Dento-skeletal components of class III malocclusions for children with normal and protruded mandibles

A random sample of 150 British school children was selected age range 9 to 12 years. Lateral skull radiographs were taken and traced. None of the subjects had any orthodontic treatment before. 27 children average age of 10 years were selected on the basis of ANB < or = 1 degree as having class III skeletal relation (15 boys and 12 girls). 16 angular and 8 linear skeletal and dental parameters were used. The sample of class III skeletal relation was divided according to the value of SNB angle into subjects with normal anteroposterior situated mandibles; (SNB < or = 79 degree 14 children) and others with protruded mandibles; (SNB > or = 79.5 13 children). Descriptive statistics for the class III skeletal sample was done and compared to the mean sample. Student t test was performed to identify significant differences between both groups of class III skeletal relation. Significant differences between both groups were found for SNA, P < 0.001; SNPog, P < 0.001; SN MP, P < 0.001; SN-occl, P < 0.001 and 1-APog, P < 0.05.