[Hard palate shape in the Japanese and Indian children on moiré topography with lateral movement of a grating].

In the present study, the hard palate of Japanese and Indian children was investigated. These children lived in different geographical areas and have different cranial characteristics, pronunciation and eating habits. Fifty-one Japanese children (26 boys and 25 girls, 3 years of age) and 66 Indian school children (31 boys and 35 girls, 5-7 years of age). The maxillary negative cast models were observed and three-dimensional measurements were taken of the hard palate with moiré Topography. The following results were obtained. 1. The palatal width and length in Japanese children was larger than the Indian children, but not in palatal height. The palatal height was significantly larger in the Indian children than in the Japanese children. 2. Observation of the moiré fringes on the deepest palate by moiré Topography shows that the Japanese children and Indian girls have a higher incidence of Crosswise type than Lengthwise type. The Indian boys have a slightly higher incidence of Lengthwise type than Crosswise type. The girls have a higher incidence of the Butterfly and Separate types than the boys. 3. The anteroposterior location on the deepest palate by moiré Topography: the Japanese children have significantly higher incidences of anterior location than the Indian children. Changes of anteroposterior location between the ages of 5 and 7 in the Indian children: the prevalence of posterior location appears to increase with age. 4. The hard palate shapes of the Japanese children appear to be broad and shallow, but those of the Indian children appear to be narrow and deep. This difference appears to be more remarkable in the boys. The shape and size of the hard palate appears to be due to genetic differences, in addition to the weather conditions, pronunciation and eating habits.