1985 Volume 31 Issue 9 Pages 2101-2112
This study investigates the electromyographic changes of mandibular prognathism indicated sagittal splitting of the mandibular ramus.
1. After surgery, duration of the temporal muscle on the chewing side decreased significantly in gum chewing. Standard deviation of duration, interval and cycle time decreased significantly in gum chewing. That is, masticatory rhythm became more regular and tended to resemble that of the normal group. In gum or rice chewing, maximum amplitudes of the temporal and masseter muscle became higher on the chewing and the nonchewing side and tended to resemble that of the normal group.
2. In the preoperation group, the muscle activity of the digastric muscle on the nonchewing side was greater than that on the chewing side. In the postoperation group, the difference of muscle activities between both side decreased significantly and tended to resemble that of the normal group.
After orthognathic surgery, the coordination of muscle activities of the temporal, masseter and digastric muscles improved and almost became similar to that of the normal group.