other mechanism is lacking. On plain film studies, the traumatic bone cyst presents as a
well-defined radiolucent lesion in the posterior mandible, often extending between the roots
of adjacent teeth. Internal scalloping and preservation of the lamina dura are
characteristic. On CT examination, traumatic bone cysts present as low-density lesions,
demonstrating cortical expansion, thinning, and internal scalloping. Extension between the
roots of adjacent teeth with preservation of the lamina dura also can be seen on CT studies.
Aneurysmal Bone Cyst. The aneurismal bone cyst is a pseudocyst believed to result from
a localized vascular reactive process resulting in vascular proliferation and localized
osteolysis. Radiographically, aneurismal bone cysts present as a nonspecific, expansile,
unilocular Radiolucency. Occasionally, aneurismal bone cysts may present as multilocular
radiolucencies with slightly irregular internal margins.
Central Giant cell granuloma central giant cell granulomas, formerly known as giant cell
reparative granuloma, occur predominantly in children and young adults. These lesions are
of uncertain etiology, and occur most often in the mandible. Mandibular lesions usually occur
in the anterior mandible and often cross the midline .A characteristic feature of this lesion is
its tendency to resorb the root tips of adjacent erupted teeth The radiographic findings
associated with central giant cell granuloma are nonspecific, often consisting of an
irregularly shaped, unilocular radiolucent lesion.
Some lesions may present with a multilocular appearances. The lesions are usually well
delineated. Radiographically, smaller unilocular lesions may simulate periapical lesions,
whereas larger multilocular lesions may simulate ameloblastomas or other multilocular
lesions.

9. Poorly Circumscribed Radiolucent Lesions: Ill-defined radiolucent lesions can result
from acute osteomyelitis, the direct extension of a neoplasm arising in tissues bordering the
jaw, a primary neoplasm arising in the jaw, or a distant metastasis. This section focuses
primarily on acute osteomyelitis. The remaining lesions are discussed in the section dealing
with lesions having a variable appearance.
Acute Osteomyelitis: Acute osteomyelitis results from either the direct extension of an
acute pulpal infection without the formation of a granuloma or from the acute exacerbation
of a chronic periapical lesion.
In the case of acute periapical abscesses developing in the absence of a pre-existing
periapical lesion, there are often no plain film findings present for the first 7 to 14 days
except for a possible widening of the periodontal space around the root apex or generalized
osteoporosis. Definitive plain film findings usually become evident between 7 and 14 days.
These include ill definition of trabeculae, single or multiple ill-defined radiolucent areas, and
loss of the lamina dura between the lucent lesion and tooth apex. Extension of the infection
into adjacent soft tissues and fascial spaces is common and often the presenting clinical
symptom for which a CT study may be ordered .CT studies on these patients should be
performed with intravenous contrast unless otherwise contraindicated, and images through
the jaw should be obtained using both soft tissue and bone windows. Information gained by
performing studies in this manner can have a definite impact on patient management.
Intravenous contrast is essential in demonstrating the presence of soft tissue abscesses,
whereas images obtained using bone windows may demonstrate a periapical abscess that
might not be apparent on plain films CT findings that may be seen in these patients
include periosteal reactions, myositis, fascitis, cellulitis, abscess formation, and sinus tracts.
Osseous changes that can be seen include localized osseous breakdown resulting from
abscess formation sequestrate & periosteal new bone formation. We have found MR imaging
useful in assessing patients presenting with acute osteomyelitis. On MR imaging
examination inflammatory changes involving both the marrow and soft tissues demonstrate

10. decreased signal on T1 sequences, intermediate signal intensity on proton density sequen
Chronic Osteomyelitis: Chronic osteomyelitis is a persistent infection of bone, resulting
from either an untreated or inadequately treated acute infection or a long-term low-grade
reaction to a sub-clinical infection. Three forms of chronic osteomyelitis occurring in the
jaws are (1) chronic sclerosing osteomyelitis, (2) chronic suppurative osteomyelitis, and (3)
Garre’s osteomyelitis (chronic osteomyoelitis with proliferative periostitis).
Chronic sclerosing osteomyelitis is an osseo-proliferative response to a low-grade
infection. Focal sclerosing osteomyelitis (condensing osteitis) usually occurs at the apex of
a tooth, and can have a variety of appearances. These include a well-defined area of
uniform opacity, a central opacity with a peripheral lucency; or a central lucency and a
peripheral opacity.
Diffuse sclerosing osteomyelitis is characterized by a generalized proliferation of
bone. Radiogrpahic findings initially consist of ill-defined osteolytic and osteosclerotic
zones. In advanced stages the sclerotic component predominates, resulting in diffuse areas
of sclerosis, poorly demarcated from noninvolved bone.
Chronic suppurative osteomyelitis results from an inadequately treated acute
osteomyelitis or from a low-grade infection that never evoked an acute phase.
The radiographic and CT appearance.
These include a loss of trabeculation a “moth-eaten” appearance representing single
or multiple areas of bone destruction or abscess formation, and foci of increased density
representing dead bone or sequestra that become more apparent as the surrounding bone

