Cemento Ossifying Fibroma

Cemento ossifying fibroma (ossifying fibroma) is a benign fibro osseous neoplasm of the jaw, composed of fibrous tissue with varying amounts of mineralised material resembling bone and cementum, enclosed in a well demarcated fibrous capsule. It is uncommon, with a peak at 20 to 40 years and a female predominance (about 5 to 1). The mandible is affected in about 70 to 90 percent, in the premolar molar region.

The cause is unknown; origin is from periodontal ligament cells with multipotent differentiation. A subgroup with HRPT2 (CDC73) mutation arises in hyperparathyroidism jaw tumour syndrome. Two aggressive variants occur in children and adolescents: juvenile trabecular ossifying fibroma and juvenile psammomatoid ossifying fibroma (the latter often in the sinonasal tract and orbit), with rapid growth and a recurrence rate of 30 to 50 percent.

Conventional lesions grow slowly, expand the jaw, and rarely recur after enucleation (under 10 percent). It is distinguished from fibrous dysplasia by its sharp demarcation and ease of enucleation.

• Slow growing, painless, firm, bony hard swelling of the jaw with buccal and lingual expansion and facial asymmetry.
• Displacement or divergence of tooth roots, malocclusion, tooth mobility; the overlying mucosa is normal.
• Large mandibular lesions: inferior border bowing, cortical thinning, pathological fracture.
• Maxillary or sinonasal tumours: nasal obstruction, proptosis, diplopia, sinus symptoms.
• Pain and paraesthesia are uncommon.
• Jaw tumour syndrome: hypercalcaemia features, kidney stones, parathyroid adenoma or carcinoma.
• Red flags: rapid growth in a child or adolescent, orbital extension, vision change, multiple lesions, and hypercalcaemia.

• Panoramic radiograph and CT: well circumscribed unilocular or multilocular lesion with a corticated margin, variable density from radiolucent (early) through mixed to dense radiopaque (mature), with a sclerotic rim and often a thin radiolucent halo; displacement of teeth and inferior alveolar canal; "egg shell" expansion.
• Cone beam CT or CT: extent, cortical perforation, orbit and skull base involvement.
• Biopsy: cellular fibrous stroma with spindle cells and mineralised tissue (trabeculae of woven bone, cementum like ossicles), sharply demarcated from surrounding bone; juvenile variants have trabeculae or psammoma like ossicles.
• Serum calcium, parathyroid hormone, and phosphate when the lesion is multiple, recurrent, or in a young patient.
• Exclude fibrous dysplasia (ground glass pattern with poor demarcation), cemento osseous dysplasia, osteoblastoma, cementoblastoma, central giant cell granuloma, ameloblastoma, and osteosarcoma.

• Surgical enucleation or curettage for conventional lesions: the tumour separates from the bone along the capsule; include peripheral ostectomy when feasible; preserve the inferior alveolar nerve.
• Large or recurrent lesions, and juvenile aggressive forms: resection with 0.5 to 1 cm bone margins, with reconstruction (fibula free flap or titanium plate) in the mandible; maxillary lesions need partial maxillectomy.
• Juvenile psammomatoid ossifying fibroma of the sinonasal tract: complete excision by endoscopic or open approach, with orbital and skull base decompression; adjuvant radiotherapy is avoided.
• Perioperative: cefazolin 1 g intravenously at induction (single dose, or every 8 hours for 24 hours for large resections); analgesia with paracetamol 1 g every 6 hours and ibuprofen 400 mg every 8 hours.
• Hyperparathyroidism jaw tumour syndrome: parathyroidectomy, genetic testing of CDC73, and screening of relatives.
• Complications: fracture, nerve injury, infection, orocutaneous fistula, and recurrence.
• Follow up: clinical and radiographic review every 6 months for 2 years, then yearly for at least 5 years; juvenile forms need closer follow up (every 3 months for the first year).
• Counselling: benign nature; recurrence risk is greater in young patients; rehabilitation of dentition.