What it is
Plaque between teeth inflames the gums (gingivitis), and in susceptible people years of that inflammation become periodontitis, which destroys the bone holding teeth in place. A toothbrush can't reach the gaps, so something else has to: floss or floss picks for tight contacts, interdental brushes for wider gaps (many adults have them), and water flossers for braces, implants or limited dexterity.
The choice of floss matters less than using it daily. Waxed, tape or coated floss slides more easily; flavors and coatings are comfort features.
How strong is the evidencelimited
A 2019 Cochrane review of 35 trials found low-certainty evidence that adding floss to brushing reduces gingivitis, and that interdental brushes may work better than floss; water-flosser evidence was limited and no trial measured decay between teeth. That reflects short, small trials in people with mild inflammation, not proof that interdental cleaning fails. The classic 1965 experiment showed plaque causes gingivitis within weeks of stopping cleaning, and treating periodontitis lowers blood sugar in people with diabetes.
The claims you’ll meet5 checked
Flossing reduces gum inflammationHolds upLow-certainty but consistent evidence of less gingivitis when floss is added to brushing.
Interdental brushes beat flossMixedThey may reduce gingivitis more where they fit; floss is still the tool for tight contacts.
Flossing prevents cavities between teethUnprovenPlausible, but no trial in the review measured decay between teeth.
Water flossers replace flossMixedShort-term gingivitis benefits in some trials but inconsistent evidence; best for braces, implants or people who won't floss.
Healthy gums protect your heartUnprovenGum disease and heart disease are associated, but treating gums hasn't been shown to prevent heart attacks or strokes. The diabetes link is firmer.
What to look for4
- ✓Interdental brushes sized to your gaps (a dentist or hygienist can size them) if you have space between teeth.
- ✓Waxed or tape floss if contacts are tight or floss shreds.
- ✓Floss picks or a water flosser if dexterity, braces, bridges or implants make string floss hard.
- ✓Whatever tool you'll actually use every day.
What to skip2
- ×Paying extra for charcoal, infused or 'whitening' floss.
- ×Skipping interdental cleaning because the evidence is 'weak'; the uncertainty is about size of effect, and harms are minimal.
How to use it3
- →Clean between teeth once a day, before or after brushing.
- →Curve the floss into a C around each tooth and slide it just under the gumline.
- →Use interdental brushes with a gentle in-and-out motion without forcing them.
Take care4
- !Some bleeding in the first week or two is common when you start; if it continues after two weeks of daily cleaning, see a dentist.
- !Don't snap floss into the gums; guide it gently and curve it around each tooth.
- !Choose PTFE floss or interdental brushes if you have many fillings that catch or shred floss.
- !Bleeding gums with easy bruising, nosebleeds or unusual tiredness should be checked by a doctor.
The studies3 cited · checked against PubMed
Home use of interdental cleaning devices, in addition to toothbrushing, for preventing and controlling periodontal diseases and dental caries ↗Worthington HV, MacDonald L, Poklepovic Pericic T, Sambunjak D, Johnson TM, Imai P, Clarkson JE · Cochrane Database of Systematic Reviews · 2019Systematic review and meta-analysis
35 trials (3,929 adults): floss or interdental brushes added to brushing may reduce gingivitis or plaque (low certainty), and interdental brushes may beat floss. Evidence on sticks and water flossers was limited and inconsistent, and no trial assessed decay between teeth.
Experimental gingivitis in man ↗Löe H, Theilade E, Jensen SB · Journal of Periodontology · 1965Experimental study
A classic experiment in which volunteers with healthy gums stopped all oral hygiene. All developed gingivitis within about 9 to 21 days as plaque accumulated, and gums returned to health once cleaning resumed. (PubMed lists no abstract; summary from the published paper.)
Treatment of periodontitis for glycaemic control in people with diabetes mellitus ↗Simpson TC, Clarkson JE, Worthington HV, MacDonald L, Weldon JC, Needleman I, Iheozor-Ejiofor Z, Wild SH, Qureshi A, Walker A, Patel VA, Boyers D, Twigg J · Cochrane Database of Systematic Reviews · 2022Systematic review and meta-analysis
35 trials (3,249 people with diabetes and periodontitis): professional gum treatment lowered HbA1c by 0.43 percentage points at 3 to 4 months versus no treatment or usual care (moderate-certainty evidence).