Vat photopolymerization 3D printing of yttria-stabilized ZrO2 ceramics: effects of a sintering additive (Na2O ̶ 2SiO2), biocompatibility, and osteointegration

Effects of a liquid-phase sodium disilicate additive on the properties of ZrO2 ceramics containing 3mol.% of Y2O3 and 2wt.% of Al2O3 are presented, including phase composition, microstructure, shrinkage, porosity, and bending strength. The distribution of elements along grain boundaries and the composition in a selected area of a lamella were investigated by transmission electron microscopy in pure and additive-containing samples. As a result of the introduction of the additive, sintering activity of the material increased, and the sintering temperature diminished down to 1150 °C. Thus, dense nanocrystalline materials with a crystallite size of 50-70nm and a bending strength of up to 450MPa were obtained. Optimized polymer-ceramic suspensions were used to produce objects with complex geometric shapes by 3D molding technology through layer-by-layer vat polymerization. According to in vitro assays, the obtained samples are nontoxic and cytocompatible with human osteosarcoma MG-63 cells, and according to in vivo experiments, are biocompatible and showing osseointegrative properties when implanted into the rat tibia.