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KMID : 0355220150400030115
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Journal of Korean Academy Oral Medicine
2015 Volume.40 No. 3 p.115 ~ p.123
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Sternocleidomastoid and Posterior Cervical Muscle Coordination in Response to Symmetrical and Asymmetrical Jaw Functions in Normal Adults
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:Im Yeong-Gwan
:Kim Jae-Hyung/:Kim Byung-Gook
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Abstract
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Purpose: The aim of this study was to elucidate the coordination patterns of the sternocleidomastoid and posterior cervical muscles in response to symmetrical and asymmetrical jaw functions in normal adults.
Methods: Twenty-seven healthy volunteers (8 females, 19 males; mean age, 30.4±2.5 years) participated in this study. Surface electromyography (EMG) was used to record activities in the masseter, suprahyoid, sternocleidomastoid, and posterior cervical muscles at rest and during maximum tooth clenching, biting of a cotton roll with the anterior teeth, unilateral biting of a cotton roll with the posterior teeth, bilateral biting of cotton rolls with the posterior teeth, and jaw opening while seated. Normalized amplitude, activity indices, and asymmetry indices were compared between the muscles and the jaw tasks.
Results: During symmetrical jaw functions (e.g., tooth clenching, biting with the anterior teeth, bilateral biting with the posterior teeth, jaw opening), the sternocleidomastoid and posterior cervical muscles showed elevated EMG amplitudes compared with the resting condition. The co-activation pattern of the sternocleidomastoid muscle was more pronounced than those of the posterior cervical muscles during these tasks. During asymmetrical jaw functions (e.g., unilateral biting with the posterior teeth), the ipsilateral sternocleidomastoid and masseter muscles showed higher contraction activity than did the contralateral muscles, but the contralateral posterior cervical muscles were more active than the ipsilateral muscles.
Conclusions: The sternocleidomastoid and posterior cervical muscles were shown to be co-activated and coordinated anteroposteriorly or bilaterally according to symmetrical or asymmetrical jaw function. These results suggest an integrated neural control mechanism for the jaw and neck muscles, and provide further evidence supporting the intimate functional coupling between the trigeminal and cervical neuromuscular systems.
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KEYWORD
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Co-activation, Coordination, Electromyography, Masticatory muscles, Neck muscles
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