The patient was a 15-year-old female, who visited our hospital in March 2000 with the chief complaints of bilateral temporomandibular joint pain and lock during mouth-opening. At the first examination, the forced mouth-opening distance was 43 mm, and anterior open bite was noted. The patient had no medical history of note. MR findings at the first examination showed bilateral anterior disc displacement without reduction, condylar erosion, and joint effusion on both sides. The symptom of intermittent lock disappeared after treatment with a mandibular stabilization-type splint between May 2000 and May 2002. In 2003, preoperative orthodontic treatment was initiated. Sagittal splitting ramus osteotomy was performed in February 2005 and the postoperative course was good. MR image findings revealed that double contour had occurred during splint therapy, and the condylar erosion disappeared. After surgery, osseous changes were gradually observed on both condyles; the condylar bone marrow signal had decreased at four years after surgery, and progression of the condylar bone resorption stopped at five years after surgery. Six years after surgery, the condylar bone marrow signal gradually increased. As a result of sagittal splitting ramus osteotomy, the molar occlusal condition was stabilized, the condylar sliding movement improved, and the bone marrow signal increased during the long-term observation. The present mouth-opening distance is 40 mm with appropriate occlusion, and the clinical course has been favorable without temporomandibular joint or muscle pain.
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