1. 657G.R.F. Krueger, L.M. Buja (eds.), Atlas of Anatomic Pathology with Imaging,
DOI 10.1007/978-1-4471-2846-5_13, © Springer-Verlag London 2013
Tooth-Related Infection and Inflammation
Caries
Caries is an infectious disease (Streptococcus mutans,
Lactobacillus, Actinomyces, etc.) that causes demineraliza-
tion of hard dental tissues (enamel, dentin, and cementum).
Four factors are necessary for the formation of caries: a tooth
surface, bacteria in a biofilm called plaque, carbohydrates,
and time. Under healthy oral conditions, there is a balance
between demineralization through plaque and remineraliza-
tion through saliva or fluoridated toothpaste. Poor oral
hygiene or excessive consumption of sugar or acidic foods
will shift this balance. In addition, some diseases (especially
autoimmune connective tissue disorders) and medications
(tricyclic antidepressants, antihypertensive agents, antial-
lergy drugs, etc.) predispose patients to develop caries
because the flow of saliva is reduced.
Occlusal caries often may be found through clinical
inspection with sufficient light or laser fluorescence, but
approximal caries often remains undetected without the use
of radiography. The radiologic size of carious lesions is nor-
mally smaller than the actual size, as infected hard tissues
demineralize slowly. Dental restorations, especially metal
ones, may impede diagnosis.
Periapical Rarefying/Sclerosing Osteitis
Profound caries or trauma (concussion, intrusion, avulsion,
crown and root fractures) may lead to an infection of the pulp.
The tooth is painful or has an increased sensitivity to heat,
cold, or sweetness. Unless the tooth is treated, this reversible
pulpitis will progress to irreversible pulpitis. The tooth is very
sensitive to heat, but cold often provides relief from the symp-
toms. In such cases, the treatment of choice is root canal ther-
apy (endodontic treatment) or extraction of the tooth.
Without treatment, necrosis of the pulp will follow and
lead to infection of the periapical tissues. The tooth is no lon-
ger sensitive to cold or electric stimuli. Radiographs will
show either osteolytic regions at the apex of the tooth or, as a
result of chronic infection, sclerotic bone at the root tip. If the
lesions are small, endodontic treatment is often successful.
Larger lesions frequently require surgery (root resections).
Periodontal Disease
The classification of periodontal disease distinguishes gingi-
vitis; chronic and aggressive periodontitis; periodontitis as a
manifestation of systemic disease; necrotizing, ulcerative
gingivitis/periodontitis; abscesses of the periodontium; and
lesions of periodontic–endodontic origin.
Untreated gingivitis may result in periodontitis. Bacteria
are the primary etiologic factor in the initiation of periodon-
tal disease. They trigger a host response that leads to
inflammation and destruction of periodontal ligament and
alveolar bone. Established risk factors for the progression of
initial lesions are specific plaque bacteria, smoking, and
poorly controlled diabetes.
The local results of periodontitis may be pain, bleeding
gums, bad breath, hypermobility of teeth, or tooth loss.
Periodontal disease and coronary artery disease seem to have
common risk factors. Low birth weight has also been linked
to the presence of bacterial pathogens frequently found in
severe chronic periodontitis.
Dental and Orofacial Pathology
Christiane Nobel, Harald Ebhardt,
and Andrea-Maria Schmidt-Westhausen
13
C. Nobel(*)
Department of Oral Medicine, Radiology, and Dental Surgery,
Center for Dentistry, Charité University Hospital,
Berlin, Germany
e-mail: christiane.nobel@charite.de
H. Ebhardt
German Center of Oral Pathology,
Potsdam, Germany
e-mail: harald.ebhardt@oralpath.de
A.-M. Schmidt-Westhausen
Department of Oral Medicine, Radiology, and Dental Surgery,
Center for Dental, Oral and Maxillofacial Medicine,
Charité University Hospital, Berlin, Germany
e-mail: schmidt-westhausen@charite.de

2. 658 C. Nobel et al.
Retained or impacted teeth may develop an infection
under the operculum, which partially covers the crown.
Retention of plaque and debris underneath leads to
inflammation. This phenomenon is often local and can be
cured through debridement and disinfection of the pocket. If
untreated, the infection may spread and cause life-threaten-
ing complications such as sepsis, mediastinitis, Ludwig’s
angina, or cavernous phlebothrombosis.
Signs of spreading infection include trismus, which indicates
involvement of the masticator space. The limited mouth opening
will impede intraoral inspection. Dysphagia and respiratory
difficulties,fever,andgeneralmalaisearefurthersignsofspreading
infection.Apainfulvenaangularismaybeasignofreactivethrom-
bosis, which may lead to cavernous sinus phlebothrombosis.
Implants
Implants are a routine treatment option to replace missing
teeth or to provide anchors for orthodontic treatment. If the
local bone is wide and high enough, implants may be placed
directly into the alveolar bone; otherwise, bone-augmenting
procedures are required.
Analogous to teeth, implants may develop peri-implant
infection, leading to inflammation, loss of alveolar bone,
mobility, and loss of the implant.
Fig. 13.1 Proximal caries (tooth 30): a typical small, triangular trans-
lucency in the enamel, which spreads after reaching the dentinoenamel
junction. The radiographic appearance of caries is not representative of
the actual size, which normally is clinically larger than its appearance
on the radiograph. Teeth 3, 4, and 29 show small lesions in the enamel
at the typical location, just below the proximal contact point of the
teeth. Radiolucent restorative materials may be misinterpreted as caries
lesions. Bitewings are the recommended type of radiographic image for
the detection of proximal caries
Fig. 13.2 Longitudinal cut of a first lower molar with calculus on the
surface of the root and proximal and secondary caries. The left proximal
side shows a small cavitation; remineralization is no longer possible. The
brown dentin below the amalgam filling is a secondary caries, and the
white stain of the right proximal side is a beginning demineralization

