658 C. Nobel et al.Retained or impacted teeth may develop an infectionunder the operculum, which partially covers the crown.Retention of plaque and debris underneath leads toinﬂammation. This phenomenon is often local and can becured through debridement and disinfection of the pocket. Ifuntreated, the infection may spread and cause life-threaten-ing complications such as sepsis, mediastinitis, Ludwig’sangina, or cavernous phlebothrombosis.Signs of spreading infection include trismus, which indicatesinvolvement of the masticator space. The limited mouth openingwill impede intraoral inspection. Dysphagia and respiratorydifﬁculties,fever,andgeneralmalaisearefurthersignsofspreadinginfection.Apainfulvenaangularismaybeasignofreactivethrom-bosis, which may lead to cavernous sinus phlebothrombosis.ImplantsImplants are a routine treatment option to replace missingteeth or to provide anchors for orthodontic treatment. If thelocal bone is wide and high enough, implants may be placeddirectly into the alveolar bone; otherwise, bone-augmentingprocedures are required.Analogous to teeth, implants may develop peri-implantinfection, 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 dentinoenameljunction. The radiographic appearance of caries is not representative ofthe actual size, which normally is clinically larger than its appearanceon the radiograph. Teeth 3, 4, and 29 show small lesions in the enamelat the typical location, just below the proximal contact point of theteeth. Radiolucent restorative materials may be misinterpreted as carieslesions. Bitewings are the recommended type of radiographic image forthe detection of proximal cariesFig. 13.2 Longitudinal cut of a ﬁrst lower molar with calculus on thesurface of the root and proximal and secondary caries. The left proximalside shows a small cavitation; remineralization is no longer possible. Thebrown dentin below the amalgam ﬁlling is a secondary caries, and thewhite stain of the right proximal side is a beginning demineralization
65913 Dental and Orofacial PathologyFig. 13.3 Patient presenting with a hard, slightly erythematous swelling;mild pain; and occasional purulent discharge. This extraoral ﬁstula is theresult of chronic apical periodontitis. Intraoral ﬁstulae are more commonFig. 13.4 Radiograph from the patient in Fig. 13.3 showing a diffuseradiolucency with loss of periodontal ligament space around the apex oftooth 31, which has a root canal ﬁlling with overextension in the distal rootand no ﬁlling in the mesial root. Tooth 32 has a small radiolucency aroundthe apex as well and is nonvital. If the origin of a ﬁstula is uncertain, it maybe ﬁlled with contrast media. The histopathologic features were consistentwith 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 forthis patient are revision of the root canal ﬁlling combined with root resec-tion or extraction of the tooth. Infectious soft tissue either will adhere tothe root after extraction or require subsequent removal
660 C. Nobel et al.Fig.13.6 Plaque and calculus promote periodontal disease. Underlyingconditions such as hormonal changes during pregnancy or the presenceof HIV/AIDS can make symptoms worse. This HIV-positive patient,with tobacco abuse and poor oral hygiene due to pain, developed anecrotizing ulcerative gingivitis/periodontitis (NUG/NUP) with thetypical necrosis that leads to permanent loss of the interdental papillaeFig. 13.7 Radiograph from the patient in Fig. 13.6 showing profoundvertical and horizontal loss of periodontal attachment. The bone level isat the apical third of the teeth, and tooth 18 has no attachment to thealveolar bone at all. (The normal bone level starts 1–2 mm below thecementoenamel junction.) Tooth 1 has a deep cemental (root) caries onthe mesial surface of the root. The calculus presents as small, triangular,radiopaque extensions on the root surface. Although small periodontallesions require intraoral radiography, panoramics usually offer a goodoverviewFig. 13.5 Typical histologicﬁndings for chronic periapicalperiodontitis (periapicalgranuloma) is granulomatoustissue inﬁltrated with lympho-cytes, plasma cells, andmacrophages. Some epithelialstrands are present
66113 Dental and Orofacial PathologyFig. 13.8 Gingival hyperplasia due to medication. This patient, whohad poor oral hygiene and chronic periodontitis, took a calcium channelblocker. Other medications that cause gingival overgrowth include anti-convulsants and cyclosporine. Systemic diseases that cause enlarge-ment are leukemia, Wegener’s granulomatosis, and sarcoidosis. Benignand malignant neoplasms of the gingival tissues and underlying boneshould be considered. Gingival changes that do not respond within10 days to cleaning and local disinfection should be reevaluated. Theunderlying cause of hyperplastic lesions must always be foundFig. 13.9 Patient with acute myelocytic leukemia. Massive swellingand bleeding on probing of the interdental papillae of the left side occureven though hardly any plaque is present. The gingiva is vulnerable andthe other oral soft tissues are pale. The general state of health of thepatient is poor. Improving oral hygiene and local disinfection will notimprove the gingival lesions; this patient needs oncologic therapyFig. 