Prevalence of congenital dental anomalies of the deciduous dentition in Japanese children.

We examined the prevalence of anomalies in deciduous dentition in 2,733 Japanese three-year-old children. The results showed that fused teeth occurs in 4.10%, congenital missing teeth in 2.38%, enamel hypoplasia in 1.50%, peg-shaped teeth in 0.55%, palatal cusps in upper deciduous incisors in 0.37%, supernumerary teeth in 0.07%, and color anomalies in 0.07%. Sixty-nine boys and 43 girls had fused teeth, percentages of 4.88 and 3.26, respectively. This difference was significant. All the fused teeth were located in the anterior region and were more frequent in the mandibular than in the maxillary arch. In the mandibular arch, 50 cases involved the lateral incisor and canine; the central incisor and lateral incisor were fused in 48 instances. There were 30 boys (2.12%) and 35 girls (2.65%) with congenitally missing deciduous teeth. This difference was not significant. Unilateral missing teeth were more frequently observed than bilateral missing ones. The lower lateral deciduous incisor was the most frequently missing tooth. The prevalences of fused teeth and congenital missing teeth were significantly higher in this study than in studies of American and Scandinavian children. These two anomalies are tending to increase in frequency in Japan.