The effect of different bleaching methods on the color and translucency of a single color universal composite

Abstract

Introduction: Bleaching is a conservative, safe and economical method to treat discolored teeth. Composites are an integral part of today's restorative treatments, and various types of composite restorations may be present in a person's mouth. During bleaching, the existing composite restorations come into contact with hydrogen peroxide agents. As a result of the bleaching process, the previous excellent color match may be lost and cause a cosmetic failure. Therefore, there will be a need to replace the restoration. In this study, the effect of three types of bleaching on the color and translucency of monochromatic universal composite was investigated.

Materials and methods: In this laboratory study, 45 Omnichroma composite discs with a diameter of 10 mm and a thickness of 2 mm were divided into three groups of 15 based on the bleaching method (home bleaching, office bleaching, and Nd:YAG laser). The color and translucency of the samples were evaluated using a spectrophotometer with the CIELAB system. Paired t-test (in case of normal) and Wilcoxon signed rank test (abnormal) were used to compare color change and translucency before and after bleaching. Also, one-way analysis of variance (in case of normal) and Kruskal-Wallis test (in case of abnormality) were used to compare the average color change and translucency among the groups. If the F test was significant, the appropriate post hoc test was used to compare two groups. The significance level in all tests was considered less than 5%. Results: According to the results of the present study, all three bleaching methods of hydrogen peroxide, carbamide peroxide and Nd:YAG laser created a significant difference in the amount of color change (∆E) of Omnichroma universal composite. The results showed that carbamide peroxide had the most significant color change (∆E=7.69) and there is no significant difference in the amount of color change caused by hydrogen peroxide (∆E=5.63) and laser (∆E=5.16). In all three bleaching groups, the increase in L* showed a increase of value. a* showed a green shift (negative values) in laser and hydrogen peroxide, and a red shift (positive value) in carbamide peroxide. b* decreased in all three groups and showed a decrease in yellowness. Regarding translucency change, all three bleaching methods had significant differences. Carbamide peroxide had the most significant changes (0.6727) and the translucency changes of hydrogen peroxide (0.2727) and laser (0.2413) did not have significant differences. Conclusion: Different bleaching methods can cause a noticeable change in the color and translucency parameters of the single-color universal resin composite. The effectiveness of the home bleaching method is greater than the in-office methods due to the longer contact time of the bleaching agent. Keywords: Color change , Translucency, Universal composite, Bleaching