The Associated Press filed Freedom of Information requests with the US government to find the evidence behind the Surgeon General's admonition to floss regularly for dental health and found that there was no good evidentiary basis for flossing.
Subsequent to this, the federal guidelines on dental health were revised, and the recommendation to floss was silently removed. The government sent a letter to the AP confirming that the government flossing recommendations had not been based on any research.
The American Dental Association and American Academy of Periodontology still insist that flossing is evidence-based, but only cite small, short-run, old, and badly designed studies in support of that position. The big floss companies -- Procter & Gamble and Johnson & Johnson -- were also at a loss to cite any reliable evidence for flossing.
The AP looked at the most rigorous research conducted over the past decade, focusing on 25 studies that generally compared the use of a toothbrush with the combination of toothbrushes and floss. The findings? The evidence for flossing is "weak, very unreliable," of "very low" quality, and carries "a moderate to large potential for bias."
"The majority of available studies fail to demonstrate that flossing is generally effective in plaque removal," said one review conducted last year. Another 2015 review cites "inconsistent/weak evidence" for flossing and a "lack of efficacy."
One study review in 2011 did credit floss with a slight reduction in gum inflammation — which can sometimes develop over time into full-fledged gum disease. However, the reviewers ranked the evidence as "very unreliable." A commentary in a dental magazine stated that any benefit would be so minute it might not be noticed by users.
Medical benefits of dental floss unproven [Jeff Donn/AP]
(Image: How To Floss - Mouth Healthy - ADA , T Sona Tacvorian, DMD - TST Dentistry)