About 40 percent of every tooth surface sits between the teeth, where a toothbrush bristle cannot reach. An interdental brush is a small wire brush designed to clean exactly that space. Used daily, it can help reduce plaque and gum inflammation, and a Cochrane review found interdental brushes may be at least as effective as floss, and in some cases better for early gum inflammation, though the overall certainty of the evidence is low.
Key takeaways
- An interdental brush cleans the triangular gaps between teeth that brushing alone leaves behind.
- The right size is the one that fits snugly without being forced. Most people need more than one size.
- Use it once a day, ideally before brushing, with a gentle in-and-out motion.
- Interdental brushes suit larger gaps and gum recession; floss often suits very tight contacts.
- A little bleeding in the first week is common and usually settles as the gums get healthier.
The one rule that matters most: fit
The single thing that decides whether an interdental brush works is whether it fits the gap. Too small and it sweeps through without touching the sides. Too big and you force it, which can hurt the gum. The brush should pass through with light resistance and gentle contact on both tooth surfaces. Because gaps vary across the mouth, most people use two or three sizes rather than one.
Interdental brushes are sized by a colour code based on the ISO scale, running from very fine (around 0.4 mm) up to wide (1.5 mm and above). If you are not sure where to start, your dentist or oral health therapist can measure your spaces and recommend the sizes that match your mouth.
How to choose your size
- Start with a fine brush at the front teeth, where gaps are usually smaller.
- Move to the back teeth, where gaps are often larger, and step up a size if the brush feels loose.
- If a brush bends sharply or will not enter, drop down a size. Never push hard.
Step by step: using an interdental brush
- Pick the right size for the gap. Keep your sizes in front of you so you can switch as you move around the mouth.
- Angle the brush. For the upper teeth, angle it slightly upward; for the lower teeth, slightly downward, following the natural shape of the gap.
- Insert gently. Guide the brush straight into the space. Do not force it or jab the gum.
- Move in and out. Use a few gentle back-and-forth strokes to sweep the plaque from both tooth surfaces.
- Work through the mouth in order. Start at one side and move along so you do not miss any gaps. Rinse the brush as needed.
- Replace the brush. Swap it when the bristles splay or the wire bends, usually after about a week of daily use.
When to use it, and in what order
Once a day is enough for most people. Doing it before brushing can help, because loosened plaque is then cleared away by the toothpaste and brush. Many people find the routine easiest at night. Consistency matters far more than the time of day. As we cover in our guide to brushing your teeth properly, the best technique is the one you will actually repeat every day.
Interdental brush or floss?
Both clean between the teeth, and the best choice depends on your spaces.
| Feature | Interdental brush | Floss |
|---|---|---|
| Best for | Larger gaps, gum recession, around bridges and implants | Very tight contacts where a brush will not fit |
| Ease of use | Often easier, no wrapping around fingers | Takes more dexterity |
| Evidence for gum health | May be at least as effective as floss for early gum inflammation | Effective when done well, though many people floss poorly |
For a fuller comparison including water flossers, see our guide to water flosser versus floss versus interdental brushes. If your contacts are too tight for any brush, our step-by-step flossing guide may suit you better.
Is bleeding normal?
If your gums bleed a little when you first start, it usually means there is inflammation that needs cleaning, not that you should stop. In most cases the bleeding settles within a week or two of daily cleaning. If it continues beyond that, see a dentist, as ongoing bleeding can be a sign of gum disease. Our article on bleeding gums when brushing explains when to act.
Frequently asked questions
How often should I replace an interdental brush?
Replace it when the bristles look worn or the wire bends, which is typically after about a week of daily use. A bent wire can scratch the gum, and worn bristles clean poorly.
Can I reuse the same brush for every gap?
You can use one brush across several gaps in a session, rinsing it as you go, but you may need different sizes for different parts of the mouth. Replace the brush once it wears out.
Do interdental brushes damage the gums?
Used at the right size with a gentle technique, they do not. Damage comes from forcing a brush that is too large or jabbing the gum. If it hurts, switch to a smaller size.
Are they suitable around implants and bridges?
Yes, interdental brushes are often recommended for cleaning around implants, bridges, and braces because they reach spaces floss struggles with. Ask your dentist which size suits your appliance.
The takeaway
An interdental brush is one of the simplest ways to clean the part of your teeth a toothbrush cannot reach. Choose a size that fits snugly, use it gently once a day, and replace it when it wears. If you would like the team at Lumi Dental to check your gum health and show you the right technique and sizes for your mouth, you can find current consultation options on our current deals page or book a general check-up. This article is general information and not a substitute for personal dental advice.
