Floss vs. Water Flosser vs. Interdental Brushes: What's Actually Better

Why Cleaning Between Teeth Matters

Dental plaque is the main cause of both tooth decay and gum disease, so disrupting it every day is the foundation of oral health. A toothbrush does a good job on the outer and inner surfaces of your teeth, but it can't reach well into the spaces between them. That is why dental professionals so often recommend an extra tool, such as floss, interdental brushes, wooden or rubber sticks, or a water flosser (also called an oral irrigator), to clean the areas the brush misses.^[1]

Those in-between spaces are also where gum inflammation often starts and where plaque that is left alone can harden into tartar. (Our explainer on plaque vs. tartar covers how that happens.) So the real question is not whether to clean between your teeth, but which tool gets the job done for you.

What the Cochrane Review Found

The most thorough look at this question is a 2019 Cochrane systematic review by Worthington and colleagues. It pooled 35 randomized controlled trials with 3,929 adults, comparing toothbrushing plus an interdental cleaning device against toothbrushing alone, and comparing different devices with each other.^[1] Here is what it found, in plain terms:

• Floss plus brushing may reduce gingivitis (gum inflammation) compared with brushing alone, at one, three, and six months. Results for bleeding and plaque were inconsistent.
• Interdental brushes plus brushing may reduce plaque more than brushing alone, and one small trial suggested less gingivitis too.
• Water flossers plus brushing may reduce gingivitis at one month, but the review did not find a clear effect at three or six months, and found no reduction in bleeding sites or plaque compared with brushing alone.
• Comparing devices directly, interdental brushes may reduce gingivitis more than floss at one and three months. Water flossers may reduce gingivitis at one month compared with floss, though the evidence was very weak.
• Safety: no serious harms were reported for any device, and minor issues such as gum irritation did not differ between groups.

The catch is in the certainty. The authors rated the overall evidence as low to very low certainty. Most trials were short, many participants started with only mild gum inflammation, no trials measured decay between teeth, and most did not look at periodontitis. The authors also cautioned that the effect sizes they saw may not be clinically important.^[1]

"Low certainty" does not mean "doesn't work." It means the studies are too small, short, or imperfect to be confident about the size of the benefit. Trials of daily habits are genuinely hard to run: you can't blind people to whether they are flossing, and few studies follow people long enough to see gum disease develop or teeth lost.

Head to Head: How the Three Tools Compare

Other reviews looking at the same body of research point in a broadly similar direction, with interdental brushes coming out on top most consistently.

A 2015 meta-review that pulled together six earlier systematic reviews found moderate evidence that interdental brushes combined with toothbrushing reduce both plaque and gingivitis. For floss, wooden sticks, and water flossers, the evidence for reducing gingivitis was weak and of unclear or small size, with no matching evidence of a plaque benefit. The authors concluded that interdental brushes are the most effective method for removing plaque between teeth, and that most studies fail to show that flossing is generally effective at removing plaque.^[2]

A 2018 network meta-analysis, a method that lets researchers rank tools even when they were never tested directly against each other, looked at 22 trials covering 10 types of interdental aids. Interdental brushes produced the largest reduction in gum inflammation, followed closely by water flossers. Those two had the highest probability of ranking "best," while floss and toothpicks ranked last. Even so, every aid except toothpicks did better than brushing alone. The authors also noted that it isn't clear how much these measured improvements translate into benefits people actually notice.^[3]

A European consensus workshop on preventing gum disease reached a practical conclusion from this kind of evidence: interdental brushes are the device of choice for cleaning between teeth, and floss is mainly recommended for spaces too tight for an interdental brush to pass through without causing damage.^[4]

Putting it together:

• Interdental brushes have the most consistent evidence, but they need to be the right size for each gap.
• Water flossers rank well for reducing gum inflammation in some analyses, but direct evidence is limited and inconsistent, especially beyond the first month.^[1][3]
• Floss has the most trials but the least impressive results on average. That may partly reflect how hard it is to floss well, rather than floss being useless.

The American Dental Association's position is that you should brush twice a day and clean between your teeth once a day with floss or another interdental cleaner, and that the choice of tool should depend on the individual. It notes that floss suits tight spaces, while interdental brushes work better for open spaces or for people with periodontitis.^[5] Not every clinician agrees on water flossers: some periodontists, for example one quoted by Cleveland Clinic, see them as an add-on to string floss rather than a replacement.^[6] Given how limited the evidence is, that difference of opinion is understandable.

Which Tool Fits Which Mouth

Because no tool wins clearly for everyone, the shape of your mouth and your own habits matter more than any ranking.

• Tight contacts and healthy gums. If your teeth sit snugly together and even the smallest interdental brush won't pass without force, floss (or a floss pick) is the sensible choice.^[4][5]
• Gum recession or open spaces. When gums have pulled back, or after gum disease treatment, the gaps between teeth get larger and harder for floss to clean well. Interdental brushes, sized to fill each gap, are generally the better fit here.^[5] If recession is part of your picture, our guide to receding gums covers causes and what helps.
• Braces. Brackets and wires trap plaque and make floss awkward to thread. In a small randomized trial of 30 people with fixed braces, both water flossing and string flossing reduced plaque and bleeding over two weeks. The water flosser group did slightly better, but the difference was not statistically significant.^[7] A 2026 systematic review of six trials found low-certainty evidence that interdental brushes may reduce plaque and gum inflammation in people with braces compared with brushing alone or floss, with no consistent advantage over water flossers.^[8] In practice, whichever tool you can use daily around your wires is the right one.
• Dental implants and bridges. Plaque around implants is a main cause of peri-implant mucositis, an early, reversible inflammation that can progress to peri-implantitis if untreated, and implant crowns often have shapes that are harder to clean around. A 2025 systematic review found that floss, interdental brushes, and water flossers all showed some benefit around implants, but evidence remains limited.^[9] If you use an interdental brush on implants, the ADA notes that implant-specific brushes have coated wire to avoid scratching.^[5] Cleveland Clinic also highlights people with implants, bridges, or larger gaps as among those most likely to benefit from adding a water flosser.^[6]
• Limited hand dexterity. If arthritis, a tremor, or simply big hands make wrapping floss around your fingers hard, the best tool is the one you will actually manage every day. Floss holders, interdental brushes on a long handle, and water flossers are all options the ADA lists as interdental cleaners.^[5] Talk to your hygienist about which one suits your grip.

Making Your Choice Actually Work

The biggest difference between tools in real life is often whether people keep using them. A few practical points:

• Size interdental brushes properly. They come in a range of sizes to match the space between teeth, in cone or cylinder shapes.^[5] Many people need two or three sizes for different parts of the mouth. The brush should fit snugly without forcing it. Ask your hygienist to size them for you.
• Be gentle. Snapping floss down onto the gums or forcing a brush that is too big can irritate tissue. Curve floss around each tooth and slide it just under the gumline.
• Aim for once a day. For people with gingivitis, daily interdental cleaning is the recommended baseline.^[4] If your gums bleed easily or you have deeper pockets, your dentist may suggest more, and our guide to the stages of gum disease explains what those signs can mean.
• Combining is fine. Nothing in the research suggests you must pick only one. Some people use interdental brushes where they fit and floss in the tightest spots, or add a water flosser around braces or implants.

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