Differential activity patterns in the masseter muscle under simulated clenching and grinding forces

Area of Science:

• Biomechanics
• Neuromuscular physiology
• Dental science

Background:

• The masseter muscle plays a crucial role in mastication, involving clenching and grinding.
• Understanding its activation patterns is vital for diagnosing and treating jaw-related disorders.

Purpose of the Study:

• To investigate differential activation of the masseter muscle during simulated clenching and grinding.
• To identify preferentially active muscle regions and force directions for enhanced activation.

Main Methods:

• Electromyographic (EMG) activity of the masseter muscle was recorded using intramuscular electrodes.
• Intraoral forces were measured using a strain gauge-equipped central bearing pin device.
• Muscle activation was analyzed across different mandibular positions and maximum voluntary contraction (MVC) directions.

Main Results:

• Masseter muscle regions displayed heterogeneous EMG activity that varied with motor tasks.
• Protrusive force directions showed the highest relative muscle activation.
• The posterior deep muscle region was identified as the most active compartment.

Conclusions:

• The masseter muscle exhibits heterogeneous activation patterns during simulated clenching and grinding activities.
• Protrusive bite forces are associated with maximal masseter activation, particularly in its posterior deep region.