The effectiveness of water fluoridation in reducing dental caries has been the focus of public health research for decades. A recent comparative study published in Cochrane Library examined cohorts of adults born before (prior to 1960) and after the widespread implementation of fluoridation, finding a positive association between lifetime exposure to fluoridated water and lower caries levels in both groups.
The review suggested that water fluoridation may reduce inequalities in dental health across social classes in five- and twelve-year-olds, as measured by the dmF (decayed, missing, filled primary teeth) and DMFT (decayed, missing, filled permanent teeth) indices. However, the evidence was limited, being derived from a small number of heterogeneous studies of relatively low quality.
Over the past 20 years, most studies evaluating water fluoridation’s impact on caries prevention have relied on cross-sectional designs with improved handling of confounding factors. Although newer studies indicate a smaller measured effect compared to earlier research, the effect remains statistically significant. This smaller effect size may stem from a "diffusion effect," occurring in areas where high proportions of the population already receive fluoride from various sources. The diffusion effect may partially diminish the unique impact of water fluoridation in such populations.
The review of dental fluorosis data reveals trends comparable to a review published in 2000 by McDonagh and colleagues. While the McDonagh review focused on fluoride concentrations of up to 5 ppm, the current analysis extended to all studies, irrespective of concentration levels. Both reviews estimated the prevalence of dental fluorosis of aesthetic concern at recommended fluoride concentrations. The current review found a slightly higher prevalence (12% vs. 9%), indicating that fluoride levels correlate with dental fluorosis prevalence. However, a broader range of fluoride exposure sources could influence these outcomes, complicating direct comparisons.
“Even in an era with widespread availability of fluoride from various sources, other studies show that community water fluoridation prevents at least 25% of tooth decay in children and adults throughout their life span. The scientific weight of sound evidence around the benefit of community water fluoridation is clear and compelling,” said Linda J. Edgar, D.D.S., president of the American Dental Association.
Current evidence suggests that water fluoridation effectively reduces dental caries, particularly in children’s primary and permanent dentition, although the magnitude of the effect may be influenced by modern fluoride exposures from multiple sources.
Sources: Cochrane Library, American Dental Association
