Orthodontic and orthopedic effects of Activator, Activator-HG combination, and Bass appliances: a comparative study.

The orthodontic and orthopedic effects of the Activator, Activator-Headgear Combination (ACHG) and the Bass appliance systems were compared by analyzing the cephalometric records of 64 subjects, who were treated for skeletal Class II malocclusion, with both conventional and Pancherz's methods. Differences between observations on the different occasions (starting and ending values) were tested with Wilcoxon's matched pairs rank test. Kruskal-Wallis nonparametric analysis of variance was carried out in different situations among all three groups. If a level of significance less than 0.05 was observed, Scheffè's method of multiple comparisons was used to determine differences among groups. The results of this study showed that greater improvement in sagittal skeletal relationship (ANB angle) was obtained in both Bass and ACHG groups than in the Activator group. The differences between the groups were most pronounced for dental variables. The Bass appliance was found to be more effective in the control of the unwanted side effects (proclination of lower incisors, retroclination of upper incisors). Unfavorable labial tipping of the lower incisors was also prevented with the ACHG appliance.