Fig. 4

SEM images of the experimental groups (n = 3) with magnifications of 2,000× and 15,000×. Bleaching treatment with (a) DW group, (b) HP group, (c) Sr-FAp 1 wt% group, (d) Sr-FAp 5 wt% group, (e) Sr-FAp 10 wt% group, and (f) the EDS mapping image of the particles on the enamel after bleaching treatment for the Sr-FAp 10 wt% group.