Color Stability of Extrinsically Colored Monolithic Zirconia: A Narrative Review

Monolithic zirconia has become a widely used restorative material in prosthodontics due to its high mechanical strength, biocompatibility, and improved esthetic properties. To further enhance esthetic outcomes, extrinsic staining is commonly applied to monolithic zirconia restorations, allowing individualized shade characterization and surface effects. However, because these coloring agents are in a superficial layer, concerns remain regarding their long-term durability and color stability under different oral conditions. This narrative review aimed to evaluate the long-term color stability and optical durability of monolithic zirconia crowns treated with extrinsic stains, under simulated aging conditions. An electronic search was conducted across PubMed, ScienceDirect, and Wiley Online Library databases between 2016 and February 2026, investigating the effects of mechanical, chemical, thermal, and hydrothermal aging on extrinsically stained monolithic zirconia. A total of 1354 articles were initially identified. After removing duplicates and screening titles and abstracts, nine articles met all inclusion criteria and were included in the final analysis. These studies primarily evaluated color variation (ΔE, ΔE₀₀), translucency-related parameters (relative translucency parameter, or RTP), and surface roughness (Ra) following simulated oral challenges. The included studies suggest that extrinsically stained monolithic zirconia demonstrated generally acceptable color stability, with most ΔE and ΔE₀₀ values remaining within clinical thresholds. Mechanical surface alterations, particularly occlusal adjustments exceeding 100 μm, were identified as the most significant factor influencing discoloration. Chemical exposure to staining agents such as coffee produced moderate color changes, and while thermocycling alone had a limited impact, it affected translucency more than color stability. Extrinsically stained zirconia crowns retain satisfactory color stability and esthetic durability over time, provided that the glaze layer remains intact, and surface adjustments are limited. Their longevity depends more on clinical handling than on oral conditions.