11. becomes osteoporotic. Sclerotic changes often are evident throughout the involved bone
and around the abscess (es) On radionuclide bone scans, areas of involvement demonstrate
intense uptake.
Garre’s osteomyelitis or chronic osteomyelitis with proliferative periostitis is a chronic
form of osteomyelitis occurring primarily in children and young adults. It typically occurs in
the posterior mandible resulting either from periapical abscess, a post extraction infection,
or an infection associated with a partially erupted tooth. Radiographically, one sees ill-
defined intraosseous lesions as well as a distinctive periosteal reaction resulting in onion-
skin reduplication of the cortex.
Nasopalatine Duct (Incisive Canal) Cyst. The nasopalatine duct cyst is the most
common non-dental developmental lesion of the maxilla, and is believed to result from the
spontaneous degeneration and proliferation of remnants of the nasopalatine duct or mucous
cells located within the incisive canal. On panoramic studies, nasopalatine duct cysts often
appear as avoid or “heart-shaped” radiolucencies between the roots of the maxillary central
incisors. Nasopalatine duct cysts are often incidental findings on CT and MR imaging studies
performed for other reasons.

12. Traumatic Bone Cyst: The traumatic bone cyst is a pseudocyst, lacking a true epithelial
lining. Although it is widely held that traumatic bone cysts result from the breakdown of an
intramedullary hematoma following trauma, conclusive evidence in support of this or any
other mechanism is lacking. On plain film studies, the traumatic bone cyst presents as a
well-defined radiolucent lesion in the posterior mandible, often extending between the roots
of adjacent teeth. Internal scalloping and preservation of the lamina dura are
characteristic. On CT examination, traumatic bone cysts present as low-density lesions,
demonstrating cortical expansion, thinning, and internal scalloping. Extension between the
roots of adjacent teeth with preservation of the lamina dura also can be seen on CT studies.

13. Central Giant cell granuloma central giant cell granulomas, formerly known as giant cell
reparative granuloma, occur predominantly in children and young adults. These lesions are
of uncertain etiology, and occur most often in the mandible. Mandibular lesions usually occur
in the anterior mandible and often cross the midline .A characteristic feature of this lesion is
its tendency to resorb the root tips of adjacent erupted teeth The radiographic findings
associated with central giant cell granuloma are nonspecific, often consisting of an
irregularly shaped, unilocular radiolucent lesion.
Radiopaque Lesions:
Discrete radiopaque lesions are nearly always benign, often representing an
overgrowth of odontogenic or osseous tissues. These lesions are often incidental findings
on both plain film and CT studies performed for other reasons. Odontogenic radiopacities
include the odontoma and cementoblastoma. Nonodontogenic radiopacities include
osteoma, osteochondroma, torus palatinus, and torus mandibulate.
Odontoma: Odontomas are hamartomas, and the most common odontogenic neoplasm.
Odontomas occur primarily in children and young adults, and are divided into two types
based on radiographic appearance. The compound odontoma appears as an accumulation
of small, fully formed teeth, whereas the complex odontoma appears as an irregular radio
opaque mass learning no resemblance to formed teeth. Odontomas are typically small,
asymptomatic lesions, usually incidentally discovered on routine radiographic examination.
Treatment is surgical excision, and there is a zero recurrence rate.

14. Cementoblastoma: The cementoblastoma is a benign odontogenic neoplasm derived from
the periodontal ligament. The cementoblastoma typically presents as a well-circumscribed,
radiopaque mass associated with the apex of a root. A radiolucent halo separating the
cemental masses from normal bone is usually present. On occasion, a large maxillary lesion
may extend into the adjacent maxillary sinus.
Osteoma: Osteoma is the most common osseous tumor of the jaws. They are slow-
growing benign tumors occurring most often in the second to fifth decade and almost
exclusively on the skull or in the facial skeleton. Multiple osteomas are associated with
Gardner’s syndrome; an autosomal dominant disorder characterized by multiple osteomas,
colonic adenomatous polyposis, fibromas of the skin, epidermal and trichilemmal cysts, and
impacted permanent and supernumerary teeth.
A radiographic examination should suggest a possible diagnosis of Gardner’s
syndrome. Radiographically, an osteoma normally appears as a small, dense, well-
delineated, radiopaque mass on both plain and CT studies.
Torus: A torus is a benign, reactive hyperplasia of osseous tissue extending outward from
the surface of the bone. Tori are named according to location. The torus palatinus occurs
in the midline of the hard palate in approximately 20% of the population, and is the most
common type of torus. On routine plain film studies, small tori palatini are often not well
demonstrated due to overlying bony structures; however, small asymptomatic lesions are
often incidentally encountered on CT studies performed for other reasons. Tori palatini on
CT studies present as nodular midline osseous protuberances of varying sizes.
Tori mandibulari are exophytic, usually bilateral lesions occurring on the lingual
surface of the mandible. Tori mandibulari occur in approximately 8% of the population and
are usually of little, if any, significance. Large tori, however, may interfere with tongue
movement or mastication. On frontal views of the mandible (Waters and Caldwell views),
tori appear as dense, exophytic lesions arising on the medial aspect of the anterior

15. mandible, whereas on lateral views mandibular tori appear as radiopacities superimposed
over the roots of the mandibular premolars. Tori mandibulari on axial CT sections present
as osseous protuberances on the medial aspect of the anterior mandible. CT, with three-
dimensional reconstruction if possible, can be useful in the preoperative evaluation of large
tori involving both the palate and mandible by demonstrating the full extent of the lesion, as
well as the point of attachment between the torus and adjacent palate or mandible.