Changes in oral functions and muscular behavior due to surgical orthodontic treatment.

The faces of fifteen adult patients who had undergone surgical orthodontic treatment were videotaped frontally and laterally in order to observe their oral circumferential behavior for function and their facial muscle posture at rest. As the ANB angle became 0.9 degrees from -3.5 degrees and the occlusal relationship improved to normal, facial morphology became harmoneous. In general observation, habits of facial muscle tensity at rest was reduced and lip sucking following forward tongue thrusting was decreased after treatment. Pronunciation of previously unclear sounds such as 'Ta' and 'Sa' improved and breath leakage decreased after treatment. The cooperative motions between lips and tongue improved significantly. Although a few subjects still had weak lip tensity and facial muscles, habits of tongue thrusting during swallowing were generally reduced and swallowing motions became more natural. As the movement of tongue tip became smoother, rhythmical chewing improved, and they became capable of chewing on both sides. Good relationships between morphology, oral function, and muscular behavior are very important in stabilization of the normal dentition after surgical orthodontic treatment. Normally maintained forces of balanced occlusion reduce the possibility of relapse.