Interdental Brush: How to Choose the Right Size and Type

Interdental brushes are small, bristled tools designed to clean the gaps between teeth, and research consistently shows they remove more plaque from those spaces than dental floss does. A systematic review of the available trials found that the majority reported a significant advantage for interdental brushes over floss on plaque scores, and individual studies have measured meaningful reductions in gum pocket depth as well. Despite this, floss remains far more widely used in many countries, partly out of habit and partly because interdental brushes were not widely available to consumers until relatively recently.

Why They Outperform Floss

The most straightforward reason interdental brushes clean better than floss is mechanical. A brush fills the space between two teeth with bristles that scrub the surface on both sides simultaneously, while floss can only contact one surface at a time and requires wrapping against each tooth individually. In a head-to-head trial of patients with moderate-to-severe gum disease, interdental brushes reduced plaque scores from about 3.1 to 2.2 over six weeks, while floss brought the same starting score down only to 2.5. The brush group also saw a larger reduction in pocket depth around their teeth.¹ A systematic review confirmed this pattern across multiple studies, finding that the majority showed a significant plaque advantage for interdental brushes compared to floss.²

One question that comes up is whether interdental brushes work better simply because the bristles compress the gum tissue between teeth, which would make gum pockets seem shallower without actually improving health. Researchers tested this using structural equation modeling and found that the observed reductions in pocket depth and gum bleeding were mostly explained by better plaque removal, not by physically squishing the gum papillae.³ The brushes genuinely clean better, and the gum improvements follow from that.

Patient preference matters here too. People who find a cleaning tool easy and comfortable are more likely to actually use it every day. Interdental brushes tend to score well on ease of use and acceptance, which likely amplifies the clinical advantage: a tool that works slightly better in a lab and gets used more consistently at home compounds that benefit over time.⁴

Getting the Right Size

The single biggest mistake people make with interdental brushes is using the wrong size. Your mouth probably needs more than one size, because the gaps between your front teeth are almost always narrower than the gaps between your back teeth. A study of young adults with healthy gums found that roughly 80% of interdental spaces required brushes in the smallest diameter range, around 0.6 to 0.7 mm. Front teeth tended to need the 0.6 mm brush, while back teeth more often needed 0.7 mm.⁵ People with gum disease or bone loss typically have wider gaps and may need larger sizes still.

Even when a dentist or hygienist helps with sizing, accuracy is surprisingly modest. When researchers compared the brush sizes people actually used to the sizes recommended by a calibrated color-coded probe, the match was only about 43%. In about a third of cases, people were using a brush that was too small for the gap.⁶ A brush that’s too small slides through without the bristles contacting the tooth surface properly, which defeats the purpose. A brush that’s too large won’t fit through and can hurt. The ideal fit is one where the brush enters with slight resistance and the bristles splay gently against both teeth.

If you’re starting from scratch, buying a multi-size starter pack is the practical move. Work through the sizes to find which ones fit each region of your mouth. Some manufacturers now design systematic sets calibrated to passage-hole diameters, aiming for more reliable sizing than the traditional trial-and-error approach.⁷ But the gold standard is still having your dentist or hygienist probe the spaces and recommend specific sizes for different parts of your mouth.

Wire Brushes Versus Rubber or Silicone Picks

Walk down the oral-care aisle and you’ll see two broadly different types of interdental cleaners beyond floss: traditional wire-core interdental brushes with nylon bristles, and newer rubber or silicone picks with flexible fins instead of bristles. Both reduce plaque and bleeding, but they are not equal in cleaning power.

In lab testing that measured plaque removal from both sides of an interdental space, wire-bristle brushes achieved about 81% cleaning efficacy compared to roughly 55% for elastomeric picks. That gap was consistent across different gap sizes and shapes.⁸ The wire brush is simply better at mechanically disrupting the biofilm.

Where rubber picks gain ground is comfort. In clinical trials, patients consistently rate rubber or silicone interdental cleaners as less painful and more comfortable to use than wire brushes. One randomized trial found no difference in plaque or bleeding improvements between a silicone-coated interdental pick and a standard wire brush over time, but patients were significantly more satisfied with the silicone pick’s comfort and cleaning feel.⁹ Another trial comparing rubber interdental bristles to conventional wire brushes found similar reductions in plaque and bleeding, with the rubber option again scoring higher on pain, comfort, and willingness to keep using the product.¹⁰

The practical takeaway: if you have the dexterity and tolerance for a wire brush, it cleans better. If a wire brush causes pain or you know you’ll skip it because it’s uncomfortable, a rubber pick that you actually use daily will serve you better than a wire brush gathering dust in a drawer.

