Study of parameters affecting abrasion test for silica and toothpaste

Objectives: The objective is to investigate the impact of different parameters such as abrasive nature, toothbrush type, and load on toothbrush on brushing mechanisms during in-vitro abrasion test. The aim is to identify tribological phenomena involved during in-vitro abrasion test and to propose solutions to improve its reliability. 

Methods: PMMA abrasion tests have been conducted in an experimental brushing machine with slurries of different abrasives (Tixosil SoftClean^TM low abrasive silica, Tixosil^® 73 standard abrasive silica and ISO11609 Ca Pyrophosphate). For each toothbrush type (Oral B P40 and Duopole), several loads (from 1,4 to 4,8N) at constant speed have been used.

Results: In-situ measurements of normal force (Fn) and friction coefficient (µ), post-mortem SEM observations of toothbrushes before and after tests evidenced the impact of abrasive morphology (Fig. 1), toothbrush characteristic (Fig.2) and load on complex abrasion mechanisms.

Conclusions: In-vitro abrasion tests represent practical lab-scale techniques to assess application properties and safety of toothpastes and oral care abrasives. However, multiple factors have been showed to impact results, leading to the necessity of both define more precise criteria for abrasion tests and deepen the understanding of tribological phenomena occurring during abrasion.