Tribological study of oral care silica

•The visualization tests highlight that flows of third body act at different scales.•The abrasive granules are fragmented or/and sheared during the toothbrushing.•At a micrometric scale small disjointed load-carrying islets, surrounded by cavities, have been highlighted.

This study focuses on the effect of mechanical parameters for a better understanding of oral care silica tribological behavior. Reciprocating motion tests were performed with variable parameters (toothbrushes design, load, brushing speed, with and without silica slurries). The analysis of the tests is based on the third body concept. The flows of third body were evaluated in-situ and post-mortem related to the evolution of the friction coefficient. Clues to understand the mechanisms involved are given, showing the multi-scales and multi-physical aspects of the problem.