前方滑走運動時の臼歯部離開に関する運動論的，形態学的解析

Abstract

The purpose of this study was to analyze the mechanism of the disclusion of posterior teeth during mandibular protrusive movement. Clinical examination was performed on 67 normal young adults, and they were divided into two groups: disclusion group and non-disclusion group. The protrusive movement was measured with the 3-dimensional mandibular movement analyzing system which can analyze movements in six-degrees of freedom, and the occlusal curve on the lower 2 nd molar was evaluated using the 3-dimensional digitizer.The sagittal inclinations of both incisal and condylar paths were significantly greater in the disclusion group than in the non-disclusion group. Especially, the difference of the incisal path inclination between them was almost 15 degrees. There was also a significant difference in their occlusal curves ; the occlusal curve in the disclusion group was steeper than that in non-disclusion group. The method of anterior guidance determination proposed by Kohno and Nakano was found to be effective for establising the posterior disclusion during protrusive movement. The findings of this study suggest that the inclination of the anterior guidance greatly contributes to the occurrence of the posterior disclusion, in comparison with the inclination of the posterior guidance and the steepness of the occlusal curve.