Prosthodonic implications and effects of orthognathic surgery on oral functions in the patients with mandibular prognathism

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Orthognathic surgery is generally employed for serious mandibular prognathism patients. In the intermaxillary fixation of orthognathic surgery, a splint is usually used due to the ease in determining the position of a segment. Accuracy of the splint effects the positioning of a segment in sagittal split ramus osteotomy. Simple and accurate materials are necessary for a splint. In the first study, we investigated the preparation time and dimensions of three resins (heat-curing, self-curing and light-curing). The test results are that the light-curing resin was the best material of the three for an orthognatic surgery splint. In sagittal split ramus osteotomy, the masseter muscle is detached from the masseric tuberosity so that the length of the masseter muscle may be changed. Furthermore, intermaxillar fixation of about 6 weeks causes the distinct atrophy of the masseter muscle. The purpose of the second study was to examine the influence of these operations on the masseter muscle elect … More romyographically (EMG). While the jaw jerk reflex was evoked by mechanical tap stimulation of the menton, the onset and peak latencies of the responses of the bi-lateral masseter muscles were measured. These latencies were compared between normal subjects and patients with mandibular prognathism before surgery. Changes in these latencies and amplitudes were also examined in patients on three different days after surgery. The results showed no significant difference in the onset and peak latencies between the normal subjects and patients before the surgery. In patients with the surgery, it was found that these latencies and amplitudes did not significantly change after the surgery.In spite of the probable decrease of muscle length and the atrophy of the muscle fibers, no change could be found in either onset and peak latencies or amplitude. This evidence suggests that the muscle spindles may not be influenced by the atrophy of the muscle fibers. The stretch reflex mechanism which remains intact after the surgery is helpful for the patients in acquiring a new jaw position and becoming skillful in oral functions as soon as possible. Less