Influence of 10% propolis extract on morphology, microhardness, chemical composition, and color of bleached enamel

The aim of this in vitro study was to evaluate the effect of 10% propolis extract on surface roughness, Knoop microhardness (KHN), ultrastructure, chemical composition, and color change of dental enamel bleached with 35% hydrogen peroxide (HP35). Eighty-eight bovine incisors were randomly assigned to four groups: NC - negative control; PE - 10% propolis extract; SF - 2% sodium fluoride; PE + SF - 10% propolis extract + 2% NaF. Bleaching was performed in three sessions at 7-day intervals, followed by the experimental treatments. Surface roughness was assessed by optical profilometry, microhardness by Knoop testing, ultrastructure by scanning electron microscopy (SEM), chemical composition by energy-dispersive X-ray spectroscopy (EDS), and color change by CIE Lab* spectrophotometry. Statistical analyses included intragroup comparisons (baseline vs. post-treatment), which were performed using the paired t-test for dependent samples, and intergroup comparisons, which were conducted using one-way ANOVA for independent samples (p ≤ 0.05)". Surface roughness showed no significant intra- or intergroup differences. KHN decreased only in the PE group, with no differences among the other groups. SEM revealed smooth and homogeneous surfaces in all groups, while EDS showed variations of less than 2% in Ca, O, and P in all groups. All groups exhibited color change, with no statistically significant differences between them. The 10% propolis extract, alone or in combination with NaF, did not affect surface roughness, enamel ultrastructure, or chemical composition of HP35-bleached dental enamel and did not compromise bleaching efficacy. However, the group treated with 10% propolis extract alone showed a reduction in KHN, whereas the group receiving the combination of propolis extract and NaF maintained KHN values.