New nano-grain dental zirconia with chairside processability and superior bio-mechanical properties

Objectives To overcome the limitations of conventional yttria-stabilized zirconia used in dental restorations, including long sintering time, relatively low fracture toughness (especially for high-translucency zirconia, such as 4Y-, 5Y-, and 6Y-PSZ), hydrothermal instability, and limited machinability, this study aims to develop a calcium-stabilized nano-grain zirconia optimized for rapid chairside processing. Methods Calcium-stabilized zirconia ceramics were fabricated and subjected to fast sintering with a total sintering time of less than 20 min, and compared with conventionally slow-sintered specimens. Microstructure, phase composition, mechanical properties, optical translucency, machinability, and biocompatibility were systematically characterized. Results Fast sintering produced a refined nano-grain microstructure with significantly improved flexural strength, fracture toughness, phase stability, and machinability compared with slow sintering. Notably, optical translucency was markedly enhanced under fast sintering conditions, attributable to the effective suppression of CaO-ZrO₂ phase separation during rapid heating. In contrast, slow sintering promoted phase segregation and inferior optical performance. Significance These results demonstrate that fast sintering (<20 min) is superior to conventional slow sintering for calcium-stabilized dental zirconia. The developed material combines rapid processing, enhanced mechanical and optical performance, and good biocompatibility, highlighting its strong potential for next-generation chairside zirconia dental restorations.