Effect of Home-Bleaching on Color and Surface Integrity of Bulkfill-Composites

To evaluate the effect of two concentrations of home bleaching agents on color stability and surface integrity of two nano-hybrid bulkfill composites. 

Method:

60 composite discs were produced (n=10, diameter=7mm, thickness=4mm) from two materials, Tetric EvoCeram Bulk Fill (ECB) (Ivoclar-Vivadent, Liechtenstein) and SonicFill (SF) (Kerr, USA), and light cured (40s, Ortholux-LED, 1600mW/cm²). Two bleaching agents of different concentrations, 44% carbamide-peroxide (CP44) (Instant White Smile, USA) and 16% carbamide-peroxide (CP16) (Philips Zoom! NiteWhite, USA), were applied 2h/d for 14d and stored in WA at 37°C; control group was stored in WA.

Specimens were incubated (37°/24h) and tested for color stability; ΔE calculated by spectrophotometer readings (Color-Eye 7000A, Gretag-Macbeth-LLC, USA). Surface integrity was measured by Vicker's microhardness (Micromet 6040, Buehler, USA, 200g, dwell-time=15s) and by SEM (x600) for surface micromorphology at baseline and at 14d.

Result:

Color changes of ECB exposed to CP44 differed significantly (p=0.001) from exposure to CP16 and WA, while application of CP44 and CP16 to SF did not differ, however, it did when compared to control group stored in WA (p=0.004). Values of ΔE≥3.3 were considered clinically unacceptable. Microhardness measurements differed significantly (p=0.01) for ECB between CP44 and WA, whereas for SF they differed (p=0.014) for CP16 and WA. Statistical analysis was performed with two-way ANOVA and post-hoc Scheffe’s. SEM images showed surface micromorphological changes in test materials, greatest in CP44, followed by CP16 and WA.

Conclusion:

CP44 had strongest effect of color and micromorphological changes on ECB. SF had greater microhardness values both before and after bleaching, while both materials showed 35% decrease in hardness values in total.