13.10 Partially retained third molar. Debris and plaque that haveaccumulated beneath the partial gingival covering of the tooth havecaused pericoronitis but are not visible in the radiograph. Teeth 31 and30 have profound proximal caries and must be ruled out as being non-vital by cold or electric pulp test, even though they show no apicalradiolucent lesionsFig. 13.11 Perimandibular abscess caused by an impacted third molar.The base of the mandible can no longer be palpated, the swelling ishard, and the patient has fever and difﬁculty swallowing. The mouthopening is severely limited
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 isclinically normalFig. 13.13 Radiograph from the patient in Fig. 13.12 showing that thedistal implant has a well-deﬁned radiolucent margin. Although theimplant is close to the inferior alveolar nerve and the cortical border ofthe nerve canal is no longer visible, no anesthesia is present. Peri-implantitis in this case is too far advanced for treatment. The rightimplant shows the beginning of peri-implantitis with vertical loss ofalveolar bone
66313 Dental and Orofacial PathologyNormal Anatomy and VariantsExostosis and ToriBony 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 thejaws, 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 themandibula in the premolar region. Symmetric bilateralappearance is a good diagnostic aid to differentiate betweentori and tumorous growth.Mandibular Salivary Gland Defect(Stafne Cavity/Cyst)This bone depression on the lingual aspect of the mandiblecontains 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 panoramicradiographs, the defect is located below the mandibular canal,between the angle of the mandible and the ﬁrst molar; it is seenas a unilocular, corticated radiolucency. CT scans or cone-beamCT imaging will show a lingual depression with a preservedcortex with soft tissue content. Sialography sometimes showsan accessory lobe of the submandibular salivary gland.Differential diagnosis includes eosinophilic granuloma orimmature 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 OsteonecrosisOsteomyelitisOdontogenic infections may cause osteomyelitis. The mostcommon causes of osteomyelitis are apical inﬂammation andperiodontal disease, infected cysts, and dental surgery duringthe acute phase of an infection. Osteomyelitis occurs mainlyin the mandible; maxillary involvement is rare. Teeth may behypermobile, and paresthesia of the inferior alveolar nervemay 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 ofthe mandible. Sequestra may be present. In chronic forms, thosediffuse radiolucencies appear next to diffuse radiopaque areas.The affected area appears ill-deﬁned and may show a moth-eatenappearance. Periosteal reaction is common in later stages.Imaging methods include CT scans, which are best able to detectsequestra, and scintigraphy, which shows increased metabolicactivity before conventional radiographs show bone alterations.OsteoradionecrosisOsteoradionecrosis (ORN) is a severe, difﬁcult-to-manage oralcomplication of radiation therapy in head and neck cancer treat-ment. Radiation causes cell changes in the oral mucosa and thedentinoenamel junction of the teeth. Salivary glands also areaffected, and xerostomia is a frequent result. The alveolar boneis 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 ofthis altered bone. Wound healing is slow or absent, allowingexposed bone and ﬁstulae to follow. Often, parts of the bone willsequestrate, and partial loss of the mandible is possible.The risk of ORN increases with radiation dose, tumor sizeand location, local trauma, dental surgery, periodontal anddental infection, immune defects, malnutrition, and abuse oftobacco or alcohol.Diagnosis is made by clinical appearance. Conventionalradiography and CT scans often underrepresent the lesions,as demineralization frequently becomes visible only duringlate stages of the disease.Bisphosphonate-Related Osteonecrosisof the JawPatients who receive bisphosphonates, especially in the man-agement of malignancy affecting the skeleton (either primaryor metastatic), are at a high risk of developing bisphospho-nate-related osteonecrosis of the jaw (BONJ). Cofactors thatseem to promote the disease are immunosuppression, dentalinfection 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, thealveoli 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 onesrequire treatment under hospital conditions, with removal ofnecrotic bone and histologic evaluation to rule out metastaticdisease. Treatment of patients with ORN and BONJ is notalways 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 sharpedges on teeth and dentures, and establishment of good den-tal hygiene before intravenous bisphosphonate therapy com-mences. If dental procedures are necessary, they should beundertaken according to appropriate guidelines.