3. 65913 Dental and Orofacial Pathology
Fig. 13.3 Patient presenting with a hard, slightly erythematous swelling;
mild pain; and occasional purulent discharge. This extraoral fistula is the
result of chronic apical periodontitis. Intraoral fistulae are more common
Fig. 13.4 Radiograph from the patient in Fig. 13.3 showing a diffuse
radiolucency with loss of periodontal ligament space around the apex of
tooth 31, which has a root canal filling with overextension in the distal root
and no filling in the mesial root. Tooth 32 has a small radiolucency around
the apex as well and is nonvital. If the origin of a fistula is uncertain, it may
be filled with contrast media. The histopathologic features were consistent
with periapical granuloma. With a well-defined circumapical radiolu-
cency, other possible diagnoses are a small radicular cyst with an epithe-
lium-lined cavity or fibrous scar tissue. The main therapeutic options for
this patient are revision of the root canal filling combined with root resec-
tion or extraction of the tooth. Infectious soft tissue either will adhere to
the root after extraction or require subsequent removal

4. 660 C. Nobel et al.
Fig.13.6 Plaque and calculus promote periodontal disease. Underlying
conditions such as hormonal changes during pregnancy or the presence
of HIV/AIDS can make symptoms worse. This HIV-positive patient,
with tobacco abuse and poor oral hygiene due to pain, developed a
necrotizing ulcerative gingivitis/periodontitis (NUG/NUP) with the
typical necrosis that leads to permanent loss of the interdental papillae
Fig. 13.7 Radiograph from the patient in Fig. 13.6 showing profound
vertical and horizontal loss of periodontal attachment. The bone level is
at the apical third of the teeth, and tooth 18 has no attachment to the
alveolar bone at all. (The normal bone level starts 1–2 mm below the
cementoenamel junction.) Tooth 1 has a deep cemental (root) caries on
the mesial surface of the root. The calculus presents as small, triangular,
radiopaque extensions on the root surface. Although small periodontal
lesions require intraoral radiography, panoramics usually offer a good
overview
Fig. 13.5 Typical histologic
findings for chronic periapical
periodontitis (periapical
granuloma) is granulomatous
tissue infiltrated with lympho-
cytes, plasma cells, and
macrophages. Some epithelial
strands are present

5. 66113 Dental and Orofacial Pathology
Fig. 13.8 Gingival hyperplasia due to medication. This patient, who
had poor oral hygiene and chronic periodontitis, took a calcium channel
blocker. Other medications that cause gingival overgrowth include anti-
convulsants and cyclosporine. Systemic diseases that cause enlarge-
ment are leukemia, Wegener’s granulomatosis, and sarcoidosis. Benign
and malignant neoplasms of the gingival tissues and underlying bone
should be considered. Gingival changes that do not respond within
10 days to cleaning and local disinfection should be reevaluated. The
underlying cause of hyperplastic lesions must always be found
Fig. 13.9 Patient with acute myelocytic leukemia. Massive swelling
and bleeding on probing of the interdental papillae of the left side occur
even though hardly any plaque is present. The gingiva is vulnerable and
the other oral soft tissues are pale. The general state of health of the
patient is poor. Improving oral hygiene and local disinfection will not
improve the gingival lesions; this patient needs oncologic therapy
Fig. 13.10 Partially retained third molar. Debris and plaque that have
accumulated beneath the partial gingival covering of the tooth have
caused pericoronitis but are not visible in the radiograph. Teeth 31 and
30 have profound proximal caries and must be ruled out as being non-
vital by cold or electric pulp test, even though they show no apical
radiolucent lesions
Fig. 13.11 Perimandibular abscess caused by an impacted third molar.
The base of the mandible can no longer be palpated, the swelling is
hard, and the patient has fever and difficulty swallowing. The mouth
opening is severely limited

6. 662 C. Nobel et al.
Fig. 13.12 Implants with single crowns. The distal implant is hyper-
mobile and must be removed. The gingiva does not show inflammation,
and neither swelling nor bleeding is present. The mesial implant is
clinically normal
Fig. 13.13 Radiograph from the patient in Fig. 13.12 showing that the
distal implant has a well-defined radiolucent margin. Although the
implant is close to the inferior alveolar nerve and the cortical border of
the nerve canal is no longer visible, no anesthesia is present. Peri-
implantitis in this case is too far advanced for treatment. The right
implant shows the beginning of peri-implantitis with vertical loss of
alveolar bone

