Effect of different dilution levels of toothpastes on the abrasive wear on enamel and dentin in in-vitro studies

In-vitro studies commonly simulate toothbrushing using toothpaste slurries of defined dilution levels. However, a recent in-vivo study indicated dilution levels in patients likely to be higher than those typically used. Therefore, this in-vitro study investigated the effects of toothpastes with different relative abrasivity and different dilution on the abrasive wear of enamel and dentin. 144 bovine enamel and dentin samples were randomly assigned to 12 groups each (n = 12). Samples were brushed according to a standardized protocol with three toothpastes of different relative abrasivity on enamel and dentin at four dilution levels (1:1, 1:2, 1:3, 1:6), using 2.5 N brushing force. Enamel samples were brushed for six hours, dentin samples for 25 min. Abrasive wear was measured profilometrically. Statistical analysis was performed with non-parametric Kruskal–Wallis tests. On enamel, dilution significantly affected abrasive wear within all toothpaste groups (p < 0.001), with wear decreasing as dilution increased. On dentin, the dilution again showed a significant effect within all groups (p < 0.001), though maximum abrasive wear occurred at different dilutions for each toothpaste. Dilution, as proved, significantly influences abrasive wear on enamel and dentin. Further studies are required to define an ideal dilution for in-vitro studies, especially for studies performed on dentin.