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Effect of experimental jaw muscle pain on EMG activity and bite force distribution at different level of clenching
Author(s) -
Shimada A.,
Hara S.,
Svensson P.
Publication year - 2013
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/joor.12096
Subject(s) - masseter muscle , medicine , bite force quotient , electromyography , visual analogue scale , anesthesia , hypertonic saline , stimulation , isotonic saline , contraction (grammar) , saline , muscle contraction , tonicity , anatomy , orthodontics , physical medicine and rehabilitation
Summary Bite force at different levels of clenching and the corresponding electromyographic ( EMG ) activity in jaw‐closing muscles were recorded in 16 healthy women before, during and after painful stimulation of the left masseter muscle. Experimental pain was induced by infusion of 5·8% hypertonic saline ( HS ), and 0·9% isotonic saline ( IS ) was infused as a control. EMG activity was recorded bilaterally from the masseter and temporalis muscles, and static bite force was assessed by pressure‐sensitive films (Dental Pre‐scale) at 5, 50 and 100% of maximal voluntary contraction ( MVC ) during each session. Visual feedback was applied by showing EMG activity to help the subject perform clenching at 5, 50 and 100% MVC , respectively. EMG activity at 100% MVC in left and right masseter decreased significantly during painful HS infusion (1·7–44·6%; P < 0·05). EMG activity at 5% and 50% MVC was decreased during HS infusion in the painful masseter muscle (4·8–18·6%; P < 0·05); however, EMG activity in the other muscles increased significantly (18·5–128·3%; P < 0·05). There was a significant increase in bite force in the molar regions at 50% MVC during HS infusion and in the post‐infusion condition ( P < 0·05). However, there were no significant differences in the distribution of forces at 100% MVC . In conclusion, experimental pain in the masseter muscle has an inhibitory effect on jaw muscle activity at maximal voluntary contraction, and compensatory mechanisms may influence the recruitment pattern at submaximal efforts.