Color stability of ceramic veneers as a function of resin cement curing mode and shade: 3-year follow-up

The influence of curing mode and shade of resin cements on the color stability of minimum-thickness ceramic veneers after a three-year storage time in distilled water was evaluated in this study. Ninety-six 0.5-mm-thick feldspathic ceramic veneers (Mark II) were luted onto resin composite substrates (Filtek Z350 XT, shade A2E) with two light-cured (NX3 Light-cure and AllCem Veneer) and dual-cured resin cements (NX3 dual-cure and AllCem) in various shades. The specimens were stored in distilled water at 37°C. Color measurements were performed with a spectrophotometer at the following times: 1h and 24h; 7, 30, and 180 days; and 1, 2, and 3 years. Data for color difference (ΔE(ab)) light-cured and dual-cured resin cements were analyzed by two-way ANOVA with repeated measures and Tukey’s test (α = 0.05). For the light-cured cements, the ΔE(ab) values were as follows: NX3-Yellow (2.37±1.35) = ACV-A1 (2.40±1.21) = ACV-Trans (2.52±1.46) = ACV-E-Bleach M (2.56±1.42) = NX3-White (2.69±1.49) = NX3-Clear (2.98±1.68). The lowest ΔE values were found for 1 h (0.61±0.36)(a), followed by 24 h (1.15±0.55)(b) and 30 days (2.48±1.11)(c). One year, 180 days, and 2 and 3 years presented higher ΔE(ab) values (3.34±0.94, 3.52±1.04, 3.52±0.95 and 3.55±1.14, respectively)(d). For the dual-cured cements, the ΔE(ab) values varied as follows: NX3-Clear (2.32±1.24)(a) = NX3-Yellow (2.37±1.32)(a) = NX3-White (2.76±1.43)(a) < AC-Trans (3.77±1.91)(b) = AC-A3 (4.13±2.11)(b) < AC-A1 (5.38±2.92)(c). Considering time, the lowest ΔE(ab) values were found for 1 h (0.48±0.25)(a), followed by 24 h (2.13 ±0.83)(b), 30 days (3.54±1.31)(c), and 180 days (3,70±1.73)(c). The follow-up times of 1 (4.43±2.15)(d), 2 (5.02±1.74)(e), and 3 years (4.90±2.12)(e) presented higher ΔE(ab) values. This study demonstrated that light-cured resin cements were less susceptible to color change than dual-cured cements. After 2 years of follow-up, all cements presented ΔE(ab) values above the acceptability threshold.