Comparison of transparency indicators of domestic samples of dental multilayer ceramics based on zirconium dioxide with indicators of a foreign analogue under different sintering modes

   Relevance. New dental materials made of zirconium dioxide include 3Y-TSP and 5Y-TSP, suitable for various clinical cases, including multilayer systems that create a transparency gradient. After milling, the pre-sintered Y-TZP frames must be subjected to final sintering in 8–10 hours, although modern technologies can reduce it to 17 minutes. However, high-speed sintering can degrade the color and transparency of finished prostheses. The new monolithic ceramic systems have increased the Y3+ content to about 4 and 5 ml. %, but the indicators of layered transparency of multilayer samples after high-speed sintering remain insufficiently studied.

   The purpose of the work. The study of layered transparency after traditional and high-speed sintering of domestic multilayer ceramics made of zirconium dioxide and its imported analog using a laboratory
spectrophotometer.

   Materials and methods. Groups of 12 samples were studied: the main one (domestic production of «Ziceram ML ET») and the control one (Chinese production of «Aidite 3D Pro»), divided into subgroups «a» (traditional sintering) and «b» (high-speed sintering). The size of all samples is 15×15×1 mm, colors A1–A3, milled by removing plates from a single layer. Subgroups «a» were fired according to traditional modes with an exposure time of 30–120 minutes. Subgroup «b» was baked in a high-speed furnace in 25 minutes. Transparency was assessed using an X-Rite Ci4200 spectrophotometer using the CIE Lab* system, calculating the ratio of the «L» luminance indicators on a white and black background.

   Conclusions. The lightness of the layers of multilayer ceramic blanks «Ziceram ML ET» and «Aidite 3D Pro» is significantly reduced after high-speed sintering compared to traditional firing. The transparency gradients of Russian and Chinese multilayer ceramics differ, with significant changes after high-speed sintering.

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