Effectiveness of Water Fluoridation at 0.7ppm
Objectives: In 2007 the level of fluoride in the water in Ireland (73% coverage) was reduced from 0.8-0.9ppm to 0.6-0.8ppm. In 2015 the US DHSS followed suit. We describe the impact of this reduction on dental caries among Irish children after 7 years.
Methods: A stratified cluster random sample of 5- and 12-year-old children was clinically examined. Parents/guardians completed a questionnaire, measuring confounders for caries. The mean caries levels for 5- and 12-year-old children in 2014 (7-years post-reduction) were compared with comparable data for these age groups in the same regions in 2002 (5-years pre-reduction). Multivariate regression analyses and the Hurdle model were used to analyse the relationship between caries and water fluoridation in 2014, while controlling for age, gender, socio-economic status, behavior and breastfeeding in infancy. Variables were considered significant at p≤0.05.
Results: After the clinical examination investigation of individual residential histories, allowed classification of 2,324, 5-year-olds and 1,595 12-year-olds as ‘Full-Fl’ or ‘Non-Fl’. Among 5-year-olds there was little difference in caries levels between 2002-2014, caries levels were lower among fluoridated groups in both studies. For 12-year-olds caries levels were lower in 2014 than in 2002; in fluoridated Dublin the mean DMFT(sd) was 0.7(1.3) in 2014 and 1.2(1.6) in 2002; in fluoridated Cork and Kerry the mean DMFT(sd) was 0.8(1.3) in 2014 and 1.4(2.0) in 2002 and in non-fluoridated Cork and Kerry the mean DMFT(sd) was 1.4(1.8) in 2014 and 2.2(2.7) in 2002. In the multivariate analysis (Hurdle Model), for 5- and 12-year-olds in 2014, having always (vs never) resided in an area with water fluoridation decreased the odds of having dentinal caries by 46.4% and 45.1% respectively, holding all other variables constant.
Conclusions: Caries levels did not increase following the reduction in fluoride levels; water fluoridation at 0.6-0.8ppm is associated with a lower caries prevalence compared with no exposure to water fluoridation.