title: Diffuse opacities in 12-year-old Hong Kong children--four cross-sectional surveys.
abstract: OBJECTIVE
  To compare the prevalence and severity of diffuse opacities among subjects whose maxillary incisors developed during periods with different concentrations of fluoride in the Hong Kong public water supply.
  
  
  METHODS
  Standardized intra-oral photographs of random samples of 12-year-old children were collected in 1983, 1991, 2001 and 2010 (n = 2658) in Hong Kong and were assessed for diffuse opacities by a calibrated and blinded examiner. The fluoride concentrations in the public water supply at the times when the enamel on their maxillary incisors developed were 1.0, 0.7, 0.5 and 0.5 ppm, respectively.
  
  
  RESULTS
  The mouth prevalence figures for diffuse opacities of these children (based on the maxillary incisors) were 89.3%, 48.5%, 32.4% and 42.1 in the years 1983, 1991, 2001 and 2010, respectively. Variation in the mouth and tooth prevalences of diffuse opacities was apparent among the four different year groups (P < 0.0001). Marked differences in severity of diffuse opacities, in terms of different subtypes and maximum extent of tooth affected, were also observed in association with the year of study (P < 0.001).
  
  
  CONCLUSIONS
  The prevalence and severity of diffuse opacities among maxillary incisor teeth of Hong Kong children decreased from 1983 and then increased in 2010; however, this change did not fully correspond to the concentration of fluoride in the drinking water during the time of enamel development.
authors.affiliation: Paediatric Dentistry & Orthodontics, Faculty of Dentistry, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Hai Ming
authors.initials: HM
authors.lastname: Wong
authors.forename: Colman
authors.initials: C
authors.lastname: McGrath
authors.forename: Nigel M
authors.initials: NM
authors.lastname: King
mesh_terms: D002648:Child; D003430:Cross-Sectional Studies; D005457:Fluoridation; D009050:Fluorosis, Dental / Q000175:diagnosis / Q000453:epidemiology* / Q000473:pathology; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007180:Incisor / Q000473:pathology; D015995:Prevalence; D012720:Severity of Illness Index
keywords: fluorosis; public health