Activity of jaw-opening and jaw-closing muscles and their influence on dentofacial morphological features in normal adults

The purpose of this study was to determine the relationship between the den tofacial morphology and the function of masticatory muscles estimated by ki nesiological measurements during isotonic jaw-opening (O) and closing (C) m uscle contractions. We examined 26 male adult subjects who had no history o f masticatory dysfunction. Three kinesiological. parameters, the maximum fo rce (F-max), maximum velocity (V-max) and maximum power (P-max) were measur ed in both O and C muscles. Correlation analysis was performed between thes e parameters and dentofacial morphological features determined on lateral r oentgenographic cephalograms. The F-max (C), V-max (O), log O/C of V-max an d P-max (O) significantly correlated with anterior overbite. P-max (C) sign ificantly and negatively correlated with SN-ArG. Furthermore, log O/C of Pm a., significantly and negatively correlated with SNA, SNB and ArG/GMe, and positively with SN-ArG. These results, combined with our previous findings that electromyographic muscle activity during isometric contraction correla ted significantly with mandibular morphology, indicate that the dentofacial morphology is influenced by the function of both O and C muscles.