7. 66313 Dental and Orofacial Pathology
Normal Anatomy and Variants
Exostosis and Tori
Bony exostoses are common on the buccal aspect of the pos-
terior region maxilla.
The torus palatinus is found in the midline of the hard pal-
ate. The covering mucosa is thin and easily traumatized.
Resulting ulcera are slow in healing. These harmless exos-
toses need to be distinguished from other swellings of the
jaws, in which ulceration is a sign of malignancy. For exam-
ple, lymphomas or carcinomas of the maxillary sinus some-
times penetrate into the oral cavity.
Similar tori may be present on the lingual surface of the
mandibula in the premolar region. Symmetric bilateral
appearance is a good diagnostic aid to differentiate between
tori and tumorous growth.
Mandibular Salivary Gland Defect
(Stafne Cavity/Cyst)
This bone depression on the lingual aspect of the mandible
contains mostly salivary gland tissue, but fatty soft tissue con-
tent also has been reported. This formation is normally asymp-
tomatic, and the finding is often incidental. In panoramic
radiographs, the defect is located below the mandibular canal,
between the angle of the mandible and the first molar; it is seen
as a unilocular, corticated radiolucency. CT scans or cone-beam
CT imaging will show a lingual depression with a preserved
cortex with soft tissue content. Sialography sometimes shows
an accessory lobe of the submandibular salivary gland.
Differential diagnosis includes eosinophilic granuloma or
immature ossifying fibroma, although these lesions gener-
ally are not corticated. Odontogenic cysts are usually situ-
ated above the mandibular canal.
Osteomyelitis, Osteoradionecrosis,
and Bisphosphonate-Related Osteonecrosis
Osteomyelitis
Odontogenic infections may cause osteomyelitis. The most
common causes of osteomyelitis are apical inflammation and
periodontal disease, infected cysts, and dental surgery during
the acute phase of an infection. Osteomyelitis occurs mainly
in the mandible; maxillary involvement is rare. Teeth may be
hypermobile, and paresthesia of the inferior alveolar nerve
may occur, with resulting numbness of the lower lip and chin.
Radiologic features occur late in the onset of the disease.
Acute osteomyelitis is characterized by a decrease in density of
the mandible. Sequestra may be present. In chronic forms, those
diffuse radiolucencies appear next to diffuse radiopaque areas.
The affected area appears ill-defined and may show a moth-eaten
appearance. Periosteal reaction is common in later stages.
Imaging methods include CT scans, which are best able to detect
sequestra, and scintigraphy, which shows increased metabolic
activity before conventional radiographs show bone alterations.
Osteoradionecrosis
Osteoradionecrosis (ORN) is a severe, difficult-to-manage oral
complication of radiation therapy in head and neck cancer treat-
ment. Radiation causes cell changes in the oral mucosa and the
dentinoenamel junction of the teeth. Salivary glands also are
affected, and xerostomia is a frequent result. The alveolar bone
is hypovascular and hypocellular. Odontogenic infections, sur-
gical treatment (e.g., tooth extraction), and ulcera due to ill-
fitting dentures or mechanical trauma may lead to infection of
this altered bone. Wound healing is slow or absent, allowing
exposed bone and fistulae to follow. Often, parts of the bone will
sequestrate, and partial loss of the mandible is possible.
The risk of ORN increases with radiation dose, tumor size
and location, local trauma, dental surgery, periodontal and
dental infection, immune defects, malnutrition, and abuse of
tobacco or alcohol.
Diagnosis is made by clinical appearance. Conventional
radiography and CT scans often underrepresent the lesions,
as demineralization frequently becomes visible only during
late stages of the disease.
Bisphosphonate-Related Osteonecrosis
of the Jaw
Patients who receive bisphosphonates, especially in the man-
agement of malignancy affecting the skeleton (either primary
or metastatic), are at a high risk of developing bisphospho-
nate-related osteonecrosis of the jaw (BONJ). Cofactors that
seem to promote the disease are immunosuppression, dental
infection and trauma, additional chemotherapy or radiother-
apy, and long-term use of corticosteroids.
Radiologic changes are either late in appearing or are miss-
ing altogether. Because almost no bone remodeling occurs, the
alveoli of extracted teeth may be seen months after surgery.
Otherwise, diagnosis is analogous to that of ORN.
Small lesions may be locally revised, but larger ones
require treatment under hospital conditions, with removal of
necrotic bone and histologic evaluation to rule out metastatic
disease. Treatment of patients with ORN and BONJ is not
always successful, and severe deformities may result.
Prophylactic measures include assessment of risk factors,
clinical and radiologic inspection of the patient’s oral status,
treatment of odontogenic infection, elimination of sharp
edges on teeth and dentures, and establishment of good den-
tal hygiene before intravenous bisphosphonate therapy com-
mences. If dental procedures are necessary, they should be
undertaken according to appropriate guidelines.

