Results: The average AHI decreased significantly after treatment (before, 23.2; after, 7.4). A significant decrease in AHI was observed even in the severe OSAS group and AHI decreased significantly in every level of severity. Based on the logistic regression analysis in the decreased group and the no change/increased group, age, baseline AHI, and amount of mandibular protrusion were selected as the final explanatory variables and the partial regression coefficients of the three variables were significant. The correlation coefficient of the regression equation was 0.60, which was significant.