Influence of Specimen Pre-staining on In Vitro Whitening Efficacy of Hydrogen Peroxide Gels

The bleaching patterns were similar for both non-stained and stained substrates, with higher concentrations of HP bleaching gels resulting in greater tooth color difference. Previous staining increased the variation in whiteness values (ΔWID) following bleaching, but specimens maintained a lower whiteness index after bleaching compared to the non-stained substrate. Staining induced alterations on the enamel surface. These factors indicate that pre-staining of specimens is not essential to evaluate the whitening efficacy of bleaching gels.