664 C. Nobel et al.a bcFig. 13.14 Loss of a maxillary implant due to peri-implantitis and dis-placement into the maxillary sinus (a). On a panoramic radiographtaken for prosthetic rehabilitation planning purposes (b), the anterior ofthe angulus beneath the alveolar nerve canal contains a homogenous,well-deﬁned radiolucency. This lesion was previously unknown, andthe 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 lesionFig. 13.15 Clinical appearance of a patient with bisphosphonate-related osteonecrosis of the jaw. Bisphosphonates are administeredintravenously to treat patients with cancer who have hypercalcemiaassociated with malignant disease such as multiple myeloma or meta-static tumors (breast, lung, prostate) in the bones. This patient receivedzolendronate for breast cancer. After simple extraction of the teeth, thewound showed no healing. This is the typical appearance of BONJ: alarge area of nonvital bone is no longer covered by mucosa, and second-ary infection leads to purulent discharge. The surgical management ofBONJ includes antibiotic therapy, surgical debridement of the necroticbone, and primary closure of the woundFig. 13.16 A cropped panoramic radiograph from the patient inFig. 13.15 shows that the alveoli of the teeth are still present 16 weeksafter 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
66513 Dental and Orofacial PathologyFig. 13.17 Histologically, BONJis characterized by active acuteinﬂammation, acellular necroticdebris, thin-walled and dilatedblood vessels, basophilic bonespiculae with scalloped bordersshowing prominent boneresorption, and often an absenceof osteoblasts and osteoclasts
666 C. Nobel et al.Table 13.1 Classiﬁcation of jaw cystsEpithelium-lined cystsDevelopmental origin/odontogenicGingival cyst of infantsOdontogenic keratocystaDentigerous cystEruption cystGingival cyst of adultsDevelopmental lateral periodontal cystBotryoid odontogenic cystGlandular odontogenic cystCalcifying odontogenic cystDevelopmental origin/nonodontogenicMidpalatal raphe cyst of infantsNasopalatinal duct cystNasolabial cystInﬂammatory originRadicular cyst, apical and lateralResidual cystParadental cyst and juvenile paradental cystInﬂammatory collateral cystNon-epithelium-lined cystsSolitary bone cystAneurysmal bone cystaThe odontogenic keratocyst is now considered a tumor because of itsgenetic properties and behaviorCysts of the JawsEpithelium-Lined CystsThe classiﬁcation of cysts of the jaw by Shear, published in1996 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 developmentalorigin, is now classiﬁed as an odontogenic tumor owing to itsbehavior, high recurrence rates, and the detection of tumor-suppressor genes. One possible classiﬁcation distinguishesepithelium-lined cysts of developmental and inﬂammatoryorigin from nonepithelial cysts (pseudocysts).The most common developmental cysts are dentigerous(follicular) cysts, which are associated with the follicle of anunerupted or impacted tooth. These cysts are found inciden-tally or because the tooth fails to erupt. They grow throughthe accumulation of ﬂuid between the enamel epithelium andthe crown of a tooth (most often third molars, maxillarycanines, or mandibular premolars). The cyst always attachesat the cementoenamel junction, so radiographic features are ahomogenous round or oval translucency around the crown ofan unerupted and sometimes displaced tooth. The borders ofthe lesion are corticated, and neighboring structures such asroots, the base of the antrum, or the alveolar nerve canal aredisplaced. Histologically, the lining consists of a thin layer ofstratiﬁed 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 residuesof the embryonic nasolacrimal duct or the fusion of the pro-cessus maxillaris and globularis. The location is in or nearthe 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 frontteeth, covered with normal mucosa.Radiologic features are a round translucency, often overly-ing the incisor teeth, with corticated borders. The nasal ﬂooror 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 theanterior nasal spine into the cyst. Differential diagnosisincludes radicular cysts and a wide nasopalatinal foramen.Histologically, the lining consists of stratiﬁed squamousor ciliated epithelium or both. The walls often contain nervetissue and blood vessels.Inﬂammatory cysts, such as the radicular cyst, are alwayslinked with nonvital teeth. (Vitality is lost as a result of largecarious lesions, trauma, or, infrequently, deep pockets.)Inﬂammatory cells stimulate proliferation of Malassez cellrests in the apical region of the tooth, producing either apicalgranulomatous tissue or the development of a cystic cavity.Radicular cysts may grow to large dimensions before theybecome painful owing to infection or pathologic fracture. Ifa tooth is removed without curettage of the apical cystic tis-sues, the remnants are called residual cyst. They are mostlyasymptomatic, and bony expansion may be the ﬁrst clinicalsign. Diagnosis may be difﬁcult without the patient’s historyor histology, because odontogenic tumors like unicysticameloblastoma or keratocystic odontogenic tumor some-times present a similar, unilocular radiolucency withoutobvious dental origin.Histologically, the cyst is lined by stratiﬁed squamousepithelium, which shows varying degrees of thickness andrete pegs, according to the degree of inﬂammation. Hyalinebodies, inﬂammatory inﬁltrate, and cholesterol crystals maybe present in the ﬁbrous walls.
