Exostoses

Exostosis is a benign bony outgrowth that forms on the surface of a bone. Exostoses are typically composed of mature lamellar bone and are covered by normal cortical bone and marrow. They can occur anywhere but are most commonly described in the jaw as torus palatinus (midline of the hard palate) and torus mandibularis (along the inner surface of the mandible) and in the external auditory canal as canal exostoses. They are often asymptomatic and may be discovered incidentally on examination or imaging.

Most exostoses are nonmalignant with multifactorial etiologies. Genetic predisposition is noted for dental exostoses, while external auditory canal exostoses have strong associations with environmental factors such as repeated cold-water exposure (the so-called surfer’s ear). They usually grow slowly and are noninvasive; jaw exostoses are often bilateral.

Clinically, jaw exostoses typically cause no symptoms. Large or multiple exostoses may interfere with denture fabrication or orthodontic treatment. Ear canal exostoses may cause conductive hearing loss, recurrent otitis externa, or cerumen buildup if they narrow the canal.

Diagnosis relies on clinical examination and imaging. Panoramic radiographs or CT can define the extent of jaw exostoses; CT of the temporal bone or ear canal is used for canal exostoses. Differential diagnosis includes osteomas or other bone lesions, especially if features are atypical or rapidly enlarging.

Management is usually not required. Indications for removal include functional impairment, infection, pain, cosmetic concerns, or obstruction. Surgical excision is generally straightforward but recurrence can occur, particularly with canal exostoses, necessitating ongoing follow-up.