title: Relative effects of pre- and post-eruption water fluoride on caries experience by surface type of permanent first molars.
abstract: OBJECTIVE
  To determine the relative pre- and post-eruption exposure effects of fluoridated water on the caries experience of different surface types of first permanent molars.
  
  
  METHODS
  Parental questionnaires covering residential history of participants were linked to the oral examinations of 6-15-year-old Australian children conducted in 1992 by the School Dental Services of South Australia and Queensland. Percentage of lifetime exposed to optimally fluoridated water pre- (PRE) and post-eruption (POST) was calculated with respect to tooth eruption age. Combined pre- and post-eruption categories were created to test PRE against POST exposure: PRE and POST = 0, PRE < POST, PRE = POST and in the range 0-90% of lifetime exposure, PRE > POST and, PRE and POST >or= 90% lifetime exposure. These categories were used as indicator variables in linear regression models with PRE and POST = 0 as reference in an analysis of first permanent molar DMFS scores overall and by surface type.
  
  
  RESULTS
  Participation rates were 69.7% in South Australia (n = 9690) and 55.6% in Queensland (n = 10 195). Compared with the reference, the categories PRE > POST (beta = -0.033), PRE = POST (beta = -0.028) in the range 0-90% and, PRE and POST >or= 90% (beta = -0.055) showed significantly lower caries overall (P < 0.01), with a similar pattern for pit and fissure surface caries (beta = -0.035, -0.031 and -0.052, respectively). Only a high PRE and POST exposure decreased caries levels significantly in the approximal (beta = -0.038; P < 0.01) and free smooth surfaces (beta = -0.023; P = 0.03).
  
  
  CONCLUSIONS
  Pre-eruption exposure was important for a caries preventive effect on first permanent molars in children 6-15 years old since post-eruption exposure alone could not lower caries levels significantly. For pit and fissure surfaces, a high pre-eruption exposure could decrease caries levels significantly. However, for other surface types, only a high pre- and post-eruption exposure produced a caries preventive effect.
authors.affiliation: Australian Research Centre for Population Oral Health, Dental School, Faculty of Health Sciences, The University of Adelaide, Adelaide, South Australia 5005, Australia.
authors.forename: Kiran A
authors.initials: KA
authors.lastname: Singh
authors.forename: A John
authors.initials: AJ
authors.lastname: Spencer
mesh_terms: D000293:Adolescent; D002648:Child; D004245:DMF Index; D003731:Dental Caries / Q000453:epidemiology / Q000517:prevention & control*; D003733:Dental Caries Susceptibility / Q000187:drug effects*; D019229:Dentition, Permanent; D004812:Epidemiologic Methods; D005260:Female; D005457:Fluoridation; D006801:Humans; D008297:Male; D008963:Molar / Q000033:anatomy & histology; D014070:Tooth / Q000033:anatomy & histology; D014078:Tooth Eruption