Analysis Of Masseter EMG Activity In Patients With Bruxism

Objective:To study the characteristics of electromyogram (EMG) of masticatory muscle in patients with bruxism. Investigateing bruxism's impact towards masseter muscle function through analyzing the summit potential of EMG and myoelectricity waves. Then comparing the difference of masseter muscle's myoelectricity during clenching in patients with bruxism group and asymptomatic group , which will provide guiding significance for clinical research and treatment in patients with bruxism.Methods:Fifteen patients with bruxism and fifteen asymptomatic subjects were applied questionnaire investigation. EMG data (myoelectricity value and graphs) was recorded by placing concentric needle electrodes on masseters(MM)during maximal voluntary clenching in intercuspal position . The myoelectricity value and masseter asymmetry index of each side is compared in experiment group and control group. Then compare myoelectricity value and graphs between these two group.Result:EMG myoelectricity waves showed single phase,diphase and heterophase in the two group during clenching. There are 15% heterophase in experiment which is higher than control group,while 10% single phase which is lower than control group. Myoelectricity value's difference was statistically significant. EMG amplitude of the left and right side in the two groups have no statistically significant difference. Although the MM asymmetry index was slightly higher in both sides of bruxism group than in the normal group, the difference was not statistically significant.Conclusion:1. The masseter muscle EMG amplitude in patients with bruxism was significantly low, It can be concluded that long-term bruxism or clenching teeth at night make the excessive contraction of the masseter muscle, and then lead to the muscle damage, decreased contractility,thus result in low potential ICP clenching masseter muscle at last.2. No significant difference was found between bilateral asymmetry index in patients with bruxism, indicating bruxism masseter muscle in the left and right side in the same patients tend to have balanced muscle tension, bruxism is considered bilateral molar movement.3. EMG needle electrode can be more objective, truthful and accurate response to the details of masticatory function, by examining the EMG of patients with bruxism, it can accurately reflect its status, which can then guide clinical treatment.