Dietary Guidelines Omit Flossing, but Patients Shouldn't

Norra MacReady

August 05, 2016

The latest version of the Dietary Guidelines for Americans issued by the US Department of Agriculture (USDA) and US Department of Health and Human Services (HHS) has given the brushoff to some time-honored advice: floss your teeth daily.

The change comes after a review of 25 studies published within the last decade suggested the evidence for flossing is weak, according to an article published by the Associated Press (AP). But medical and dental experts say the lack of a guideline does not mean patients should skip flossing.

"Our position is that flossing is still good," said Robert Wergin, MD, board chair and immediate past president of the American Academy of Family Physicians. "There's not much of a downside. Cleaning between the teeth is an important part of oral health, and good oral health is part of total health."

Dr Wergin told Medscape Medical News that the issue may be more absence of evidence, rather than clear evidence that flossing has no benefit. "One of my staff members conducted a literature search on the long-term benefits of flossing, and there wasn't a lot," he said. "There's no data that [flossing] is harmful, but are there evidence-based data to make recommendations [to floss]? No."

The AP conducted the review after filing a Freedom of Information Act request last year for the evidence used by the HHS and USDA to make the recommendation. Federal law states the dietary guidelines must be evidence-based.

The evidence for flossing is " 'weak, very unreliable,' of 'very low' quality, and carries 'a moderate to large potential for bias,' " AP National Writer Jeff Donn notes in a description of the review. He cites one paper in which the authors conclude that most of the studies fail to demonstrate that flossing helps with plaque removal.

The strongest evidence in favor of flossing was in a study of children 4 to 13 years of age with low exposure to fluoride. Professional flossing in that population every school day for 1.7 years was associated with a 40% reduction in the risk for caries (relative risk, 0.60; 95% confidence interval, 0.48-0.76; P < .001). Self-flossing, however, did not affect caries risk.

An HHS spokesperson explained in an e-mailed statement that "since neither the 2010 nor 2015 Advisory Committees reviewed evidence on brushing and flossing teeth, the authors of the current edition decided not to carry forward the information on brushing and flossing included in past editions of the guidelines. By doing so, they were not implying that this is not an important oral hygiene practice. It is also important to note that, although dental floss was mentioned in past editions of the Guidelines, it was most likely identified as a supporting recommendation along with brushing teeth, with the primary emphasis being on the nutrition-based recommendation to reduce added sugars." The 2010 guidelines mention flossing only once, as one of the components of an oral health regimen.

The type of evidence required for the dietary guidelines "cannot be obtained," Paulo Camargo, DDS, MBA, told Medscape Medical News. "Dental caries and periodontal disease take a long time to develop, so to really study the effects of flossing, researchers would have to compare people who floss to those who do not floss and follow them for many years, and that would be unethical." Indeed, many of the studies cited in the AP analysis followed patients for 6 months or less.

Oral diseases are caused by bacteria that completely cover the teeth, said Dr Camargo, chairman of the Department of Periodontics, University of California, Los Angeles, School of Dentistry. Anything that can get between and along the sides of the teeth helps disrupt this bacterial growth. Floss, interdental brushes, and even wooden toothpicks all are effective, "but flossing is easiest and least invasive. I think it's a disservice to patients to tell them they don't need to floss regularly."

"The success of flossing in preventing periodontal disease shows up over a lifetime," said Matthew Messina, DDS. Dr Messina, consumer advisor to the American Dental Association (ADA) and a private practitioner in Cleveland, Ohio, said he asks patients to brush their teeth and then floss, and to look at the debris flossing removes. "The ADA started advocating flossing in 1908, and it's been a tremendous success. We now have people living into their 80s and 90s and keeping most or all of their teeth. Why go back and re-research something when we know intuitively it works? We forget how much better Americans' oral health is today than it was 50 years ago."

But not everyone agrees those improvements are tied to flossing. "Oral health is better today thanks to the use of fluoride products and sealants, and less smoking, not the use of dental floss," said Philippe Hujoel, DDS. In fact, "the evidence is pretty good that flossing has not contributed to the improved oral health of Americans," continued Dr Hujoel, professor of oral health sciences and adjunct professor of epidemiology at the University of Washington School of Dentistry, Seattle.

The two main causes of dental disease are sugar and tobacco, Dr Hujoel told Medscape Medical News. He believes one danger of urging people to floss is that it may lull them into thinking it can compensate for poor lifestyle habits. "Flossing is definitely not a magic antidote if you continue to eat sugar and smoke."

Flossing does decrease gingival inflammation, Dr Hujoel said. "But don't make a leap of faith to say it prevents destructive periodontal disease; there's a lot of evidence that that's not true."

If patients eat an unhealthy, sugar-laden diet or smoke, Dr Hujoel urges them to use fluoride toothpaste and mouth rinses. Mechanical interventions such as brushing and flossing can help with bleeding gums.

Beyond that, he said, "you've got to tell the truth: there's no good evidence that flossing prevents cavities."

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