Interdental Brushes v. String Floss: What the Science Really Says

Interdental Brushes vs. String Floss: What the Science Really Says

For decades, the mantra of “brush and floss daily” has echoed through dental surgeries, TV ads, and oral health campaigns. String floss has been positioned as the gold standard of interdental cleaning. But in recent years, an alternative has gained momentum: interdental brushes (IDB)

So, which is better? Should floss still be the default, or is it time to update the advice? Fortunately, we don’t need to rely on opinion—there’s solid research, including systematic reviews and meta-analyses, that helps us answer this question.

Why Cleaning Between Teeth Matters

Toothbrushing alone removes much of the plaque that builds up on tooth surfaces, but it simply cannot reach into interproximal spaces  that Plaque that remains here the process can continue to become calculus , these processes in turn cause gingival inflammation, and lead to periodontal disease. That’s why dental professionals  have long recommended interdental cleaning as an essential companion to brushing.

For many years, floss was the only widely available option. It’s inexpensive, portable, and reasonably effective if used with perfect technique on an already health Periodontium  But therein lies the problem: few people use floss consistently or correctly. Interdental brushes, on the other hand, are often easier to handle, more forgiving of imperfect technique, and can physically disrupt more plaque due to their bristled design.

What the Evidence Shows

1. Imai et al. (2012) Meta-Analysis

A pivotal meta-analysis published in International Journal of Dental Hygiene compared interdental brushes and floss across several randomized controlled trials. Over 4–12 weeks, interdental brushes reduced bleeding more effectively than floss (p = 0.003) and also showed a statistically significant improvement in plaque removal (treatment effect ≈ 0.13; p = 0.024).
Translation: IDBs don’t just make gums look healthier, they actually help them stop bleeding—a strong indicator of reduced inflammation.

2. Cochrane Review (2019)

Cochrane Reviews are widely regarded as the gold standard of evidence synthesis. In 2019, Slot and colleagues reviewed 35 studies on interdental cleaning methods. Their findings were telling:interdental brushes may reduce gingivitis more than floss after one to three months. Evidence on plaque removal was mixed, but the trend still favored brushes. Importantly, the reviewers noted that most studies were short-term and of low to very-low certainty, but the pattern was consistent: IDBs generally outperformed floss.

3. Network Meta-Analysis (Sharma et al., 2018, Journal of Periodontology)

To get a clearer picture, Sharma and colleagues conducted a network meta-analysis ranking multiple interdental cleaning methods. The results were striking: interdental brushes and oral irrigators (water flossers) ranked highest for reducing gingival inflammation, while string floss sat near the bottom of the hierarchy.
In other words, when all methods are compared simultaneously, IDBs consistently come out on top.

4. Earlier Systematic Reviews (Slot et al. 2008; EBD summary 2009)

Even before these large reviews, evidence was stacking up. Slot’s 2008 review concluded thatinterdental brushes, when used with toothbrushing, removed more plaque than floss. A 2009 summary in Evidence-Based Dentistry put it succinctly: “The use of interdental brushes along with toothbrushing removes most plaque.”

Why Interdental Brushes Work Better

Several reasons explain why IDBs outperform floss in practice:

• Mechanical action: The bristles sweep across tooth surfaces and gingival margins disrupting more plaque than a thin filament of floss.
• Ease of use: Most people find brushes easier to maneuver, particularly for back teeth.
• Compliance: Because they are simpler and more comfortable, patients are more likely to use them regularly.
• Adaptability: Interdental brushes come in multiple sizes to fit different spaces; larger embrasures (gaps) especially benefit from them.

Where Floss Still Has a Place

It’s worth noting that floss isn’t obsolete. For very tight contacts—where even the smallest interdental brush won’t fit—floss is still useful. Orthodontic patients with fixed appliances may also need specialized floss threaders. But for the majority of adults,  especially those with gingival inflammation then interdental brushes are more effective and more user-friendly.

What Dental professionals Should Tell Patients

Given this body of evidence, dental professionals worldwide are updating their guidance. Instead of “brush and floss daily,” a more evidence-based message might be:

• “Brush twice daily with fluoride toothpaste, and clean between your teeth daily with an interdental brush where it fits. Use floss only if the spaces are too tight.”

This advice is more practical, more personalized, and more aligned with the science.

Patient Preference: The Missing Piece

Another overlooked factor is patient preference. In studies where patients were asked, most said they preferred interdental brushes to floss. Ease of use is critical because oral hygiene is only effective if it is actually done. By recommending tools that patients are more willing to use, we increase adherence—and that leads to better long-term oral health outcomes.

Limitations of the Evidence

It’s important to be transparent:

• Many of the studies were short-term (weeks to months). We need more long-term data.
• The certainty of evidence in some reviews wasrated low due to small sample sizes and variability in study design.
• Not every interdental space is the same—results may differ depending on anatomy, age, and periodontal status.

Still, when multiple independent reviews reach similar conclusions, the direction of evidence is hard to ignore.

The Bottom Line

The science is clear enough to support a shift in advice:

• Interdental brushes are generally more effective than string floss at reducing plaque and gingival bleeding.
• Patients prefer them, and they are easier to use correctly.
• Floss still has a role in very tight contacts, but it should no longer be the automatic, universal recommendation.

So next time you’re stocking your bathroom cabinet or advising a patient, remember: it might be time to retire the floss cliché and embrace the brush.

References (for readers who want to dig deeper)

• Imai, P.H. et al. (2012). Interdental brush versus dental floss for interdental plaque removal: a systematic review and meta-analysis. Int J Dent Hyg.
• Slot, D.E. et al. (2008). The efficacy of interdental brushes on plaque and periodontal parameters. J Clin Periodontol.
• Cochrane Oral Health Group (2019). Interdental brushing for the prevention and control of periodontal diseases and dental caries in adults.
• Sharma, A. et al. (2018). Interdental cleaning and gingival inflammation: A systematic review and network meta-analysis. J Periodontol.
• Evidence-Based Dentistry (2009). The use of interdental brushes along with toothbrushing removes most plaque. Evid-Based Dent 10(3):74.