66713 Dental and Orofacial PathologyNon-Epithelium-Lined CystsThe 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 presentas multiloculated, mostly corticated radiolucencies, whichexpand and thin the cortex of the mandible as they grow.Macroscopicallyandhistologicallytheyappearasblood-ﬁlledcaverns 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 themandible of a young adult, which is either empty or ﬁlled withserous or bloodlike ﬂuid. The etiology is unknown. The cyst israrely painful and is often found by chance. Radiologically, itoften presents as a well-deﬁned, scalloped radiolucency thatextends between the roots of the teeth. These cysts are foundmainly in the posterior region of the mandible and are sometimesassociated with ﬁbrous dysplasia or cemento-osseous lesions.Fig. 13.18 Scintigraphy is the most sensitive imaging modality fordetecting early metastatic involvement. It shows intense radionuclideactivity in the jaw and metastatic bone diseaseFig. 13.19 Patient with two impacted and displaced third molars. Theleft molar shows a pericoronal well deﬁned radiolucency, which beginsat the cementoenamel junction. This is the typical appearance of a smalldentigerous (follicular) cyst. The right third molar is displaced into theramus. It also shows a pericoronal, well-deﬁned radiolucency. The cor-tex of the mandible is thin, scalloped, and shows expansion. Rootresorption 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
668 C. Nobel et al.Fig. 13.20 Histologically afollicular or dentigerous cystshows a thin, regular layer ofcuboidal epithelium (reducedenamel epithelium) or nonkerati-nized, stratiﬁed squamousepithelium lining withﬁbromyxomatous connectivetissue free from inﬂammatory cellinﬁltration
66913 Dental and Orofacial Pathologya bFig. 13.21 Panoramic (a) and occlusal views (b) of a patient with anasopalatinal duct cyst. Nasopalatinal duct cyst is a common develop-mental nonodontogenic cyst that occurs predominantly in men in thefourth 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 displacementcan be seen. The nasopalatinal foramen is no longer visible and theanterior nasal spine projects into the cyst. Clinically, patients report aslow-growing swelling behind the incisors, in the area of the incisivepapilla. The mucosa is normal, and the swelling is mostly soft, as thereis no bone coveringFig. 13.22 Squamous cellepithelium and ciliaryrespiratory-type epithelium arealmost always observed innasopalatinal duct cysts. The wallmay be ﬁbrous tissue, or it maycontain nerve and blood vesselsbecause of its location within thenasopalatinal foramen
670 C. Nobel et al.abFig. 13.23 The radicular cyst is the most common inﬂammatory cystin the second dentition. They rarely (in <0.5 % of cases) arise fromdeciduous teeth. (a) The radiograph shows a canine with root canalﬁlling and a homogenous, well-deﬁned radiolucency around the apex.The apex has an irregular shape because of resorption resulting fromlong-term infection. (b) The transverse view of the cone-beam CT scanshows the expansion of the alveolar ridge and the loss of vestibular andpalatinal cortex. Treatment options are enucleation with root resectionor extraction of the tooth
67113 Dental and Orofacial PathologyFig. 13.24 The thick wall of theradicular cyst consists of ﬁbroustissue, which is lined withstratiﬁed squamous epitheliumderived from the epithelial cellrests of Malassez. The initiationof inﬂammation and thefollowing epithelial proliferationare largely caused by bacterialtoxins, which originate in thenecrotic pulp chamber. Thecontent of radicular cysts is eithera yellowish ﬂuid containingcholesterol crystals or a brownﬂuid containing blood and itsproducts of decomposition
672 C. Nobel et al.acdbFig. 13.25 Residual cysts may arise from persisting tissue of radicularcysts after removal of the cause, the nonvital tooth. These cysts oftenremain asymptomatic and may ﬁll large parts of the mandible beforethey 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 withsharp, often sclerotic margins—unless infection is present. (b, c)Removal may be performed by either enucleation or marsupializationdepending on size; neighboring structures, such as the alveolar inferiornerve; and the general condition of the patient. (d) The macroscopicspecimen shows the capsule of ﬁbrous tissue, which (unless infected)separates easily from the alveolar bone
