Optical stability of 3D-printed and milled zirconia after artificial aging and immersion in liquids: An in vitro study.

Purpose: To assess the impact of artificial aging and immersion in common liquids on the optical properties of 3D-printed and milled zirconia.

Materials and methods: Monolithic zirconia discs (N = 100) were fabricated using two methods: 3Y-TZP for milling (e.max ZirCAD LT BL, Ivoclar Vivadent) and printable 3Y-TZP material (LithaCon 3Y 230) for 3D printing. The flat surfaces of the discs were mechanically polished. Color measurements were taken at baseline, after 10,000 thermal cycles and storage in various liquids for 20 days (T₁), and after 20,000 thermal cycles and storage for 40 days (T₂) using a spectrophotometer. Samples were stored in distilled water, tea, coffee, red wine, or Coca-Cola (n = 10 per group). Color differences (ΔE) were calculated between baseline and T₁ as well as baseline and T₂ using the CIEDE2000 formula, while contrast ratio (CR) and translucency parameter (TP) were calculated for each time point. Kruskal-Wallis nonparametric tests with Bonferroni corrections were used for comparisons between zirconia types, liquids, and time points. Shapiro-Wilk tests were applied for time-point comparisons (α ≤ 0.05).

Results: At T₁ and T₂, significant differences in TP and CR were observed after storage in tea, coffee, and red wine for both zirconia types. ΔE values following immersion in distilled water remained below clinically perceptible levels, while tea, wine, and coffee resulted in unacceptable ΔE at T₁ and T₂.

Conclusions: 3D-printed and milled zirconia demonstrated comparable color stability after artificial aging and immersion in common liquids, with no significant differences between the materials in terms of color change (ΔE).