The effect of premolar occlusal contact on the occlusal forces.

Clarifying the effects of changes in the number of occlusal contact points on occlusal function is important. In the present study, we measured occlusal forces using dental prescale films to ascertain the effects of changes in premolar occlusal contact. Subjects were seven adult males with normal occlusion. Subjects were instructed to bite a dental prescale film as hard as possible while using a maxillary bite plate (every mandibular tooth made contact with the plate), to measure occlusal forces. Next, the surface of each bite plate that came into contact with the mandibular premolars was ground so that mandibular premolars did not come into contact with the plate. Subjects were then asked to use the ground bite plate and repeat the test. The results were as follows: (1) when premolar occlusal contact was absent, the total occlusal force was significantly lower than that when premolar occlusal contact was present; (2) when premolar occlusal contact was absent, the level of occlusal forces applied to the molar region was significantly greater than that when premolar occlusal contact was present; and (3) in particular, when premolar occlusal contact was absent, the level of occlusal forces applied to the first molar region was significantly greater than that when premolar occlusal contact was present. Conversely, occlusal forces applied to the second molar demonstrated minimal change, irrespective of premolar occlusal contact. These findings suggest that premolar occlusal contact affects the distribution of occlusal forces applied to the other teeth. In particular, changes in premolar occlusal contact affect the level of occlusal forces applied to the neighboring first molar, and are involved in the expression of maximum occlusal forces.