The daily use of dental floss in addition to toothbrushing is frequently recommended for the prevention of caries and periodontal diseases. The aim of this Cochrane review was to assess the effects of flossing in addition to toothbrushing, as compared with toothbrushing alone, in the management of periodontal diseases and dental caries in adults.

A detailed search was undertaken is a number of databases (Cochrane Oral Health Group Trials Register, Cochrane Central Register of Controlled Trials, Medline.Embase,Cinhal,LILACS, ZETOC, Web of Science conference proceedings, Clinicaltrials.gov and the metaRegister of Controlled Clinical Trials) for randomised controlled trials comparing toothbrushing and flossing with only toothbrushing, in adults. There were no language restrictions.

Two review authors independently assessed risk of bias for the included studies and extracted data. Trial authors were contacted for further details.  Meta-analysis was conducted using a random-effects models with standardised mean difference (SMD) as the main effect measure. Heterogeneity was explored.

Twelve trials (582 participants) were included, with 7 being assessed as at unclear risk of bias and 5 at high risk of bias.

They found

Flossing plus toothbrushing showed a statistically significant benefit compared to toothbrushing in reducing gingivitis at the three time points studied.

•  1 month,   SMD -0.36 (95% CI -0.66 to -0.05)
• 3 months  SMD -0.41 (95% CI -0.68 to -0.14)
• 6 months  SMD -0.72 (95% CI -1.09 to -0.35)

The 1-month estimate translates to a 0.13 point reduction on a 0 to 3 point scale for Loe-Silness gingivitis index, and the 3 and 6 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 1 or 3 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.

The authors concluded:-

 There is some evidence from twelve 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 1 and 3 months. No studies reported the effectiveness of flossing plus toothbrushing for preventing dental caries.

Sambunjak D, Nickerson JW, Poklepovic T, Johnson TM, Imai P, Tugwell P,Worthington HV. Flossing for the management of periodontal diseases and dental caries in adults. Cochrane Database of Systematic Reviews 2011, Issue 12. Art. No.: CD008829. DOI:10.1002/14651858.CD008829.pub2.