Peripheral ossifying fibroma

Peripheral ossifying fibroma (POF) is a benign reactive hyperplastic lesion that occurs exclusively on the gingiva.[1] It is the most common reactive fibro-osseous process affecting the gingival soft tissues.[2] The lesion is thought to arise from cells of the periodontal ligament or gingival periosteum, driven by local irritants such as dental plaque, calculus, microorganisms, masticatory forces, ill-fitting restorations, or trauma.[3] Whether POF represents a true reactive process or a neoplastic one remains debated; however, the prevailing view favors a reactive hyperplastic pathogenesis.[1][3] The lesion characteristically presents as a well-circumscribed gingival mass, most often arising from the interdental papilla, and contains variable amounts of mineralized tissue including bone, cementum-like material, and dystrophic calcifications within a fibrocellular stroma.[1][4] On dental radiographs, scattered radiopaque foci may be visible within or superimposed on the soft tissue mass. Management is excisional biopsy with removal of local irritants; recurrence is a recognized concern.

• Peripheral ossifying fibroma (POF) is the currently accepted name in oral pathology and is the term used in standard texts and major classification systems.[1][2]
• POF is classified as a reactive gingival lesion, distinct from the central (intraosseous) ossifying fibroma, which the WHO classifies as a benign fibro-osseous neoplasm of bone.[5][6]
• Before the 1980s, the terms "peripheral ossifying fibroma" and "peripheral odontogenic fibroma" (POdF) were used interchangeably, particularly in North America. These are now recognized as two separate entities: POF is defined by the presence of bone and mineralized tissue without a significant odontogenic epithelial component, whereas POdF contains odontogenic epithelium as a defining feature.[2][7]
• The combined term "peripheral odontogenic (ossifying) fibroma" is obsolete and should be avoided.[2]
• Synonyms occasionally encountered in older literature include "peripheral cementifying fibroma" and "peripheral cemento-ossifying fibroma"; these reflect historical emphasis on the type of mineralized product and are no longer preferred.

• POF is one of the most common gingival growths, accounting for approximately 18% of reactive hyperplastic lesions of the gingiva and alveolar ridge.[8][9]
• There is a clear female predominance, with women representing approximately 70–72% of cases.[1][4]
• Peak incidence occurs in the third and fourth decades of life, though POF can present across a wide age range.[1][4]
• The anterior maxillary gingiva is the most frequently affected site, followed by the anterior mandibular gingiva. Lesions characteristically arise from the interdental papilla.[1][3]
• Most lesions are smaller than 2 cm at diagnosis.[1][4]

Presentation and examination findings

• POF presents as a well-circumscribed, exophytic gingival mass that is typically pedunculated, though sessile forms occur. The lesion most commonly arises from the interdental papilla and may extend facially or lingually.[3][8]
• Color ranges from normal mucosal pink to erythematous or reddish, depending on the degree of vascularity, inflammation, and surface ulceration. Lesions with a higher mineralized content may feel firm to palpation, whereas less mature or ulcerated lesions may be softer.[8]
• Surface ulceration is common and is associated with dystrophic calcification within the lesion.[1]
• Growth is typically slow and progressive. Most lesions are painless, though discomfort may occur with ulceration or secondary infection.

Complications and red flags

• Tooth displacement and widening of the interdental space may occur with larger or long-standing lesions.
• Superficial erosion or cupping of the underlying alveolar crestal bone can develop from pressure resorption.
• Recurrence after excision is a well-recognized complication (see Management).
• Rapid growth, large size, or unusual clinical behavior should prompt consideration of alternative diagnoses, including peripheral giant cell granuloma or, rarely, a malignant process.

POF is a soft tissue lesion of the gingiva; therefore, it does not produce a primary intraosseous radiolucency or radiopacity. Radiographic findings are limited to changes visible within the soft tissue mass and secondary effects on adjacent hard structures. Many POFs are radiographically occult on conventional dental radiographs, and the diagnosis is primarily clinical and histopathologic.[1][4]

Location and distribution

• The lesion is confined to the gingival soft tissues and is most commonly located in the anterior maxilla, followed by the anterior mandible.[1][3]
• It characteristically arises from the interdental papilla region, projecting from the alveolar crest between adjacent teeth.[3]

Internal architecture

• When mineralization is sufficient, scattered radiopaque foci may be visible within the soft tissue mass on periapical or panoramic radiographs. These foci correspond histologically to deposits of mature or immature bone, cementum-like material, or dystrophic calcifications.[1][4]
• The pattern of internal calcification is variable and reflects the maturation stage of the lesion. Early or immature lesions are commonly radiolucent (i.e., the soft tissue mass shows no discernible radiopacity), while more mature lesions develop increasingly conspicuous radiopaque deposits.[1]
• On CBCT, the mineralized foci are more readily identified than on two-dimensional radiographs. The calcifications appear as discrete high-density foci scattered within a soft tissue density mass, without a defined capsule or corticated border within the mass itself.

Periphery and shape

• The lesion presents as a well-circumscribed, dome-shaped or lobulated soft tissue mass projecting from the gingival surface.
• There is no bony cortex surrounding the lesion, as it is entirely extraosseous. The interface between the mass and the underlying alveolar bone is typically smooth.

