Hybrid manufacturing converging cold isostatic pressing, ceramic sintering, and CAD/CAM process has been recently introduced for complex dental restoration instead of conventional wax casting. In this work, sintering behavior of 3% yttriastabilized tetragonal zirconia polycrystal (3Y-TZP) was comparatively studied using three types of commercial spray-dried nano-powder. Cold isostatic pressed powders were sintered at 1250 οC ~1450 οC for 2 hours in order to fabricate fully sintered dental block of very fine tetragonal grain structure and high strength. Structural evolutions including relative density, shrinkage rate, grain growth, and fraction of monoclinic phase were investigated with sintering temperature. The observed sintering behaviors were discussed in relation with the characteristics of starting materials such as property of spray-dried granule as well as powder size and morphology. The fracture toughness of sintered blocks was in the range of 5.2~6.7MPa.m1/2. Furthermore, for statistical analysis of the flexural strength based on failure probability, the shape and scale factor were determined from Weibull regression plot using 30 strength data for each type of powder. The sintered block of polygonal-shaped spray-dried nano-powders shows the highest shape factor and scale factor, implying that it is the most reliable and predictable in terms of fracture strength of sintered dental 3Y-TZP block.

Keywords: 3Y-TZP, Dental zirconia, Cold isostatic press, Sintering, Weibull analysis.