Effect of Repeated Firings on Color Stability of Zirconia- Reinforced Lithium Silicate and Lithium Disilicate Ceramics.

Purpose: The purpose of this invitro study was to assess the changes in the color attributes of high-translucency (HT) lithium disilicate and zirconia-reinforced lithium silicate in BL3/0M1, A1, A2, and A3 shades during first, second, and third firing cycles.

Materials And Methods: Eighty specimens of two ceramic systems (IPS e.max CAD and Vita Suprinity) in BL3/0M1, A1, A2, and A3 shades, were prepared in thickness of 1 mm (n=10). Each group was subjected to 3 firing cycles and the CIE L*a*b* color parameters of specimens were measured after each firing cycle by a reflectance spectrophotometer. The color change (ΔE) between each two firing cycles was calculated by the relevant equation. Data were analyzed by one-way ANOVA and Tamhane post hoc test.

Results: All ΔE values were significant (P⟨0.001) except for ΔE2-1 (color difference between second and first firing) and ΔE3-2 (color difference between third and second firing) in A2 shade of IPS e.max (P=0.436) and ΔE2-1 and ΔE3-2 in 0M1 shade of Suprinity (P=0.345).

Conclusion: Repeated firing resulted in generally higher ΔE in ZLS than LDS, and 0M1 Suprinity experienced maximum ΔE after repeating firing.