The aim of this study was to elucidate the relationship between the craniofacialmorphology and the activity of the masticatory muscles.
The samples for this study consisted of 5 patients with mandibular protrusion (skeletal Class III group) and 5 control subjects with normal occlusion (normal group).
Electromyographic activities in the masseter and anterior part of temporal muscles were recorded using bi-polar surface electrodes when subjects were instructed to bite in the intercuspal position (ICP) at several levels of bite force.
We evaluated the relationship between total. amount of activity on bilateral masseter and temporal muscles and the activity of each muscle, using normalized value relative to maximum voluntary clenching (MVC).
Simple linear regression analysis was performed in each subject. The results were as follows:
In normal group, slopesof regression line of the masseter muscle were gentler than those of the temporal muscle, while in skeletal Class III group, slopes of regression line of the masseter muscle were steeper than those of the temporal muscle.
Therefore, innormal occlusion, the masseter muscle might predominantly be working as a majorpower generator at any clenching level.
In contrast, in skeletal Class III group, the temporal muscle appeared to be predominant compared with the masseter muscle in its activity at any clenching level. Further, at high clenching level, the temporal muscle is possibly working as a major power generator, and working as apower generator as well as a jaw positioner at low clenching level.

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To assess whether patients were satisfied with the results of treatment, questionnaires were sent to 291 patients who had undergone orthognathic surgery for correction of jaw deformities and 133 questionnaires were returned with valid answers. The chief problem of 94 (71%) of these patients was appearance. Dysfunctions such as masticatory disturbance and speech difficulties were the primary reason for which 38 (29%) of the patients sought treatment. Seventy-five percent of the patients answered that they were satisfied with the results in regard to their chief problems. A favorable change in appearance was recognized by 125 patients, whereas five patients noticed no major changes and three patients were displeased with their postoperative faces. The patients'evaluations of their appearance seemed to be influenced by the responses of other peoPle to the surgical-results, and objective improvements did not always satisfy their expectations. Improvements in masticatory function and speech were recognized by 92 and 54 patients, respectively. Eighty patients had TMJ signs and symptoms such as click and/or pain before treatment, which disappeared in 53 (66%) of the symptomatic patients after the surgery. On the other hand, TMJ signs and symptoms appeared postoperatively in 7 (15%) of 47 patients without those before treatment. Psychologically, 42 patients noted favorable changes in personality after the surgery. Eight patients with mandibular set back noted the onset or worsening of snoring after the surgery.

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In two cases with temporomandibular joint (TMJ) ankylosis caused in early childhood, TMJ mobilization operation was performed at an early stage. Their jawdevelopments were observed till adulthood. In Case 1, TMJ osteoarthrotomy was performed on both sides at the age of 2 years and 9 months. In this case, the position of the maxilla at age 12 and age 21 changed to lower forward direction compared to that at age 3. With respect to the development of the maxilla, while vertical development of the maxilla was deficient at age 3, its development was almost normal at age 12 and age 21. The mandible was positioned in the lower forward direction at age 12. At age 21, the position was changed further in the lower direction compared to that at age 3 and the horizontal development of the mandible showed significantly deficient growth at age 3, age 12 and age 21. On the other hand, the vertical development of the mandible at age 2, age 12 and age 21 were all close to normal.
In case 2, TMJ osteoarthrotomy was performed on the right side of the TMJ at the age of 2 years and 5 months.In this case, the positions of the maxilla at age 10 and age 18 were also lower forward compared to that at age 2. While the vertical development of the maxilla was deficient at age 2, it was almost normal at age 10 and age 18. The position of the mandible at age 10 was lower forward compared to that at age 2. At age 18, the position was changed further in the lower direction compared to that at age 2. The horizontal development of the mandible showed significantly deficient growth at age 2, age 10 and age 18. The vertical development at age 2, age 10 and age 18 on the affected side showed deficient growth but on the healthy side, growth at age 2, age 10 and age 18 were all close to normal.
From the above, it was found that even if the functions of the jaw are retrieved through early TMJ mobilization operation for TMJ ankylosis in childhood, the horizontal development of the mandible will remain deficient.

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