How to Use Interdental Brushes: Sizes, Technique and Common Mistakes
- Health
- Published
- 4 min
Quick take Those tiny bottle-brush tools look fiddly, but once the sizes are right they take a couple of minutes. Here is how to pick them, use them and avoid the usual slip-ups.
What this answer covers
4 min · Nov 9, 2026A toothbrush cleans the outside, inside and biting surfaces of the teeth well enough. The trouble is the narrow strip where two teeth meet the gum. Bristles skim past it, plaque settles in, and that is where many gum problems and some decay begin. Floss is one answer. For a lot of people, especially those with slightly wider gaps, interdental brushes are an easier one.
They look like miniature bottle brushes on a short handle. Used once a day, they can reach the spaces a toothbrush misses, and most people get quicker with them after the first week or two.
Choosing the right size
Size is the part that puts people off, because the gaps in one mouth are rarely all the same. Brushes come in a range of widths, usually marked by colour, and most people end up using two or three sizes in different parts of the mouth.
- The right fit feels snug. The brush should slide in with gentle pressure and you should feel the bristles touching both teeth.
- Too small does little. If it slips through with no resistance, it is mostly passing air.
- Too big should not be forced. If you need to push, or the wire bends, drop down a size.
- Front gaps are often tighter than the gaps between the back teeth.
A dentist or hygienist can check which sizes suit which gaps at your next visit, and many will show you on a model or in your own mouth. Starting with a mixed pack is a sensible way to find your sizes at home.
Step by step
- Stand in good light in front of a mirror, so you can see where the gaps are.
- Bend the neck of the brush slightly for the back teeth if the instructions allow it, which makes the angle easier to reach.
- Place the brush at the gum line between two teeth and guide it in gently, straight or with a slight angle following the gap.
- Move it in and out a few times. There is no need to twist or scrub.
- Rinse the brush under the tap as you move between gaps, and work round the mouth in the same order each time so none get missed.
- Clean from the tongue side too on back teeth if your hygienist suggests it.
- Rinse and dry the brush when you finish, and replace it once the bristles look flattened or the wire starts to bend.
Once a day is usually enough. Many people find the evening easiest, before or after brushing, so the gaps are clean for the night. Toothpaste is not needed on the brush, though a small smear is fine if you like the taste.
Bleeding in the first days
Some bleeding is common when you start, especially if the gums between the teeth are inflamed. In many people it reduces within a week or two of daily cleaning as the gums settle. Do not stop because of a little blood, but do not push harder either.
If bleeding carries on beyond a couple of weeks, gets worse, or comes with soreness, swelling, a bad taste or loose teeth, book a dental check. Smokers should be extra watchful: smoking can make gums bleed less even when they are unhealthy, so a lack of blood is not always reassuring. Former smokers may notice more bleeding for a while as the gums recover, which is one of several changes after stopping that our answer on smoker's cough after quitting puts in context.
Brushes, floss or a water flosser?
| Tool | Suits | Less suited to |
|---|---|---|
| Interdental brushes | Visible or medium gaps, people who find floss awkward, bridges, braces, implants | Very tight contacts where even the smallest size will not fit |
| Floss or tape | Tight contacts, especially at the front | Wider gaps where it slides past the plaque |
| Water flosser | Rinsing around fixed braces and bridges, people with limited hand movement | Replacing a brush or floss entirely for most mouths |
Many people use a mix: brushes where they fit, floss where the teeth are tight. The best choice is the one you will actually use every day.
Implants, bridges and braces
Interdental brushes are especially useful where food and plaque can gather around dental work. Around implants, brushes with a coated wire are often recommended, so bare metal does not rub the implant surface; ask the practice which type they prefer. Cleaning the gum line around an implant crown matters just as much as around a natural tooth, because inflamed gum can affect the bone that holds it. Our guide to what to expect from an implant, from consultation to crown explains how that aftercare fits into the wider treatment.
Under a bridge, a brush can be threaded beneath the false tooth to clean the gum underneath. With fixed braces, small brushes help clear food from around the brackets and under the wire, though the orthodontist may suggest a particular shape.
Common mistakes
- Forcing a brush that is too big, which can hurt the gum and bend the wire.
- Using one size everywhere and skipping the gaps it does not fit.
- Scrubbing or twisting instead of a gentle in-and-out stroke.
- Keeping a brush too long. Worn bristles clean poorly and a kinked wire can scratch.
- Giving up after two days because of bleeding or awkwardness. It nearly always gets easier with practice.
- Sharing brushes. Like toothbrushes, they are for one person only.
Making it a habit
Keep the brushes next to the toothbrush, not in a drawer, so they are in sight when you need them. Doing the same gaps in the same order each night turns it into a routine that takes two or three minutes. Children and anyone with sensitive gums, gum disease, a bleeding disorder or a recent operation in the mouth should check with their dentist or hygienist about how and when to start.