Effect of vertical load and speed on toothbrush stiffness measurements

Dental abrasion can be caused by aggressive brushing or using a toothbrush with stiff bristles. Because this damage to the oral cavity is irreversible, prevention is ideal. The international standards for testing toothbrushes for safety and efficacy are International Organization for Standardization (ISO) 22254, ISO 20126, and ISO 20127. American National Standards (ANSI)/American Dental Association (ADA) 119 is an adoption of ISO 22254 and ISO 20126 for manual toothbrushes, and ANSI/ADA 120 is an adoption of ISO 20127 for powered toothbrushes. ISO 22254 contains a test method for the resistance of the tufted portion to deflection, from which toothbrush stiffness is calculated. Key variables of this test method, such as changing the vertical load (VL) applied to the tufted portion of the brush head during testing and changing the velocity of the brushing table of the toothbrush stiffness test machine, were examined.

Twenty-eight different manual (n = 5) and powered (n = 23) toothbrushes were tested with modification according to the resistance to deflection method in ANSI/ADA 119. The means of the stiffness values at each VL or brushing table velocity for each toothbrush were compared using 2-sample t tests.

Most of the toothbrush stiffness values were statistically significantly different at different VLs. However, most toothbrush stiffness values exhibited no statistical differences between the 2 velocities tested.

Most modern toothbrushes cannot withstand the VL required in the ANSI/ADA standard. The VL used for testing significantly affects stiffness measurements, whereas the velocity of the brushing table during testing did not significantly affect the stiffness values obtained.