Functional and craniofacial characteristics in patients with coexisting pain-related temporomandibular disorders and probable sleep bruxism: a cross-sectional study

BACKGROUND: The coexistence of pain-related temporomandibular disorders (TMD) and sleep bruxism (SB) has been associated with functional alterations of the masticatory system; however, integrated evaluation of muscle activity, occlusal function, and craniofacial morphology remains limited. This study investigated masticatory muscle activity (MMA), occlusal function, and craniofacial morphology in patients with TMD and probable SB (TMD P&SB) compared with healthy controls and explored associations between functional and morphological parameters. METHODS: Fifty-four adults were divided into a TMD P&SB group (n = 27) and a control group (n = 27). MMA of the masseter and anterior temporalis muscles was recorded using surface electromyography during maximum voluntary clenching (MVC) and at rest. Occlusal contact area (OCA) and bite force (BF) were assessed using a pressure-mapping system. Craniofacial morphology was evaluated through lateral cephalometric analysis. Between-group differences and correlations between functional and morphological parameters were analyzed. RESULTS: Compared with controls, the TMD P&SB group exhibited greater bite force, altered MMA patterns characterized by higher masseter MMA during MVC and lower masseter MMA at rest, and a smaller gonial angle. In the TMD P&SB group, sagittal craniofacial morphology was associated with functional parameters, whereas in the control group, vertical craniofacial morphology was associated with MMA. CONCLUSION: Patients with coexisting pain-related TMD and probable SB demonstrate distinct functional-morphological patterns involving MMA, occlusal function, and craniofacial morphology. These findings suggest that integrated assessment of muscle activity, occlusal function, and craniofacial morphology may provide additional insight into the functional characteristics of this subgroup while supporting more individualized clinical evaluation. Because SB was identified through clinical assessment and self-report without polysomnographic confirmation, the findings should be interpreted as reflecting probable SB.