Water-Based Yttria-Stabilized Nano-Zirconia Pastes for Direct Ink Writing of Dental Structures

In this work, zirconia ceramic structures were fabricated by Direct Ink Writing (DIW) using water-based, yttria-stabilized nano-zirconia pastes. The pastes were prepared from 3 mol% yttria-stabilized zirconia nanopowders synthesized by sol–gel and co-precipitation routes. The effects of dispersant concentration and organic additives on paste preparation and printability were investigated, and the rheological behavior of the printable formulations was evaluated. The microstructure of the sintered 3D-printed specimens was examined by scanning electron microscopy (SEM), while apparent porosity, density, and compressive strength were determined. All printable pastes exhibited shear-thinning behavior. After sintering at 1500 °C, the printed specimens showed submicron grain sizes and apparent porosities as low as 3%. The formulation prepared without acrylamide and crosslinking agent (O12X) exhibited an apparent porosity of 3% and a compressive strength of 350 ± 25 MPa. The co-precipitated-powder formulation (2N) reached compressive-strength values of up to 360 ± 25 MPa. These results demonstrate the feasibility of using high-solids, water-based nano-zirconia pastes for DIW fabrication of dense zirconia structures and support further investigation of this approach for dental applications.