8. 664 C. Nobel et al.
a b
c
Fig. 13.14 Loss of a maxillary implant due to peri-implantitis and dis-
placement into the maxillary sinus (a). On a panoramic radiograph
taken for prosthetic rehabilitation planning purposes (b), the anterior of
the angulus beneath the alveolar nerve canal contains a homogenous,
well-defined radiolucency. This lesion was previously unknown, and
the patient has no pain. The cystlike appearance is caused by a depres-
sion in the lingual aspect of the mandible, which is filled with an acces-
sory lobe of the submandibular gland or fatty tissue. It is not a true cyst,
as there is no cavity in the bone and no epithelial lining. CT scans (c)
show the lingual depression and the cortical border of the lesion
Fig. 13.15 Clinical appearance of a patient with bisphosphonate-
related osteonecrosis of the jaw. Bisphosphonates are administered
intravenously to treat patients with cancer who have hypercalcemia
associated with malignant disease such as multiple myeloma or meta-
static tumors (breast, lung, prostate) in the bones. This patient received
zolendronate for breast cancer. After simple extraction of the teeth, the
wound showed no healing. This is the typical appearance of BONJ: a
large area of nonvital bone is no longer covered by mucosa, and second-
ary infection leads to purulent discharge. The surgical management of
BONJ includes antibiotic therapy, surgical debridement of the necrotic
bone, and primary closure of the wound
Fig. 13.16 A cropped panoramic radiograph from the patient in
Fig. 13.15 shows that the alveoli of the teeth are still present 16 weeks
after extraction. The mandible has an overall radiolucent appearance,
and below its base, a periosteal reaction is present in the form of ill-
defined radiopaque layers parallel to the cortex of the mandible

9. 66513 Dental and Orofacial Pathology
Fig. 13.17 Histologically, BONJ
is characterized by active acute
inflammation, acellular necrotic
debris, thin-walled and dilated
blood vessels, basophilic bone
spiculae with scalloped borders
showing prominent bone
resorption, and often an absence
of osteoblasts and osteoclasts

10. 666 C. Nobel et al.
Table 13.1 Classification of jaw cysts
Epithelium-lined cysts
Developmental origin/odontogenic
Gingival cyst of infants
Odontogenic keratocysta
Dentigerous cyst
Eruption cyst
Gingival cyst of adults
Developmental lateral periodontal cyst
Botryoid odontogenic cyst
Glandular odontogenic cyst
Calcifying odontogenic cyst
Developmental origin/nonodontogenic
Midpalatal raphe cyst of infants
Nasopalatinal duct cyst
Nasolabial cyst
Inflammatory origin
Radicular cyst, apical and lateral
Residual cyst
Paradental cyst and juvenile paradental cyst
Inflammatory collateral cyst
Non-epithelium-lined cysts
Solitary bone cyst
Aneurysmal bone cyst
a
The odontogenic keratocyst is now considered a tumor because of its
genetic properties and behavior
Cysts of the Jaws
Epithelium-Lined Cysts
The classification of cysts of the jaw by Shear, published in
1996 by the World Health Organization (WHO) (Table 13.1),
has not been revised, except that odontogenic keratocyst, for-
merly classified as an odontogenic cyst of developmental
origin, is now classified as an odontogenic tumor owing to its
behavior, high recurrence rates, and the detection of tumor-
suppressor genes. One possible classification distinguishes
epithelium-lined cysts of developmental and inflammatory
origin from nonepithelial cysts (pseudocysts).
The most common developmental cysts are dentigerous
(follicular) cysts, which are associated with the follicle of an
unerupted or impacted tooth. These cysts are found inciden-
tally or because the tooth fails to erupt. They grow through
the accumulation of fluid between the enamel epithelium and
the crown of a tooth (most often third molars, maxillary
canines, or mandibular premolars). The cyst always attaches
at the cementoenamel junction, so radiographic features are a
homogenous round or oval translucency around the crown of
an unerupted and sometimes displaced tooth. The borders of
the lesion are corticated, and neighboring structures such as
roots, the base of the antrum, or the alveolar nerve canal are
displaced. Histologically, the lining consists of a thin layer of
stratified squamous epithelium and a connective tissue wall,
which may contain islands of odontogenic epithelium.
Developmental nonodontogenic cysts arise from epithe-
lium. For example, a cyst of the nasopalatinal duct or a naso-
labial (nasoalveolar) cyst may result from epithelial residues
of the embryonic nasolacrimal duct or the fusion of the pro-
cessus maxillaris and globularis. The location is in or near
the nasopalatinal foramen or in the nasopalatinal canal.
These slow-growing cysts are found after the fourth decade.
A typical clinical sign is a soft swelling behind the front
teeth, covered with normal mucosa.
Radiologic features are a round translucency, often overly-
ing the incisor teeth, with corticated borders. The nasal floor
or the roots of the front teeth may be displaced. The nasopa-
latinal foramen can no longer be seen. In occlusal radiographs,
a heart-shaped appearance is the result of the projection of the
anterior nasal spine into the cyst. Differential diagnosis
includes radicular cysts and a wide nasopalatinal foramen.
Histologically, the lining consists of stratified squamous
or ciliated epithelium or both. The walls often contain nerve
tissue and blood vessels.
Inflammatory cysts, such as the radicular cyst, are always
linked with nonvital teeth. (Vitality is lost as a result of large
carious lesions, trauma, or, infrequently, deep pockets.)
Inflammatory cells stimulate proliferation of Malassez cell
rests in the apical region of the tooth, producing either apical
granulomatous tissue or the development of a cystic cavity.
Radicular cysts may grow to large dimensions before they
become painful owing to infection or pathologic fracture. If
a tooth is removed without curettage of the apical cystic tis-
sues, the remnants are called residual cyst. They are mostly
asymptomatic, and bony expansion may be the first clinical
sign. Diagnosis may be difficult without the patient’s history
or histology, because odontogenic tumors like unicystic
ameloblastoma or keratocystic odontogenic tumor some-
times present a similar, unilocular radiolucency without
obvious dental origin.
Histologically, the cyst is lined by stratified squamous
epithelium, which shows varying degrees of thickness and
rete pegs, according to the degree of inflammation. Hyaline
bodies, inflammatory infiltrate, and cholesterol crystals may
be present in the fibrous walls.

