Flossing to reduce gum disease and tooth decay

It is assumed that removing plaque (a layer of bacteria in an organic matrix which forms on the teeth) will help prevent gum disease (gingivitis) and tooth decay (dental caries). Gum disease, which appears as red, bleeding gums, may eventually contribute to tooth loss. Untreated tooth decay may also result in tooth loss. Toothbrushing removes some plaque, but cannot reach in-between the teeth, where gum disease and tooth decay are common. This review looks at the added benefit of dental flossing, in people who brush their teeth regularly, for preventing gum disease and tooth decay.

Twelve trials were included in this review which reported data on two outcomes (dental plaque and gum disease). Trials were of poor quality and conclusions must be viewed as unreliable. The review showed that people who brush and floss regularly have less gum bleeding compared to toothbrushing alone. There was weak, very unreliable evidence of a possible small reduction in plaque. There was no information on other measurements such as tooth decay because the trials were not long enough and detecting early stage decay between teeth is difficult.

Authors' conclusions: 

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.

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Background: 

Good oral hygiene is thought to be important for oral health. This review is to determine the effectiveness of flossing in addition to toothbrushing for preventing gum disease and dental caries in adults.

Objectives: 

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.

Search strategy: 

We searched the following electronic databases: the Cochrane Oral Health Group Trials Register (to 17 October 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 4), MEDLINE via OVID (1950 to 17 October 2011), EMBASE via OVID (1980 to 17 October 2011), CINAHL via EBSCO (1980 to 17 October 2011), LILACS via BIREME (1982 to 17 October 2011), ZETOC Conference Proceedings (1980 to 17 October 2011), Web of Science Conference Proceedings (1990 to 17 October 2011), Clinicaltrials.gov (to 17 October 2011) and the metaRegister of Controlled Clinical Trials (to 17 October 2011). We imposed no restrictions regarding language or date of publication. We contacted manufacturers of dental floss to identify trials.

Selection criteria: 

We included randomised controlled trials conducted comparing toothbrushing and flossing with only toothbrushing, in adults.

Data collection and analysis: 

Two review authors independently assessed risk of bias for the included studies and extracted data. We contacted trial authors for further details where these were unclear. The effect measure for each meta-analysis was the standardised mean difference (SMD) with 95% confidence intervals (CI) using random-effects models. We examined potential sources of heterogeneity, along with sensitivity analyses omitting trials at high risk of bias.

Main results: 

Twelve trials were included in this review, with a total of 582 participants in flossing plus toothbrushing (intervention) groups and 501 participants in toothbrushing (control) groups. All included trials reported the outcomes of plaque and gingivitis. Seven of the included trials were assessed as at unclear risk of bias and five were at high risk of bias.

Flossing plus toothbrushing showed a statistically significant benefit compared to toothbrushing in reducing gingivitis at the three time points studied, the SMD being -0.36 (95% CI -0.66 to -0.05) at 1 month, SMD -0.41 (95% CI -0.68 to -0.14) at 3 months and SMD -0.72 (95% CI -1.09 to -0.35) at 6 months. 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.