Masking performance of structural-color composites as luting agents for high-translucency zirconia-reinforced lithium silicate veneers.

PURPOSE: To evaluate the aging-related masking performance of structural-color composites used as luting agents for ultrathin, high-translucency (HT) zirconia-reinforced lithium silicate (ZLS) veneers, comparing a dedicated blocker against its universal counterpart, conventional light-cure veneer cements, and preheated composites. MATERIALS AND METHODS: ZLS discs (VITA Suprinity 0M1-HT; 10 × 0.50 mm2; n = 35; n = 5 per group) were luted to standardized zirconia substrates. Luting media included RelyX Veneer (Translucent, A3, WO), Omnichroma Universal, Omnichroma Blocker, Filtek Z250 XT B1, and Vittra APS E-Bleach. Specimens were aged by thermocycling (10,000 cycles, 5-55°C) followed by coffee immersion (7 days, 37°C). Color was measured over white and black backgrounds at baseline and post-aging using a spectrophotometer. Outcomes included CIEDE2000 color difference (ΔE00), whiteness index change (ΔWID), and translucency parameter change (ΔTP00). Data were analyzed using one-way ANOVA with Holm-adjusted pairwise comparisons (α = 0.05). Results were interpreted against established perceptibility and acceptability thresholds (PT00 = 0.8, AT00 = 1.8; whiteness perceptibility threshold = 0.72, whiteness acceptability threshold = 2.62; TPT00 = 0.62, TAT00 = 2.62). RESULTS: Luting medium significantly affected all optical outcomes (p < 0.001). For the primary endpoint (ΔE00 over black background), Omnichroma Universal showed the smallest change (0.27 ± 0.10), whereas Vittra APS E-Bleach showed the largest (4.38 ± 0.34), exceeding the acceptability threshold in all specimens. Omnichroma Blocker (0.57 ± 0.15) did not differ significantly from Omnichroma Universal after Holm adjustment for the primary endpoint. Filtek Z250 XT B1 (1.30 ± 0.22) exceeded the perceptibility threshold in all specimens. For whiteness change, Vittra APS E-Bleach exceeded the acceptability threshold in all specimens (ΔWID = 6.51 ± 1.29), whereas Omnichroma groups showed negative ΔWID values (-0.80 ± 0.36 and -0.73 ± 0.52). Translucency changes remained below clinically detectable thresholds across all groups. CONCLUSIONS: For ultrathin, HT ZLS veneers, aging-related optical stability was highly luting material-specific. Omnichroma Blocker did not provide superior aging-related masking stability compared with Omnichroma Universal for the primary dark-background endpoint. Vittra APS E-Bleach showed color and whiteness changes that exceeded acceptability thresholds under the tested aging conditions, whereas translucency changes remained limited across all luting media.