Use Around Dental Implants

Implants create a unique cleaning challenge. The connection between an implant crown and the gum tissue is different from a natural tooth, and the spaces around implants tend to be shaped in ways that floss handles poorly. Floss can also fray against the rough surface of the implant abutment underneath the crown, potentially leaving fibers behind that irritate the tissue. A randomized trial comparing interdental brushes, water flossers, and dental floss around single-implant crowns found that brushes and water flossers were preferable for maintaining peri-implant health, in part because they avoid these fraying risks.¹¹

A systematic review and meta-analysis looking specifically at interproximal cleaning around implant-supported restorations found that both oral irrigators and interdental brushes showed greater improvement in signs of peri-implant mucositis (the early stage of gum inflammation around implants) compared to floss, though the difference did not quite reach statistical significance.¹² The trend was consistent enough that the clinical recommendation leans toward interdental brushes or water flossers for implant care. If you have implants, ask your dentist which brush size fits the spaces around your specific restoration, since implant spacing can be quite different from natural tooth spacing.

With Braces and Orthodontic Appliances

Keeping teeth clean around brackets and archwires is notoriously difficult. Standard brushing misses the areas between brackets and under the wire, and threading floss under an archwire is slow enough that most patients give up. Interdental brushes slide between brackets and under wires more easily. In a randomized trial of adolescents undergoing orthodontic treatment, interdental brushes significantly reduced plaque regardless of brush head design, and the patients reported less pain and better access behind the archwire compared to other cleaning tools.¹³

Not all interdental brush designs perform equally around brackets, though. A multicenter study tested two different interdental brush shapes specifically for plaque removal around the base of orthodontic brackets. One conical brush design achieved substantially higher cleaning efficacy than a cylindrical one, particularly in the hardest-to-reach areas directly beside and beneath the bracket wings.¹⁴ If you’re in braces, it’s worth asking your orthodontist which brush shape works best for your bracket type, because the geometry matters more than you might expect.

What Happens to Bacteria

Beyond just removing visible plaque, interdental brushing changes the bacterial community living between your teeth. A controlled trial in young adults tracked specific bacterial groups over three months and found that people who used calibrated interdental brushes saw significant decreases in bacteria from the orange and red complexes, which are the groups most associated with destructive gum disease. Meanwhile, bacteria associated with gum health, from the blue complex, actually increased in the brushing group.¹⁵ People who didn’t use interdental brushes showed no such shift. The takeaway is that regular interdental brushing doesn’t just physically remove bacteria; it shifts the microbial balance toward species that are less harmful.

Brush Shape and Handle Design in Gum Disease Treatment

If you’re already being treated for gum disease, your dentist may recommend interdental brushes as part of a nonsurgical treatment plan. A clinical trial compared waist-shaped (hourglass-profile) brushes with straight cylindrical ones during nonsurgical periodontal therapy. Both designs produced significant reductions in pocket depth and bleeding on probing. The waist-shaped brush did not outperform the straight one in a clinically meaningful way.¹⁶ This suggests that consistent use matters more than obsessing over the perfect brush profile. Whichever shape fits your spaces comfortably and gets used every day is the right one.

How Interdental Brushes Compare to Water Flossers

Water flossers (oral irrigators) are the other main alternative to string floss, and their comparison to interdental brushes is more nuanced than the brush-versus-floss story. In a trial of patients with bonded orthodontic retainers (the thin wire glued behind lower front teeth after braces), a water flosser group showed significantly lower plaque and gum inflammation scores than the interdental brush group. Both groups saw improvements in pocket depth and attachment level, with no difference between them on those measures.¹⁷

Another four-week trial compared a water flosser to interdental brushes specifically for gum bleeding. Both groups showed significant reductions, but the water flosser group had lower bleeding-on-marginal-probing scores at the end of the study. Gum abrasion, a common concern with wire brushes, was no different between the two groups.¹⁸ Water flossers may have an edge for reducing bleeding, while interdental brushes tend to be better at physically removing plaque. They serve somewhat different purposes, and some clinicians recommend using both.

