Abstract
Objective Does water fluoridation have negative effects? This objective was broken down into four sections: fluorosis, bone fracture and bone development effects, cancer, and other possible adverse effects.
Data sources See page 37.
Study selection A total of 88 studies met the inclusion criteria for fluorosis. All studies were level C, except one of level B. The mean validity score was only 2.8 out of 8.0.
Data extraction and synthesis Because the studies used different indices to assess fluorosis, the percentage prevalence of fluorosis was the outcome of interest. Regression analysis was used to investigate the association of water fluoride level with the prevalence of dental fluorosis. A multilevel model was used to combine studies.
Results Regression analysis showed a significant dose–response relationship for both methods of measuring the prevalence of fluorosis. The pooled estimate of the prevalence of fluorosis and fluorosis of aesthetic concern are shown in the Table 1 below.
A rough approximation of the number of people who would have to be exposed to water fluoride levels of 1.0 ppm when compared with 0.4 ppm for one additional person to develop fluorosis of any level is six [95% confidence interval (CI), 4–21—the number needed to harm (NNH)]. This rises to 22 (95% CI, 14–28) for fluorosis of aesthetic concern. A sensitivity analysis of the regression analysis was conducted in which all data-points above 1.5 ppm were excluded it was suggested that the higher water fluoride levels could potentially force the regression line to show a relationship that may not actually exist for the lower levels of fluoride. The proportions predicted by this model are similar to the initial analysis but with wider CI (Table 2).
An increase in the prevalence of fluorosis over time was not seen in this analysis of water fluoridation studies. While this finding is counterintuitive, no explanation is evident from the data.
Conclusions These results show a strong association between water fluoride concentration and the proportion of the population with dental fluorosis.
McDonagh M, Whiting P, Bradley M, Cooper J, Sutton A, Chestnutt I, et al. A Systematic Review of Public Water Fluoridation. September 2000. Publications Office, NHS Centre for Reviews and Dissemination, University of York, York YO10 5DD, UK. ISBN 1 900640 16 3
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Address for reprints: Publications Department, NHS Centre for Reviews and Dissemination, University of York, Heslington, York YO10 5BB, UK.
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O'Mullane, D. Strong association between water fluoride concentration and proportion of the population with dental fluorosis. Evid Based Dent 3, 43–44 (2002). https://doi.org/10.1038/sj.ebd.6400100
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DOI: https://doi.org/10.1038/sj.ebd.6400100