Hemimandibular hyperplasia.

True hemimandibular hyperplasia is an uncommon maxillofacial deformity. Patients with this affliction present clinically with varying degrees of asymmetry characterized by an increase in ramus height, a rotated facial appearance with kinking at the mandibular symphysis, and prominence of the lower border of the mandible. In the advanced form, maxillary and mandibular alveolar bone overgrowth result in a compensatory canting of the occlusal plane and a significant functional malocclusion requiring bimaxillary surgical correction. Nine patients with the above condition were treated with various surgical methods over a 9-year period. The clinical results were satisfying and the long-term results showed good postoperative stability. The pathology of hemimandibular hyperplasia is described and the preexisting nomenclature further defined.