The United States’ federal government published an update to the 2015-2020 Dietary Guidelines for Americans omitting their previous recommendation of daily flossing and other references to oral health that had been in place since 1979.18 The omitted paragraphs are as follows:
Drinking fluoridated water and/or using fluoride-containing dental products helps reduce the risk of dental caries. Most bottled water is not fluoridated. With the increase in consumption of bottled water, Americans may not be getting enough fluoride to maintain oral health.
During the time that sugars and starches are in contact with teeth, they also contribute to dental caries. A combined approach of reducing the amount of time sugars and starches are in the mouth, drinking fluoridated water, and brushing and flossing teeth, is the most effective way to reduce dental caries.
In response to this omission, the Associated Press [AP] submitted a Freedom of Information Act [FOIA] request and was told the flossing recommendation was excluded due to a lack of definitive scientific evidence stating flossing prevents dental caries.19 In the AP’s publication, it is argued that due to the lack of randomized controlled trials demonstrating efficacy in dental caries reduction, flossing should be considered “unnecessary.”19 It is important to note that lack of scientific evidence is not proof of absence of effect and, as such, the conclusion of this article may be misinterpreted and hyperbolic. Based upon the underlying scientific discourse, what can reliably be said is that further evidence is necessary to demonstrate flossing’s efficacy for the prevention and/or treatment of caries and periodontitis. Nevertheless, the initial AP headline was repeated manifold in the lay press and garnered significant amounts of attention. It should be noted that there were counterbalances to this initial report. For example, in his response to the AP article, “Flossing and the Art of Scientific Investigation,” the New York Times’ Jamie Holmes points out the pitfalls of performing the definitive studies on flossing, including securing funding for such studies and the ethical challenges of randomization based upon known benefits of flossing.50 Media publications and sensational headlines often do not comport with the nuances of scientific interpretation and the coverage of the omission in the Dietary Guidelines for Americans in the lay press resulted in confusion for members of the public. It is therefore important to understand the underlying science and challenge the assumption that flossing should be considered worthless, while continuing to critically evaluate emerging data to provide person-centered dental healthcare.
The Cochrane review meta-analysis, which is cited in the U.S. government’s justification for the omission of oral health and hygiene references in the 2015-2020 Dietary Guidelines for Americans, states that current scientific evidence does not allow for the conclusion that flossing results in decreased rates of caries and periodontitis.2 Specifically, the review states, “There is some evidence from twelve studies that flossing in addition to toothbrushing reduces gingivitis compared to toothbrushing alone. There is weak, very unreliable evidence from 10 studies that flossing plus toothbrushing may be associated with a small reduction in plaque at 1 and 3 months. No studies reported the effectiveness of flossing plus toothbrushing for preventing dental caries.”2 The review also suggests further long-term interventional trials that would allow for conclusive data on the efficacy of flossing.2 However, there are several roadblocks to the performance of such studies. First, there are ethical dilemmas in performing a long-term randomized controlled trial where the intervention would require a lack of flossing for long periods of time and observations about the development of caries or periodontitis, particularly as these are irreversible conditions. Secondly, there are randomized controlled trials that demonstrate flossing and other interdental cleaning methods are effective as an adjunct to toothbrushing in removing plaque, the primary etiology of both dental caries and periodontal disease and in reducing levels of gingival bleeding and inflammation.2,51-54 Finally, in observational trials, there is evidence, albeit less definitive than in randomized controlled studies, that interdental cleaning frequency is associated with lower rates of dental caries, periodontal disease, and increased overall longevity.55-60
It is widely accepted by a vast array of experts, including the U.S. Surgeon General,60 the CDC,4 the National Institutes of Health (NIH),3 the ADA,8,14,15 the Academy of General Dentistry (AGD),59 and the AAP60 that interdental cleaning is an essential part of optimal oral hygiene. As dental healthcare providers, an awareness of the impetus for the changes to the Dietary Guidelines for Americans and the overall evidence for the performance of oral hygiene measures is important to convey to our patients so that they can do their part to prevent and treat the two most prevalent oral diseases: dental caries and periodontal disease.