11. 66713 Dental and Orofacial Pathology
Non-Epithelium-Lined Cysts
The etiology of non-epithelium-lined cysts is undetermined.
These cysts may represent a reactive bone lesion, occur sec-
ondary to central giant cell granuloma or fibrous dysplasia,
or signify a neoplasm.
Aneurysmal bone cysts occasionally occur in the poste-
rior mandible of young adults, mainly women. They present
as multiloculated, mostly corticated radiolucencies, which
expand and thin the cortex of the mandible as they grow.
Macroscopicallyandhistologicallytheyappearasblood-filled
caverns with fibroblastic tissue, osteoclast-like giant cells,
and osteoid or new bone formation.
A simple bone cyst (also known as a traumatic, solitary, hem-
orrhagic, unicameral, or idiopathic bone cyst) is a cavity in the
mandible of a young adult, which is either empty or filled with
serous or bloodlike fluid. The etiology is unknown. The cyst is
rarely painful and is often found by chance. Radiologically, it
often presents as a well-defined, scalloped radiolucency that
extends between the roots of the teeth. These cysts are found
mainly in the posterior region of the mandible and are sometimes
associated with fibrous dysplasia or cemento-osseous lesions.
Fig. 13.18 Scintigraphy is the most sensitive imaging modality for
detecting early metastatic involvement. It shows intense radionuclide
activity in the jaw and metastatic bone disease
Fig. 13.19 Patient with two impacted and displaced third molars. The
left molar shows a pericoronal well defined radiolucency, which begins
at the cementoenamel junction. This is the typical appearance of a small
dentigerous (follicular) cyst. The right third molar is displaced into the
ramus. It also shows a pericoronal, well-defined radiolucency. The cor-
tex of the mandible is thin, scalloped, and shows expansion. Root
resorption of the second molar is evident, and the lesion has a mul-
tilocular appearance. This is an odontogenic tumor, an ameloblastoma.
These tumors sometimes develop in dentigerous cysts

12. 668 C. Nobel et al.
Fig. 13.20 Histologically a
follicular or dentigerous cyst
shows a thin, regular layer of
cuboidal epithelium (reduced
enamel epithelium) or nonkerati-
nized, stratified squamous
epithelium lining with
fibromyxomatous connective
tissue free from inflammatory cell
infiltration

13. 66913 Dental and Orofacial Pathology
a b
Fig. 13.21 Panoramic (a) and occlusal views (b) of a patient with a
nasopalatinal duct cyst. Nasopalatinal duct cyst is a common develop-
mental nonodontogenic cyst that occurs predominantly in men in the
fourth to sixth decade of life. It is a well-defined, homogenous, corti-
cated radiolucency. In this case, the floor of the nasal cavity is elevated.
The periodontal ligament of the incisors is normal and no displacement
can be seen. The nasopalatinal foramen is no longer visible and the
anterior nasal spine projects into the cyst. Clinically, patients report a
slow-growing swelling behind the incisors, in the area of the incisive
papilla. The mucosa is normal, and the swelling is mostly soft, as there
is no bone covering
Fig. 13.22 Squamous cell
epithelium and ciliary
respiratory-type epithelium are
almost always observed in
nasopalatinal duct cysts. The wall
may be fibrous tissue, or it may
contain nerve and blood vessels
because of its location within the
nasopalatinal foramen

14. 670 C. Nobel et al.
a
b
Fig. 13.23 The radicular cyst is the most common inflammatory cyst
in the second dentition. They rarely (in <0.5 % of cases) arise from
deciduous teeth. (a) The radiograph shows a canine with root canal
filling and a homogenous, well-defined radiolucency around the apex.
The apex has an irregular shape because of resorption resulting from
long-term infection. (b) The transverse view of the cone-beam CT scan
shows the expansion of the alveolar ridge and the loss of vestibular and
palatinal cortex. Treatment options are enucleation with root resection
or extraction of the tooth

15. 67113 Dental and Orofacial Pathology
Fig. 13.24 The thick wall of the
radicular cyst consists of fibrous
tissue, which is lined with
stratified squamous epithelium
derived from the epithelial cell
rests of Malassez. The initiation
of inflammation and the
following epithelial proliferation
are largely caused by bacterial
toxins, which originate in the
necrotic pulp chamber. The
content of radicular cysts is either
a yellowish fluid containing
cholesterol crystals or a brown
fluid containing blood and its
products of decomposition

16. 672 C. Nobel et al.
a
c
d
b
Fig. 13.25 Residual cysts may arise from persisting tissue of radicular
cysts after removal of the cause, the nonvital tooth. These cysts often
remain asymptomatic and may fill large parts of the mandible before
they are identified because of swelling of the jaw or infection and result-
ing pain. The mandibular premolar region is most often involved. (a)
The radiographic appearance is a homogenous, radiolucent lesion with
sharp, often sclerotic margins—unless infection is present. (b, c)
Removal may be performed by either enucleation or marsupialization
depending on size; neighboring structures, such as the alveolar inferior
nerve; and the general condition of the patient. (d) The macroscopic
specimen shows the capsule of fibrous tissue, which (unless infected)
separates easily from the alveolar bone

