Fig. 1

Schematic for mechanical testing of toothbrush samples. The toothbrush handles were fixed in position using a 3D-printed form-fitted holder and epoxy resin to prevent uncontrolled bending of the toothbrush. The form-fitting holder was necessary because a conventional fixation for the toothbrushes creates additional pivot points. This would result in bending of the handle while testing, which does not reflect how toothbrushes behave in practical use, and affects the resulting forces. Using individual sample holders increases the contact surface on the handle and reduces the amount of pivot points. This provides a good representation of actual toothbrushing and minimises the influence of the handle on the measurements