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Antero‐posterior activity changes in the superficial masseter muscle after exposure to experimental pain
Author(s) -
Türp Jens C.,
Schindler Hans J.,
Pritsch Maria,
Rong Qiguo
Publication year - 2002
Publication title -
european journal of oral sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.802
H-Index - 93
eISSN - 1600-0722
pISSN - 0909-8836
DOI - 10.1034/j.1600-0722.2002.11198.x
Subject(s) - masseter muscle , hypertonic saline , medicine , tonicity , electromyography , isotonic , anesthesia , anatomy , saline , electrophysiology , physical medicine and rehabilitation
The aim of this randomized, controlled, double‐blind study was to examine how the activation pattern of the masseter muscle changes during natural function when experimental pain is induced in a discrete anterior area of the muscle. In 20 subjects, three bipolar surface electrodes and three intramuscular fine‐wire electrodes (antero‐posterior mapping) were simultaneously attached above and in the right masseter muscle to record the electromyographic (EMG) activity during unilateral chewing before and after infusion of a 0.9% isotonic and 5% hypertonic saline bolus in the anterior area of the muscle. The activity of the contralateral masseter muscle was registered by surface electrodes. In addition, the development of pain intensity was quantitatively measured with a numerical rating scale (NRS). While both saline concentrations caused pain, the hypertonic solution evoked stronger pain. The experiments also provided evidence of a significant although differential activity reduction of the ipsilateral masseter muscle in the antero‐posterior direction. The activity reduction decreased with increasing distance from the location of the infusion. The results support the idea that the strategy of differential activation protects the injured muscle while simultaneously maintaining optimal function.