Abstract
The degree of tooth formation was studied quantitatively using 1101 orthopantomograms (533 males and 568 females) obtained from Japanese children aged 2 to 15 in the pediatric clinic of Fukuoka Dental College. The assessment was based on the tooth formation stages by Moorrees, et al. slightly modified by the authors. They were divided into 14 stages for permanent first and third molars.
Each stage consisted of points ranging from 1 to 14.
The following results were obtained.
1. The permanent first and third molars on one side developed at the same rate as its counterpart on the other side regardless of sex or arch differences.
2. The tooth germ of the upper third molar was found first at age 6 and the lower third molar at age 5.
3. The occurrence time of the tooth germ of third molar was almost the same as the root-apex formation of the first molar. The occurrence of the right and left sides was 76%.
We concluded that the root formation of the permanent first molar can serve as an index of the tooth germ formation of the third molar, and also this finding contributes to the radiation reduction in children.
