Abstract
We have already investigated the incidence of congenital abnormalities of deciduous teeth including fused teeth, congenitally missing teeth, peg-shaped teeth, and supernumerary teeth in threeyear-old children. The purpose of this study was to compare the incidence of congenital abnormalities of deciduous teeth in Chinese children with our data. The subjects in Japan were 12, 812 children aged three years who visited a Public Health Center in the east district of Fukuoka City for oral examinations during 1983-1990. The subjects in China were 10, 804 children aged from two to six who lived in Shanghai City during 1989-1990.
There was no difference in sex of the incidence of congenital abnormalities of deciduous teeth between Japan and China. Total rate of incidence of congenital abnormalities was 7.42% in China, and 4.89% in Japan. The incidence of supernumerary teeth was 0.44% in China, and 0.01% in Japan. In Japan, the incidence of fused deciduous teeth on the right side was significantly higher than that of the left side (p<0.005). The incidence on the left side was significantly higher than on the right side (p<0.005) in China. Most fused teeth were found in the lower teeth in both countries. Fused teeth were mostly found in central and lateral incisors in Japan, but most fused teeth were found in canine and lateral incisors in China. Unilaterally occurring fused deciduous teeth were detected more frequently than bilaterally fused deciduous teeth in both countries, but no significant difference was observed between Japan and China.
