If you're among the many people who spend their dentist appointments feeling guilty about never flossing, there's good news: you don't need to floss your teeth. In 2011, a systematic review of 12 different studies found only "weak, very unreliable" evidence that adding flossing to regular toothbrushing was associated with even a tiny reduction in plaque. That review didn't find any studies that even looked at the relationship between flossing and cavities and gum disease, so there's no proof that flossing is effective in preventing them. Another review did find that floss could slightly reduce gum inflammation, but the effect size was almost too small to notice and the study authors noted that the evidence was pretty unreliable. In 2016, the U.S. government even removed flossing from its dietary guidelines, which are required by law to be based in scientific evidence. Despite this, the American Dental Association claims that flossing helps remove plaque and prevent gum disease. But why?
One reason may be tradition. Floss was first invented in the early 1800s, and by the time it was patented in 1874, many dentists recommended it despite having no proof of its effectiveness. The American Dental Association began promoting its use in 1908 because, as dentist Marcelo W.B. Araujo of the ADA told the Associated Press, "They just looked into what they did every day in their clinical practice and what they would recommend for patients." Another reason may be financial. The ADA charges thousands of dollars to floss manufacturers for its Seal of Acceptance, which evaluates the effectiveness of each product. The association claims that they make no profit off of the program, but even still, the studies these evaluations are based on can be designed by the companies themselves. This leaves a lot of room for bias. Explore the sometimes unexamined science of dentistry with the videos below.