The Cochrane Oral Health Group Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) Medline, Embase, CINAHL, LILACS, ZETOC Conference Proceedings, Web of Science Conference Proceedings, Clinicaltrials.gov and the metaRegister of Controlled Clinical Trials databases were searched. Manufacturers of dental floss were also contacted to identify any trials.
Randomised controlled trials comparing toothbrushing and flossing with only toothbrushing, in adults were, included. There were no restrictions regarding language or date of publication.
Data extraction and synthesis
Two review authors independently assessed risk of bias for the included studies and extracted data. Trial authors were contacted for further details where these were unclear. Meta-analysis was conducted using random-effects models, the main effect measure being standardised mean difference (SMD) with 95% confidence intervals (CI). Potential sources of heterogeneity were examined and a sensitivity analysis conducted omitting trials at high risk of bias.
Twelve trials were included in this review. These included a total of 582 participants in flossing plus toothbrushing (intervention) groups and 501 participants in toothbrushing (control) groups. Seven trials had unclear risk of bias and five had high risk of bias. All the trials reported the outcomes of plaque and gingivitis.
Flossing plus toothbrushing showed a statistically significant benefit compared to toothbrushing in reducing gingivitis. Standardised mean differences and 95% confidence intervals are shown for one, three and six month intervals.
The one month estimate translates to a 0.13 point reduction on a 0 to 3 point scale for Loe-Silness gingivitis index, and the three and six month results translate to 0.20 and 0.09 reductions on the same scale.
Overall there is weak, very unreliable evidence which suggests that flossing plus toothbrushing may be associated with a small reduction in plaque at one or three months. None of the included trials reported data for the outcomes of caries, calculus, clinical attachment loss or quality of life. There was some inconsistent reporting of adverse effects.
There is some evidence from 12 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 one and three months. No studies reported the effectiveness of flossing plus toothbrushing for preventing dental caries.
About this article
This paper is based on a Cochrane Review published in the Cochrane Library 2011, issue 12 (see www.thecochranelibrary.com for information). Cochrane Reviews are regularly updated as new evidence emerges and in response to feedback, and the Cochrane Library should be consulted for the most recent version of the review.