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 degrees 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 (DeltaEab) light-cured and dual-cured resin cements were analyzed by two-way ANOVA with repeated measures and Tukey's test (alpha = 0.05). For the light-cured cements, the DeltaEab 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 DeltaE 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 DeltaEab 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 DeltaEab 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 DeltaEab 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 DeltaEab 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 DeltaEab values above the acceptability threshold.