Effect of Office Bleaching on Composite Roughness, Microhardness, and Wear

In-office tooth bleaching is a popular treatment to improve esthetics. Although numerous studies have investigated the effect of at home bleaching on restorative materials, little information is available on the effect of in-office bleaching on restorative materials. Objective: It was the aim of this investigation to evaluate the effect of 38% hydrogen peroxide (Opalescence Xtra Boost) on the surface roughness, microhardness, and wear of a nanocomposite (Filtek Supreme) and a microhybrid composite (Point 4). Methods: Twenty composite cylinders (14mm diameter x 2mm thick) of each composite were cured, according to manufacture’s recommendations, in a PVS mold placed between two glass slides, to achieve a uniform surface. Then the air inhibited layer was polished off with diamond paste and the samples were stored in 100% humidity at 37°C to simulate the oral environment. Ten cylinders of each composite was randomly selected and subjected to three 30 minute bleaching treatments. The remaining cylinders served as the control and remained in the 100% humidity at 37°C. Wear was evaluated on a pin-on-disk wear apparatus. The samples were subjected to 3,000 cycles with a load of 908g. Surface roughness and wear measurements were carried out using profilometry. Knoop micohardness measurements were taken. Data were analyzed with ANOVA and Tukey HSD a=0.05. Results: There were no significant differences found between bleached and unbleached composite for either material. Significant differences were found between the two materials. The surface roughness was approximately 38% higher with the nanocomposite than the microhybrid composite. The microhardness was approximately 28% higher with the nanocomposite than the microhybrid composite. The amount of wear of the microhybrid composite was approximately 55% higher compared to the nanocomposite. Conclusion: Concentrated in-office bleaching agents are not detrimental to roughness, microhardness, and wear of composite material tested in this study. Supported in part by NIH Grant DE07101.