University of York systematic review (2000)
Since 2000, seven systematic reviews of the available scientific evidence on the benefits of water fluoridation have been published.
The first was undertaken by the Centre for Reviews and Dissemination at the University of York, whose research team looked at 26 previously conducted studies to see whether a trend could be identified (1). They found that:
Water fluoridation reduces the number of decayed, missing and filled teeth in children aged 5 to 15 by, on average, 2.25 teeth per child. This works out as an overall reduction in tooth decay of approximately 40% in fluoridated areas (2).
Water fluoridation increases the percentage of children totally free from tooth decay by, on average, 14.6%.
The reduction in the number of decayed, missing and filled teeth following fluoridation is greatest in those areas where children had the highest levels of tooth decay at the outset.
Significant population-wide dental benefits achieved
On a population-wide basis, these benefits are very significant. However, the average reductions in tooth decay cannot be assumed to apply to all children in all fluoridated areas. The York figures were based on studies of children of different ages in different countries at different times. They also combined results from studies of both primary and permanent teeth.
Greatest improvements likely in areas with the highest decay levels before fluoridation
Some children may experience a greater reduction in tooth decay than the figures suggest. Others may experience a lower reduction. According to the York review, the greater the average level of tooth decay among children before a fluoridation scheme starts, the greater the average reduction in tooth decay it is likely to achieve.
Reassurance for public health professionals that water fluoridation prevents tooth decay
Jos Kleijnen, who led York team, subsequently co-authored a paper describing how systematic reviews are carried out (3). Using the York review as a case study, Kleijnen and his co-authors explained how public health professionals in fluoridated areas could make use of its findings: “On the issue of the beneficial effect of water fluoridation, the review reassures you that the health authority was correct in judging that fluoridation of drinking water prevents caries.”
McDonagh M, Whiting P, Bradley M, Cooper J, Sutton A, Chestnut I (2000): A systematic review of public water fluoridation. Centre for Reviews and Dissemination, University of York.
Worthington H, Clarkson J. The Evidence Base for Topical Fluorides. Community Dental Health, 2003, 20: 74-76.
Khan KS, Kunz R, Kleijnen J, Antes G (2003): Five steps to conducting a review. Journal of the Royal Society of Medicine, 96: 118-121.