The purpose of this study was to evaluate the ability of three resin composite systems to mask a severely discolored background by the application of a layering technique through CIELAB and CIEDE2000 analysis. Ninety 1.5-mm-thick disc specimens were produced from three different resin composite restoration systems: IPS Empress Direct (Ivoclar Vivadent), Charisma Diamond (Heraeus Kulzer), and Filtek Z350 XT (3M-ESPE). The specimens were divided into groups according to the restoration system and the resin composite shade combination used for the layering technique (enamel, body, and dentin shades). Color measurements were performed by a reflectance spectrophotometer (SP60, EX-Rite) against a C4 shade background and an inherent color background, which simulates a severely discolored background and a tooth surface with no discoloration, respectively. The total color difference between both color measurements was calculated by CIELAB (ΔE*) and CIEDE2000 (ΔE) formulas. The mean ΔE* and ΔE values were analyzed by analysis of variance (general linear models) and Tukey's post hoc tests (α=0.05). Three groups presented clinically acceptable color difference values (ΔE*≦3.46 and ΔE≦2.25): 1.5 mm dentin, 1.0 mm dentin/0.5 mm body, and 1.0 mm dentin/0.5 mm enamel; ie, all the groups from the Z350 XT restoration system. The resin composite layering technique is an effective way to mask severely discolored backgrounds. The Filtek Z350 XT system was the only restoration system capable of masking the C4 background.

Specimens totally immersed in staining solutions could in somehow overestimate the color change, once that in most clinical conditions not all of the restoration surfaces are exposed to the oral environment. Moreover, as the surface sealant application produces color change values that are clinically acceptable, it might be used in esthetic restorations as an adjunct treatment.