To investigate the factors affecting the non-chewing side contact, the relationship among simulated non-chewing side tooth contact, jaw displacement, and masticatory muscle activity was evaluated.
Seven healthy male subjects volunteered for this study. They were asked to clench on a central bearing device, and vertical displacements of lower bilateral second molars were measured by linear variable transformers. Simultaneously, EMG activity was measured from masseter and anterior temporal muscles. Thesubjects were also asked to clench with film strips in place on unilateral premolars in order to simulate the occlusal phase of the chewing cycle. Occlusal registrations on the contralateral sides were recorded, and then the occlusal contact area was calculated for each side.
Comparison of bilateral tooth contact area and second molar displacements showed that the contact area tended to be larger on the side where larger molar displacement was found. The side difference of the contact area was significantly correlated to that of second molar displacement (Pearson's r =0.85 p= 0.01), however, not to EMG activity.