Abstract
The Main Occluding Area is thought to be located between the functional cusps of the upper and lower first molar. However, there are several differences between the upper and lower molars in various aspects. We hypothesise that the Main Occluding Area location is influenced by the occlusal relationship between upper and lower dentitions. We investigated the impact of upper and lower dentitions and the occlusal relationship as determinants of the Main Occluding Area. The location of the Main Occluding Area was analysed in 20 normally dentate subjects (40 molar dentitions). According to the method by Kato et al., temporally filling materials were used to evaluate the locations of the Main Occluding Area. To evaluate the occlusal contact area in the intercuspal position, subjects were instructed to bite the occlusal contact checking material with a moderate bite force. The origin of coordinate system was the central fossa of the first molar for detailed quantitative investigation of the centroid of the Main Occluding Area. As a result, the Main Occluding Area was concentrated on the functional cusps of the upper first molar and dispersed on lower first and second molars. In subjects whose upper first molar was in occlusal contact with the lower first and second molar at the intercuspal position, the Main Occluding Area was located significantly more distally than in subjects whose upper first molar made contact only with the lower first molar under the lower coordinate system; no significant difference was found between the groups under the upper coordinate system. In this study, the location of the Main Occluding Area was more selectively concentrated on the occlusal surface of the upper first molar than on the lower first molar, and it was suggested that the assessment of the occlusal relationship between the upper and lower molars is indispensable for clarifying the Main Occluding Area.
