Figure 3. Data of enamel microhardness change. Values adjusted to quadratic fits (with pellicle—p < 0.05, r² = 0.66; w/out pellicle—p < 0.05, r² = 0.61) toward the erosive challenges. Average (SD) values of groups: (with pellicle) 0, –20.92 (7.15); 10, –34.68 (15.14); 20, –50.48 (16.44); 30, –70.94 (14.27); (w/out pellicle) 0, –19.90 (8.13); 10, –49.12 (15.66); 20, –60.51 (20.18); 30, –73.56 (19.06) (n = 12). Different letters at each erosive challenge mean statistical difference (p < 0.05).