Effects on teeth and adjacent structures

• Displacement of adjacent teeth and widening of the periodontal ligament space may be seen occasionally with larger lesions.
• Superficial erosion or saucerization of the alveolar crestal bone beneath the lesion is an occasional finding, resulting from pressure resorption by the overlying mass.
• Root resorption of adjacent teeth is uncommon but has been reported in isolated cases.
• The lamina dura of adjacent teeth is typically preserved unless there is concurrent periodontal disease.

Growth pattern and extent

• POF is a slow-growing, expansile soft tissue mass that remains confined to the gingiva. It does not invade the underlying bone.
• Most lesions are less than 2 cm at diagnosis. Rarely, neglected lesions may reach larger dimensions.[1][4]

Recognized variants and pitfalls

• The degree of internal mineralization varies widely; a completely radiolucent POF on conventional radiographs is common and does not exclude the diagnosis.
• When radiopaque foci are present within a gingival mass on periapical radiographs, they may be superimposed on the roots or alveolar crest, potentially mimicking periapical pathology or a calculus deposit. Correlation with the clinical examination is essential.
• CBCT can help confirm the extraosseous location of the mass and exclude an intraosseous origin, which is the key distinction from central ossifying fibroma.[5]

The clinical differential diagnosis of a gingival soft tissue mass with or without radiographic calcification centers on the group of reactive hyperplastic lesions of the gingiva. These entities share overlapping clinical presentations—exophytic, well-circumscribed gingival masses—and definitive distinction requires histopathologic examination.[8][9]

The highest-risk diagnostic pitfall is failing to distinguish POF from peripheral giant cell granuloma, as the latter may produce more aggressive superficial bone resorption and has a higher recurrence rate if incompletely excised. All exophytic gingival masses should be submitted for histopathologic examination following excisional biopsy to establish a definitive diagnosis.[8][9]

Diagnostic microscopic findings

• POF consists of a proliferation of moderately cellular fibrous connective tissue covered by stratified squamous epithelium. The stroma is composed of spindle-shaped fibroblasts and myofibroblasts arranged without a discernible architectural pattern.[1][4]
• The defining feature is the presence of mineralized tissue within the fibrous stroma. This mineralized component exists along a spectrum and may include:[1][4]
  • Mature lamellar bone — the most common mineralized product, present in the majority of cases
  • Immature (woven) bone — frequently seen, particularly in smaller or more recently developed lesions
  • Cementum-like material — basophilic, acellular, ovoid deposits
  • Dystrophic calcifications — amorphous mineralized deposits, often associated with surface ulceration
• Most lesions contain a combination of these mineralized products, supporting the concept that they represent a maturation continuum.[1]

Surface and inflammatory features

• Surface ulceration is common and is frequently accompanied by an acute or chronic inflammatory infiltrate, fibrin deposition, and bacterial colonization.[1][9]
• The intact surface epithelium may show hyperplasia. Rarely, florid pseudoepitheliomatous hyperplasia adjacent to areas of transepithelial elimination of bony sequestrae can mimic squamous cell carcinoma; awareness of this pitfall prevents misdiagnosis.[2]

Immunohistochemistry and radiologic-pathologic correlation

• Stromal cells stain positively for smooth muscle actin and CD68, consistent with myofibroblastic differentiation. These markers do not predict biologic behavior.[4]
• The variable radiographic density of POF directly reflects the type and quantity of mineralized tissue: lesions rich in mature bone produce more conspicuous radiopaque foci, while those with predominantly immature bone or dystrophic calcification may be radiographically occult.[1]
• Lesions containing cementum-like material without bone formation may have a higher recurrence rate, suggesting that the absence of osseous maturation could be a marker of incomplete differentiation.[4]

Distinction from related entities

• POF is distinguished from peripheral odontogenic fibroma by the absence of odontogenic epithelial islands.[2][7]
• Unlike central ossifying fibroma, POF lacks a fibrous capsule separating it from adjacent bone and is entirely extraosseous.[5]

Treatment

• Excisional biopsy is the standard treatment. The lesion should be excised down to the periosteum, including the base and a margin of clinically normal tissue. Thorough curettage of the underlying bone surface and removal of local irritants (calculus, plaque, defective restorations) from adjacent teeth are recommended to reduce recurrence risk.[3][11][12]
• Aggressive excision in the anterior maxilla can produce esthetic gingival defects. Soft tissue grafting procedures—including subepithelial connective tissue grafts, laterally positioned flaps, or coronally positioned flaps—can be performed simultaneously or as a secondary procedure to restore gingival contour.[3][11]
• For recurrent lesions, re-excision with a wider margin (1–2 mm of normal tissue), removal of the underlying periosteum, and curettage of adjacent bone and periodontal ligament are recommended.[12]

Recurrence

• Recurrence rates are reported at approximately 16–20%. Incomplete excision and failure to eliminate local irritants are the primary risk factors.[4][11]
• Lesions containing predominantly cementum-like material without bone formation may carry a higher recurrence risk.[4]
• No reliable histologic feature predicts recurrence with certainty.

Surveillance and prognosis

• Clinical follow-up at regular intervals for at least 12 months after excision is advisable, with attention to the excision site for signs of regrowth.
• Prognosis is excellent. POF does not undergo malignant transformation. Morbidity is limited to local recurrence and potential esthetic compromise from surgical defects in the anterior region.