67313 Dental and Orofacial Pathologya bcFig. 13.26 (a) Cropped panoramic radiograph of a young woman withan adenomatoid odontogenic tumor involving the left upper canine. Thelesion presents as a sharply delineated radiolucency lateral to the vitaltooth. (b) Intraoral inspection shows a painless, hard vestibular swell-ing and a slightly displaced tooth. Canines are associated with morethan 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 withcentral spaces, which may contain small foci of calciﬁcation or homog-enous eosinophilic material
674 C. Nobel et al.Odontogenic TumorsThe WHO classiﬁes odontogenic tumors according to thetissue 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 themaxilla 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, alteredocclusion, and ill-ﬁtting dentures may be the ﬁrst clinicalsigns. Malignant odontogenic tumors are rare; they may arisein benign lesions as ameloblastomas or may represent pri-mary intraosseous carcinomas.Radiologic characteristics are varied. Because hard tissueforms within some tumors, those present as mixed lesions,radiolucencies with central radioopacities. The radioopaci-ties may vary in intensity and increase over time. Typicalexamples are the common odontomas, the less common ade-nomatoid odontogenic tumor, calcifying cystic odontogenictumor, calcifying epithelial odontogenic tumor, and the rareameloblastic odontoma and ameloblastic ﬁbro-odontoma.Other lesions present as multilocular radiolucencies. Themost 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 mucoepidermoidcarcinoma, and glandular odontogenic cyst.Central giant cell granuloma, aneurysmal bone cyst, andcherubism 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. Malignanttumors must be radically resected. Locally aggressive lesionssuch as the ameloblastoma or myxoma require resection withan adequate margin. The rate of recurrence with enucleationand curettage is high, and the lesion may recur after morethan 10 years. Keratocystic odontogenic tumor, ameloblasticﬁbroma, and the calcifying epithelial odontogenic tumor alsohave a high recurrence rate. They need in sano resection,with a small safety margin. Odontomas and cementomasnormally may be treated by curettage and enucleation.AmeloblastomaThe most common benign tumors are ameloblastomas, kera-tocysticodontogenictumors,andodontomas.Ameloblastomasare locally aggressive. Four different clinical and histologicsubtypes are recognized: solid/multicystic ameloblastoma,peripheral ameloblastoma, desmoplastic ameloblastoma, andunicystic ameloblastoma (with intramural and intraluminalsubtypes),Posteriorpartsofthemandiblearethemostcommonlocationsfor multicystic ameloblastomas. Small ameloblastomas are foundincidentally; later, they may present as swelling of the jaws. Painand paresthesias or anesthesia of the chin and lip due to compres-sion of the inferior alveolar nerve occur seldomly. Radiographicsigns are multilocular radiolucencies, resorption of the roots, anderosion 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 clinicalfeatures and have a similar prognosis. Desmoplastic amelo-blastomas are similar to multicystic ameloblastomas but aremore often located in the anterior mandible.Table 13.2 Simpliﬁed classiﬁcation of odontogenic tumorsMalignant tumorsOdontogenic carcinomasMetastasizing (malignant) ameloblastomaAmeloblastic carcinomaPrimary intraosseous squamous cell carcinomaClear cell odontogenic carcinomaGhost cell odontogenic carcinomaOdontogenic sarcomasAmeloblastic ﬁbrosarcomaAmeloblastic ﬁbrodentinosarcoma and ﬁbro-odontosarcomaBenign tumorsOdontogenic epithelium with mature, ﬁbrous stroma withoutodontogenic ectomesenchymeAmeloblastomaSquamous odontogenic tumorCalcifying epithelial odontogenic tumorAdenomatoid odontogenic tumorKeratocystic odontogenic tumorOdontogenic epithelium with odontogenic ectomesenchyme, withor without hard tissue formationAmeloblastic ﬁbromaAmeloblastic ﬁbrodentinomaAmeloblastic ﬁbro-odontomaOdontomaOdontoameloblastomaCalcifying cystic odontogenic tumorDentinogenic ghost cell tumorMesenchyme and/or odontogenic ectomesenchyme with orwithout odontogenic epitheliumOdontogenic ﬁbromaOdontogenic myxoma/myxoﬁbromaCementoblastomaBone-related lesionsOssifying ﬁbromaFibrous dysplasiaOsseous dysplasiaCentral giant cell lesion (granuloma)CherubismAneurysmal bone cystSimple bone cystFrom Barnes et al. 
