Evaluation of the posterior maxillary teeth movements during Class II correction : 3-dimensional superimposition of casts

Abstract

AIM AND OBJECTIVES: The aim of this study was to analyze the changes of the posterior dentition during Class II correction with the crown Herbst appliance (cHerbst) and intermaxillary Class II elastics. SAMPLE: Class II patients were divided into 2 groups: those who were treated with the cHerbst appliances (n=40, mean age 14.1±1.3) and those who were treated with fixed appliances and Class II elastics (n=20, mean age 16.7±2.7). MATERIALS AND METHODS: The scans of pre- and post-treatment casts the patients were superimposed and registered using the freeware Blender 2.67. The linear measurements in the anteroposterior, transversal and vertical planes along with the rotation angles of the first molars were assessed. RESULTS: In the cHerbst group clinically significant derotation (13.8±5.0°) and distalization (3.2±1.2 mm) of the upper first molars were recorded compared to the intermaxillary Class II elastics group (4.2±5.5°, -0.3±1.5, respectively). In the cHerbst group the second and first premolars followed the distal movements of the upper first molars. The premolars expanded slightly more than the molars in both groups. The posterior teeth extruded in both groups, except the molars in the cHerbst group. CONCLUSIONS: The crown Herbst appliance is significantly more effective in molar derotation and distalization than intermaxillary Class II elastics.