To Floss or Not To Floss

That is the question, thanks to recent contrarian news stories, and the answer is probably not the one you’re hoping for

woman flossing her teeth

When a news item questioning the scientific evidence behind flossing made the rounds earlier this summer, it could have been considered a blow to those in the tooth business. Yet Tufts dentists—who, like most of their colleagues, have heard their share of no-flossing excuses—remain undaunted. In fact, they say the story has been a good way to draw attention to the often-neglected topic of oral hygiene.

“It’s been a wonderful opportunity to explain to our patients how important it is to maintain periodontal health,” says Evangelos Papathanasiou, DG11, an assistant professor of periodontology at Tufts School of Dental Medicine. “It’s been a very good challenge to have to explain what we are trying to do.”

On Aug. 2, the Associated Press published an article questioning the scientific evidence behind tooth flossing. It examined 25 peer-reviewed studies that compared the effectiveness of brushing and flossing vs. brushing alone. In general, the studies found “weak, very unreliable” evidence that flossing has long-term benefits. Media outlets were quick to spread the catchy headline about a personal hygiene ritual that’s never enjoyed a particularly glamorous reputation. During a short walk through one of the dental school’s clinics shortly after the story broke, Professor Charles Rankin, D79, DG86, discovered that seven out of 10 patients were aware of the news, although some were indeed skeptical of the conclusion.

Within dentistry, flossing has traditionally been considered helpful for removing bacteria and preventing plaque that can lead to tooth decay, particularly in areas between teeth. It is regarded as a bedrock practice in minimizing the risk of inflammation that can lead to gum disease. According to the federal Centers for Disease Control and Prevention, 47 percent of Americans over 30 have some form of gum disease. Both the American Dental Association and the American Academy of Periodontology continue to advise people to floss once a day.

The rub, the dentists say, is that a long-term, scientifically rigorous study on the efficacy of flossing has yet to be funded and conducted, although dentists and hygienists have been observing positive results from flossing for decades.

“They’re not saying flossing is not good. No study has been done that says it’s not the right thing to do,” says Alan Epstein, D82, an assistant professor of comprehensive care. “In treating patients, both at the dental school and in my private practice, it’s my direct observation—granted, anecdotally—that gingival tissues are healthier in people who floss; there is less decay in people who floss. Why not do something that intuitively seems helpful, even if the scientific evidence is not yet there?”

Papathanasiou, the periodontist, concurs. Many of the studies that sought to evaluate flossing, he says, were poorly designed—small sample sizes, brief duration, poor controls, inadequate assessments, to name a few issues—leading to the lackluster or questionable results.

What has been shown, Papathanasiou says, is that consistent oral hygiene closely correlates with good oral health and the ability to retain more teeth over a lifetime—and flossing promotes oral hygiene.

But floss is only one of the tools that we need to clean between our teeth, he says. Among others are rubber-tip gum stimulators; soft picks or small brushes, especially for those who have wider spaces between teeth because of previous bone loss; and water picks, especially for those with bridges and implants. “We should try not to see floss as a separate tool, but as something used in combination with other tools,” Papathanasiou says.  

Are there any drawbacks to flossing—any risks that could outweigh possible benefits? “There’s no downside,” says Richard McNulty, D79, clinical assistant professor of comprehensive care. While poor flossing technique may be ineffective, it’s not harmful—unlike improper brushing, which can lead to gum recession. Some patients tell McNulty they don’t floss because they’re afraid of pulling out a filling. But he says that “if the filling is in that loosely, it’s to their benefit that it comes to our attention.”  

It’s no secret that flossing is not a preferred activity. In a 2015 poll conducted for the American Academy of Periodontology, more than a third of those surveyed said they would rather do another unpleasant chore—like cleaning a toilet, or sitting in gridlocked traffic—than floss. And 27 percent confessed they lie to their dentist about their oral hygiene habits.

Those 27 percent may only be fooling themselves. Like Santa, dentists know when you’ve been bad or good—at least in regard to flossing. “It’s instantly apparent to us,” Epstein says.

Helene Ragovin can be reached at

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