Effect of a Chemically-Activated Versus Light-Activated Bleaching Agents on Color Stability of Different Resin Composite Filling Materials

Objectives: To evaluate and compare the effect of chemical and light activated teeth bleaching agents on color stability of three different resin composite restorative materials.
 Material and methods:  The materials tested  include one Nanofilled (Filtek Z350 XT - 3M ESPE), one Nanohybrid (Tetric–N–Ceram - Ivoclarvivadent), and one Microhybrid resin composite (Herculite Classic – KERR). From each material, 20 cylindric specimens were prepared according to the manufacturer’s instructions using specially designed Teflon mold (diameter 10 mm and thickness 2 mm), finished and polished. A baseline color measurements were assessed for all the specimens using spectrophotometer (Vita Easyshade). From each material, half of the specimens (n=10) were exposed to chemically activated teeth bleaching agent (Power Whitening YF 40% HP (mixed 32% HP) - WHITE smile GMBH), however the other half exposed to light activated one (Light whitening AC (Mixed 32% HP)- WHITE smile GMBH). A second color assessment were done after bleaching procedures. The data were analyzed using The Kolmogorov-Smirnov test to verify the normality of distribution, Quantitative data were described using range (minimum and maximum), mean, standard deviation and median. Significance of the obtained results was judged at the 5% level. 
Results: There was color change of all groups after bleaching regardless of bleaching material, but that change not detected by naked eye as ΔE <3.3 for all groups. There was significant difference between two bleaching agents used regardless of composite type. Color change between composite types was non significant different regardless of bleaching type. Nanofilled resin composite showed the lowest color change followed by microhybrid and nanohybrid resin composites.
Conclusion: Teeth bleaching doesn’t significantly affect the color of resin composite restorations, that color change not detected by naked eye. Light activated bleaching agents have higher effect than chemical activated bleaching agents.