MAXIMAL VOLUNTARY ISOMETRIC ACTIVITY OF ELEVATOR MASTICATORY MUSCLES AT DIFFERENT OCCLUSAL POSITIONS OF THE MANDIBLE IN SUBJECTS WITH NORMAL OCCLUSION

Mean voltages of right temporal and masseter muscle (RAT RM) and left temporal and masseter muscle (LAT LM) during maximum voluntary clenchi ng in maximal intercuspal position (MI), retruded contact position (RK P), incisal position. (P) and right (ROI and left ILO) occlusal positi ons were examined. There was no significant difference between the sex es in none of the examined positions (p<0.05). For symmetric positions of the lower jaw (MI, P, RKP), there was a slightly higher muscle act ivity on the right side, although not significant (p<0.05). The bigges t reduction of masseter muscle was in RKP and the biggest reduction of temporal muscle was in P, indicating masseter muscle being more respo nsible for the protrusive isometric contraction and temporal muscle fo r the retrusive isometric activity. In P all muscles reduced activity significantly, indicating the reflexive inhibitory input on the nucleu s motorius n. trigemini from the periodontal receptors of the frontal teeth. Except in P, the biggest reduction of temporal muscle activity during voluntary clenching was in RO and LO on the side without latera l occlusal contact (contralateral side), indicating that temporal musc le is more sensitive to the reduction of the posterior teeth contact t han. the masseter muscle.