The evidence on flossing and other methods of cleaning between the teeth

Tooth decay and gum diseases affect most people. They can cause pain, difficulties with eating and speaking, low self-esteem, and, in extreme cases, may lead to tooth loss and the need for surgery. The cost to health services of treating these diseases is very high.

As dental plaque is the root cause, it is important to remove plaque from teeth on a regular basis. While many people routinely brush their teeth to remove plaque up to the gum line, it is difficult for toothbrushes to reach into areas between teeth (‘interdental’), so interdental cleaning is often recommended as an extra step in personal oral hygiene routines. Different tools can be used for interdental cleaning, such as dental floss, interdental brushes, tooth cleaning sticks, and water pressure devices known as oral irrigators.

 What was the research?

A systematic review to examine the effectiveness of home-use interdental cleaning devices, plus toothbrushing, compared with toothbrushing only or use of another device, for preventing and controlling gum disease, tooth decay and plaque.

Who conducted the research?

The research was conducted by a team led by Helen Worthington of Cochrane Oral Health. Laura MacDonald, Tina Poklepovic Pericic, Dario Sambunjak, Trevor M Johnson, Pauline Imai and Janet E. Clarkson were also on the team.

What evidence was included in the review?

Review authors working with Cochrane Oral Health searched for studies up to 16 January 2019. We identified 35 clinical trials with 3,929 adults. Those taking part in the trials knew that they were in an experiment, which might have affected their teeth cleaning or eating behaviour. Some studies had other problems that might make their findings less reliable, such as people dropping out of the study or not using the assigned device.

The clinical trials evaluated floss (15 studies), interdental brushes (2 studies), wooden cleaning sticks (2 studies), rubber/elastomeric cleaning sticks (2 studies) and oral irrigators (5 studies). Four devices were compared with floss: interdental brushes (9 studies), wooden cleaning sticks (3 studies), rubber/elastomeric cleaning sticks (9 studies), oral irrigators (2 studies). Three studies compared rubber/elastomeric cleaning sticks with interdental brushes.

The results were measured after four to six weeks (short term) or between three and six months (medium term).

What did the evidence say?

We did not find any evidence that interdental cleaning using any of the devices reduces severe gum disease (periodontitis) or interproximal caries (caries between the teeth).

Less severe gum disease (gingivitis) may be reduced in the short and medium term by using dental floss in addition to toothbrushing, and in the short term by using an interdental brush. Interdental brushes may be better than flossing for gingivitis at one and three months, but the evidence for plaque is inconsistent.

Dental plaque may be reduced in the short term by using an interdental brush, but the evidence was unclear on whether flossing reduces dental plaque.

Available evidence for cleaning sticks and oral irrigation aids is limited and inconsistent.

The studies that measured ‘adverse events’ (side effects) found no serious effects and no evidence of differences between study groups in minor effects such as gum irritation.

 How good was the evidence?

The evidence is low to very low-certainty, which means that we cannot be certain of the results. The effects observed may not be clinically important. The clinical trials measured results mostly in the short term (up to six weeks) and many participants had a low level of gum disease at the beginning of the studies.

What are the implications for dentists and the general public?

Additional use of floss or interdental brushes compared to toothbrushing alone may reduce gingivitis or plaque, or both, and interdental brushes may be more effective than floss. The evidence is low to very low-certainty, and the effect sizes observed may not be clinically important. Available evidence for cleaning sticks and oral irrigation aids is limited and inconsistent. Adverse events reported were minor; there were no serious adverse events and no evidence of a difference between study arms.

What should researchers look at in the future?

The findings do not allow us to be certain whether or not home use of interdental cleaning devices makes a clinically significant impact on periodontal diseases, and they provide no information about the impact on dental caries. Most of the trials in this review were of short duration and involved many participants with only a low level of gum inflammation at baseline. In addition, all studies were at risk of performance bias, and 33 of the 35 included trials were at risk of other types of bias. If future trials are of a similar nature to those included in this review, they may not be able to add meaningfully to the current evidence base. We believe future trials should be long-term, sufficiently powered to assess the effects of interdental cleaning devices or oral hygiene regimens on caries and periodontitis, and should include estimates of costs. Any future trials should report on the extent of gingivitis and the stage of periodontitis at the beginning of the trial, according to the new periodontal diseases classification. An agreement on a preferred way of measuring gingivitis and plaque, along with differences considered clinically important, would aid future evidence synthesis and interpretation.


Worthington  HV, MacDonald  L, Poklepovic Pericic  T, Sambunjak  D, Johnson  TM, Imai  P, Clarkson  JE. Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries. Cochrane Database of Systematic Reviews 2019, Issue 4. Art. No.: CD012018. DOI: 10.1002/14651858.CD012018.pub2.