Laboratory evaluation of fibre quality and passage hole diameter of interdental toothbrushes

Abstract The market offers a wide range of interdental toothbrushes varying in design, price, and environmental characteristics; however, the relationship between these factors and product quality remains unclear. As correct sizing is essential for safe and efficient use, this study evaluated the quality of bristles (fibres) in commercially available ISO 3 interdental toothbrushes and compared manufacturer-declared ISO sizes with values obtained through laboratory measurements. Eight sets of ISO 3 labelled interdental toothbrushes from different manufacturers were examined. Bristle tip quality, bristle arrangement, wire twisting, and the diameters of wires and bristles were assessed using stereomicroscopy and scanning electron microscopy. Bristle tip morphology was evaluated according to the Silverstone and Featherstone classification modified by Reiter and Wetzel. Compliance with declared ISO sizes was verified by measuring the passage hole diameter. The results revealed considerable variability in bristle quality among the tested products. More than 86% of bristles in every group were classified as non-acceptable according to the applied morphological classification. In addition, significant discrepancies were found between the declared and measured ISO sizes. These results highlight the necessity for stricter regulatory oversight and improved quality control to ensure the reliability and safety of interdental toothbrushes.