Sleep bruxism, maximum bite force, and home electromyography: a cross-sectional study

Sleep bruxism is a sleep-related masticatory muscle activity that may occur during sleep as rhythmic (phasic) or non-rhythmic (tonic) muscle contractions and, in otherwise healthy individuals, is not considered a movement disorder or a sleep disorder. Its relationship with maximum bite force remains unclear. This study aimed to compare maximum bite force between adults with and without sleep bruxism using a combined clinical assessment and multi-night, at-home surface electromyography monitoring. This cross-sectional study enrolled 60 adults aged 18–45 years (30 with sleep bruxism and 30 controls). Sleep bruxism was identified using a multimodal approach that combined self-report, clinical signs, and three nights of at-home single-channel surface electromyography recorded over the masseter muscle with the FLA-500-SD device (GC Corporation, Japan), in accordance with the American Academy of Sleep Medicine criteria. Maximum bite force was measured bilaterally at the first molar, second premolar, and central incisor regions using a digital occlusal force gauge (BFM, 4th generation, Vietnam). Three measurements were conducted per site, and the highest value was used for analysis. Electromyography outcomes included the bruxism episode index (BEI) and the percentage of maximum voluntary contraction (%MVC). Between-group differences were evaluated using the independent-samples t-test or the Mann-Whitney U test ( p < 0.05). Maximum bite force at the molar region did not differ between groups, whereas values at the premolar and incisor regions were higher in the sleep bruxism group ( p < 0.05). Across all tooth regions, men showed higher maximum bite force than women ( p < 0.01). Participants with sleep bruxism exhibited higher maximum bite force in the premolar and incisor regions, while first molar bite force did not differ from controls. These findings may have been influenced by concomitant awake bruxism and should be further investigated in future studies.