Evaluation of the effect of different bleaching techniques on surface roughness and color change in new and aged composites

Objectives: The aim of this study was to investigate the effect of 35% hydrogen peroxide (Whiteness HP) and 16 % carbamide peroxide (Whiteness Perfect) on the surface roughness and color change of new and aged microhybrid composites ( Filtek Z 250). Materials and Methods: A Teflon matrix (10 x 2 mm) was used to fabricate 120 specimens which, after polishing with 600 and 1200 grit silicon carbide paper and 24 hours stored in distilled water divided into 2 main groups (n 60). Afterwards, the specimens of one group were placed on 1000 cycles in thermocycling device and the specimens of the other group were placed on 10000 cycles. After the thermocycling, the initial color and surface roughness readings were performed by using the spectrophotometer and profilometer respectively. The specimens of each group were then randomly divided into three subgroups (n 20) according to surface treatments: distilled water (control), 16% Carbamide Peroxide (CP), and 35% hydrogen peroxide (HP). The 16% CP agent was applied 4 h daily for 2 weeks and 35% HP agent was applied 45 minute/week. After 14 days of treatment, the color change (ΔE1) and the surface roughness readings were performed. After bleaching procedure, half of each 20 subgroup were polished with Sof-Lex pop-on system while the other half were kept without polishing. After that, the polished and unpolished specimens were immersed in vials containing 5 ml of coffee solution for one week at room temperature. The second color changes (ΔE2) were then assessed. Results: There was a significant increase in the surface roughness values of the bleached and the control groups for the new tested composite, but no significant changes were detected for the aged composite group. Bleaching of the new and aged composite groups did not show any significant change in the surface roughness when compared the bleached groups with the control groups. As regarding the color variation, the color change (ΔE1) differences between the new and aged composite groups were statistically significant; as the means in the aged composite group was higher. The color change differences between the bleached and control groups for the new and aged tested composite were insignificant. Conclusion: It can conclude that in this study both the bleaching systems used had minimal effects on the surface roughness and the color change of the new and aged tested composites.