Dental changes in the mandible during initial Bass appliance therapy

The aim of this study was to analyse movements of lower molars and incisors during 6 months of Bass appliance therapy and to evaluate the dental arch space attained. The sample consisted of 53 patients with severe Class II, division 1 malocclusions. The analyses were performed on lateral cephalograms and dental casts. Sixteen of the patients were followed for 6 months before treatment. Dental space in the lower jaw decreased 0.7 mm (n = 16) during the observation period and increased 1.8 mm (n = 53) during the 6 months of treatment. The molars moved posteriorly a total of 0.7 and tipped distally 2.4 degrees during treatment. The incisors moved anteriorly 0.3 mm and tipped mesially 0.5 degree.