If you are choosing between an interdental brush and floss, the main difference is not that one is always better. The tools make contact with the space between teeth in different ways.
Floss is a flexible strand that can slide through a tight contact and curve around the side of each tooth. An interdental brush has a small bristled head that passes through a space and brushes the facing tooth surfaces. The better fit can vary from one space to another, which is why brush size and professional guidance can matter.
Interdental brushes vs. floss at a glance
| What matters | Interdental brush | Floss |
|---|---|---|
| Cleaning action | Bristles sweep the facing surfaces as the brush moves through the space. | A flexible strand wipes against one tooth surface and then the other. |
| Space fit | Often considered when there is enough room for the brush to pass through without force. | Often useful where neighboring teeth meet too closely for a brush to fit safely. |
| Sizing | Available in different sizes; more than one size may be needed across a mouth. | Strand thickness and texture vary, but floss does not need to fill the whole gap. |
| Handling | A small handle can reduce finger wrapping, but the brush still needs a suitable angle and size. | Requires both hands or a holder and enough control to curve the strand around each tooth. |
| Research | May have a short-term advantage for some gum-inflammation measures, but the evidence is uncertain. | May also reduce gingivitis when added to brushing; the evidence is uncertain and technique-sensitive. |
This is a tool comparison, not a recommendation for a particular mouth. Tooth spacing, gum shape, dental work, hand control, and technique can change what works in each area.
How the two tools clean differently
An interdental brush looks like a very small bottle brush. Designs come in several sizes and may have a cylindrical or cone-shaped bristled head. The brush is guided through a space so that the bristles contact the sides of the neighboring teeth.
Floss works with a thin, flexible strand. After it passes through the contact between two teeth, the strand is curved into a C shape around one tooth and moved along its side. It is then curved around the neighboring tooth so both surfaces are cleaned.
That difference in mechanics matters. An interdental brush needs enough room for its bristles to enter and make contact. Floss can pass through a much narrower contact, but it needs to be guided against each tooth rather than moved once through the middle.
For a step-by-step look at the strand technique, see how to floss properly.
Space fit is often the deciding difference
The American Dental Association notes that floss may suit tight spaces, while interdental brushes may suit more open spaces or some people with periodontitis. The NHS similarly says interdental brushes can be used especially where there are gaps and that the brush should fit snugly.
“Snug” does not mean jammed. An interdental brush should pass through without being forced. A brush that bends sharply, splays, gets stuck, or hurts may not be the right size or angle for that space.
The spaces across one mouth may not all be alike. A brush may fit one area but not another, and different brush sizes may fit different areas. Floss may still be practical in contacts that are too narrow for even a small brush.
This is also why choosing the largest-looking brush or copying someone else’s color code is not a reliable sizing method. Product size and color systems can vary. A dentist or dental hygienist can check the spaces directly, demonstrate the angle, and show which size fits without trauma.
Handling and reach can change the experience
Interdental brushes usually have a short handle or holder. Some people find that easier to grip than wrapping floss around their fingers. The in-and-out motion may also feel simpler in an open, easy-to-reach space.
That does not make every brush easy to use everywhere. Back teeth may require a different handle angle, and a brush that is too large or too small will not become suitable just because its handle is convenient.
String floss takes more finger coordination. You have to hold a short working section, guide it through the contact, curve it around each tooth, and move to a clean section as you continue. Its flexibility can be helpful around tight contacts and changing tooth shapes.
If the difference you are considering is a handle rather than a brush, the separate guide to floss picks vs. string floss compares those two floss formats.
What does the evidence say?
Research does not support calling either tool the universal winner.
A 2019 Cochrane review included 35 randomized trials of home interdental-cleaning devices used with toothbrushing. In direct comparisons, interdental brushes may have reduced gingivitis more than floss at one and three months. Evidence for plaque was inconsistent, and there was no clear difference for the periodontitis measure of probing depth.
Those findings have important limits:
- The evidence was rated low to very low certainty.
- Most outcomes were measured over short periods.
- Many participants started with little gum inflammation.
- The size of the observed differences may not have been clinically important.
- No included trial measured cavities between teeth, and most did not evaluate periodontitis.
So a short-term average in a study cannot tell you which tool fits a particular space, which one you will use correctly, or which one will produce better long-term results for you. The evidence supports cleaning between teeth and matching the tool to the space without turning a category-level result into a personal prescription.
Do you have to use only one?
Not necessarily. “Clean between your teeth” describes the goal, not a rule that every space must be cleaned with the same device.
Some people may use a brush in spaces that can accept it and floss where contacts are tighter. Others may have one tool that fits their whole routine. Using two tools is not automatically more thorough, and using a brush and floss in the same space is not required simply because both exist.
Water flossers are another category with different mechanics. If that is the comparison you are trying to make, see are water flossers as good as floss?.
When professional help is useful
A dentist or dental hygienist can help if:
- you do not know which brush size fits a space;
- a brush bends, splays, catches, or will not pass comfortably;
- floss repeatedly shreds or gets stuck in one area;
- braces, a bridge, an implant, or another restoration changes access;
- limited hand control makes either technique difficult; or
- cleaning keeps causing pain, swelling, or persistent bleeding.
A demonstration is not a verdict that one product category is best for everyone. It is a way to match the tool, size, and technique to the area being cleaned. Ongoing bleeding, pain, or swelling also deserves evaluation rather than repeated switching between products.
Common questions
Are interdental brushes better than floss?
Not for every person or every space. Low-certainty evidence suggests that interdental brushes may improve some short-term gum-inflammation measures more than floss, but plaque results are inconsistent and long-term disease outcomes were not established. Fit and technique still matter.
Can an interdental brush replace floss?
It may serve as the between-teeth cleaner in spaces where an appropriately sized brush fits without force. Floss may remain useful in contacts that are too tight for a brush. A dental professional can help map different sizes or tools to different spaces.
Should an interdental brush feel tight?
It should fit snugly enough for the bristles to contact the tooth surfaces, but it should not need to be forced. If the brush bends, splays, gets stuck, or hurts, stop forcing it and ask for sizing or technique help.
Is a bigger interdental brush more effective?
Not automatically. A brush that is too large may not pass safely, while one that is too small may not make useful contact. The appropriate size depends on the space, and one mouth may need more than one size.
Bottom line
Interdental brushes use bristles to sweep through spaces that can accommodate them. Floss uses a flexible strand to wrap around tooth surfaces and can reach tighter contacts.
Neither tool is universally superior. The useful comparison is whether the tool fits the space without force, can contact both tooth surfaces, and is manageable enough to use consistently. If brush sizing or access is unclear, a dentist or dental hygienist can provide a direct demonstration without turning general guidance into a one-size-fits-all choice.
Sources
- Dental Floss/Interdental Cleaners — American Dental Association
- How to keep your teeth clean — NHS
- Home use of devices for cleaning between the teeth (in addition to toothbrushing) to prevent and control gum diseases and tooth decay — Cochrane
- How to Clean Between Your Teeth Effectively — Oral Health Foundation