Trials show flossing plus brushing reduces gum inflammation, but the evidence is weak and low-quality.
What the evidence shows
Flossing is near-universal dental advice, so it surprised many when journalists noted in 2016 that the evidence base was thin. This does not mean flossing is useless — it means the studies are poor.
The Cochrane review by Sambunjak et al. (2011) concluded that flossing plus brushing probably reduces gingivitis (gum inflammation) more than brushing alone, but that the evidence was of low quality — trials were small, short, and at risk of bias — and there was little reliable evidence about preventing cavities. Absence of strong proof is not proof of absence: flossing is cheap and low-risk, and dentists still recommend it. But the confident claim that its benefits are well-established is contested; the honest statement is 'probably helps gums, but the evidence is weak.'
Sources
Sambunjak, D., Nickerson, J. W., Poklepovic, T., et al. (2011). Flossing for the management of periodontal diseases and dental caries in adults.
Cochrane Database of Systematic Reviews, (12), CD008829
Flossing plus brushing likely reduces gingivitis versus brushing alone, but the evidence is weak and low-quality, with scant caries data.
DOI: 10.1002/14651858.CD008829.pub2 →