Tabriz University of Medical Sciences Journal of Dental Research, Dental Clinics, Dental Prospects 2008-210X 18 4 2024 12 14 Colorimetric changes of zirconia-reinforced lithium disilicate with varied thicknesses under UV aging conditions 264 271 10.34172/joddd.41390 EN AbdelRahman Moammad Abdelhameed https://orcid.org/0000-0003-0255-7753 Hussein Ramadam Mohammed https://orcid.org/0000-0001-7051-5913 Ahmad Mohammad Yousri El Kouedi https://orcid.org/0000-0001-8726-5543 Journal Article 10.34172/joddd.41390 2024 06 18 2024 08 22 Background. Zirconia-reinforced lithium disilicate (ZLD) is a promising material for esthetic dental restorations due to its strength, translucency, and color stability. However, its durability under accelerated aging conditions needs further investigation. The present in vitro study evaluated the effect of UV accelerated aging on the translucency and color stability of ZLD at varying thicknesses, using IPS e.max Press (LD) as a reference. Methods. Seventy-two samples were divided into two groups: high translucent (HT) Vita Ambria (ZLD) and IPS e.max Press (LD) (n=36, each). Each group was further subdivided into four thicknesses: 0.5, 1.0, 1.5, and 2.0 mm (n=9). The samples were fabricated, polished, and subjected to UV weathering for 384 hours, simulating one year of clinical service. Translucency and color changes were assessed using a spectrophotometer. Data were analyzed using SPSS 20, with independent t-test, paired t-test, and one-way ANOVA at a significance level of P≤0.05. Results. Vita Ambria exhibited significantly higher translucency before and after aging compared to IPS e.max press at all thicknesses (P=0.000). In both materials, translucency decreased when the thickness increased (P=0.000), observed before and after UV aging. Vita Ambria also displayed a greater color change (ΔE=2000) compared to IPS e.max press across all thicknesses (P=0.000). Conclusion. ZLD exhibited higher translucency than LD before and after accelerated artificial aging, indicating that the accelerated aging process adversely impacted the optical properties of the tested material. However, LD demonstrated superior color stability.