The effect of treatment with the Bass appliance on skeletal class II malocclusions: a cephalometric investigation

The purpose of this investigation was to study the short-term effects of treatment with the Bass appliance by comparative evaluation of treated and untreated skeletal Class II malocclusions. The subjects consisted of forty-seven Class II, division 1 malocclusion cases. Twenty-seven (14 girls, 13 boys) were treated with the Bass appliance for an average of 6 months. The remaining 20 cases (6 girls, 14 boys) served as a control. At the end of the 6 month treatment period the statistically significant treatment changes could be summarized as follows: the sagittal skeletal relationship was improved as a result of favourable growth responses in both the maxilla and the mandible. The overjet was reduced and the molar relationship was corrected as a result of the extended skeletal changes. Distal movement of the upper dentition was evident, with unchanged inclination of the maxillary incisors. Both anterior and posterior facial heights were increased without changes in the inclinations of the palatal and mandibular planes. No significant dental movement was observed in the mandible.