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Small vertical changes in jaw relation affect motor unit recruitment in the masseter
S Terebesi1, N N Giannakopoulos1, F Brüstle1
1Department of Prosthodontics, Dental School, University of Heidelberg, Heidelberg, Germany.
Journal of Oral Rehabilitation
|December 29, 2015
Summary
This study reveals that the masseter muscle (a jaw muscle) adjusts its motor unit (MU) recruitment based on subtle changes in jaw position during biting. This fine motor control enhances jaw function and may aid in managing temporomandibular disorders.
Area of Science:
- Biomechanics
- Neuroscience
- Dental Science
Background:
- Motor unit (MU) recruitment strategies in the masseter muscle during varying vertical jaw relations remain unexplored.
- Understanding masseter muscle function is crucial for diagnosing and treating temporomandibular disorders (TMDs).
Purpose of the Study:
- To investigate the impact of minor vertical jaw relation changes on masseter muscle MU recruitment patterns.
- To analyze MU recruitment in different regions of the masseter during controlled biting tasks.
Main Methods:
- Intramuscular electromyographic (EMG) activity was recorded from the masseter muscle in 20 healthy subjects.
- Motor units (MUs) were identified using decomposition software, and root-mean-square (RMS) EMG values were calculated.
- Analysis focused on MU recruitment across seven different jaw relation tasks.
Main Results:
- Six hundred and eleven MUs exhibited significantly different recruitment behaviors based on jaw relation (P < 0.001).
- RMS EMG values varied significantly between tasks and recording sites (P < 0.01).
- Deeper masseter regions showed greater overall MU recruitment (P < 0.05), with recruitment decreasing as jaw separation increased (P < 0.01).
Conclusions:
- The masseter muscle demonstrates differential MU recruitment in specific subvolumes in response to small changes in vertical jaw relations.
- These findings suggest sophisticated fine-motor control contributing to the muscle's adaptability.
- This understanding may inform therapeutic interventions for TMDs, such as oral splint use.
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