67513 Dental and Orofacial PathologyExtraosseous ameloblastomas occur in the sixth decadewithin the gingiva, either as remnants of the dental lamina orfrom the surface epithelium. They can be excised with asmall 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 animpacted wisdom tooth and presents as a unilocular, peri-coronal radiolucency. Intraluminal ameloblastomas have alow recurrence rate and may be treated with enucleation. Ifhistologic examination shows an intramural ameloblastoma,subsequent bloc resection may be necessary, as the recur-rence rate is high.Keratocystic Odontogenic TumorKeratocystic odontogenic tumors are unilocular or multiloc-ular radiolucencies, often associated with impacted and dis-placed teeth and occurring mainly between the ages of 10and 40. Most appear in the posterior mandible; only one thirdaffect the maxilla.Recurrence rates are high, perhaps because of the thinepithelial layer, satellites of the epithelium spreading into thesurrounding connective tissue, and remains of the tumor aftersimple enucleation. If multiple tumors are present or theyappear 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 nevoidbasal cell carcinoma (Gorlin’s) syndrome, which is auto-somal dominant. Other symptoms that occur in more than50 % of patients are epidermal cysts of the skin, occult spinabiﬁda, rib anomalies, calciﬁed falx cerebri, and diaphragmasellae. The paranasal sinus may be hyperpneumatized.Medulloblastomas in young children have been described.OdontomasOdontomas are hamartomas that consist of common enamel,dentin, and sometimes cementum and pulp tissue. The WHOclassiﬁes two subtypes, compound and complex. Enamel,dentin, and sometimes cementum and pulp tissue are presentin both types, but compound odontomas resemble multiplemalformed toothlike structures, whereas the hard tissues incomplex odontomas are much less organized.The radiographic appearance of a complex odontomaconsists of a roundish, inhomogeneous radiopacity with aradiolucent margin. This margin will decrease in size as thehard tissue formation continues. Both forms of odontomasare found mainly in young children or adolescents, oftenbecause permanent teeth fail to erupt.Multiple odontomas and osteomas of the jaws may be a signof Gardner syndrome. Other symptoms are multiple intestinalpolyposis 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 forgrowth. Both the maxilla and mandible are often affected. Theradiographic appearance resembles cotton wool.Osseous DysplasiaOsseous dysplasia occurs in the tooth-bearing parts of themaxilla and mandible and probably arises from the periodon-tal ligament. The etiology is unknown; there is a predilectionfor middle-aged black women. The radiographic appearancevaries 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.) Laterstages 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, lamellarbone, and woven bone without a capsule. Cementum-likestructures may be found, but because it is unclear whetherthey really represent odontogenic cementum, the termcemento-osseous dysplasia is no longer used.Often the lesions are asymptomatic and found during rou-tine examination. They require no therapy, except for ﬂoridforms or the closely related gigantiform cementoma. Bothmay 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 withdiffuse borders have been described. Ameloblastic carcino-mas and primary intraosseous squamous cell carcinomas orthose 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 alveolarnerve is involved; and hypermobility of teeth.
