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Lack of evidence to support a difference between use of interproximal floss in addition to manual tooth brushing

Susan Parker RDH, B.S., MEd, MBA .


Systematic Review Conclusion

The evidence does not support the routine use of interproximal floss in conjunction with manual tooth brushing to reduce plaque and gingivitis scores, but it may be beneficial in individual cases.

Critical Summary Assessment

This systematic review including 11 randomized clinical trials with heterogeneous methodology found no significant difference between toothbrushing with flossing compared to toothbrushing alone.

Evidence Quality Rating

Limited Evidence

Structured Abstract

Clinical Questions:

What is the effect of the use of dental floss in adult patients as an adjunct to manual toothbrushing, as compared to manual toothbrushing alone, on plaque and the clinical parameters of periodontal inflammation?

Review Methods:

The authors searched two electronic database searches as well as English-only articles published up to December 2007. They selected randomized and/or controlled clinical trials that compared toothbrushing alone to toothbrushing and flossing. Levels of plaque and gingivitis were the measured clinical outcomes. They presented descriptive and statistical comparisons for brushing alone or brushing and flossing. They assessed the methodological quality of the individual studies. The authors combined the data through a meta-analysis and assessed heterogeneity.

Main Results:

Only 11 publications met the eligibility criteria. Although all studies were randomized clinical trials (RCT), allocation concealment was not described for most of the studies. Blinding was present in most studies but losses-to-follow-up were described in only half the studies Treatment duration varied between four and six months. Number of participants varied from 24 to 158. Most of the studies found no significant difference for plaque (7 vs. 3), bleeding (3 vs. 1) and gingivitis (8 vs. 0) between the groups that carried out interproximal flossing in addition to toothbrushing compared to those who carried out toothbrushing alone.


The dental professional should determine on an individual patient basis whether flossing is an achievable goal. There was no detectable significant difference in the plaque and gingivitis index between the manual tooth brushing and flossing group compared to the manual tooth brushing only group.

Source of Funding:

Seven RCT’s were industry sponsored. Three did not report industry funding and one did not report conflict of interest.


Importance and Context:

Bacterial plaque is an important factor for periodontal diseases. (1) Mechanical removal of plaque remains the primary method for controlling supra-gingival accumulations. The ADA even reports that up to 80% of plaque may be removed by this method. (2) Flossing has been suggested for more than 100 years as a beneficial adjunctive procedure to tooth brushing to remove dental plaque. There are few available studies that compare the effectiveness of flossing and manual toothbrushing with toothbrushing alone. 1. Carranza's Clinical Periodontology. Newman MG et al. Saunders Elsevier. 10th Ed. 2006. 2. Council on Dental Therapeutics, Accepted Dental Therapeutics’ 40th edn. Section III. Chicago, USA, American Dental association, 1984.

Strengths and Weaknesses of the Systematic Review:

This systematic review followed generally accepted criteria, but had some weaknesses: 1) the authors searched only two databases and; 2) they only accepted studies published in English; Further, the authors used a non-standard approach to conduct the meta-analysis by combining the baseline data and the end-point data separately rather than looking at the difference over time. Hence, the results of the meta-analysis needs to be considered with caution.

Strengths and Weaknesses of the Evidence:

Only 11 RCT's fulfilled the selection criteria. Not all the selected studies evaluated the effect of interproximal flossing on all the outcomes (plaque, bleeding and gingivitis). Some of the selected studies only provided mean values and did not provide information on the standard deviations and hence could not be included in the meta-analysis. Patient compliance was not monitored to reflect real-life situations; there was heterogeneity in the initial levels of prophylaxis and oral hygiene instruction; test groups in two of the studies were dental students, but even with dental education, no difference was found. Although baseline plaque and ginigival scores were described, the characteristics of the patient population were not defined making it difficult to generalize the findings of the review. All but four of the studies were sponsored by industry.

Implications for Dental Practice:

Based on the included trials, there is lack of scientific evidence to support routine interproximal flossing as an adjunct to manual toothbrushing to reduce plaque and gingivitis scores. The dental professional should determine on an individual patient basis whether a flossing regimen in addition to manual toothbrushing has the potential to provide an oral health benefit.

Critical Summary Publication Date:


These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association © 2019