[Inclination and area of occlusal facets in natural dentition]

The characteristics of occlusal facets are important criteria used in the functional assessment of the stomatognathic system. A new system of optically quantifying the facets using a graphic image-processor has been developed, which makes it possible to measure the area and the inclination angles of each facet in the frontal and sagittal sections. In this study, the occlusal facets were investigated in 5 cases with normal dentition concerning the inclinations, areas, locations and occlusal contacts. The facets which made contact with their opposing ones in the intercuspal and lateral occlusal positions were selectively analyzed. The frontal inclination angles of the facets increased or decreased according to their mesio-distal locations in the working-facet or balancing-facet series, respectively. The sagittal ones indicated that most of the facets on the lateral excursion belonged to either the mesial or distal slopes of the cusps in each case. The angles made by the upper and lower facets which made contact were greater in the lateral occlusal positions than in the intercuspal position. Most of the areas of the upper facets were larger than those of the lower ones, which fact was remarkable on the facets related to the occlusal contacts between the intercuspal position and the cusp-to-cusp positions of the canines.