17. 67313 Dental and Orofacial Pathology
a b
c
Fig. 13.26 (a) Cropped panoramic radiograph of a young woman with
an adenomatoid odontogenic tumor involving the left upper canine. The
lesion presents as a sharply delineated radiolucency lateral to the vital
tooth. (b) Intraoral inspection shows a painless, hard vestibular swell-
ing and a slightly displaced tooth. Canines are associated with more
than 60 % of these tumors, more than half of which are diagnosed dur-
ing the second decade. (c) The histology of these tumors shows colum-
nar, ameloblast-like cells forming duct- or tubule-like structures with
central spaces, which may contain small foci of calcification or homog-
enous eosinophilic material

18. 674 C. Nobel et al.
Odontogenic Tumors
The WHO classifies odontogenic tumors according to the
tissue they contain, which is primarily odontogenic epithe-
lium, odontogenic ectomesenchyme, or both (Table 13.2).
Hard tissue formation may be present.
Most of these lesions occur in the alveolar ridge of the
maxilla and mandible. Peripheral lesions in the gingival tis-
sues are rare. Most (<95 %) of these tumors are benign,
growing slowly and painlessly. Expansion of the jaws, altered
occlusion, and ill-fitting dentures may be the first clinical
signs. Malignant odontogenic tumors are rare; they may arise
in benign lesions as ameloblastomas or may represent pri-
mary intraosseous carcinomas.
Radiologic characteristics are varied. Because hard tissue
forms within some tumors, those present as mixed lesions,
radiolucencies with central radioopacities. The radioopaci-
ties may vary in intensity and increase over time. Typical
examples are the common odontomas, the less common ade-
nomatoid odontogenic tumor, calcifying cystic odontogenic
tumor, calcifying epithelial odontogenic tumor, and the rare
ameloblastic odontoma and ameloblastic fibro-odontoma.
Other lesions present as multilocular radiolucencies. The
most common of these are keratocystic odontogenic tumor,
ameloblastoma, and central giant cell granuloma. Less com-
mon are aneurysmal bone cyst and odontogenic myxoma.
Rare but important are cherubism, central mucoepidermoid
carcinoma, and glandular odontogenic cyst.
Central giant cell granuloma, aneurysmal bone cyst, and
cherubism are bone-related lesions that show some charac-
teristics of tumors but also may represent reactive lesions.
Odontogenic tumors are graduated according to their dif-
ferent clinical features and prognostic criteria. Malignant
tumors must be radically resected. Locally aggressive lesions
such as the ameloblastoma or myxoma require resection with
an adequate margin. The rate of recurrence with enucleation
and curettage is high, and the lesion may recur after more
than 10 years. Keratocystic odontogenic tumor, ameloblastic
fibroma, and the calcifying epithelial odontogenic tumor also
have a high recurrence rate. They need in sano resection,
with a small safety margin. Odontomas and cementomas
normally may be treated by curettage and enucleation.
Ameloblastoma
The most common benign tumors are ameloblastomas, kera-
tocysticodontogenictumors,andodontomas.Ameloblastomas
are locally aggressive. Four different clinical and histologic
subtypes are recognized: solid/multicystic ameloblastoma,
peripheral ameloblastoma, desmoplastic ameloblastoma, and
unicystic ameloblastoma (with intramural and intraluminal
subtypes),
Posteriorpartsofthemandiblearethemostcommonlocations
for multicystic ameloblastomas. Small ameloblastomas are found
incidentally; later, they may present as swelling of the jaws. Pain
and paresthesias or anesthesia of the chin and lip due to compres-
sion of the inferior alveolar nerve occur seldomly. Radiographic
signs are multilocular radiolucencies, resorption of the roots, and
erosion of the basal cortical border of the mandible.
There are two histologic types of ameloblastomas, plexi-
form and cystic, which seem to present the same clinical
features and have a similar prognosis. Desmoplastic amelo-
blastomas are similar to multicystic ameloblastomas but are
more often located in the anterior mandible.
Table 13.2 Simplified classification of odontogenic tumors
Malignant tumors
Odontogenic carcinomas
Metastasizing (malignant) ameloblastoma
Ameloblastic carcinoma
Primary intraosseous squamous cell carcinoma
Clear cell odontogenic carcinoma
Ghost cell odontogenic carcinoma
Odontogenic sarcomas
Ameloblastic fibrosarcoma
Ameloblastic fibrodentinosarcoma and fibro-odontosarcoma
Benign tumors
Odontogenic epithelium with mature, fibrous stroma without
odontogenic ectomesenchyme
Ameloblastoma
Squamous odontogenic tumor
Calcifying epithelial odontogenic tumor
Adenomatoid odontogenic tumor
Keratocystic odontogenic tumor
Odontogenic epithelium with odontogenic ectomesenchyme, with
or without hard tissue formation
Ameloblastic fibroma
Ameloblastic fibrodentinoma
Ameloblastic fibro-odontoma
Odontoma
Odontoameloblastoma
Calcifying cystic odontogenic tumor
Dentinogenic ghost cell tumor
Mesenchyme and/or odontogenic ectomesenchyme with or
without odontogenic epithelium
Odontogenic fibroma
Odontogenic myxoma/myxofibroma
Cementoblastoma
Bone-related lesions
Ossifying fibroma
Fibrous dysplasia
Osseous dysplasia
Central giant cell lesion (granuloma)
Cherubism
Aneurysmal bone cyst
Simple bone cyst
From Barnes et al. [1]

