EMG response to alteration of tooth contacts on occlusal splints during maximal clenching.

Maximum clenching on an equilibrated occlusal splint yielded an increase of 17% in overall muscle activity over that of maximum intercuspation contributed mainly by masseter muscles. Maximum clenching on an anterior occlusal splint yielded a decrease of 13% in overall muscle activity compared with that of an equilibrated occlusal splint. When maximum clenching was performed with six left-sided teeth removed from contact while the left second molar remained in contact, there was no significant change in muscle activity when compared with that of an equilibrated occlusal splint. When left-sided muscles were compared with right-sided muscles for the same situation, there was no significant change. When maximum clenching was performed with all left-sided teeth removed from contact, there was a decrease of 21% in overall muscle activity compared with that of an equilibrated occlusal splint. When left-sided muscles were compared with right-sided muscles for the same situation, there was no significant change. Changes in the number of tooth contacts did not cause changes in the overall muscle activity during maximum clenching. Changes in the position of the tooth contacts altered the overall muscle activity during maximum clenching. Changes in occlusal contact symmetry did not cause changes in symmetry of muscle pairs during maximum clenching. Unilateral support produced the subjective response of pressure on the contralateral TMJ during maximum clenching.