Earlier this year, the US federal government released its dietary guidelines, omitting the recommendation to floss for the first time since 1979. The Associated Press—in a tremendous feat of investigative reporting to uncover the truth the slightly lazier-than-average American public deserves to know—questioned the reasoning and followed up with requests under the Freedom of Information Act. This week, the government revealed that the effectiveness of flossing had never been adequately researched.
According to the American Dental Association, flossing is "an essential part" of dental care, in that it helps remove plaque from between teeth and helps prevent gum disease and cavities. The AP, however, looked at 25 studies from the past decade to see where the research actually lies, focusing on the effectiveness of using a toothbrush versus the combination of toothbrushes and floss. According to The Guardian, journalists found that the "evidence for flossing is 'weak, very unreliable,' of 'very low' quality, and carries 'a moderate to large potential for bias.'"
For example, one study found gum inflammation, which can lead to gum disease, was slightly reduced after flossing, but the reviewers found the evidence "very unreliable." Other studies were deemed too short in duration or used too few test subjects.
The AP also found that floss companies like Johnson & Johnson and Proctor & Gamble couldn't offer adequate evidence to back up their claims that the practice is really that effective. In fact, floss manufacturers can also take part in the research studies. "The funding can come from companies—no problem at all," Marcelo WB Araujo, a dentist and vice-president of the ADA's Science Institute, and formerly an executive for Johnson & Johnson, told the AP. "The design can start from the company."
Mark Wolff, a dentist and professor at the New York University College of Dentistry, tells Broadly that "floss has minimum downsides" and can actually be a contributing factor in a regime of improved oral health care that reduces gingival inflammation. "When I say to you, I need you to brush and floss and really keep your teeth clean because your gums are bleeding and you have a problem, you really start paying attention to your home care," Wolff says. "Now, all of a sudden, things get better. Did floss work or did you just become more diligent?"
In terms of dietary guidelines, Wolff says flossing is a moot point. To prevent tooth decay, he explains, people should brush their teeth well with a fluoride-containing toothpaste and cut back on sugary foods. That should be doable for the 10 and 40 percent of non-flossing Americans out there, for whom vindication may taste just as sweet.