In the 1986-87, the National Institute of Dental Research (NIDR) conducted the largest ever study of childhood dental health in the United States. The study examined the teeth of 39,207 schoolchildren from 84 communities across the country, including communities that fluoridate water and communities that do not. The results of the study were published in two papers–one authored by anti-fluoridationist scientist Dr. John Yiamouyiannis and one authored by the pro-fluoridation scientists Janet Brunelle and James Carlos. As discussed below, both analyses found very little practical difference in tooth decay between children who had lived their entire lives in fluoridated areas and those who had lived their entire lives in nonfluoridated areas.

The Two Analyses: DMFT & DMFS

In the study by Yiamouyiannis, tooth decay was measured in terms of Decayed, Missing, and Filled Teeth (DMFT). In the study by Brunelle & Carlos, tooth decay was measured as Decayed, Missing, and Filled Surfaces (DMFS). Whereas DMFT reflects the total number of impacted teeth, DMFS reflects the total number of impacted tooth surfaces.

Since a grown child has up to 28 teeth and 128 tooth surfaces in their mouth, the maximum DMFT score is 28, while the maximum DMFS score is 128. DMFS thus provides a more sensitive measurement of dental decay than DMFT. As such, dental treatments — particularly th0se that have little effect on tooth decay — can reduce DMFS without actually reducing DMFT.

DMFT Results

When the NIDR’s findings are expressed in terms of DMFT, no statistically significant difference can be detected between children living their entire lives in either fluoridated and children living in unfluoridated areas. Children in the fluoridated areas had an average DMFT of 1.97, whereas children in the non-fluoridated areas had an average DMFT of 2.05.  This represents a relative difference of just 4%, and an absolute difference of less than 1/10th of a tooth.

DMFS Results

When the NIDR’s findings are measured in terms of DMFS, the size of the effect is again notably small. The average DMFS for children in fluoridated areas was 2.79, while the average DMFS for children in the non-fluoridated areas was 3.39. This represents a relative difference of 18%, but an absolute difference of just 0.6 tooth surfaces. Although the NIDR trumpeted this finding as proof that water fluoridation has played a “dominant role” in the decline of tooth decay in the United States, 0.6 tooth surfaces amounts to an absolute difference of less than 1% of the 100-plus tooth surfaces in a child’s mouth.  Although the DMFS analysis was conducted by trained epidemiologists, the study never mentions whether this small difference in DMFS is statistically significant.

Conclusion

Whether one uses the DMFT or DMFS index, it is clear that NIDR’s national survey found very little practical difference in tooth decay between fluoridated and unfluoridated communities in the United States. This result, while consistent with other recent studies, starkly contradicts the claims of fluoridation’s benefits that continue to be made by some its enthusiastic promoters. As noted in a review by Dr. David Locker of the University of Toronto’s School of Dentistry:

“The magnitude of [fluoridation’s] effect is not large in absolute terms, is often not statistically significant and may not be of clinical significance.”

Addendum

Following the publication of NIDR’s findings, fluoridation proponents argued that the small difference in tooth decay was a result of the “multiplier effect.” The multiplier effect refers to the process by which fluoridated water ends up in unfluoridated communities via processed foods and drinks. The problem with this explanation, h0wever, is that the decline of tooth decay has occurred in every western country — the majority of which do not fluoridate their water. The “multiplier effect,” therefore, can not explain the reduction of tooth decay that has occurred in the western world. A more reasonable explanation (if we assume that fluorides are the primary factor involved in the decline of decay), is that the lack of difference in tooth decay is a result of the widespread use of topical fluorides. Other factors–including changing dietary patterns, increased use of antibiotics, and greater attention to oral hygiene–may also be playing a role as well. Whatever the explanation, however, it is clear that — despite 60 years of hype — water fluoridation has a remarkably meager effect on the rate of tooth decay in the population.

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