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Dental floss (or dental tape) and other interdental cleaners (e.g., small brushes, special wooden or plastic picks, sticks or water flossers) removes food trapped between the teeth and removes the film of bacteria that forms there before it has a chance to harden into plaque.1 Toothbrush bristles alone cannot clean effectively between these tight spaces.2

Plaque that is not removed can harden into tartar, a hard mineral deposit that forms on teeth and can only be removed through professional cleaning by a dental professional.3 When this happens, brushing and cleaning between teeth become more difficult, and gum tissue can become swollen or may bleed. This condition is called gingivitis, the early stage of gum disease. Interproximal cleaning techniques (e.g., manual or powered interdental cleaners, water flossers, interdental brushes), appear to add benefits in plaque reduction when used in association with conventional manual brushes.3 The choice between technique type should be made in relation to the characteristics of the patient; for example, dental floss could be indicated in individuals with closed interdental spaces, and interproximal brushes in patients with periodontitis or in those with more open interproximal spaces.3

Interdental cleaning helps remove debris and interproximal dental plaque, the plaque that collects between two teeth.3 Dental floss and other interdental cleaners help clean these hard-to-reach tooth surfaces and reduce the likelihood of gum disease and tooth decay.1 A news release from the ADA4 reaffirmed the use of an interdental cleaner (like floss) as an essential part of taking care of teeth and gums. The U.S. Department of Health and Human Services also reaffirmed flossing as "an important oral hygiene practice" in an August 2016 communication to ADA News.5

While floss is a flexible strand, other interdental cleaners specifically made for this purpose include dental/floss picks, pre-threaded flossers, tiny brushes that reach between the teeth, powered air or water flossers, or wooden plaque removers.

Interdental brushes are small-headed toothbrushes that are available in a range of different sizes to match the space between teeth.9 They can be cone shaped or cylindrical. Brushes for use for cleaning around implants have coated wire to avoid scratching the implants or causing a shock.9

A 2019 Cochrane review10 on home-use of interdental cleaning devices in addition to toothbrushing for preventing or controlling periodontal disease or dental caries found no randomized, controlled trials assessing effect on interproximal caries and very few studies evaluating periodontitis. The authors found that use of floss or interdental brushes in addition to toothbrushing may reduce gingivitis or plaque, or both, more than toothbrushing alone and that interdental brushes may be more effective than floss.10 Available evidence for tooth-cleaning sticks and oral irrigators was reported to be limited and inconsistent. Outcomes were mostly measured in the short term (i.e., 1 to 3 months) and participants in most studies had a low level of baseline gingival inflammation. Overall, the evidence was graded as low to very low-certainty, and the effect sizes observed may not be clinically important. The authors recommended that future trials report participant periodontal status according to the new periodontal diseases classification, and last long enough to measure outcomes for interproximal caries and periodontitis.10

A 2011 Cochrane systematic review evaluating the evidence for the impact of flossing on managing gingivitis11 found that by the standards of the GRADE Working Group, the evidence on this question was of very low quality, due to uncertainty about the estimate because of the small number of studies, sample sizes, and some concerns regarding interpretation of the results. With these caveats and limitations in mind, the summary of results of these short-term (i.e., up to 6 months of follow-up) investigations were that when flossing was added to toothbrushing, there was a statistically significant, albeit clinically small, reduction in the measures of gingivitis.11 An earlier meta-analysis by Berchier et al.12 explored the impact of adding flossing to brushing on indices of plaque and gingival health and failed to find statistically significant improvement. They nonetheless concluded that a first consideration ought to be whether high-quality flossing is an achievable goal.

A meta-analysis of studies examining the impact of flossing on interproximal caries13 found that regular (5 days per week) professional flossing resulted in a statistically significant reduction in interproximal caries, a result that was not seen with intermittent (every 3 months) professional flossing nor self-flossing.

When’s the best time to floss?

The ADA recommends brushing twice a day and cleaning between teeth with floss (or another interdental cleaner) once a day. Some people prefer to floss in the evening before bedtime so that the mouth is clean while sleeping. Others prefer to floss after their midday meal. Still others chose to floss first thing as a part of their morning ritual. The bottom line is that best time to floss is the time that fits well with the individual’s schedule.

Should I brush or floss first?

Either way is acceptable as long as you do a thorough job. Some people like to floss before brushing to better ensure that any material between teeth is swept out of the mouth. Others prefer to first clean their mouth by brushing before working with floss between their teeth. However, those who brush their teeth and skip flossing because they think their mouth feels clean or are short on time or tired and postpone flossing for some later time are likely missing out because flossing may never happen.

Can I rinse and reuse floss?

The ADA does not recommend using a floss strand more than once. Used floss might fray, lose its effectiveness, or may deposit bacteria in the mouth. Discard after use.

Look for the ADA Seal—your assurance that the product has been objectively evaluated for safety and efficacy by an independent body of scientific experts, the ADA Council on Scientific Affairs.  A company earns the ADA Seal for floss or other interdental cleaners by producing scientific evidence demonstrating the safety and efficacy of its product in reducing plaque and gingivitis, which is evaluated according to objective requirements for manual or powered interdental cleaners.

To qualify for the Seal of Acceptance, the company must provide evidence that:

Department of Scientific Information, Evidence Synthesis & Translation Research, ADA Science & Research Institute, LLC.

Content on the Oral Health Topics section of ADA.org is for informational purposes only.  Content is neither intended to nor does it establish a standard of care or the official policy or position of the ADA; and is not a substitute for professional judgment, advice, diagnosis, or treatment.  ADA is not responsible for information on external websites linked to this website.