title: Hypodontia and hyperdontia of permanent teeth in Hong Kong schoolchildren.
abstract: This study was performed to determine the prevalence of hypodontia and hyperdontia of permanent teeth amongst Southern Chinese children in Hong Kong. The sample consisted of 1093 12-yr-old children on whom a panoramic radiograph was taken. The prevalence of congenitally missing teeth (third molars excluded) was 6.1% in boys, 7.7% in girls, and 6.9% for both sexes combined. On the average, each child was missing 1.5 teeth. The most commonly absent tooth was the mandibular incisor, affecting 58.7% of the children with hypodontia. Thirty children (2.7%) had supernumerary teeth, with a male:female ratio of 6.5:1; in four cases the tooth had erupted. Three children had fourth molars and one case of a supplemental premolar was recorded (all unerupted). Four cases of a maxillary supernumerary tooth and hypodontia in the mandible were seen.
mesh_terms: D000848:Anodontia / Q000453:epidemiology* / Q000208:ethnology; D002648:Child; D005260:Female; D006723:Hong Kong; D006801:Humans; D007180:Incisor / Q000002:abnormalities; D008297:Male; D014096:Tooth, Supernumerary / Q000453:epidemiology* / Q000208:ethnology