Composites roughness and microhardness after different bleaching techniques

Abstract

Aims: The purpose of this study is to evaluate the surface roughness and microhardness of a recent nanohybrid composite, SonicFill™ (Kerr Corporation, Orange, USA), and compare it with another nanofilled, Filtek™ Supreme (3M ESPE, St. Paul, MN, USA) after the submission of both to the action of two bleaching agents: 10% carbamide peroxide and 35% hydrogen peroxide. Methods and materials: Sixty cylindrical specimens (10mmx2mm) of each composite were prepared and stored in artificial saliva at 37⁰C for 24 hours. The specimens were then polished and stored in artificial saliva at 37⁰C. After 24 hours, specimens were divided into 6 groups (n=20). Groups 1, 2: stored in artificial saliva. Groups 3, 4: 10% carbamide peroxide. Groups 5, 6: 35% hydrogen peroxide with LED lamp activation. 24 hours after treatments, specimens went through 500 cycles of thermocycling between 5ºC and 55ºC with a dwell time of 30 seconds. A mechanical roughness tester was employed to measure the surface roughness parameters and the Vickers test to measure microhardness on the top surface of each specimen. One-Way-ANOVA, Tukey and Bonferroni methods with a significance level of 5% were used for the statistical analysis. Results: For SonicFill™, there was no statistically significant difference in microhardness between the control group (1) and the bleached groups (3, 5). However there was difference between home bleaching (group 3) and in-office treatment (group 5). For Filtek Supreme XTE™ there was no significant difference in microhardness among all groups. In case of roughness, there was no significant difference in roughness average (Ra) and root mean square roughness (Rq) among all groups. The mean roughness depth (Rz) parameter showed no statistically significant differences among all groups for SonicFill™ but, in Filtek Supreme XTE™ there was a significant increase between control (group 2) and bleaching treatments (groups 4, 6). Roughness skewness (Rsk) showed no statistically significant differences among all groups for SonicFill™ and Filtek Supreme XTE™, except for groups 2 and 4, where the Rsk increased with CP. Conclusion: The microhardness of Filtek Supreme XTE™ and SonicFill™ is not affected by bleaching treatments. Both bleaching treatments affect Rz of Filtek Supreme XTE™ groups, in contrast to the SonicFill™ groups. The carbamide peroxide 10% treatment affects the Rsk of group Filtek Supreme XTE™ with no significant effect in the SonicFill™ group.