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The medial pterygoid muscle: a stabiliser of horizontal jaw movement
Author(s) -
Chen H.,
Whittle T.,
Gal J. A.,
Murray G. M.,
Klineberg I. J.
Publication year - 2017
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.12542
Subject(s) - movement (music) , physical medicine and rehabilitation , electromyography , closing (real estate) , lateral pterygoid muscle , anatomy , medicine , psychology , philosophy , political science , law , aesthetics , condyle
Summary There is limited information of the normal function of the human medial pterygoid muscle ( MP t). The aims were to determine whether (i) the MP t is active throughout horizontal jaw movements with the teeth apart and (ii) whether single motor units ( SMU s) are active during horizontal and opening–closing jaw movements. Intramuscular electrodes were placed in the right MP t of 18 participants who performed five teeth‐apart tasks: (i) postural position, (ii) ipsilateral (i.e. right) jaw movement, (iii) contralateral movement, (iv) protrusive movement and (v) opening–closing movement. Movement tasks were guided by a target and were divided into BEFORE , OUT , HOLDING , RETURN and AFTER phases according to the movement trajectories recorded by a jaw tracking system. Increased EMG activity was consistently found in the OUT , HOLDING and RETURN phases of the contralateral and protrusive movement tasks. An increased RETURN phase activity in the ipsilateral task indicates an important role for the MP t in the contralateral force vector. Of the 14 SMU s active in the opening–closing task, 64% were also active in at least one horizontal task. There were tonically active SMU s at the postural jaw position in 44% of participants. These new data point to an important role for the MP t in the fine control of low forces as required for stabilisation of vertical mandibular position not only to maintain postural position, but also throughout horizontal jaw movements with the teeth apart. These findings provide baseline information for future investigations of the possible role of this muscle in oro‐facial pain conditions.