Dento-skeletal components of class II malocclusions for children with normal and retruded mandibles

A random sample of 150 British school children aged 9 to 12 years was selected. Lateral skull radiographs were taken and traced. None of the subjects had any orthodontic treatment before. Out of the sample of 150 children, 41 children (18 boys and 23 girls) were selected on the basis of ANB angle > or = 4.5 degrees, as having class II skeletal relationship. Average age of the children was 10 years, 16 angular and 8 linear, skeletal and dental parameters were used. The 41 class II skeletal sample was divided according to the value of SNB angle into subjects with normal anteroposterior positioned mandibles (SNB > or = 76 degrees--19 children) and retruded mandibles (SNB < or = 75.5 degrees--22 children). Descriptive statistics for the skeletal class II sample was done, which confirmed earlier studies. In addition, descriptive statistic was done for each SNB group in order to characterize them. Student t test was done to identify significant differences between both groups of skeletal class II. The results revealed significant difference for SNA (P < 0.001); SN-Pog (P < 0.001); NS Gn (P < 0.001); SN-MP (P 0.001); ANS-PNS-Go-Me (P, 0.01); SN-occl (P < 0.001); 1-MP (P < 0.01); N-Me (P < 0.001); N-ANS (P < 0.05).