Impact of Artificial Aging on the Optical Properties of High-translucent Zirconia and Lithium Disilicate: An In Vitro Analysis

Purpose: This study evaluates the effects of artificial aging on the optical properties of high-translucent zirconia and lithium disilicate used for esthetic restorations. Materials and methods: About 36 disk-shaped specimens (10 mm diameter, 1 mm thickness) were fabricated from three materials: high-translucent zirconia (4Y-PSZ, Cercon^® ht, Dentsply Sirona; <i>n</i> = 12), extra-translucent zirconia (5Y-PSZ, Cercon^® xt, Dentsply Sirona; <i>n</i> = 12), and lithium disilicate (IPS e.max^® CAD, Ivoclar Vivadent; <i>n</i> = 12). Optical properties, including color change (ΔE), contrast ratio (CR), and translucency parameter (TP), were measured before and after artificial aging. Artificial aging was simulated by autoclaving specimens at 2 bar pressure and 134°C for 5 hours, equivalent to approximately 10–15 years of clinical aging. Data were tested for normality and expressed as mean ± standard deviation. Statistical analyses were conducted using parametric tests, with the significance level at <i>p</i> ≤ 0.05. Results: Lithium disilicate demonstrated the highest color stability following artificial aging (ΔE = 1.73 ± 0.16), outperforming high-translucent zirconia (4Y-PSZ, ΔE = 2.91 ± 0.23) and extra-translucent zirconia (5Y-PSZ, ΔE = 2.73 ± 0.30). It also exhibited the closest initial translucency to enamel (TP = 16.05 ± 0.12), significantly higher than 4Y-PSZ (TP = 11.99 ± 0.19) and 5Y-PSZ (TP = 13.59 ± 0.19). Artificial aging resulted in reduced translucency for all materials, with lithium disilicate showing the smallest decrease (ΔTP = –0.52 ± 0.17), compared to 4Y-PSZ (ΔTP = –1.01 ± 0.41) and 5Y-PSZ (ΔTP = –0.95 ± 0.31). These changes, although statistically significant, were likely clinically imperceptible. Conclusion: Lithium disilicate demonstrated superior resistance to artificial aging, maintaining better color stability and translucency compared to high- and extra-translucent zirconia. Its optical properties, closely resembling natural enamel, highlight its clinical advantage for long-term esthetic restorations. While aging-induced changes were observed in all materials, these were unlikely to be clinically perceptible. How to cite this article: Aboulhawa MA, Amin SA, Abdelaziz AN. Impact of Artificial Aging on the Optical Properties of High-translucent Zirconia and Lithium Disilicate: An <i>In Vitro</i> Analysis. Int J Prosthodont Restor Dent 2025;15(1):3–9.