Digital light processing of zirconia prostheses with high strength and translucency for dental applications

The present study describes the manufacturing of 4 mol% yttria partially stabilized zirconia (4Y-PSZ) prostheses with high mechanical properties and translucency using digital light processing (DLP). To formulate 4Y-PSZ suspensions with high solid loading and appropriate viscosity, as-received granules were calcined at 900 °C for 3 h and then crushed into fine particles. In addition, a mixture of low-viscosity hexanediol diacrylate (HDDA) monomer and decalin as the diluent was employed as the photopolymerizable medium. To achieve strong bonding between layers and high accuracy, the photocuring time during DLP process was optimized. 4Y-PSZ prostheses were almost fully densified after sintering at 1,500 °C for 2 h, which had a relative density of 99.4%. Also, no visible interfaces between the layers were noticed. The sintered 4Y-PSZ samples showed high flexural strength of 831 (±74) MPa and high optical transmittance of 30 (±1.2) %.