We herein report manufacturing of dental crowns made of 5-mol% yttria partially stabilized zirconia (5Y-PSZ) with desired mechanical properties, optical translucency and dimensional accuracy using digital light processing (DLP). To this end, all processing parameters were carefully controlled and optimized. First, 5Y-PSZ particles with a bimodal distribution were prepared via calcination of as-received granules and subsequent ball-milling and then used to formulate 5Y-PSZ suspensions with a high solid loading of 50 vol% required for high densification after sintering. Dispersant content was also optimized. To provide high dimensional accuracy, initial dimensions of dental crowns for 3D printing were precisely determined by considering increase and decrease in dimensions during photopolymerization and sintering, respectively. Photopolymerization time was also optimized for a given layer thickness of 50 μm to ensure good bonding between layers. A multi-step debinding schedule with a slow heating rate was employed to avoid formation of any defects. After sintering at 1500 °C for 2 h, 5Y-PSZ could be almost fully densified without noticeable defects within layers and at interfaces between layers. They had high relative densities (99.03 ± 0.39%) with a high cubic phase content (59.1%). These characteristics allowed for achievement of reasonably high mechanical properties (flexural strength = 625.4 ± 75.5 MPa and Weibull modulus = 7.9) and % transmittance (31.4 ± 0.7%). In addition, 5Y-PSZ dental crowns showed excellent dimensional accuracy (root mean square (RMS) for marginal discrepancy = 44.4 ± 10.8 μm and RMS for internal gap = 22.8 ± 1.6 μm) evaluated by the 3D scanning technique.

Unidirectionally macrochanneled tetragonal zirconia polycrystals (TZP) scaffolds, comprising elongated microporous frameworks, were fabricated via vat photopolymerization (VP) using a solution of 75 wt% camphene and 25 wt% 1,6-hexanediol diacrylate (HDDA) as a phase-separable, photopolymerizable vehicle. The camphene/HDDA solution underwent phase separation at 5 °C, accompanied by the recrystallization and dendritic growth of camphene, thereby generating three-dimensionally interconnected camphene crystal networks enclosed by HDDA. Following the photopolymerization of HDDA, the scaffolds were freeze-dried to remove the camphene crystals and subsequently heat-treated for debinding to eliminate organic phases, including photopolymerized HDDA, the dispersant, and the photoinitiator. The effect of sintering temperature on the geometry of the micropores and the densification of the TZP walls was examined. The optimum sintering condition (1500 °C for 3 h) enabled the creation of elongated micropores with a volume fraction of 61.17 ± 0.90 vol%, surrounded by highly densified TZP walls. The fabricated scaffolds exhibited well-defined macrochannels arranged in a hexagonal pattern, separated by microporous frameworks. Their overall porosity was as high as 74.65 ± 0.73 vol%, owing to the high framework microporosity. Despite their high porosity, the scaffolds achieved a compressive strength of 53.10 ± 8.19 MPa and a compressive modulus of 364.38 ± 70.90 MPa.