Hypericum perforatum L.: A Potent Antioxidant Source for the Treatment of Oxidized Dentin: An Experimental In Vitro Study

Aim: To evaluate the therapeutic antioxidant effect of Hypericum perforatum L. (HPL) extract on oxidized dentin as well as to address the following research question: Is experimental HPL-derived antioxidant treatment protocol as effective as sodium ascorbate in terms of reversing the compromised resin bonding to bleached dentin? Materials and Methods: Eighty bovine permanent mandibular incisors were included in the shear bond strength (SBS) test and randomly assigned into four groups (n = 20) as follows: negative control (NC), positive control (PC), sodium ascorbate (SA), and Hypericum perforatum L. (HPL). Group NC did not receive bleaching treatment. All specimens except the NC group were oxidized by bleaching with 35% hydrogen peroxide. Experimental antioxidant solutions were prepared from SA powder and HPL extract at 10% concentrations. The bleached specimens in the SA and HPL groups were treated with respective antioxidant solutions. The SBS test was performed at a crosshead speed of 1 mm/min. The SBS data were analyzed with one-way analysis of variance using the post-hoc Bonferroni correction. The total phenolic content and the antioxidant activity of HPL extract were assessed by using the Folin–Ciocalteu assay and the 2,2-diphenyl-1-picrylhydrazyl free-radical scavenging activity test, respectively. Results: Considering the SBS test results, statistically significant the highest and the lowest mean values were observed in NC and PC, respectively (P <.05). SA and HPL were not significantly different (P > .05). The total phenolic content (104 ± 1.740 mg gallic acid equivalents (GAE)/gram (GAE/g) dry HPL extract) and the antioxidant activity of the HPL extract were demonstrated. Conclusions: The natural HPL plant extract was as effective as SA in reversing the compromised resin bonding to bleached dentin. Antioxidant treatment derived from the HPL extract may enable immediate resin restoration of oxidized dentin.