Comparative analysis of myoelectric activity and mandibular movement in healthy and temporomandibular disorder subjects

Abstract Objectives: Temporomandibular disorders (TMD) are one of the leading causes of craniofacial pain, and a high incidence of TMD in young adults has been reported. Previous studies have used surface electromyography (sEMG) and mandibular kinematic analysis to diagnose TMD. This study aimed to provide normal reference values of sEMG and mandibular kinematics in Chinese young adults, compare the sex differences and assess the diagnosis value of these indices. Materials and methods: This was an observational study that 90 healthy young adults (49 women and 41 men) with individual normal occlusion were strictly selected by diagnosis standard, and 26 TMD patients with disc displacement (13 with reduction and 13 without reduction) were recruited. The sEMG signals of the anterior temporalis (TA), masseter (MM), and sternocleidomastoid and digastric were recorded in the mandibular postural positions (MPP) and during maximal voluntary clenching (MVC) with K7 electromyograph. Mandibular kinematics, including maximum opening and opening/closing velocities, were assessed by K7 kinesiograph. Results: In healthy subjects, the sEMG reference values ranged from 3.0 to 4.3 μV in the MPP. The sEMG values during MVC, maximum opening, and opening velocity were significantly higher in males than in females, and also these indices showed good diagnostic efficiency for articular TMD. Conclusions: Reference values and sex differences in sEMG and mandibular kinematics in healthy subjects were determined. Compared with them, TMD patientsshowed significantly lower myoelectric activity during maximal biting and restricted mouth opening range and velocity, which may assist in TMD diagnosis. Clinical relevance: By analyzing sEMG of masticatory muscle and mandibular kinematics data from healthy Chinese young adults and TMD patients with disc displacement, this study evaluated the sex difference and diagnosis value of these indices for TMD. Clinical Trial Registration ID: NCT06372769