Jaw tremor as a physiological biomarker of bruxism

Objective: To determine if sleep bruxism is associated with abnormal physiological tremor of the jaw during a visually-guided bite force control task. Methods: Healthy participants and patients with sleep bruxism were given visual feedback of their bite force and asked to trace triangular target trajectories (duration = 20 s, peak force <35% maximum voluntary force). Bite force control was quantified in terms of the power spectra of force fluctuations, masseter EMG activity, and force-to-EMG coherence. Results: Patients had greater jaw force tremor at similar to 8 Hz relative to controls, along with increased masseter EMG activity and force-to-EMG coherence in the same frequency range. Patients also showed lower force-to-EMG coherence at low frequencies (<3 Hz), but greater coherence at high frequencies (20-40 Hz). Finally, patients had greater 6-10 Hz force tremor during periods of descending vs. ascending force, while controls showed no difference in tremor with respect to force dynamics. Conclusion: Patients with bruxism have abnormal jaw tremor when engaged in a visually-guided bite force task. Significance: Measurement of jaw tremor may aid in the detection/evaluation of bruxism. In light of previous literature, our results also suggest that bruxism is marked by abnormal or mishandled peripheral feedback from the teeth. (C) 2015 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology.