Aim: To determine the association between dentinal caries (D3vcMFT) and water fluoridation (0.6ppm at least) in
12-year-old children in the FACCT (Fluoride And Caring for Children’s Teeth) study, in counties Cork and Kerry,
Republic-of-Ireland. The Clinical Research Ethics Committee of the Cork University Teaching Hospitals gave ethics
Methods: A stratified cluster random sample of 12-year-old children individually categorised as having lifetime
exposure to water fluoridation(‘Full-Fl’) or no exposure to water fluoridation(‘Non-Fl’) were clinically examined and
D3vcMFT recorded. Parents/guardians provided demographic, socioeconomic, oral hygiene and dietary information
including whether breastfed.Multivariate regression analyses (Poisson model, negative binomial model (NBRM)), and
the Hurdle model (logit and zero-truncated negative binomial models) were used to analyse the relationship between
D3vcMFT and water fluoridation, while controlling for age, gender, socio-economic status, behaviour variables
including whether breastfed. Variables were considered significant at p≤0.05.
Results: In total 47% (n=469) of the 998, 12-year-old children examined and individually categorised as ‘Full-Fl’
or ‘Non-Fl’ had a D3vcMFT>0. In the NBRM, which was a better fit for the data than the Poisson model, categorised
as ‘Full-Fl’ rather than ‘Non-Fl’ decreased the expected number of D3vcMFT by 32.0%, holding all other variables
constant; brushing twice/day or more at 12-years-old and having been breastfed also decreased the expected number
of D3vcMFT. Being economically disadvantaged increased the expected number of D3vcMFT by 43.5%, holding all
other variables constant. In the first part of the Hurdle model, being in the Full-Fl group decreased the odds of
D3vcMFT>0 by 45.1%; having been breastfed decreased the odds of D3vcMFT>0 by 29.2%; being categorised as
disadvantaged increased the odds of having decayed teeth by 49.2%, holding all other variables constant.
Conclusion: For 12-year- olds, exposure to domestic water fluoridation at a concentration of at least 0.6 ppm is
associated with a lower number of teeth with dentinal caries and lower odds of having any dentinal caries compared
with no exposure to domestic water fluoridation.