Impact of Reducing Water Fluoride on Dental Caries and Fluorosis

Guidance intended to reduce fluoride toothpaste ingestion in early childhood was introduced in Ireland in 2002. In 2007, water fluoride concentration was adjusted from 0.8-1.0 to 0.6-0.8 ppm. The objective of this study was to determine the difference in caries and fluorosis levels following introduction of these 2 policy measures. A before-and-after study compared caries and fluorosis in random samples of 8-y-olds in Dublin (n = 707) and Cork-Kerry (n = 1148) in 2017 with 8-y-olds in Dublin (n = 679) and Cork-Kerry (n = 565) in 2002. Dentinal caries experience (primary teeth, d(3vc)mft(cde)) and fluorosis (permanent teeth, Dean's index of very mild or higher) were clinically measured. Lifetime exposure to community water fluoridation (CWF) was classified as "full CWF"/"no CWF." Effect of examination year on caries prevalence and severity and fluorosis prevalence was assessed using multivariate regression adjusting for other explanatory variables. There was little change in commencement of fluoride toothpaste use at <= 24 mo following introduction of toothbrushing guidance. Among children with full CWF, there was no statistically significant difference in caries prevalence or severity between 2017 and 2002. In 2017, caries prevalence was 55% in Dublin (full CWF) and 56% in Cork-Kerry (full CWF), and mean d(3vc)mft(cde) among children with caries was 3.4 and 3.7, respectively. Caries severity was less in 2017 (mean 4.2) than 2002 (mean 4.9) among children with no CWF (P = 0.039). The difference in caries severity between children with full CWF and no CWF was less in 2017 than in 2002 (interaction P = 0.013), suggesting a reduced benefit for CWF in 2017. In 2017, fluorosis prevalence was 18% in Dublin (full CWF) and 12% in Cork-Kerry (full CWF). Fluorosis was predominantly "very mild" with no statistically significant difference between 2017 and 2002. CWF at 0.6 to 0.8 ppm is an effective caries-preventive measure. Results suggested low uptake of toothbrushing guidance, a reduced caries-preventive effect for CWF in primary teeth, and no reduction in fluorosis following introduction of the policy measures.