The Effects of Experimental Temporalis Muscle Pain on Jaw Muscle Electromyographic Activity During Jaw Movements and Relationships with Some Psychological Variables

Aims: To determine if the effects of experimental temporalis muscle pain on jaw muscle activity vary with the jaw task performed, jaw displacement magnitude, participant being studied, and with psychological measures. Methods: Jaw movement was tracked, and electromyographic (EMG) activity was recorded from the masseter and anterior temporalis and digastric muscles in 14 asymptomatic participants during standardized opening/closing jaw movement, free chewing, and standardized chewing tasks. Tasks were repeated in three blocks: Block 1 (baseline), Block 2 (during 5% hypertonic or 0.9% isotonic saline infusion into the anterior temporalis), and Block 3 (during infusion of the opposite solution). Participants also completed the Depression, Anxiety, and Stress Scales 21 (DASS 21), the Fear of Pain Questionnaire (FPQ III), the Pain Self-Efficacy Questionnaire (PSEQ), and the Pain Catastrophizing Scale (PCS). Analyses involved linear mixedmodel analysis and Pearson correlations. P .05 was considered statistically significant. Results: The presence of a significant difference in jaw muscle EMG activity between hypertonic and isotonic saline infusions varied between tasks and between jaw muscle agonists and antagonists, but not in displacement magnitude. There were qualitative differences between participants in the effects of infusion on EMG activity. During hypertonic saline infusion, significant positive correlations were noted between jaw-closing EMG activity and anxiety, fear of medical pain, and PCS scores. Conclusion: Noxious stimulation of the temporalis muscle results in changes in jaw muscle activity, which can vary with the task, the muscle, the participant, and some psychological variables. Parole chiave: electromyography, jaw, mastication, masticatory muscles, pain, psychological scales