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Prevention2 min read · July 22, 2026

by Dr.ssa Irene Ferrara

Floss or interdental brush? How to really clean between teeth

A toothbrush does not reach a third of your tooth surfaces. Which tool you need, how to use it, and what the Cochrane reviews say.

If you brush carefully twice a day but skip interdental cleaning, you are leaving out roughly a third of your tooth surfaces. That is not a detail: it is exactly where many cavities start and where most gum inflammation begins.

What the evidence says

The Cochrane review on home-use interdental cleaning devices, in addition to toothbrushing, indicates a benefit in reducing gingivitis and plaque compared with brushing alone. The practical message is simple: adding something is better than adding nothing.

Floss or interdental brush: the space decides

It is not a matter of preference but of anatomy:

  • Dental floss — when teeth are in tight contact and the gum papilla fills the space. Typical of front teeth in healthy mouths.
  • Interdental brush — when there is space between teeth: receded gums, naturally wide spaces, implants or prosthetics. Where it fits, an interdental brush is usually simpler and more effective than floss.

Brush size is not chosen by eye: it should enter with slight resistance, without forcing. Often two different sizes are needed in the same mouth. We calibrate this together during a hygiene session.

How to use floss (without hurting yourself)

Initial bleeding is alarming, but it usually signals existing inflammation rather than damage you are causing. It generally settles within one or two weeks of regular use.

  • Wind the floss and guide it gently between the teeth, without snapping it onto the gum.
  • Once below the contact point, hug the side of the tooth in a C shape and move up. Then repeat on the neighbouring tooth: there are two surfaces, not one.
  • A clean length of floss for each space.

When to do it

The order is not decisive, consistency is: once a day, ideally in the evening, when night-time salivary flow decreases. Thirty seconds every evening beats five minutes once a week.

If you wear braces or have implants

You need dedicated tools: floss with a threader, correctly sized interdental brushes, possibly a water flosser as a complement — not as a replacement. In these cases it is genuinely worth being shown the technique rather than improvising.

Sources

Frequently asked questions

Does a water flosser replace floss and interdental brushes?

No, treat it as a complement. It is useful around braces and complex prosthetics, but it does not remove adherent biofilm the way the mechanical contact of floss or a brush does.

My gums bleed when I floss: should I stop?

No. In most cases bleeding indicates existing inflammation and settles within one or two weeks of daily use. If it persists beyond that, book a check-up.

Clinical review: Dr.ssa Irene Ferrara

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