title: Reported prevalence of congenitally missing teeth in two Norwegian counties.
abstract: OBJECTIVE
  The prevalence of hypodontia (congenital absence of one or more teeth) has been reported to vary between 2.2 and 10.1%, but few studies on the prevalence of oligodontia (congenital absence of six or more permanent teeth, third molars excluded) have been performed. The aims of the present study were to examine the reported prevalence of hypodontia and oligodontia among 18-year-old individuals in two Norwegian counties. A further aim was to examine the distribution of missing teeth in this sample.
  
  
  METHODS
  The survey was conducted among 18-year-old subjects in the counties of Oslo and Akershus (n = 9,532, 49% females). Public dentists were asked to count registered congenitally missing and extracted teeth.
  
  
  RESULTS
  The reported prevalence of hypodontia was found to be 4.5%, and was significantly higher among females (5.1%) than males (4.0%). The teeth most often missing were the mandibular second premolars (47% of all missing teeth) followed by the maxillary second premolars and lateral incisors (both 20% of all missing teeth). The reported prevalence of oligodontia was found to be 0.084%.
  
  
  CONCLUSIONS
  Hypodontia was seen in 450 of 1000 and oligodontia 8.4 of 10.000 persons in this sample.
authors.affiliation: Department of Oral Surgery and Oral Medicine, Faculty of Dentistry, University of Oslo, Oslo, Norway. hildeno@odont.uio.no
authors.forename: Hilde
authors.initials: H
authors.lastname: Nordgarden
authors.forename: Janicke Liaaen
authors.initials: JL
authors.lastname: Jensen
authors.forename: Kari
authors.initials: K
authors.lastname: Storhaug
mesh_terms: D000293:Adolescent; D000848:Anodontia / Q000145:classification / Q000453:epidemiology*; D001641:Bicuspid / Q000002:abnormalities; D005260:Female; D006801:Humans; D007180:Incisor / Q000002:abnormalities; D008297:Male; D008334:Mandible; D008437:Maxilla; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D012189:Retrospective Studies; D012737:Sex Factors; D013223:Statistics as Topic