The brush should slide into the gap with a little resistance, touching the teeth on both sides, and without bending or needing a push. If it falls through loosely it is too small and is barely cleaning; if you have to force it, it is too big and can hurt the gum. Getting that fit right matters more than any other part of the technique.
Interdental brushes are small, bottle-shaped brushes made for the triangular spaces between teeth, where toothbrush bristles do not reach. For many adults they are easier to handle than floss.
Most mouths need more than one size
Gaps between teeth are rarely the same size all the way round. Spaces between the front teeth are often narrow, while gaps between the back teeth, or anywhere the gum has receded, are usually wider. That is why many people end up with two or three sizes.
Brushes are colour-coded by size, but the colours and measurements are not identical between brands, so it helps to stick with one range once you have found sizes that suit you. A dentist or oral health therapist can check your spaces at a visit and suggest where to start.
Finding your fit at home
Try the smallest size first in a front gap. If it moves freely with no contact, go up one size. In the back teeth, try a larger size, and drop back down if the wire bends or the brush will not enter. A brush that fits one gap may be wrong for the next, so test as you go the first few times.
Using it, gap by gap
- Hold the brush between your thumb and finger, close to the head, for control.
- Angle it slightly to follow the gap: a little upwards for the top teeth, a little downwards for the bottom teeth.
- Guide it gently into the space close to the gumline, without jabbing the gum.
- Move it in and out a few times so the bristles sweep both tooth surfaces.
- Rinse the brush and move to the next gap, working along each side of the mouth in the same order every time.
Many people find it easiest to reach the back teeth with a brush that has a longer handle or an angled head. Bending the neck of a straight brush can weaken the wire, so it is better to choose a shape that reaches comfortably.
Replace it before the wire gives way
Swap the brush once the bristles look flattened or splayed, or the wire has bent. A worn brush cleans poorly, and a kinked wire can scratch the gum. Rinse it after each use and let it air dry.
What the evidence shows
A 2019 Cochrane review led by Worthington looked at home cleaning between the teeth in 35 trials. It found low certainty evidence that interdental brushes may reduce gum inflammation more than floss at one and three months, and that adding interdental brushes to toothbrushing may reduce plaque compared with brushing alone. The overall evidence was low to very low certainty and the trials were short, so the size of the benefit is not settled. The Australian Dental Association recommends cleaning between your teeth at least once a day, using a method that suits your mouth.
Brush or floss
Interdental brushes tend to suit wider gaps, receded gums and the spaces around bridges, implants and braces. Floss tends to suit very tight contacts where even the finest brush will not fit. Many people use both in different parts of the mouth. Our guide to flossing properly covers the tight spots, and our comparison of water flossers, floss and interdental brushes looks at all three. Around fixed bridges and some implant work, floss threaders and superfloss can reach spaces a brush cannot.
Timing is flexible. Cleaning between the teeth before brushing is a common choice, and many people find the evening routine easiest to keep. Our guide to brushing properly covers the rest of the routine.
Common questions
Is some bleeding normal at first?
Yes, often. Inflamed gums tend to bleed when they are first cleaned, and this usually eases as they settle. If your gums are still bleeding after 3 to 4 days of good brushing and between-teeth cleaning, see a dentist or OHT. Our article on bleeding gums when brushing explains why.
Can interdental brushes damage the gums?
Used at the right size and with gentle pressure, they are unlikely to. Problems usually come from forcing a brush that is too large. If a gap hurts, try a smaller size.
Can I use one brush for the whole mouth?
You can use the same brush in several gaps during one session, rinsing as you go, as long as it fits each gap. Where gaps differ, switch sizes.
If you would like your gums checked and help choosing sizes, the dentists and oral health therapists at Lumi Dental can show you in the chair. See our current offers or book a general check-up. This article is general information and not a substitute for personal dental advice.
