Water fluoridation and disparities in oral health among children: A multi-level analysis

Objective: To investigate the effect of water fluoridation in reducing dental caries in 6-7 year-old children who have had access to dental care throughout their lives. We investigated the effect of water fluoridation on the association between the severity of dental caries and socio-economical status. Methods: A representative sample of first graders was selected by a stratified multi-stage sampling of primary schools in Nova Scotia, Canada (n = 1,614). The response rate was 78.8%. The severity of dental caries was measured by two trained dentists based on modified WHO criteria (non-cavitated pits and fissures were scored separately from cavitated decayed surfaces). Only life-long residents of Nova Scotia (n=955) were included in this analysis. Water fluoride concentration was measured from the water supply of each school. SAS was used for descriptive analysis while Hierarchical Linear Model 5 (HLM 5) was used for multilevel analysis. Results: Fluoride concentration in the school water supply and parents' education are negatively associated with children's dental caries. The multi-level analysis shows that as the concentration of fluoride in the school water increases, the association between parent education and decayed tooth surface weakens. That is, water fluoridation may be effective in reducing disparities in caries among children with different parental education levels. However, this result is not statistically significant. Conclusion: The findings indicate that water fluoridation is effective in reducing caries, but the disparities in caries among children of different socioeconomic statuses remain even with water fluoridation and life-long dental insurance coverage.