Research review contends fluoride in water is less effective than in 1970s

ADA notes limitations, exclusions in review, reaffirms support for fluoridation

A new review published Oct. 4 by the Cochrane Library contends community water fluoridation is less effective now than it was in the 1970s, but an expert committee of the ADA points out limitations and exclusions in the report.

Researchers from the Universities of Manchester, Dundee and Aberdeen in the United Kingdom examined 157 studies— 135 on fluorosis and 22 on decay prevention — that compared communities in high-income countries that had fluoride added to their water with those that had no additional fluoride in the water. They conclude that the benefit of fluoridation has declined since the 1970s, when fluoride toothpaste became more widely available. However, they state “the impact of community water fluoridation in low- and middle-income countries is less clear, due to the absence of recent research.”

“Optimally fluoridated water is accessible to communities regardless of socioeconomic status, education or other social variables,” said ADA President Linda J. Edgar, D.D.S. “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.”

Following the review’s release, the ADA issued a statement saying it “believes the review does not present any new or significant findings on the subject” and the Association continues to endorse fluoridation as beneficial to oral health. The American Academy of Pediatric Dentistry, American Academy of Pediatrics and Centers for Disease Control and Prevention continue to endorse the practice.

The ADA’s media statement cited information on the U.S. Centers for Disease Control and Prevention’s website which states, “Water fluoridation and fluoride toothpaste work together to help prevent tooth decay and offer more protection against decay than using either one alone. Fluoridated water keeps a low level of fluoride in the mouth throughout the day, while fluoride toothpaste delivers higher concentrations at important times of the day, such as bedtime^. 

The National Fluoridation Advisory Committee, an expert committee of the ADA, examined the review and noted limitations in the criteria the investigators used for the inclusion of studies and omission of significant findings.

The ADA and National Fluoridation Advisory Committee said there are many other recent studies excluded from the Cochrane review that show negative impacts on public health once fluoride is removed from the water supply.

“The study’s exclusion criteria means that highly relevant research from over the past decade that show significant increases in tooth decay in communities like Juneau, Alaska, Calgary, Canada and other countries after their decision to remove fluoride from water supplies were not included” says Catherine Hayes, D.M.D., member of the National Fluoridation Advisory Committee.

The NFAC also notes that the review did not rely on enough high-quality studies. NFAC suggested the authors must emphasize caution in interpreting results based on the very small number of recent studies.

“Normally, meta-analyses and systematic reviews are only conducted with substantial numbers of relevant high-quality studies,” Dr. Hayes said. “However, there were only a small number of recent studies on which the conclusions are based ¾ only two for primary caries [cavities in baby teeth] outcomes and maybe a few more for permanent caries [cavities in adult teeth]. The analysts at Cochrane also excluded reliable studies because of the year of data collection rather than the quality and reliability of the data. This is an important oversight that cannot be ignored. In addition, Cochrane researchers noted a significant cost-savings due to fluoridation, and this was also not included in the summary.”

The review advises, “the implementation or cessation of CWF [community water fluoridation] requires careful consideration of this current evidence, in the broader context of a population’s oral health, diet and consumption of tap water, movement or migration and the availability and uptake of other caries (cavity) prevention strategies.”