The Use of Composite Layering Technique to Mask a Discolored Background: Color Analysis of Masking Ability After Aging-Part II.

The aim of this study was to evaluate the effectiveness of the layering technique to mask a discolored background (C4) after one year of water aging. The technique was used with three resin composite restorative systems (IPS Empress Direct, Charisma Diamond, and Filtek Z350XT). Ninety 1.5-mm-thick specimens were divided into groups and subgroups according to the restorative system and resin composite shade combination used in the layering technique (enamel, body, and dentin). The color measurements were made by reflection spectrophotometer (SP60, EX-Rite) over the C4 substrate at two time points: after 24-hour water immersion (T) and after one-year water aging (T). The masking ability was evaluated by calculating the ΔE between an inherent color background and a C4 background at T and T. CIELAB and CIEDE2000 formulas were used for comparative analysis between T and T color measurements. Analysis of variance and Turkey's test (=0.05) were performed to analyze ΔE and ΔE mean values. The Z350XT restorative system presented adequate masking ability in the combinations of 0.5 mm body + 1.0 mm dentin, 0.5 mm enamel + 1.0 mm dentin, and 1.5 mm dentin after 24-hour water immersion. The masking ability was affected negatively by water aging in most of the combinations. The IPS Empress Direct was the only system that remained stable after aging in the combinations of 0.5 mm enamel + 1.0 mm dentin and + 1.5 mm dentin (=0.05 and =0.47 for CIELAB; =0.15 and =0.51 for CIEDE2000), although it did not present adequate masking ability in both time points. None of the combinations of any system presented adequate masking ability after prolonged water aging.