Statistical analysis
dentine surface loss
Data were evaluated with Shapiro-Wilk normality test and due to lack of normal distribution of some groups, non-parametric tests were used. Kruskal-Wallis for comparison between groups, considering each subgroup (with and without pellicle) separately, was performed for each response variable: dentine surface loss after 10 cycles (dSL-10), total dentine surface loss (dSL-total), amount of degraded collagen (dColl) and calcium released to the citric acid (CaR). Post hoc Dunn’s test with p corrected for multiple comparisons was performed. Each group was analyzed with Mann-Whitney U test considering the subgroups (P and NP). Moreover, the effect of fluoride was analyzed with Mann-Whitney U test for each plant extract, and for the controls (deionized water and fluoride). Significance level was set at 5% and the analyses were performed with GraphPad Prism 7 for Mac.