Optimizing the microstructure, mechanical, and optical properties of recycled zirconia for dental applications

Efficient recycling of dental zirconia residues from computer-aided design/manufacturing processes is crucial for sustainable development in dentistry. This study employed ball milling to modify recycled zirconia powder (RZP). Initial RZP and ball-milled RZP (RZP-BM) were pre-sintered at 1000-1150 °C and then final sintered at 1500 °C. Initial RZP had irregular shapes, while RZP-BM showed finer and more uniform morphology, higher packing density, and improved de-agglomeration after 6 h of ball milling. For pre-sintered zirconia, RZP-BM samples achieved properties comparable with commercial zirconia at 1100 °C, whereas initial RZP required 1150 °C. For final sintered zirconia, initial RZP samples exhibited lower Vickers microhardness, density, strength, and transmittance, with numerous defects in its microstructure. RZP-BM samples showed significant improvement in mechanical and optical properties, comparable with commercial zirconia. This study establishes a viable approach for recycling dental zirconia residues, enhancing its properties for potential reuse as dental materials.