EMG-characteristic of masticatory muscles in patients with class II malocclusion and temporomandibular disorders

Introduction: A stable state of musculoskeletal system is provided by harmony of occlusion, the anatomy of temporomandibular joints, and the activity of the masticatory muscles under the control of peripheral and central nervous system. Surface electromyography (EMG) is a well-used modality and is used in dentistry to access the status of the muscles of mastication. The aim of the research was to evaluate the EMG-characteristic of masticatory muscles in patients with TMD and Angle Class II malocclusion.

Materials and methods: The study comprised 23 patients with Angle Class II malocclusion and TMD. The average age of the subjects was 26,5 ± 2,3 years. Malocclusion was evaluated according to Angle classification, TMD - according to the Research Diagnostic Criteria (RDC/TMD). Registration of EMG-activity of masseter and anterior temporalis muscles was performed during maximum voluntary clenching, clenching on the right and left sides.

Results: EMG-activity of masticatory muscles are characterized by: 1) increased values of EMG-activity of temporal and masseter muscles - peak and average amplitude in tests of unilateral clenching and maximum clenching (values are greater than 2000 μV); 2) in unilateral clenching of jaws (on the left or right) the increased EMG-activity was detected on the balancing side; 3) in unilateral clenching of jaws (on the left or right) the increased muscle activity on the working side with disproportional (asymmetric) load distribution between masseter and temporal muscles has been found.

Conclusions: Patients with Angle Class II malocclusion and TMD were found features of EMG-activity of masticatory muscles.