The Media's Flossing Follies

August 11, 2016  ·  Michael Fumento  ·  Real Clear Health

Toss the floss! It turns out dental flossing is barely useful, maybe even worthless. So reported the Associated Press (AP) and subsequently more than 150 news outlets, including The Washington Post (The Shaky Evidence for Flossing) and The New York Times’ more powerful Feeling Guilty about Not Flossing? Maybe There’s No Need.

The denture industry must be ecstatic; ultimately all this is driven by flipping on its head the old maxim that “absence of evidence is not evidence of absence.” Few studies have been done on flossing and there are several reasons for this, but the most ironic is that the benefit of flossing is obvious and has been observed by so many experts for so long.

So when the AP last year filed Freedom of Information Act requests with the HHS and the Department of Agriculture to provide the publication with evidence that flossing works, it was a bit like asking for studies proving that the sun rises in the morning. Subsequently, the flossing recommendation was removed from this year’s federal dietary guidelines, which by law must be evidence-based.


While massive amounts of anecdotal observation by experts may not satisfy as “evidence based,” it does not deserve to be dismissed out-of-hand. Dentists don’t tell patients to floss – much less floss better than they have been – just because of published guidelines. During their professional careers, they observe the difference between flossers and non-flossers. In fact, dentist recommendations of flossing appear to go back to 1815, although it wasn’t until 1898 that any large company, specifically Johnson & Johnson, cashed in on it.

Jesús Galván, chief dental officer for Delta Dental in New Mexico, the largest dental benefits carrier in the state, told the Albuquerque Journal that things such as his 40 years of sticking his face and tools into patients’ mouths is why his organization recommends flossing. Yes, this is anecdotal evidence, but it’s a lot of anecdotes by a lot of professionals.

In absence of other evidence, we also normally look to what’s called “biological plausibility.” “People daily build up a bio-film on their teeth called plaque, which is a layer of organic matter that contains some 500 bacterial species, food debris and other substances,” notes Galván in his interview with the Albuquerque Journal. “In order to prevent the adverse effects of plaque, you disrupt it or break it apart by flossing so the bacteria in the plaque does not have an opportunity to cause tooth decay or periodontal disease.” That wouldn’t seem to be in the same category as leaching.


In 2011 the esteemed Cochrane Collaboration released a review of studies that showed only weak evidence of benefit, though evidence nonetheless. “Flossing plus tooth brushing showed a statistically significant benefit compared to tooth brushing in reducing gingivitis at the three time points studied” one month, three months, and six months. Regarding plaque, “Overall there is weak, very unreliable evidence which suggest that flossing plus tooth brushing may be associated with a small reduction in plaque at 1 or 3 months.”

How does that translate to “no need”?

Certainly the statistical evidence isn’t robust. Why? Unfortunately, part of it is because very few people have researched what is so very obvious: rotting food pressed against a mucous membrane or tooth enamel has got to be bad. Add that with countless floss sellers, no individual one has much economic interest in funding an expensive study.

Finally, a flossing study isn’t as simple as might seem. Rats and mice stubbornly refuse to floss, while the gold standard of a clinical trial is a double-blinded placebo—meaning neither the subjects nor the researchers know who is using the real deal and who is using a fake substitute. That’s fine for medications and other things, but what is a placebo for dental floss? Hence the Cochrane Group only came up with 12 studies at all useful.

The American Academy of Periodontology reverses the take of a lack of good scientific evidence means toss the floss. “In the absence of quality research, patients should continue to include flossing as a part of their daily oral hygiene habit,” it says.


Matthew Messina, a spokesman for the American Dental Association, put it bluntly: “Do you need to floss? It depends on whether you want to keep your teeth or not.”

More than just teeth, gum disease has been linked to a host of other illnesses—57 according to an article in the May 2016 issue of the Journal of Periodontal Disease. Correlation doesn’t necessarily equal causation, of course. However, “Your mouth is your primary portal to your body,” explains Natalie Archer, former vice-president of the Royal College of Dental Surgeons of Ontario. “If you can’t keep it clean, all that bacteria is going through the rest of your body. …Having good bacteria in the mouth versus a lot of a bad bacteria…it affects our gut flora, everything.”

Heart disease is a major concern. A study from Thoracic Cardiovascular Surgery last year reported, “Our results demonstrate the presence of oral bacterial DNA in human cardiac tissue, as well as inflammatory markers potentially indicating connection of Periodontal Disease and Vascular Heart Disease.” Meanwhile, the correlation between type II diabetes and periodontal disease is overwhelming, and while clearly much of the gum disease is a result of the diabetes, there’s also good evidence that periodontal treatment improves control of blood sugar.

So add to the possibility of losing your teeth the possibility of losing eyesight, limbs, and life. On the risk side of the equation, almost anything can kill you—except maybe flossing. And at the very least it reduces incidence of halitosis, clearly a public good.

If there were a paucity of studies on health effects of decapitation, it’s doubtful the media would represent this a lack of evidence that decapitation is fatal. But there’s a big difference here. Not many of us have an interest in decapitation one way or another. But we’re told flossing is good for us even as many of us dislike it. Nearly 15 percent of adults would rather clean a toilet than floss their teeth according to an AAP survey. So much of this flossing folly is demand-driven. It’s confirmation bias; not the truth.

Ultimately, how many extra cavities, various other illnesses, and premature deaths will come from this hysteria is definitely something no study will ever be able to show.