Effect of sintering regimes and thickness on optical properties of zirconia ceramics for dental applications

In dentistry, monolithic zirconia restorations have been preferred over all-ceramic restorations in recent years. Translucency is an aesthetic demand in dental restorations, and it can be identified with translucency parameter (TP). Zirconia thickness, Y2O3 content, and sintering conditions are important parameters that influence the translucency of the restorations. It is crucial to investigate monolithic zirconia ceramics under different sintering regimes and reveal the critical parameters for dental restorations. The aim of this study was to determine the optical and microstructural behaviors of monolithic zirconia ceramics containing different amounts of yttria depending on various sintering regimes and thicknesses. Therefore, a conventional zirconia CopranZri (CZI) and two monolithic zirconia materials, CopraSupreme (CSP), CopraSmile (CSM) were used. Slow, normal, speed, and translucency sintering regimes with thicknesses of 0.7, 1.0, 1.3 mm were selected. TP of the specimens was calculated, and statistical analyses were performed by using one-way ANOVA and Tukey-Kramer post hoc tests. Characterization of the specimens was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) techniques. The results showed that the effect of different sintering programs is more critical for CSP and CSM in terms of translucency variations and translucency program led to the most grain growth.