STATISTICAL-ANALYSIS OF DIFFERENTIAL LISSAJOUS EMG FROM NORMAL OCCLUSION AND CLASS-III MALOCCLUSION

The method of differential lissajous electromyography (DL-EMG) was app lied to investigate the relationship among the integrated EMG activity , timing, and coordination of the bilateral superficial anterior tempo ral and masseter muscle activities in normal occlusion and Class III m alocclusion subjects. In both Class III malocclusion and normal occlus ion subjects, the working side muscles showed a higher mean cumulative voltage (MCV) and mean maximum peak voltage (MMPV) compared with the balancing side. In addition, a higher MCV and MMPV of the working side masseter was observed in the normal occlusion group compared with tha t seen in the Class III group during both right and left side chewing (p<0.01). Discriminant analysis applied to examine the distribution, t he size and the shape of DL-EMG pattern further indicated a statistica l difference between subject groups (p<0.01). Finally, there was a sig nificantly higher percentage of clockwise DL-EMG pattern-generation in the normal group compared with that seen for Class III subjects (p<0. 01). These data indicate that, compared with normal subjects, patients with a Class III malocclusion have a demonstrably abnormal masticator y muscle balance which is well characterized by the DL-EMG method.