Occlusion, jaw function and nocturnal muscle tone in obstructive sleep apnea with and without sleep bruxism.

Objectives: Sleep bruxism (SB) is highly prevalent among patients with obstructive sleep apnea (OSA), yet its etiology remains unclear. This prospective clinical trial aimed to evaluate the diagnostic relevance of occlusion, jaw function, and electromyographic (EMG) muscle tone in OSA patients with and without SB.

Materials and methods: A total of 105 OSA patients (74 males, 31 females; mean age: 56.1 ± 11.4 years) were assessed, including those with SB and without SB (NSB). Evaluations included occlusal parameters, the Jaw Functional Limitation Scale (JFLS-20), and polysomnography with EMG muscle tone analysis. Descriptive statistics, inter-group comparisons, Spearman's correlation analyses, and Receiver Operating Characteristic (ROC) curve analyses were performed.

Results: No significant differences in occlusal parameters were observed between the SB and NSB groups. However, SB patients exhibited significantly higher JFLS-20 scores compared to NSB patients (P = 0.002; mean global score: 20.79 ± 31.96 vs. 6.52 ± 9.70). EMG muscle tone showed significant correlations with JFLS mobility (P = 0.015) and overall jaw function (P = 0.046). ROC curve analysis for EMG muscle tone revealed an Area Under the Curve (AUC) of 0.911 (P < 0.001). An optimal cutoff value of 9.79 µV for EMG muscle tone demonstrated a sensitivity of 78.6% and specificity of 87.9%.

Conclusion: EMG muscle tone may serve as a preliminary reference point for differentiating SB from NSB in OSA patients, whereas occlusion lacks diagnostic significance.

Clinical relevance: These findings highlight the importance of incorporating functional assessments into the diagnostic workflow for SB in OSA patients. Therapeutic strategies should prioritize functional management rather than occlusal corrections.