Masticatory muscle activity during deliberately performed oral tasks

Area of Science:

• Biomechanics
• Neuroscience
• Physiology

Background:

• Understanding masticatory muscle function is crucial for diagnosing and treating orofacial disorders.
• Previous research has explored muscle activity during basic tasks like chewing and clenching.
• Detailed analysis of muscle-specific electromyography (EMG) patterns across a wide range of oral tasks is lacking.

Purpose of the Study:

• To investigate and characterize electromyographic (EMG) activity in masticatory muscles during various functional and non-functional oral tasks.
• To determine how muscle activation patterns differ based on specific oral behaviors.
• To identify task-specific EMG signatures for the masseter, anterior temporalis, and suprahyoid muscles.

Main Methods:

• Surface electromyography (EMG) was recorded from unilateral masseter, anterior temporalis, and suprahyoid muscles in 11 healthy adults.
• Subjects performed 30 distinct oral tasks under computer guidance.
• Data were analyzed using descriptive statistics, ANOVA, and hierarchical cluster analysis.

Main Results:

• Maximum EMG amplitude was higher during hard chewing than maximum clenching tasks for masseter and anterior temporalis muscles.
• The relative contribution of masseter and anterior temporalis muscles varied significantly across tasks (p < 0.001).
• Masseter muscle was more active during incisal biting, jaw protrusion, laterotrusion, and jaw cupping (p < 0.05).
• Anterior temporalis muscle was more active during tasks in intercuspal position, tooth grinding, and hard chewing on the working side (p < 0.01).
• Hierarchical cluster analysis grouped the 30 oral tasks into six distinct clusters based on muscle activity patterns.

Conclusions:

• Distinct electromyographic (EMG) patterns exist for masticatory muscles during different functional and non-functional oral tasks.
• The masseter and anterior temporalis muscles exhibit task-specific activation profiles, providing insights into their roles in various oral behaviors.
• These findings contribute to a better understanding of orofacial muscle function and can inform clinical assessments and treatments.