title: Longitudinal changes in developmental defects of enamel.
abstract: OBJECTIVE
  Epidemiological studies on developmental defects of enamel (DDE) have focused on its potential contributory factors and prevalence while there is limited evidence on the longitudinal changes in the epidemiological profile of DDE. Thus, the objective of this longitudinal study was to investigate whether any type of DDE changes with time.
  
  
  METHODS
  A total of 668 participants were initially recruited in 2010, and 432 participants were successfully followed up and examined for DDE both at the age of 12 in 2010 and 15 in 2013. The central incisor, lateral incisor and first molar in each quadrant were chosen as index teeth and were examined 'wet' by two trained and calibrated examiners using the modified FDI (DDE) Index.
  
  
  RESULTS
  The mouth prevalence and tooth prevalence of 'any defect' showed a significant decrease from 2010 to 2013 (P < 0.001). This was predominantly due to the decrease in diffuse opacities (P < 0.001). Significant difference in the distribution of the extent of DDE was also found for diffuse opacities at both the participant and tooth levels irrespective of the types of tooth (P < 0.0001). Median extent score for diffuse opacities in 2013 was lower than those in 2010 at both participant and tooth level irrespective of the types of tooth (P < 0.001).
  
  
  CONCLUSIONS
  Diffuse opacities, in terms of prevalence and severity, did fade out over time. The observed overall change in DDE was due to the dominating effect of diffuse opacities over demarcated opacities and hypoplasia.
authors.affiliation: Paediatric Dentistry & Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
authors.forename: Hai Ming
authors.initials: HM
authors.lastname: Wong
authors.affiliation: Paediatric Dentistry & Orthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
authors.forename: Yi Feng
authors.initials: YF
authors.lastname: Wen
authors.affiliation: Paediatric Dentistry, School of Dentistry, Faculty of Medicine, Dentistry and Health Sciences, The University of Western Australia, Perth, WA, Australia.
authors.forename: Nigel Martyn
authors.initials: NM
authors.lastname: King
authors.affiliation: Periodontology & Public Health, Faculty of Dentistry, The University of Hong Kong, Hong Kong.
authors.forename: Colman Patrick Joseph
authors.initials: CP
authors.lastname: McGrath
mesh_terms: D000293:Adolescent; D002648:Child; D003743:Dental Enamel / Q000002:abnormalities*; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007180:Incisor / Q000002:abnormalities; D008297:Male; D015995:Prevalence; D014071:Tooth Abnormalities / Q000175:diagnosis / Q000453:epidemiology*
keywords: epidemiology; fluoride