The effect of community water fluoridation on dental caries in children and young people in England: an ecological study

Background: The protective effect of community water fluoridation (CWF) against dental caries may be modified by secular changes in health behaviour. We aimed to determine the contemporary association between fluoride in public water supplies (PWS) and dental caries indicators and inequalities in England. Methods: We estimated exposure to CWF and PWS fluoride concentrations from national monitoring data, using Geographic Information Systems and water supply boundaries, categorizing mean period exposure into <0.1, 0.1-<0.2, 0.2-<0.4, 0.4-<0.7 and ≥0.7 mg/l. We used area-level health outcome and confounder data in multivariable regression models to determine the association between fluoride and caries outcomes and calculated preventive fractions using these coefficients. Results: The odds of caries and of severe caries in 5-year-olds fell with increasing fluoride concentration in all SES quintiles (P < 0.001 to P = 0.003). There was a negative trend between increasing fluoride concentration and dental extractions (P < 0.001). Compared to PWS with <0.2 mg/l, CWF prevented 17% (95% confidence interval (CI): 5-27%) to 28% (95% CI: 24-32%) of caries (high-low SES) and 56% (95% CI: 25-74%) of dental extractions. The association between fluoride concentration and caries prevalence/severity varied by socioeconomic status (SES) (P < 0.001). Conclusions: Exposure to fluoride in PWS appears highly protective against dental caries and reduces oral health inequalities.