676 C. Nobel et al.acbFig. 13.27 Multilocular cystlike appearance of an odontogenic tumorin the left mandible of a 45-year-old woman (a). Borders are poorlydeﬁned and the internal structure contains coarse and ﬁne septa. In atransverse 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 30and 50 years are typical for odontogenic myxoma (c). Odontogenicmyxoma 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. Ifcollagen ﬁbers dominate in the stroma, the tumor may be designated asodontogenic myxoﬁbromaa bFig. 13.28 Ameloblastoma (also referred to as adamantinoma) withthe typical multilocular, “soap bubble” radiologic appearance (a). Thecortex is thinned but root resorption is minimal, involving only the apexof tooth 27. The mandible is involved more than four times as often asthe maxilla. Clinical signs include swelling but seldom includeparesthesia or hypoesthesia of the alveolar inferior nerve. Follicularameloblastoma with cystic changes (b) shows basal cells lined up in apalisaded fashion with columnar cells with reversed polarity of theirhyperchromatic nuclei, surrounding a core of loosely arranged polyhe-dral cells, resembling stellate reticulum. The latter may undergosquamous metaplasia and form keratin (not shown here)
67713 Dental and Orofacial Pathologya bFig. 13.29 (a) Keratocystic odontogenic tumors may present similarradiographic features as dentigerous cysts (root resorption and a scal-loped, thinned cortex) and involve the crown of an impacted tooth. Eventhough keratin is present in the center of the tumor, the internal struc-ture is usually radiolucent. (b) This keratocystic odontogenic tumor islined by ﬁve to eight layers of parakeratinized, stratiﬁed squamous epi-thelium with a well-deﬁned, palisaded basal layer of hyperchromaticcolumnar or cuboidal cells. Note the desquamated keratin in the cavityof this tumorFig. 13.30 Radiography shows two large, pericoronal, radiolucentlesions in a 12-year-old boy, representing two keratocystic odontogenictumors. 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 ofnevoid basal cell carcinoma syndrome (NBCCS, or Gorlin’s syndrome).Other signs are basal cell carcinomas under the age of 20, palmar andplantar pits, calciﬁcation of the falx cerebri, biﬁd ribs, and a ﬁrst-degreerelative with NBCCS
678 C. Nobel et al.acbFig. 13.31 Compound odontoma. This benign hamartoma comprisesmultiple malformed toothlike structures (a). On radiography (b), theradiopacity has a density that resembles enamel, dentin, and the follicleof multiple unerupted teeth. The eruption of permanent teeth may behindered, but growth is mostly self-limited and there is no recurrenceafter enucleation. Ameloblastic ﬁbro-odontoma (c) is composed of softand hard odontogenic tissue. The soft tissue component consists ofodontogenic ectomesenchyme with ameloblastoma-like epithelialstrands and islands in a myxoid cell–rich stroma. The hard tissue com-ponent is built of dentin and enamel in varying proportionsFig. 13.32 Osseous dysplasia, also known as periapical cemental dys-plasia or apical cementoma. A radiopaque central structure extendsaround the roots of the vital teeth 30 and 31. The margin is a radiolucentband. If asymptomatic, no treatment is necessary
67913 Dental and Orofacial Pathologya bFig. 13.33 Large osseous dysplasia adjacent to the root of an impactedwisdom 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 isthinned. Diagnosis is made by clinical and radiologic appearance.Elective tooth extraction should be avoided, as infection of the scleroticbone masses may result and lead to complications, as the internal struc-ture is predominantly avascular. The development of simple bone cystswithin or next to these lesions has been described
680 C. Nobel et al.a bcFig. 13.34 Fibrous dysplasia may be polyostotic or mono-osteitic andis often diagnosed in children or in young adults. (a) Symptoms includebone deformities and sometimes mild pain. When orofacial structuresare involved, misalignment of the teeth may result. Polyostotic ﬁbrousdysplasia, autonomous endocrine hyperfunction (which may result inprecocious puberty), and café-au-lait pigmentation are symptoms ofMcCune-Albright syndrome. (b) Radiologic features include homoge-neous opacities with a ground-glass appearance and loss of trabecularpattern. The maxilla of this man shows abnormal growth of the alveolarridge and zygomatic bone. (c) Fibrous dysplasia consists of irregularlyshaped trabeculae of immature bone in a cellular ﬁbrous stroma. Thebone trabeculae are considered to arise by metaplasia. They are not sur-rounded by osteoblasts. The lesional bone fuses directly to normal boneat the periphery of the lesion
68113 Dental and Orofacial PathologyFig. 13.35 Peripheral giant cellgranuloma shows a proliferationof multinucleated giant cells withup to 12 nuclei. The giant cells liein a stroma of plump, ovoidmesenchymal cells with severalmitotic ﬁgures (seen in the centerof the image) and hemorrhagicareas throughout the lesionReference1. Barnes L, Eveson JW, Reichart P, Sidransky D, World HealthOrganization, editors. Classiﬁcation of tumors. Pathology and genet-ics of head and neck tumors. Lyon: IARC Press; 2005.