Changes of Chewing Movement Before and After Orthognathic Surgical Treatment in Skeletal Class III Patients

Orthognathic surgical treatment has been provided for many patients with skeletal Class M malocclusion in order to correct deviated dentofacial morphology and to improve the impeded oro-facial function. In this study, we investigated the relationship between dentofacial morphology and mandibular movement in subjects with skeletal Class M malocclusion, while they were chewing gum. The subjects were 16 patients with skeletal Class M malocclusion scheduled to undergo orthognathic surgical treatment (jaw deformity group) and 21 with norrnal occlusion (normal group). In the jaw deformity group, records taken before treatment and at 1-6 months after completion of active treatment were used for this study. The dentofacial morphology was analyzed using lateral roentgen cephalograms. The rnandibuiar movement was recorded by tracing the incisal point (the midpoint between mandibular central incisors) while chewing gum using the integrated jaw function testing system (gnathohexagraph system, JM-1000, Ono Sokki Tokyo, Japan). The following results were obtained, 1. The mean duration of a chewing cycle was significantly longer in the jaw deformity group than in the normal group, 2. After treatment, the mean duration got shorter and approached that in the normal