To study the calcification of second molars in Class I malocclusion with normal craniofacial structure, the author examined cephalograms, orthopantomograms, periapical films of 538 children from 7 y 0 xn to 15y l im old who had Class I malocclusion with normal craniofacial structure, and observed the calcification stage of upper and lower r,Pcond molars.
The results are as follows.
1. The mean ages of crown completion of upper and lower second molars are 8.82±1.14, 8.72± 0.75 in boys, and 8.60±1.46, 8.22±0.92 in girls.
2. The mean ages of root completion of upper and lower second molars are 14.25±1.46, 14.15± 0.83 in boys, and 14.12±0.93, 14.15±0.83 in girls.
3. There are no difference between the calcification stages of upper second molars and those of lower second molars in both sexes.
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