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Functional relationships between the masseter and sternocleidomastoid muscle activities during gum chewing:
Kazuo Shimazaki1, Nozomu Matsubara, Masataka Hisano
1Orthodontic Science, Department of Orofacial Development and Function, Division of Oral Health Science, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. shimazaki.orts@tmd.ac.jp
The Angle Orthodontist
|April 28, 2006
Summary
Muscle fatigue alters chewing patterns. Masseter muscle activity shortens, while sternocleidomastoid muscle activity lengthens, affecting head and jaw movements during mastication.
Area of Science:
- Biomechanics
- Neuromuscular physiology
- Dental science
Background:
- Mastication involves complex coordination between jaw muscles and head posture.
- Understanding muscle fatigue's impact on these coordinated movements is crucial for functional analysis.
Purpose of the Study:
- To investigate the functional relationship between masseter muscle (MM) and sternocleidomastoid muscle (SCM) activities.
- To examine the relationship between mandibular and head movements during mastication under experimental muscle fatigue.
Main Methods:
- 12 adults with normal occlusion chewed gum before, immediately after, and 3 minutes after maximum clenching.
- Electromyography (EMG) measured MM and SCM activity.
- A motion capture system recorded mandibular and head movements.
Main Results:
- Masseter muscle activity duration decreased post-fatigue, while sternocleidomastoid muscle activity duration increased.
- Mandibular movement distance showed no significant change, but head movement distance increased post-fatigue.
- The onset timing difference between MM/SCM activity and mandibular/head movements decreased after fatigue.
Conclusions:
- Experimental muscle fatigue alters the temporal coordination of masseter and sternocleidomastoid muscle activities during mastication.
- Fatigue influences head movement patterns more than mandibular movement patterns.
- A functional relationship exists between these muscle activities and head/jaw movements, which is modified by fatigue.
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