Cementoblastoma

Cementoblastoma is a rare benign odontogenic tumour of cementum forming cells, attached to the root of a tooth. It makes up under 1% of odontogenic tumours.

It affects patients under 30 in about half of cases, with equal sex distribution, and the mandibular first permanent molar and premolars are the usual site. The tooth is vital and pain is a common feature.

Pathophysiology. The tumour arises from cementoblasts and produces mineralised cementum like tissue fused to the root and replacing the periodontal ligament space. Peripheral growth leads to expansion of the cortex.

It grows slowly but continuously, and it can resorb the root. The mass is surrounded by a thin fibrous capsule and a radiolucent rim.

Pain in more than half, swelling of the jaw, cortical expansion and tooth displacement, with a vital tooth in most. Occasionally the pain is relieved by non-steroidal anti-inflammatory drugs. A swelling may be painless and found by chance.

Rapid growth, numbness or destructive features should lead to suspicion of osteoblastoma or osteosarcoma.

• Periapical radiograph: a well defined radiopaque mass fused to the root or roots of a tooth, with a thin radiolucent rim and loss of the root outline from fusion and resorption.
• Cone beam CT: extent, relation to the inferior alveolar canal and cortex, and planning.
• Pulp sensibility tests: usually vital.
• Histology after removal: sheets of mineralised cementum with prominent reversal lines, with rimming by cementoblasts and fibrovascular tissue at the periphery.
• Biopsy before surgery when there is doubt about malignancy.

Differential diagnosis.

• Hypercementosis
• Osteoid osteoma and osteoblastoma
• Condensing osteitis and idiopathic osteosclerosis
• Complex odontoma
• Cemento osseous dysplasia
• Central ossifying fibroma
• Osteosarcoma

• Removal of the whole mass together with the affected tooth, because the mass is fused to the root. Alternatively, enucleation of the mass with root resection and root canal treatment, preserving the crown in a selected case.
• Incomplete removal is associated with recurrence, reported at about 20 to 35%. Complete removal with the tooth makes recurrence uncommon.
• Send the specimen for histology.
• Antibiotics only for infection with spread: amoxicillin 500 mg orally three times daily for 5 days (reduce to 500 mg every 12 hours at eGFR 10 to 30), or clindamycin 300 mg four times daily in penicillin allergy.
• Analgesia: paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food.
• Restore the space with an implant, bridge or orthodontic space closure after healing.

Special groups. Children need weight based dosing and long term review of growth and tooth development.

Monitoring. Radiographs at 6 and 12 months, then annually for 3 to 5 years, with review of the surgical site for recurrence.

Referral and escalation. Refer to oral and maxillofacial surgery. Urgent referral for rapid growth, destructive features or histology suggesting osteoblastoma or osteosarcoma.