19. 67513 Dental and Orofacial Pathology
Extraosseous ameloblastomas occur in the sixth decade
within the gingiva, either as remnants of the dental lamina or
from the surface epithelium. They can be excised with a
small safety margin, but follow-up is necessary.
The radiographic appearance of the unicystic ameloblas-
toma may be misinterpreted as a dentigerous cyst or a kera-
tocystic odontogenic tumor. It often is associated with an
impacted wisdom tooth and presents as a unilocular, peri-
coronal radiolucency. Intraluminal ameloblastomas have a
low recurrence rate and may be treated with enucleation. If
histologic examination shows an intramural ameloblastoma,
subsequent bloc resection may be necessary, as the recur-
rence rate is high.
Keratocystic Odontogenic Tumor
Keratocystic odontogenic tumors are unilocular or multiloc-
ular radiolucencies, often associated with impacted and dis-
placed teeth and occurring mainly between the ages of 10
and 40. Most appear in the posterior mandible; only one third
affect the maxilla.
Recurrence rates are high, perhaps because of the thin
epithelial layer, satellites of the epithelium spreading into the
surrounding connective tissue, and remains of the tumor after
simple enucleation. If multiple tumors are present or they
appear at a young age, the patient should be examined care-
fully for basal cell carcinoma, as these keratocystic odonto-
genic tumors may represent a partial symptom of nevoid
basal cell carcinoma (Gorlin’s) syndrome, which is auto-
somal dominant. Other symptoms that occur in more than
50 % of patients are epidermal cysts of the skin, occult spina
bifida, rib anomalies, calcified falx cerebri, and diaphragma
sellae. The paranasal sinus may be hyperpneumatized.
Medulloblastomas in young children have been described.
Odontomas
Odontomas are hamartomas that consist of common enamel,
dentin, and sometimes cementum and pulp tissue. The WHO
classifies two subtypes, compound and complex. Enamel,
dentin, and sometimes cementum and pulp tissue are present
in both types, but compound odontomas resemble multiple
malformed toothlike structures, whereas the hard tissues in
complex odontomas are much less organized.
The radiographic appearance of a complex odontoma
consists of a roundish, inhomogeneous radiopacity with a
radiolucent margin. This margin will decrease in size as the
hard tissue formation continues. Both forms of odontomas
are found mainly in young children or adolescents, often
because permanent teeth fail to erupt.
Multiple odontomas and osteomas of the jaws may be a sign
of Gardner syndrome. Other symptoms are multiple intestinal
polyposis of the colon or rectum, often with malignant trans-
formation, epidermoid cysts, and a tendency to develop a vari-
ety of neoplasms. The osteomas have a limited potential for
growth. Both the maxilla and mandible are often affected. The
radiographic appearance resembles cotton wool.
Osseous Dysplasia
Osseous dysplasia occurs in the tooth-bearing parts of the
maxilla and mandible and probably arises from the periodon-
tal ligament. The etiology is unknown; there is a predilection
for middle-aged black women. The radiographic appearance
varies greatly over time. In the beginning, these lesions pres-
ent as radiolucencies, often around the apex of a vital tooth.
(This form may be misinterpreted as a radicular cyst.) Later
stages show a central radiopacity with a translucent rim,
which grows smaller with time.
On histology, the lesion is characterized by the replace-
ment of normal bone through cellular fibrous tissue, lamellar
bone, and woven bone without a capsule. Cementum-like
structures may be found, but because it is unclear whether
they really represent odontogenic cementum, the term
cemento-osseous dysplasia is no longer used.
Often the lesions are asymptomatic and found during rou-
tine examination. They require no therapy, except for florid
forms or the closely related gigantiform cementoma. Both
may lead to profound swelling of the jaws.
Malignant odontogenic tumors are rare and occur predom-
inantly in elderly patients. Their radiographic appearance var-
ies: inhomogeneous, radiolucent/radiopaque structures with
diffuse borders have been described. Ameloblastic carcino-
mas and primary intraosseous squamous cell carcinomas or
those deriving from keratocystic odontogenic tumors or den-
tigerous cysts are the most common of these rare lesions.
Clinical signs include swelling; bleeding; anesthesia or par-
esthesia, especially of the lip and chin if the inferior alveolar
nerve is involved; and hypermobility of teeth.

