The study on the occlusal facets of molars from the standpoint of harmony with jaw movements.

概要

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The purpose of this study was to determine the optimum morphology of occlusal facets of molars from the standpoint of harmony with jaw movements. First, we defined a simplified occlusal reference surface (ORS) on both the working and nonworking sides in the following manner: A working-side ORS was defined by using the trajectories of retrusive and lateral sliding movements obtained with a 6-degree-of-freedom measuring device, while a nonworking-side ORS was defined by using the trajectories of protrusive and lateral sliding movements. Then, three different occlusal facets were introduced, one equivalent to the ORS (harmonious occlusal facet) and two comparative ones whose orientations were intentionally deviated from that of the ORS (inharmonious occlusal facet) . Occlusal contacts on these facets formed in antagonistic second molars of two subjects were evaluated during lateral excursions and chewing movement through computer simulation. Results were as follows: 1) the harmonious working-side and nonworking-side occlusal facets induced no considerable interference with jaw movement during the fourth and fifth phases of the chewing cycle, respectively; and 2) the inharmonious facets with a steeper inclination (15 degrees) tended to interfere with jaw movements at lateral excursive positions, while those with a gentler inclination (-15 degrees) tended to cause disocclusion at lateral excursive positions.
日本顎口腔機能学会の論文