Assessment of Awake and Sleep Bruxism in Fibromyalgia Patients with Temporomandibular Disorders

Background/Objectives: Fibromyalgia (FM) is a chronic pain syndrome often associated with musculoskeletal tenderness, fatigue, and sleep disturbances. Temporomandibular disorders (TMDs) and bruxism are frequently observed comorbidities in patients with FM, yet their objective assessment remains limited. This study aimed to evaluate masticatory muscle activity in patients with fibromyalgia and temporomandibular disorders using both static surface electromyography (sEMG) and a 24 h portable EMG device (Dia-BRUXO^®). Methods: Thirty female patients (mean age 53.6 ± 10.5 years) underwent comprehensive clinical and gnathological evaluations, followed by static EMG recordings of the masseter and temporalis muscles and continuous monitoring of the left masseter over a 24 h period. Results: Results revealed a significantly higher number of bruxism episodes during wakefulness (80.9 ± 130.8) compared to sleep (24.0 ± 26.8; p < 0.0001). The Masseter Time Index (MTI) and Masseter Work Index (MWI) were also significantly higher during wakefulness (p < 0.001), indicating a predominance of daytime masticatory muscle activity. Static sEMG analysis showed generally preserved bilateral muscle symmetry, accompanied by mild imbalances in occlusal load distribution and increased global muscle activation. Conclusions: These findings suggest that patients with fibromyalgia and temporomandibular disorders exhibit increased baseline masticatory muscle activity, particularly during wakefulness, possibly reflecting sustained neuromuscular tension. Continuous EMG monitoring appears to provide an objective tool for characterizing bruxism patterns and complements clinical assessment and self-reported data. However, the absence of a control group and the exclusive inclusion of female patients limit the generalizability of the results. Further studies including appropriate comparison groups are needed to clarify the specificity and clinical implications of these findings.