Evaluation of Tuft Retention of Polymeric Non-Nylon Bristles on Toothbrushes

Objectives: The prevalence of toothbrushes with polymeric non-nylon bristles (PNNBs) has increased significantly in recent years. Little is known about the safety, or retention, of these PNNBs relative to nylon bristle tufts. Current ISO and ANSI/ADA standards for evaluating toothbrushes contain several requirements and test methods including tuft retention. The objective of this study was to determine if PNNBs meet the tuft retention requirement when using the test method in these standards.
Methods: Seven different manual toothbrush types and two different powered toothbrush types (n=2-3/type) with various types of PNNBs were purchased. All toothbrushes were tested according to the standards. Briefly, all PNNBs and nylon tufts surrounding the PNNBs to be tested were removed. Each toothbrush head was placed into a spring-loaded toothbrush vice, a tuft vice was locked in place halfway down the length of a PNNB and attached to a universal testing machine (Instron, Model-5582), and the toothbrush vice was secured in place. The PNNBs were pulled at 20mm/min, and the maximum force was recorded.
Results: The average maximum force required to tear apart, remove, or release the PNNBs per toothbrush type varied with a range of 3.8±0.5N to 12.4±1.2N. The average maximum force across all 90 individual measurements was 5.9±3.0N. All individual measurements except one failed to meet the tuft retention requirement of 15N. All the PNNBs stretched while the testing was conducted. Most PNNBs tore off at various points, with some tearing at the tip, some at the base, and a few in between. Two PNNBs stretched until they slipped out from the vice without tearing.
Conclusions: The ISO and ANSI/ADA requirement and test method for tuft retention, which were developed for nylon bristle tufts, are not suitable for PNNBs. Further exploration is needed to determine the best test method and appropriate requirement for polymeric non-nylon bristles.