Menu
We often assume that if a patient is using interdental brushes (IDBs), the battle is won. However, a 2025 study suggests that simply “using” the tool isn’t enough. If we aren’t prescribing the specific ISO size, we are setting even our most motivated patients up for failure.
The study analyzed 36 patients who were already regular IDB users. The researchers didn’t just ask about habits; they measured 643 specific interdental sites using Interdental Access Probing (IAP) to determine the Passage Hole Diameter (PHD).
The results revealed a massive disconnect between patient effort and clinical accuracy.
Despite being experienced users, only 9.8% of the interdental sites were being cleaned with a brush that met strict ISO PHD criteria for efficacy.
Clinicians often fear that prescribing larger, tighter brushes will cause pain and lower compliance. This study found the opposite.
Post-intervention, subjective satisfaction scores increased significantly.
The study noted confusion caused by inconsistent manufacturer sizing. A “blue” brush from one brand may not match the wire diameter of a “blue” from another.
The study sized patients at a single point in time. However, we know that as inflammation resolves, edema reduces, and embrasures “open.”
While the data confirms that 2–3 sizes are ideal, the logistics of asking a patient to buy three different packs can be a barrier.
This study confirms that an interdental brush is not a generic commodity; it is a precision medical device. When patients use a brush that is too small, they don’t feel the benefit. By taking the extra minute to measure the space—using a color-coded probe or the brushes themselves as gauges—you don’t just improve their plaque control. You actually improve their confidence in the tool.
Sim HJ, Kim HJ, Kim KM, Yoon S. Assessment of Interdental Space and Satisfaction Change in Interdental Toothbrush Size Application and Usage According to Interdental Gap Measurement. Oral Health Prev Dent. 2025;23:339–345. PMID: 40552651.
