非作業側咬合接触が閉口筋筋活動へ及ぼす影響

抄録

The influence of nonworking side's contacts was investigated in vivo in the eccentric position to the response of the jaw closing muscles during clenching. This study was performed by changing the degree of clenching and the distance between upper and lower canines on the working side. Furthermore, the distance between the lower second molar and a splint inserted on the upper molars was changed using various thicknesses of metal plates. The thickness of the plate which allowed the first occlusal contact on the nonworking side during clenching was called D₀.
At 100% maximum voluntary clenching (MVC) and a distance of 1.5 mm between the upper and lower canines on the working side, the nonworking side's temporal muscle activity at D₀ showed the lowest value. At the edge-to-edge contact of the working side's canines, the same results were obtained. However, at 50% MVC and the distance of 1.5 mm between the upper and lower canines, the activity, when no contact on the nonworking side was allowed, showed the lowest value.
These findings indicate that nonworking side's contacts like that at D₀ protect physiologically the temporomandibular joint from hypermobility during clenching in the eccentric position, and this protection is related with the degree of clenching.