Water fluoridation, bone mass and fracture: a quantitative overview of the literature.

OBJECTIVE: To use the technique of meta-analysis to address the following research questions: Is water fluoridation associated with altered fracture risk at a population level and are the differences between studies consistent with confounding or chance variation between studies? METHOD: The data sources utilised were Medline 1966-97, reviews and bibliographies. The search terms were fluoridation, bone mass and/or fracture. We included all observational studies published in English relating water fluoridation to bone mass and/or fracture in the initial assessment. RESULTS: Water fluoridation had no evident effect on fracture risk (RR 1.02, 95% CI 0.96-1.09, n = 18 studies). There was marked heterogeneity between studies which could be explained, in part, by the combination of gender, urbanicity and study quality (R2 0.25, p = 0.05, weighted analysis). CONCLUSIONS: Water fluoridation both at levels aimed at preventing dental caries and, possibly, at higher naturally occurring levels appears to have little effect on fracture risk, either protective or deleterious, at a population level. The small effect on bone mass seen in studies performed at the individual level is consistent with this finding. Variation between studies is also likely to be due to differences in the distribution of other recognised fracture risk factors between different populations. Confirmation of these findings is required in large studies performed at the individual level.