Surface Hardness of Restorative Materials After Staining and Bleaching

Objective:The aim of this study was to investigate the effect of two staining solutions and three bleaching systems on the surface microhardness of two composite resins. Methods: Filtek Supreme and Esthet X were used. Forty-five samples from each material were prepared using a Teflon mold (2.5 x 5mm). The samples were then divided into three groups of 15 samples and immersed into three staining solutions (coffee, wine, and distilled water as control) for 3 hours daily over a 40-day test period. The three groups were then divided into three subgroups and 3 bleaching agents (Crest Night Effects, Colgate Simply White Night, and Opalescence Quick) were applied to the surface of the specimens over a 14-day period. Vickers hardness measurements were obtained before and after staining and after bleaching. Results were compared with repeated measures factorial variance analysis. Significant results were evaluated with Duncan's test. Results: Hardness(Vickers) of materials at baseline were 63.0 for Esthet-X and 56.9 for Filtek-Supreme. After staining the hardness of Esthet-X for coffee, wine and water were 50.7, 47.5, 64.2 respectively. For Filtek-Supreme groups hardness values were 51.3, 51.6 and 60.9. Statistically, a significant decrease was found in the microhardness values for both materials after staining with coffee and wine (p < 0.05). For the control group (water), microhardness values were found to be higher than baseline values. After bleaching, a significant decrease was found for the two materials and three staining solutions (p <0.05). No significant difference was found between bleaching agents. Conclusion:The results of this study showed that beverages like wine or coffee and bleaching agents result in decreases in composite surface microhardness from baseline values.