Effect of eccentric clenching on mandibular deviation in the vicinity of mandibular rest position

Although the mechanical compression of the temporomandibular joint (TMJ), w hich could be caused by bruxism, would probably result in a slight change o f the occlusal relationship, the effect of clenching in the eccentric mandi bular position on the occlusal contact has not pet been clarified. This stu dy aimed to investigate the effect of eccentric clenching on bilateral cond ylar position and thus to estimate any change of occlusal contact. Before a nd after voluntary clenching, with one third of the maximal voluntary clenc hing force, for 3 min at the canine edge-to-edge position, vertical deviati on of the bilateral condyles was measured at the 1 mm open mandibular posit ion. This was regulated by the three-dimensional position of the anterior r eference point which stands for the incisor point. The mean vertical displa cement of the highly deviated side of the condyle was 141 +/- 55 mu m, and the calculated mean displacement of the mandibular first molar region of th e highly deviated side was 65 +/- 27 mu m. From the results of this study, it was revealed that the eccentric clenching gave rise to three-dimensional deviation of the mandible even when the mandible was in the vicinity of th e rest position.