幼若永久歯の総合的研究

The purpose of this study was to find out the actual condition of imature permanent teeth, the care of imature permanent teeth and the establishment of oral health care during childhood. A study organaization was organized under 29 professors of the Departments of Pediatric Dentistry of dental collages and universities in Japan for this study.<BR>The subjects,4,080 children (2,015 boys and 2,065 girls) ranging from 5 to 16 years of age, were examined transversally.<BR>This report is concerned with results of an investigation into the degree of eruption, developmental disuturbance of tooth structure, and the pattern of occlusion.<BR>The findings were as follows.<BR>1) There were no differences in degree of eruption of the right and left teeth with the same name between the boys and girls in any age group. The girls showed a tendency toward more accelerated eruption compared with the boys. Among the boys and the girls as well, the teeth which showed the most accelerated eruption were the mandibular central incisors, while the mandibular teeth except the second premolars tended to show more accelerated eruption compared with the teeth with the same name in the maxilla.<BR>2) Developmental disuturbances of the tooth structure were found most frequently in the mandibular lateral incisors among the boys and the girls as well. The frequency of enamel hypoplasia was 1% or below for any tooth. Pegged teeth and incisive blind foramen were found most frequently in the maxillary lateral incisors. Of abnormal tubercles, the Carabelli tubercle was observed most frequently. The frequency of incisive tubercles/central tubercles was 1% or below in all teeth.<BR>3) As for malocclusion, crowding was observed most frequently and open-bite was observed most rarely. Prognathism tended to be found more frequently among the girls than the boys, and it was suggested that the frequency rises with age until around the age of 12. The frequency of either reversed occlusion or open-bite was 10% or below among the boys as well as the girls of any age group. Crowding showed a higher frequency and a tendency toward earlier development among the girls compared with the boys.