Evidence of sex-specific differences in masticatory jaw movement patterns.

The complexity of human oral functional movements has not been studied in detail quantitatively, and only recently have studies begun to evaluate whether such movements contain sex-specific characteristics. Therefore, the purposes of this study were: (1) to quantify in detail the jaw movements and associated masticatory electromyographic activity occurring during gum chewing, and (2) to explore these data for evidence of sex specificity. Fourteen male and 17 female subjects participated in the study. Approximately 11 right- and 11 left-sided chewing cycles and associated masticatory electromyographic activity were sampled from each subject. The samples were quantified into 165 variables per chewing cycle, averaged to create a single multivariate vector for each subject, and then analyzed by a step-wise discriminant analysis. With a combination of 6 variables, a jackknifed cross-validation test found the probability of correct classification to be 93.5%. These findings support the hypothesis that masticatory jaw movements contain sex-specific features.