Association between mandibular chewing patterns and sleep bruxism characteristics: a clinical observational study.

BACKGROUND: Sleep bruxism (SB) is a sleep-related movement behavior characterized by rhythmic or non-rhythmic masticatory muscle activity that may contribute to tooth wear, jaw discomfort, and temporomandibular disorders. While SB is commonly assessed using polysomnography (PSG) and electromyography (EMG), daytime functional markers that predict SB intensity and phenotype remain insufficiently defined. Chewing patterns reflect neuromuscular coordination of mandibular movement and may share motor control pathways with SB-related masticatory activity. OBJECTIVE: To investigate whether mandibular chewing patterns are associated with SB characteristics, including episode frequency, EMG intensity, and activity phenotype. METHODS: In this clinical observational study, 120 adults underwent standardized chewing assessments with three-dimensional jaw tracking during controlled chewing tasks. Chewing patterns were classified into: (i) bilateral alternating, (ii) unilateral preferred-side, and (iii) irregular/unstable pattern. Participants then completed one-night laboratory PSG with bilateral masseter EMG and audio-video monitoring. SB characteristics were quantified as Bruxism Episode Index (BEI, episodes/hour), phenotype distribution (phasic/tonic/mixed), burst count, episode duration, peak EMG amplitude (%MVC), and temporal coupling with cortical micro-arousals. Multivariable regression models tested associations between chewing pattern and SB metrics controlling for age, sex, BMI, caffeine intake, smoking, perceived stress, and apnea-hypopnea index (AHI). RESULTS: Compared with bilateral alternating chewers, unilateral preferred-side chewers had higher BEI (median [IQR], 3.2 [2.2-4.6] vs. 1.9 [1.2-2.8]) and higher peak EMG (%MVC) (38.4 ± 12.6 vs. 29.1 ± 10.8). Irregular chewers demonstrated the highest tonic proportion (27.8% vs. 14.3% in bilateral group) and longer episode duration (8.9 ± 2.7 s vs. 6.4 ± 2.1 s). In multivariable models, unilateral and irregular chewing patterns independently predicted BEI (β = +0.88 and + 1.21 episodes/h, respectively) and peak EMG (β = +6.1%MVC and + 8.4%MVC, respectively). The association persisted after adjusting for AHI and micro-arousal index. CONCLUSIONS: Mandibular chewing patterns are associated with SB intensity and phenotype. Unilateral preferred-side and irregular chewing patterns may indicate altered sensorimotor control that corresponds to more intense and tonically weighted SB. Daytime chewing assessment may provide a practical functional marker for SB risk stratification and individualized management.