Cemento-osseous dysplasia

Cemento-osseous dysplasia (COD) is the most common benign fibro-osseous lesion of the jaws and is non-neoplastic and self-limiting.[1][2] It arises exclusively in the tooth-bearing regions, with a strong mandibular predominance, and is thought to originate from cells of the periodontal ligament, which accounts for its intimate periapical relationship and its content of both bone and cementum-like material.[2][3][4] The etiology is otherwise unknown, although recent sequencing implicates activation of the RAS-MAPK pathway in a subset of cases.[5]

Normal medullary bone is progressively replaced by fibrous tissue that mineralizes over time, producing the signature evolution from a radiolucent lesion to a mixed and ultimately densely radiopaque lesion retaining a thin peripheral radiolucent rim.[6][7] Most lesions are discovered incidentally and require no treatment; recognition matters chiefly to avoid unnecessary endodontic or surgical intervention and to prevent secondary infection of the poorly vascularized mineralized masses.[3][8]

The 2017 and 2022 WHO classifications use "cemento-osseous dysplasia" (the 2005 edition used "osseous dysplasia"); the term reflects the cementum-like calcifications.[9] Classification is based on anatomic distribution rather than histology, since all forms share identical microscopy.[1][5]

• Periapical COD — localized to the periapical region of the mandibular anterior teeth.[1][10]
• Focal COD — a single site, typically the posterior jaws, most often the posterior mandible.[1][4]
• Florid COD — multifocal, involving two or more quadrants, frequently bilateral and symmetric.[3][9]
• Familial florid COD — a rare autosomal dominant presentation recognized as a distinct subtype.[11][12]

Obsolete terms that still cause confusion include cementoma and periapical cemental dysplasia (for the periapical form) and cemental dysplasia.[9][10] Familial gigantiform cementoma is a separate, more aggressive hereditary entity and should not be conflated with familial florid COD.[9]

COD overwhelmingly affects middle-aged women, most commonly in the fourth and fifth decades, with a pronounced predilection for individuals of African descent and a recognized, somewhat later-onset pattern in East Asian populations.[1][2][4] In one large focal-COD cohort, 89% of patients were women and 64% were Black.[22] East Asian series report a mean age near 47 years.[4]

• Site — the mandible is affected far more often than the maxilla; in florid disease the mandible is essentially always involved and the maxilla in roughly two-thirds of cases.[9]
• Distribution — periapical disease centers on the mandibular incisors, focal disease on the posterior mandible, and florid disease across multiple quadrants.[1][4]
• Detection — the majority are asymptomatic and found incidentally on routine imaging, so true prevalence is likely underestimated because the diagnosis is made clinically and radiographically without biopsy.[1][8]

Most patients are asymptomatic, and the lesion is identified on radiographs obtained for unrelated reasons.[3][8] The associated teeth are vital and respond normally to pulp testing, a feature central to distinguishing COD from inflammatory periapical disease.[7][12]

• Tempo — slow growth followed by spontaneous stabilization; lesions mature and mineralize over years, and expansion is uncommon. When expansion occurs it is almost always in the florid subtype.[1][5][9]
• Symptoms — pain, swelling, and drainage are generally secondary to infection rather than to the dysplasia itself.[13][14]
• Complications and red flags — the mature masses are sclerotic and hypovascular, predisposing to secondary infection, bone sequestration, and chronic osteomyelitis that is difficult to treat and responds poorly to antibiotics. Risk rises with mucosal breakdown over the lesion, as beneath ill-fitting tissue-borne dentures in edentulous ridges, or after extraction, advanced periodontitis, or endodontic manipulation. New-onset rapid growth, marked expansion, paresthesia, or pain in the absence of infection should prompt reconsideration of the diagnosis.[3][9][10][13][15]

The radiographic appearance is often diagnostic, and the pattern of distribution defines the subtype.[3][4] Lesions evolve through recognizable stages, so appearance depends on maturity at the time of imaging.[6][7]

Location and distribution

• Confined to tooth-bearing/alveolar bone, centered on the periapical region.[2][3]
• Periapical form clusters at the mandibular incisor apices; focal form is solitary, usually in the posterior mandible; florid form is multiquadrant and frequently bilateral and symmetric.[1][4][9]
• Lesions remain anchored to the alveolus and, in edentulous patients, the calcified masses persist in the ridge rather than resorbing with the alveolar bone after tooth loss.[10]

Relationship to teeth and the alveolar process

• Centered on root apices of vital teeth, superimposed on or replacing the periapical trabecular bone.[3][7]
• The periodontal ligament (PDL) space can often be traced around the apex, although the apical lamina dura may be lost; pulp vitality is the key discriminator.[9]

Periphery and shape

• Individual lesions are usually well defined and surrounded by a thin radiolucent rim, often with an outer sclerotic band.[7][9]
• In the mature periapical form this yields a characteristic target or bull's-eye appearance around each apex.[9]
• Radiographically COD is usually well defined, but it is unencapsulated and blends histologically with adjacent bone; cemento-ossifying fibroma is typically sharply demarcated and concentrically expansile, and may displace teeth. Focal lesions are variably described with well-defined or more ill-defined margins.[4][11]

