Whitening efficacy and enamel properties of 30% hydrogen peroxide solution incorporated with strontium-containing...

This study evaluated the effects of 30% hydrogen peroxide (HP) solution incorporated with strontium-containing Fluorapatite (Sr-FAp) on whitening efficacy and enamel surface properties, aiming to minimize enamel damage during bleaching. A total of 60 extracted bovine teeth were stained with black tea and divided into five groups (n = 12): DW (distilled water), 30% HP, 1 wt% Sr-FAp + HP, 5 wt% Sr-FAp + HP, and 10 wt% Sr-FAp + HP. DW and HP solutions with or without Sr-FAp were applied three times for 20 min each. The surface color alteration, gloss, roughness, microhardness, and enamel microstructure were analyzed before and after bleaching. All experimental groups showed significantly higher ΔE_ab values than those of the DW group (p < 0.05), with no significant differences between Sr-FAp concentrations (p > 0.05). ΔWI_D and ΔE₀₀ followed similar trends. Gloss decreased in all HP-treated groups compared to the DW group (p < 0.05), with the 10 wt% Sr-FAp group showing the lowest gloss (p < 0.05). There were no significant differences in surface roughness (p > 0.05), whereas the 10 wt% Sr-FAp group showed the highest microhardness value (p < 0.05). Observations of the enamel surface revealed the presence of Sr-FAp nanoparticles in all Sr-FAp groups. HP containing Sr-FAp effectively whitened the teeth while preserving the enamel microhardness and structure via a protective Sr-FAp layer. Sr-FAp shows promise as a remineralizing filler for whitening treatments, maintaining whitening efficacy while minimizing enamel damage.