Treatment changes of Class II malocclusion cases corrected with Class II force system of the Tweed method

Abstract

In the Tweed method, the Class II force system using bulbous loops and sliding jigs is recommended for correction of the Class II molar relationship. However, there have been few studies on the effects of the Class II force system. We therefore evaluated the effects of the Class II force system in the treatment of Class II malocclusion. The subjects were 9 patients with skeletal Class II malocclusion requiring premolar extraction and maximum anchorage (Cl II FS group), and no matter the type of malocclusion, 8 patients requiring premolar extraction and maximum anchorage (control group). In all patients, morphological changes and tooth movements were examined using cephalometric analysis and cast model analysis, and the t-test was used for statistical analysis. The results were as follows. 1. Follwing treatment, decreases in SNA and ANB, lingual inclination of the upper incisors, and clockwise rotation of the occlusal plane were observed in the Cl II FS group, while lingual inclinations of the upper and lower incisors were observed in the control group. 2. Greater intrusion of the lower incisors, greater clockwise rotation of the occlusal plane, and less mesial movement of the upper first molar were observed in the Cl II FS group than in the control group. The results indicate that the Class II force system is effective as a strong anchorage control system.