Hydrothermal recycling of 3%-mol yttria stabilized zirconia and microsphere preparation via spray granulation

Backgrounds and aim Recycling of dental zirconia waste, primarily from 3%-mol yttria-stabilized tetragonal zirconia (3Y-TSZ), presents challenges due to the material’s intrinsic mechanical and chemical stability. This study investigates a hydrothermal treatment combined with ball milling to facilitate the recycling of zirconia and optimize granulation via spray-drying for use in dental prosthetics. Materials and methods Zirconia waste from pre-sintered blanks was subjected to hydrothermal treatment at 275°C and 10.5 MPa, followed by wet ball milling. The milled powders were used to create slurries with varying solid content, dispersant, and binder levels, which were then spray-dried. Results Particle size analyses revealed that hydrothermal treatment significantly reduced milling time and particle size, yielding finer powders compared to untreated zirconia. The optimized slurry formulation, containing 70 wt% solid content and 0.3 wt% dispersant, was granulated into microspheres, achieving spherical morphology and uniform size distribution. Conclusion The study demonstrates the feasibility of recycling zirconia waste using a combined hydrothermal and spray-drying approach, providing a sustainable route for fabricating dental ceramics.