Short-term Changes of EMG of the Masticatory Muscles due to Wearing an Experimental Prematurity

Abstract

The influences of vertical (V-type) and horizontal (H-type) prematurities with approximately 115μm in thickness on the jaw closing muscles were electromyographically evaluated. EMGs were obtained of the posterior portion of the temporal and masseter muscles bilaterally during successive jaw tapping and chewing gum chewing. Recordings were made on just before, immediately after, and 2, 7 and 14 days after wearing the experimental prematurity.
After wearing the prematurity, increased APSP and decreased AOSP with the day were observed in the Hgroup, while little fluctuant APSP and immediately decreased and then gradually increased AOSP were recognized in the V-group.
Coefficient of variation (CV) of APSP proved higher after wearing the prematurity, although it reduced to the control level at 2 days and 7 days after wearng the prematurity in the H-and V-groups respectively.
Regarding duration and integrated EMG activity, smaller values in the H-group and larger ones in the V-group were found after wearing the prematurity.
CV-coordination of burst activity obtained in the prematurity-wearing side chewing showed balancing-Mm predominant pattern in the V-group, and working-Tp predominant pattern in the H-group.
From above mentioned results, it became clear that the responses of the masticatory motor system to the prematurities differed with the type of given premature contact. Furthermore, an injuriousness of the prematurity has been inferred from the view point of a force regulating mechatnism of the masticatory motor system.