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Electromyographic heterogeneity in the human masseter muscle
N G Blanksma1, T M Van Eijden, W A Weijs
1Academic Center for Dentistry Amsterdam (ACTA), Department of Functional Anatomy, The Netherlands.
Journal of Dental Research
|January 1, 1992
Summary
The human masseter muscle shows distinct regional activation patterns during biting, suggesting functional divisions beyond the typical deep and superficial parts. These findings reveal a more complex organization for masseter muscle function.
Area of Science:
- Biomechanics
- Human Anatomy
- Neuromuscular Physiology
Background:
- The human masseter muscle, crucial for mastication, possesses a complex pennate structure.
- Existing anatomical divisions (deep and superficial) may not fully capture its functional complexity.
Purpose of the Study:
- To investigate regional differences in human masseter muscle activation patterns.
- To determine if functional subdivisions exist beyond the commonly recognized deep and superficial parts.
Main Methods:
- Electromyography (EMG) was used to record muscle activity.
- Bipolar fine-wire electrodes were inserted into three deep and three superficial regions.
- Recordings were taken during static bite tasks in various directions and at a set bite force.
Main Results:
- A linear relationship was observed between bite force and EMG activity.
- Muscle regions exhibited varied activation patterns depending on bite-force direction.
- The posterior deep region displayed unique activation, particularly during posterolateral bites.
- Significant heterogeneity in activation was noted for certain bite directions, while others showed minimal variation.
Conclusions:
- The masseter muscle appears to be functionally partitioned into at least three distinct parts: anterior deep, posterior deep, and superficial.
- The posterior deep region exhibits a specialized role, especially in posterolateral biting.
- Further subdivision of the superficial masseter may exist but requires more detailed investigation.