20. 676 C. Nobel et al.
a
c
b
Fig. 13.27 Multilocular cystlike appearance of an odontogenic tumor
in the left mandible of a 45-year-old woman (a). Borders are poorly
defined and the internal structure contains coarse and fine septa. In a
transverse view (b), extreme thinning of the cortical plate can be seen.
Differential diagnosis for those lesions includes odontogenic myxoma,
ameloblastoma, central giant cell granuloma, and central hemangiomas.
The perforation of the cortical plate is an indication of osteosarcoma.
Location in the premolar region of the mandible and age between 30
and 50 years are typical for odontogenic myxoma (c). Odontogenic
myxoma consists of scanty, spindle-shaped cells with long anastomos-
ing processes, distributed in abundant connective-tissue ground sub-
stances. They may contain small strands of odontogenic epithelium. If
collagen fibers dominate in the stroma, the tumor may be designated as
odontogenic myxofibroma
a b
Fig. 13.28 Ameloblastoma (also referred to as adamantinoma) with
the typical multilocular, “soap bubble” radiologic appearance (a). The
cortex is thinned but root resorption is minimal, involving only the apex
of tooth 27. The mandible is involved more than four times as often as
the maxilla. Clinical signs include swelling but seldom include
paresthesia or hypoesthesia of the alveolar inferior nerve. Follicular
ameloblastoma with cystic changes (b) shows basal cells lined up in a
palisaded fashion with columnar cells with reversed polarity of their
hyperchromatic nuclei, surrounding a core of loosely arranged polyhe-
dral cells, resembling stellate reticulum. The latter may undergo
squamous metaplasia and form keratin (not shown here)

21. 67713 Dental and Orofacial Pathology
a b
Fig. 13.29 (a) Keratocystic odontogenic tumors may present similar
radiographic features as dentigerous cysts (root resorption and a scal-
loped, thinned cortex) and involve the crown of an impacted tooth. Even
though keratin is present in the center of the tumor, the internal struc-
ture is usually radiolucent. (b) This keratocystic odontogenic tumor is
lined by five to eight layers of parakeratinized, stratified squamous epi-
thelium with a well-defined, palisaded basal layer of hyperchromatic
columnar or cuboidal cells. Note the desquamated keratin in the cavity
of this tumor
Fig. 13.30 Radiography shows two large, pericoronal, radiolucent
lesions in a 12-year-old boy, representing two keratocystic odontogenic
tumors. Tooth 31 is displaced toward the inferior cortex of the mandi-
ble. Teeth 19, 20, and 20 are displaced toward the nasal cavity and max-
illary sinus. Root resorption of the overlying deciduous teeth is evident.
Multiple keratocystic odontogenic tumors are one of the major signs of
nevoid basal cell carcinoma syndrome (NBCCS, or Gorlin’s syndrome).
Other signs are basal cell carcinomas under the age of 20, palmar and
plantar pits, calcification of the falx cerebri, bifid ribs, and a first-degree
relative with NBCCS

22. 678 C. Nobel et al.
a
c
b
Fig. 13.31 Compound odontoma. This benign hamartoma comprises
multiple malformed toothlike structures (a). On radiography (b), the
radiopacity has a density that resembles enamel, dentin, and the follicle
of multiple unerupted teeth. The eruption of permanent teeth may be
hindered, but growth is mostly self-limited and there is no recurrence
after enucleation. Ameloblastic fibro-odontoma (c) is composed of soft
and hard odontogenic tissue. The soft tissue component consists of
odontogenic ectomesenchyme with ameloblastoma-like epithelial
strands and islands in a myxoid cell–rich stroma. The hard tissue com-
ponent is built of dentin and enamel in varying proportions
Fig. 13.32 Osseous dysplasia, also known as periapical cemental dys-
plasia or apical cementoma. A radiopaque central structure extends
around the roots of the vital teeth 30 and 31. The margin is a radiolucent
band. If asymptomatic, no treatment is necessary

23. 67913 Dental and Orofacial Pathology
a b
Fig. 13.33 Large osseous dysplasia adjacent to the root of an impacted
wisdom tooth, as seen on cone-beam CT scan (a). There is a thin radio-
lucent rim around the lesion, and the central radiopacity has the homog-
enous, dense appearance typical of mature lesions (b). Cortical bone is
thinned. Diagnosis is made by clinical and radiologic appearance.
Elective tooth extraction should be avoided, as infection of the sclerotic
bone masses may result and lead to complications, as the internal struc-
ture is predominantly avascular. The development of simple bone cysts
within or next to these lesions has been described

24. 680 C. Nobel et al.
a b
c
Fig. 13.34 Fibrous dysplasia may be polyostotic or mono-osteitic and
is often diagnosed in children or in young adults. (a) Symptoms include
bone deformities and sometimes mild pain. When orofacial structures
are involved, misalignment of the teeth may result. Polyostotic fibrous
dysplasia, autonomous endocrine hyperfunction (which may result in
precocious puberty), and café-au-lait pigmentation are symptoms of
McCune-Albright syndrome. (b) Radiologic features include homoge-
neous opacities with a ground-glass appearance and loss of trabecular
pattern. The maxilla of this man shows abnormal growth of the alveolar
ridge and zygomatic bone. (c) Fibrous dysplasia consists of irregularly
shaped trabeculae of immature bone in a cellular fibrous stroma. The
bone trabeculae are considered to arise by metaplasia. They are not sur-
rounded by osteoblasts. The lesional bone fuses directly to normal bone
at the periphery of the lesion

25. 68113 Dental and Orofacial Pathology
Fig. 13.35 Peripheral giant cell
granuloma shows a proliferation
of multinucleated giant cells with
up to 12 nuclei. The giant cells lie
in a stroma of plump, ovoid
mesenchymal cells with several
mitotic figures (seen in the center
of the image) and hemorrhagic
areas throughout the lesion
Reference
1. Barnes L, Eveson JW, Reichart P, Sidransky D, World Health
Organization, editors. Classification of tumors. Pathology and genet-
ics of head and neck tumors. Lyon: IARC Press; 2005.