A consensus-based expert panel noted that the choice between devices should consider individual dexterity, not just clinical efficacy. Water flossers may be better suited for people with limited hand function, such as older adults or people with conditions affecting grip strength, while interdental brushes remain the first-line recommendation for most people who can use them comfortably.¹⁹

Use in Children

Most conversations about interdental brushes focus on adults, but children can benefit too, especially once their permanent teeth come in and interdental contacts tighten. A study comparing floss, interdental brushes, and oral irrigators as supplements to toothbrushing in children found that both interdental brushes and oral irrigators removed significantly more plaque than toothbrushing alone. Floss, somewhat surprisingly, did not add a significant benefit beyond the toothbrush in this study’s pediatric population.²⁰ For children who lack the manual dexterity to handle string floss effectively, an interdental brush with a handle can be a more realistic daily option.

Can You Add Medication to the Brush?

Some interdental brushes come pre-coated with antiseptic agents like chlorhexidine or cetylpyridinium chloride, and you can also dip a plain brush in a mouthwash before inserting it. The idea is to deliver an antimicrobial agent directly to the interdental space where bacteria thrive. A systematic review found only seven studies on the topic, most involving medicated dental floss rather than medicated brushes, so the evidence base is thin.²¹ The concept makes mechanical sense, since the brush already contacts the surfaces you want to treat, but there isn’t yet strong evidence that adding a chemical agent to the brush produces meaningful clinical improvements beyond what the mechanical cleaning alone achieves. It’s an area where more research is needed before making firm recommendations.

Bad Breath

One benefit of interdental cleaning that people notice quickly is the effect on breath. The spaces between teeth harbor bacteria that produce volatile sulfur compounds, which are a major contributor to oral malodor. A clinical case report documented how incorporating proper interdental brushing into a patient’s routine reduced severe bad breath to an acceptable level and improved the patient’s self-reported quality of life.²² Anyone who has smelled an interdental brush after pulling it out of a neglected gap understands this intuitively. If you’ve been brushing your teeth diligently but still notice persistent bad breath, the interdental spaces are worth investigating before blaming your stomach or your sinuses.

Environmental Considerations

Interdental brushes are typically made of a metal wire core, nylon bristles, and a plastic handle, which makes them harder to recycle than a piece of string floss. But a lifecycle analysis that compared the environmental footprint of different interdental cleaning products found that the picture is more complicated than just materials. Floss picks, the Y-shaped plastic holders pre-threaded with floss, had the largest environmental footprint across most impact categories. Among interdental brushes, bamboo-handled versions had the lowest overall environmental impact, scoring best in climate change, fossil fuel use, and freshwater eutrophication. Brushes with replaceable heads also performed well, because you discard only the small bristle insert and reuse the handle.²³

Standard string floss, plain nylon on a spool, actually landed in the lower-impact range for several environmental categories. But very few people use basic spool floss anymore; pre-cut floss picks dominate the consumer market, and their plastic holders push the footprint much higher. If you’re environmentally motivated and committed to interdental brushes, bamboo or replaceable-head designs are the best current options.²⁴

A Brief History

Interdental brushes feel like a modern invention, but twisted wire brushes intended for oral hygiene were mentioned in dental literature as far back as the late 1800s. Their specific use in interdental spaces likely began in the early twentieth century, and documented clinical use dates to at least 1960. Publications evaluating their effectiveness began appearing in the 1970s. For decades the reception was mixed, with some clinicians enthusiastic and others skeptical about whether the brushes could justify the effort compared to floss. By the early 2000s, accumulating trial data tipped the consensus, and interdental brushes came to be considered the preferred tool for interdental cleaning in most clinical guidelines. The development of ISO standard 16409 attempted to bring uniformity to sizing and labeling, though challenges in helping patients select the right size have persisted.²⁵ Decades of engineering refinement in bristle materials, wire flexibility, handle ergonomics, and brush profiles have brought the modern interdental brush a long way from those early twisted-wire prototypes, even if the basic principle hasn’t changed at all.