The Effect of Different Bleaching Methods on the Mechanical and Surface Properties of Single-Shade Universal Composite Resin

Abstract

Introduction: Composite resins, compared to metallic and ceramic restorative materials, are more prone to chemical changes due to the presence of an organic matrix in their chemical structure.

Objective: This study aimed to investigate the impact of various bleaching methods on the mechanical and surface properties of a single-shade universal composite.

Materials and Methods: Sixty disc-shaped composite resin samples measuring 2 mm in thickness and 8 mm in diameter, 60 cylindrical samples measuring 3 mm in height and 6 mm in diameter, and 60 cylindrical samples measuring 25 mm in length, 2 mm in width, and 2 mm in height were prepared for evaluating microhardness, surface roughness, and flexural strength. These samples were divided into a control group and four bleaching groups: home bleaching, office bleaching, office bleaching with light, and office bleaching with laser. After conducting the relevant tests, the data were analyzed using Kruskal-Wallis tests, one-way ANOVA, and Dunn's analysis (p < 0.05).

Results: Microhardness increased in the office bleaching with light (p = 0.0007) and home bleaching (p = 0.03) groups after treatment, while it decreased for the office bleaching group (p < 0.0001). Surface roughness significantly decreased in the home bleaching and office groups (p < 0.0001). No statistically significant difference was observed in the flexural strength of the studied groups compared to the control group.

Conclusion: Various bleaching methods have different effects on the mechanical properties of universal composite resin. The office bleaching with light and office bleaching groups had the highest and lowest microhardness and surface roughness compared to the control group, respectively.