[A study of mandible chewing movement in patients with developmental lateral jaw deformity]

The purpose of the present study was to investigate effects of developmental lateral jaw deformity (DLJD) on masticatory movement.Three coordinates of mandibular movement signals were recorded in 35 young healthy adults with normal occlusion and 28 patients with DLJD by means of a Sirognathography System during gum chewing movement. Paired and unpaired t-tests were used to compare significant difference of intra-group and inter-groups in displacement and speed. P0.05 was chosen as significance level.(1) The rhythm and directional sequence of chewing trajectory in both frontal and sagittal planes were normal in control group, while anomalies of rhythm and distribution (n = 9) and reversed sequencing (n = 7) were found in DLJD group. (2) The maximum magnitude of jaw retrusion and average speed were significant higher in DLJD group than those in control group (P0.01). The spatial displacement and average speed in horizontal plane and in chewing phase were also higher in DLJD group compared with control group (P0.05).DLJD patients showed anomalies in chewing pattern as well as chewing speed and displacement in horizontal plane.