To study the calcification of second molars in skeletal class II malocclusion, the author examined cephalograms., orthopantomograms, periapical films of 391 children from 7y o m to.15y 11 m years old who had skeletal class II malocclusion, and observed the difference in the calcification stage between upper and lower second molars. .
The results areas follows.
1. The mean ages of crown completion of upper and lower second´ molars are
8.7 ± 1.75, 8.8 ± 1.13 in. boys,.and 8.4 ± 0.81, 8.5 ± 0.91 in girls.
2. The mean ages of root completion of upper and lower second molars are 14.0
1.09, 14.5 ± 0.52 in boys, and 13.7 ±1.15, 13.8 ± 1.18 in girls.
3. The calcification stages of upper second molars are more advanced than those
of lower second molars at 5% level in both sexes.
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