Association Between Mandibular Chewing Patterns and Sleep Bruxism Characteristics: A Clinical Observational Study

Introduction: Sleep bruxism (SB) is a sleep-related movement disorder characterised by rhythmic masticatory muscle activity associated with tooth wear and temporomandibular disorders. Although polysomnography (PSG) remains the diagnostic reference standard, accessible daytime functional markers capable of predicting SB severity and phenotype have not been established. Mandibular chewing patterns reflect sensorimotor coordination of masticatory motor programmes and may share neural control pathways with nocturnal bruxism activity.

Methods: In this clinical observational study, 120 adults underwent standardised three-dimensional jaw-tracking during controlled chewing tasks. Chewing patterns were classified as: (i) bilateral alternating, (ii) unilateral preferred-side, or (iii) irregular/unstable. Participants subsequently completed one-night attended laboratory PSG with bilateral masseter EMG and audio-video monitoring. Sleep bruxism was quantified as Bruxism Episode Index (BEI, episodes/h), phasic/tonic/mixed phenotype proportions, peak EMG amplitude (%MVC), episode duration, and temporal coupling with cortical micro-arousals. Multivariable regression examined associations between chewing pattern and SB metrics, controlling for age, sex, BMI, caffeine intake, smoking, perceived stress (PSS-10), and apnea-hypopnea index (AHI).

Results: Compared with bilateral alternating chewers, unilateral preferred-side chewers demonstrated higher BEI (median [IQR]: 3.2 [2.2-4.6] vs. 1.9 [1.2-2.8] episodes/h) and greater peak EMG amplitude (38.4+/-12.6 vs. 29.1+/-10.8 %MVC). Irregular/unstable chewers exhibited the highest tonic episode proportion (27.8% vs. 14.3%) and longest episode duration (8.9+/-2.7 vs. 6.4+/-2.1 s). Multivariable models confirmed that unilateral (beta=+0.88 episodes/h; +6.1 %MVC) and irregular (beta=+1.21 episodes/h; +8.4 %MVC) chewing patterns independently predicted greater SB severity after adjustment for AHI and micro-arousal index.

Conclusions: Mandibular chewing patterns are independently associated with sleep bruxism intensity and phenotype. Unilateral and irregular chewing may reflect altered sensorimotor regulation predisposing to more severe and tonically weighted SB. Daytime jaw-tracking assessment offers a practical, non-invasive functional biomarker for SB risk stratification and individualised clinical management.