Effects of dopants with varying cationic radii on the mechanical properties and hydrothermal aging stability of dental 3Y-TZP ceramics fabricated via vat photopolymerization

In this study, the mechanical properties and hydrothermal aging stability of small amounts of cation dopant M-doped 3Y-TZP (M = Er₂O₃, CeO₂, Nb₂O₅) prepared via vat photopolymerization were investigated. Four zirconia ceramic slurries with high solid content (58 vol%) and low viscosity were prepared by adding three different dopants, along with an undoped control. The phase composition and lattice parameters were analyzed using X-ray diffraction (XRD) and Rietveld refinement. The microstructure was examined via scanning electron microscopy (SEM). Mechanical properties were evaluated for hardness, toughness and the three-point flexural strength with Weibull analysis. Hydrothermal aging stability was also assessed. The dopants had little effect regarding the shrinkage and density of the ceramics in comparison to the undoped ceramics. However, the average grain size of sintered 3Y-TZP at 1500 °C increased with dopant addition. X-ray diffraction showed that both doped and undoped ceramics were predominantly tetragonal, although the monoclinic phase content increased with doping. The doped ceramics also exhibited improved fracture toughness. After 20 h of low-temperature degradation (LTD), 3Y-TZP ceramics exhibited a time-dependent transformation from the tetragonal to the monoclinic phase during aging, with the monoclinic phase content in the Er₂O₃-doped 3Y-TZP reaching only 18.30 %. Additionally, Er₂O₃-doped 3Y-TZP exhibited lower tetragonality (c/a√2 = 1.0142) and demonstrated flexural strength exceeding 800 MPa. Dental Er₂O₃-doped 3Y-TZP, prepared using the VPP technology, demonstrates high LTD resistance and excellent mechanical properties.