We present a very rare case of an exostosis at the mandibular angle associated with inflammatory symptoms of the oral floor caused by sialolithiasis of the submandibular gland. A 52-year old woman was referred to our clinic in March 1993 because of tenderness at the left mandibular angle. At presentation, clinical examination revealed diffuse swelling at the left side of the oral floor. Radiographically, there was a radiopaque image inside the left mandibular angle. It appeared to be a salivary stone, and it was impossible sialographically to depict the mandibular gland because of an obstacle at the salivary duct. A computed axial tomogram obtained parallel to the mandibular plane revealed a dense bony oval mass contiguous with the lingual cortical bone of the mandible behind the submandibular gland. Magnetic resonance images showed that the submandibular gland was dislocated because of pressure applied by the bony mass. Surgical excision of the mass, measuring 10×8×7mm, was performed with the patient under general anesthesia. The pathological diagnosis was not an osteoma but an exostosis of mandibular bone. Postoperative sialography depicted a normal submandibular gland without inflammation. The inflammatory signs and symptoms around the submandibular gland were apparently caused by pressure applied by the exostosis.
