No Dental Floss? No Problem: Evidence on Flossing's Benefits Is 'Weak'

"Do you floss?" At the dentist's office, it's the question that launched a thousand guilt-ridden trips to the pharmacy and—until this week—seemed a major part of ensuring the future of your dental health. But now, according to an investigation by the Associated Press, it may all be a bunch of baloney.


Last year journalists from the AP asked the U.S. Departments of Health and Human Services and Agriculture for their evidence that proves flossing works. This was soon followed by a Freedom of Information Act written request. Months later in a followup letter to the AP, the government noted that the actual efficacy of flossing had never been researched as required.

The U.S. government has since removed its official recommendation on the basis that there is no scientific evidence to prove the benefits of flossing. The National Health Service in Britain is now preparing to review its own dental guidelines too.

Flossing was first patented in 1874 by the dentist Levi Spear Parmly. By 1908 the American Dental Association had jumped on the bandwagon in promoting floss. It took until 1979 for the federal government to formally recommend flossing in a surgeon general’s report and later in their official Dietary Guidelines for Americans, which is issued every five years. However, as the recent removal of this recommendation demonstrates, by law these guidelines need to be based on scientific evidence.

Prior to the AP investigation, the official recommendation for using dental floss stated that it helps “prevent gum disease by getting rid of pieces of food and plaque from between your teeth.” Says who, you may rightfully wonder.

According to further investigations by the AP, a bunch of “weak, very unreliable” studies. The AP reviewed 25 studies published in leading journals over the past decade, which revealed that the evidence for the health benefits of flossing was of a “very low” quality, and carries “a moderate to large potential for bias.” Perhaps the most damning review of flossing studies conducted last year noted, “The majority of available studies fail to demonstrate that flossing is generally effective in plaque removal.”

The overarching problem of these studies seems to come down to duration and outdated methods. “The difficulty is trying to get good evidence,” confirmed Damien Walmsley, British Dental Association scientific adviser to the AP. “People are different and large studies are costly to do ... until then you can’t really say yes or no.”

It’s estimated the global market for floss will reach almost $2 billion by next year, with half of that revenue coming from the United States, according to publisher MarketSizeInfo.com. It’s unsurprising then to learn that up until now, most of the studies into flossing have been paid for and designed by this very industry.

Here’s where it really gets good. These same companies are partnered with the ADA through its Seal of Acceptance program. An endorsement by the ADA, as the AP report notes, “directly affects the purchase decisions of consumers.” In turn, the ADA charges each manufacturer $14,500 for the evaluation, followed by “additional annual fee of $3,500.”

In a comment to the AP, the ADA responded saying it “rigorously evaluates products and makes no profit from the program.” Which is easy enough to say when said evaluations come directly from floss company-designed studies.

Wayne Aldredge, president of the periodontists’ professional association, offered comment to the AP on its findings. “It’s like building a house and not painting two sides of it,” he said on the benefits of flossing. “Ultimately those two sides are going to rot away quicker.”

It’s worth noting that Aldredge admitted his organization's endorsement of flossing may be the result of taking “the ADA’s lead.”

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