The purpose of the present investigation was to ascertain the virtical mandibular maximal opening capacity, measuring the incisal edge to edge distance of both jaws and to establish a norm or average range of values in children. The subjects were 2207 children (1114 boys and 1093 girls) ranged 3 to 15 years old.
The results obtained were as follows;
1. The mean value of the maximal opening capacity increased with age, and the values were greater in boys than in girls.
2. The amount of increase throughout the period of from 3 to 15 years of age was 16.7 mm in boys and 12.1 mm in girls.
3. The minimal values of the mandibular opening were 32.7 mm for 3 to 5 year olds,33.8 mm for 6 to 8 year olds,37.5 mm for 9 to 11 year olds and 35.8 mm for 12 to 15 year olds.