The effect of artificial aging on translusency of monolithic zirconia materials in different sinterization degrees

The purpose of this study is to investigate the translucency of new generation zirconia materials. The null hypothesis is that the translucency of zirconia materials will not change as a result of artificial aging. The second null hypothesis is that the differences in sinterization temperatures will not change the translucency value in zirconia materials. The materials used in this study are Katana UTML (Kuraray Noritake Dental Inc), Prettau Anterior (Zirkonzahn, Germany) and VITA YZ XT (VITA Zahnfabrik BAD Sackingen, Germany). Katana UTML is a partially stabilized zirconia with 5 mol yttrium, Prettau Anterior contains approximately 12 mol yttrium and VITA YZ XT is a fully stabilized zirconia containing up to 9 mol yttrium. The samples are divided into two subgroups of different sinterization temperatures (1450 ℃, 1550 ℃) and designed with 15 mm diameter and 1 mm thickness in A2 color, (n = 5, N = 35). Delay time, temperature increase rate and temperature decrease rate for sinterization were arranged according to manufacturer recommendations. IPS e.max CAD LT (Ivoclar Vivadent, Schaan, Liechtenstein), the ceramic group, samples were prepared in the same dimensions (15x1 mm) as zirconia samples (n = 5, N = 35). The artificial aging of all samples was operated using a thermal cycle tester (SD Mechatronic Thermocycler, Germany) with 10,000 thermal cycles (5-55 C) and a chewing simulator (SD Mechatronic Chewing Simulator CS-4, Germany) by applying 100,000 mechanical installations (50N). Translucency parameter (TP) was calculated by measuring with VITA Easyshade Advance 4.0 (VITA Zahnfabrik BAD Sackingen, Germany). While the overall translucency parameter of monolithic zirconia increased significantly (p> 0.05), the translucency of the lithium disilicate samples used in the control group did not change (p = 0.35). It did not significantly affect the translucency parameter (p <0.05). There is a significant difference in translucency parameter. Fully stabilized zirconia have a statistically significantly higher translucency parameter compared to Katana UTML, which are partially stabilized zirconia in general (p = 0.009). IPS e.max CAD, which is the control group, showed the highest translucency parameter value, before and after aging compared to zirconia groups (p = 0.009). Our goal in dental prostheses is to provide a durable and functional restoration as well as aesthetic results. In aesthetics, translucency is the main criteria. Zirconia materials need to mimic the translucency of the natural tooth in order to obtain aesthetic results. Although the translucency of zirconia materials increase, they need to be improved to catch up with lithium disilicate materials. The material selection and material knowledge is very important for us in order to make a restoration that meets patient expectations. In light of this information, we can achieve restorations with superior aesthetic properties by choosing the right materials that are suitable for indications. Keywords: Monolithic zirconia, sinterization degree, translucency parameter, artificial aging.