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

Background Sleep bruxism is a common parafunctional activity marked by involuntary tooth grinding or clenching during sleep and has been linked to tooth wear, masticatory muscle discomfort, and temporomandibular joint loading. However, its association with maximum bite force and awakening masticatory symptoms remains unclear. This study aimed to compare maximum bite force and morning masticatory symptoms between adults with and without sleep bruxism using a combined clinical assessment and multi-night, at-home surface electromyography monitoring. Methods 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. Participants completed a structured questionnaire on awakening masticatory symptoms and underwent a standardized assessment of occlusal wear. 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 and the percentage of maximum voluntary contraction. Between-group differences were evaluated using the independent-samples t-test or the Mann-Whitney U test, with a two-sided significance level of 0.05. Results Participants with sleep bruxism reported more frequent awakening symptoms, including jaw stiffness, jaw fatigue, and temporal headache (p < 0.01). 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). Conclusions Adults with sleep bruxism showed higher anterior bite force and more frequent awakening masticatory symptoms than controls, while molar bite force did not differ. However, awakening symptoms alone are insufficient for identifying sleep bruxism. A multimodal approach that integrates clinical assessment with instrumental measures, such as electromyography, may improve diagnostic accuracy. Trial registration Not applicable.