Effect of Ion Release on Color Stability of Zirconia: A Comparative Study

Abstract

Zirconia ceramics are widely used in dentistry, but maintaining long-term color stability remains challenging. This study investigated the combined effects of specimen thickness, immersion duration, and aging of coloring solutions on the color stability of two multilayer commercial zirconia materials: TT ONE Multilayer (TT) and DD cubeX2 ML (DD). Discs (1.0–2.5 mm thick) were immersed in A2-shade coloring liquids for 30 s, 1 min, 3 min, and 5 min and evaluated after three months of solution aging. Color parameters (L*, a*, b*, C*, ΔE) were assessed, along with pH variation and Fe/Er ion concentrations using ICP-MS. Thinner specimens showed higher ΔE values and greater chromatic shifts than thicker ones. Aging of the coloring solutions increased L* values and discoloration, particularly in TT. ICP-MS revealed rising Fe and declining Er levels, correlating with observed optical changes. DD showed greater chemical and optical stability under identical conditions. These findings highlight the need to control zirconia thickness and coloring solution aging to preserve long-term esthetics.

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