study was undertaken to investigate the changes of maximum bite force, range of mouth opening, and muscle activity in EMG after orthognathic surgery.
The maximum bite force, range of mouth opening, and muscle activity in EMG were measured in 20 dentofacial deformity patients, aged 19-38(mean age 23.95) years, before surgery and at 2, 3 and 6 months after surgery. These patients were divided
into
three groups according to operation methods, that is 3 in IVRO group, 8 in BSSO group, and 7 in two-jaw surgery group.
Thereafter the recovery of maximum bite force and the effect of duration of intermaxillary fixation were assessed.
@ES The results, were as follows.
@EN 1.The presurgical maximum bite force was 12.13 kg in upper first molar(Lt. Side 12.15kg, Rt. side 12.15kg respectively). being much lower than that of normal occusion, and maximum mouth opening was 48.45mm, falling in the normal range.
2. Maximum bite force and mouth opening were much increased 3 months after surgery in BSSO group and 3 months to 6 months after in IVRO and two-jaw surgery groups.
3. Muscle activity in EMG during maximal bite was lower than that of normal occlusion and approaching to the presurgical value or above at follow up examination 6 months after surgery.
4. It takes approximately 6 months after surgery for the bite force to recover to its presurgical value.
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