Internal architecture

• Radiolucent in the early osteolytic phase, mixed in the intermediate cementoblastic phase, and densely radiopaque in the mature osteogenic phase, always retaining the peripheral radiolucent rim.[6][7]
• Mature florid disease produces lobulated, confluent radiopaque masses; coalescence yields the classic cotton-wool pattern reported in roughly half of COD cases.[9][12]

Effects on adjacent structures

• Effects on teeth are generally minimal; tooth displacement and root resorption are each uncommon, each present in roughly one in seven cases in a mixed fibro-osseous series, with root resorption regarded as a marker of lesion severity.[12]
• Cortical expansion is not a usual feature and, when present, favors florid disease; sectional imaging shows that cortical thinning, expansion, and even perforation occur more often than conventional films suggest. Inferior displacement of the inferior alveolar nerve canal can occur in extensive florid lesions.[2][9][16]

Recognized variants

• Well-defined radiolucent zones alongside the mineralized masses represent associated simple (traumatic) bone cysts, a recognized accompaniment of florid COD.[9][10]
• Secondary infection alters the picture, producing an irregular lucency with a central hyperdense focus corresponding to a sequestrum.[2]

COD is distinguished primarily by its periapical location at vital teeth, its characteristic lucent-to-radiopaque maturation with a radiolucent rim, and its lack of true expansion; pulp vitality testing and whole-jaw imaging resolve most diagnostic uncertainty.[4][7][12] The entities below are the lesions most often mistaken for it.

The highest-risk pitfall is treating early osteolytic or infected COD as endodontic disease: root canal therapy or periapical surgery on vital teeth is unnecessary and, by breaching hypovascular dysplastic bone, can precipitate chronic osteomyelitis.[3][7] Pulp vitality testing and panoramic survey of all quadrants should precede any intervention; biopsy is reserved for atypical focal lesions where cemento-ossifying fibroma cannot be excluded, because needless biopsy itself risks secondary infection.[4][12]

All three subtypes are histologically identical, so microscopy alone cannot subclassify the lesion.[1][5] COD is unencapsulated and consists of a cellular, well-vascularized fibroblastic stroma of variable cellularity containing a heterogeneous mineralized component of woven bone and rounded cementum-like deposits.[1][12] The stroma frequently harbors extravasated red blood cells, and lesional bone characteristically merges directly with adjacent native bone rather than being demarcated from it.[12] Osteoblastic rimming of the trabeculae is uncommon, a useful contrast with ossifying fibroma.[1][11]

As lesions mature, cellularity declines while the woven bone and cementum coalesce into larger, heavily mineralized, hypocellular masses that correspond to the radiopaque imaging phase.[1][16] The lesion is benign; malignant transformation is exceptionally rare.[1]

Radiologic-pathologic correlation

The proportion of fibrous to mineralized tissue tracks the imaging stage: immature radiolucent lesions are fibrous-rich, whereas mature radiopaque lesions are dominated by confluent mineralized matrix.[16] The avascular, sclerotic nature of mature masses explains both the dense radiographic appearance and the clinical susceptibility to infection and sequestration.[10][13]

Molecular findings

Targeted sequencing identifies activating RAS-MAPK pathway mutations (BRAF, HRAS, KRAS, NRAS, FGFR3) in roughly a quarter of cases, with additional alterations such as NOTCH4 reported.[5][11] Critically, COD lacks the GNAS mutations of fibrous dysplasia and the SATB2 rearrangements of psammomatoid ossifying fibroma, and methylation and copy-number profiling can separate benign fibro-osseous lesions from low- and high-grade osteosarcoma in difficult cases.[1][17] Immunohistochemistry for non-collagenous bone matrix proteins has not proven reliable for distinguishing COD from fibrous dysplasia or ossifying fibroma.[18]

For asymptomatic disease, the diagnosis is established by clinical and radiographic correlation, and no treatment is required beyond periodic clinical and radiographic follow-up.[3][8] Periapical and florid forms are generally diagnosed without biopsy; the focal form more often warrants biopsy to exclude cemento-ossifying fibroma when radiographic features are atypical or expansile.[10][12]

Preventive measures

Because the mature masses are hypovascular and heal poorly, prevention of infection is central.[9][10] Practical measures include:

• Meticulous oral hygiene and prompt management of caries and periodontal disease to avoid odontogenic infection.[9]
• Avoidance of elective extractions, implant placement, and unnecessary surgery in affected bone, and caution with tissue-borne dentures that can perforate the mucosa over the lesion.[9][10]
• Confirming pulp vitality before any endodontic intervention.[7]

Treatment of complications

Secondary infection converts an observation lesion into a surgical problem. When osteomyelitis or sequestration develops, antibiotics alone are frequently inadequate owing to poor lesional penetration, and surgical intervention, typically curettage or sequestrectomy with removal of nonviable bone and soft-tissue coverage such as a buccal fat pad flap, is used to arrest progression; wound dehiscence and the need for repeat surgery are recognized.[13][19] When infection stems from an adjacent tooth, appropriate endodontic therapy of that tooth can resolve symptoms conservatively.[14]

Outcome and prognosis

The prognosis is excellent. Lesions are self-limiting, stabilize spontaneously, and malignant change is exceptionally rare; new lesions may nonetheless appear elsewhere in the jaws over time.[1][4] The principal determinants of outcome are not the dysplasia itself but the prevention and control of secondary infection, which is more likely in extensive florid and edentulous disease.[9][13]