engleski

Maximum Voluntary Isometric Activity of Elevator Masticatory Muscles at Symmetrical Occlusal Positions of the Mandible

Mean voltages of right and left temporal and masseter muscle (RAT, LAT, RM, LM) during maximum voluntary clenching in maximal intercuspal position (MI), retruded contact position (RCP) and incisal position (IP) were examined. There was no significant difference between sexes in any of the examined positions (p>0.05). For the symmetric positions of the lower jaw (MI, P, RCP) there was slightly higher muscle activity on the right side, although not significant (p>0.05). The biggest reduction of the activity of masseter muscle was observed in RCP and the biggest reduction of the activity of temporal muscle was observed in IP, indicating that masseter muscle is more responsible for the protrusive isometric contraction and temporal muscle is more responsible for the retrusive isometric activity. Greater inhibitory input was observed on the masseter motoneurons than on the motoneurons of the temporal muscle in RCP, while greater inhibitory input was observed on the motoneurons of the temporal muscle than on the motoneurons of the masseter muscle in IP, indicating that various receptors might be responsible for the reduction of maximal voluntary clenching efforts: spatial receptors in temporomandibular joints and muscle tendon organs, as well as the receptors in periodontal membrane of the anterior and posterior teeth.

EMG; masseter muscle; anterior temporal muscle; symmetrical occlusal positions

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