[The occlusal contact mode during lateral excursion]

The purpose of this study is to clarify the occlusal contact mode between the upper and lower molars on the working side of group function occlusion during lateral excursion. After the intercuspal position (IP) and two lateral positions (L1, the middle point between IP and L2; L2, the edge-to-edge occlusal position of the molars) on the Gothic arch were defined, occlusal contact relations in these three occlusal positions were recorded, using black silicone. Digital data of real occlusal contacts and visualized data of close (less than 30 microns) occlusal areas, by computer image processing, were analyzed. The conclusions are as follows: 1. Although the numbers of real occlusal contacts and the visualized occlusal area tend to decrease toward L2 during lateral excursion, the former, in some cases, goes up and down. 2. Functional cusps play an important part in occlusal contact at the intercuspal position. 3. Occlusal contact points are on the functional cusps of the upper and lower molars, which can be clinically regarded as certain points, and these points slide on the inclining non-functional cusps of antagonistic teeth during lateral excursion. 4. Each upper and lower molar has 2 to 6 occlusal contact points near the top functional cusps at the intercuspal position, and some of them contact continuously during lateral excursion.