[Comparative study of the palatal rugae and shape of the hard palatal in Japanese and Indian children].

The materials for study were serial upper jaw plaster casts of 58 Japanese (29 boys and 29 girls) aged 3 to 7 years, and 93 Indians (46 boys and 47 girls) aged 5 to 8 years. I observed and measured the palatal rugae, the papilla incisiva and the shape of the hard palate using the method of Yamazaki, following Lysell's and Hauser's. The differences according to population (1-5), palatal findings (6) and sex (7) are summarized as follows. 1. The number of primary rugae of Japanese children were more than those of Indian children, but the number of transverse palatal rugae were the same. 2. There were differences between Japanese and Indian children in the primary rugae shapes, the posterior limit of the rugae zone, the number and position of the secondary rugae and fragmentary rugae. 3. The papilla incisiva of the Japanese children were a little larger than those of the Indians. Generally the papilla incisiva of the two populations were pear-shaped, but the Indians showed more variability. 4. The palatal raphe of the Japanese were wider than those of the Indians. The number of children with no palatal raphe branch was large for Indian children, but small for Japanese. 5. The frontal view of the hard palate of Japanese children was broad and that of Indian children was narrower than the Japanese. The palatal shape of the two populations was almost trapezoid. The occlusal view of the two populations was broad and U-shaped. 6. There were many transverse palatal rugae in the two populations at the left side. The posterior limit of the ruga zone of the left side was shifted further back than the right side. 7. There were no significant differences between sexes for most of the above points.