Osteoma is a benign tumor arising from cancellous or compact bone. Frontal sinus is the most common site, followed by the ethmoidal sinus, maxillary sinus, sphenoidal sinus, maxilla and mandible. Very few cases involving the mandible have been described.
A 26-year-old woman who had a limited range of mouth opening was reffered to our clinic. The limited opening had been gradually increasing in severity after first operation(reduction malarplasty and angle resection). Computed tomography images showed a radiopaque mass between left mandibular notch and zygomatic arch. After surgical removal of mass, diagnosis of mass was osteoma from clinical pathology. The postoperative course was uneventful, the patient could open the mouth about 40 mm, 5 months after the operation.