Effect of aging and bleaching on the color stability and surface roughness of a recently introduced single-shade composite resin.

Objectives: To assess the effects of aging and bleaching procedures on the color stability and surface roughness of a new single-shade composite versus multi-shade composite resins.

Methods: A single-shade composite resin (Charisma Diamond One, CDO) and 3 multi-shade composite resins (Tetric NCeram, Filtek Z350 XT, Clearfil Majesty Posterior) were tested. Thirty specimens of each material were subjected to one of the aging procedures respectively: immersion in distilled water (12 days/37 °C), immersion in coffee (12 days/37 °C), or water thermocycling (10,000 cycles/5-55 °C). All specimens underwent in-office bleaching after aging. Kruskal-Wallis tests and analysis of variance were used for statistical analysis (α=0.05).

Results: All materials exhibited a change of color (ΔE), translucency (RTP), whiteness (WI) and surface roughness parameters (Sa,Sv) after aging and bleaching procedures. CDO showed the highest ΔE among all resins with the highest RTP value, regardless of the aging procedures. Immersion in coffee led to the significantly highest ∆E values and lowest RTP values for nearly all resins. Positive ΔWI1 (WI(bleaching)-WI(baseline)) values were found in distilled water immersion and thermocycling groups, while negative ΔWI1 values were found in the coffee immersion group for all materials. Besides, positive ΔWI2 (WI(bleaching)-WI(aging)) values were found in all aging groups for nearly all materials. All materials showed an increasing trend in Sa and Sv after bleaching.

Conclusions: CDO showed more pronounced discoloration than multi-shade composite resins. Although the whiteness of all resins increased after bleaching, none was completely restored in the coffee immersion group. Bleaching significantly increased the surface roughness of all materials.

Clinical Significance: Charisma Diamond One is more susceptible to discoloration, which may affect its long-term success rate. Bleaching could partially reduce the color change of the composite resins but did not return them completely to their original state. The roughness of the resins increased after bleaching, prompting dentists to repolish them after bleaching.