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.

Treating peripheral nerve injury (PNI) is a prevalent clinical challenge. The improper dispersion of regenerating axons makes it difficult to develop nerve guidance conduits (NGCs) for treating PNI. The multichannel NGCs, designed to mimic the fascicular structure of nerves, are proposed as an alternative to single hollow lumen NGCs. Hydrogel-based NGCs with microscale multichannels resembling actual nerve fascicles are fabricated using digital light processing as 3D printing. Gelatin methacryloyl (GelMA) and polyethylene glycol diacrylate (PEGDA), which are biodegradable and photocurable, are used as the printing solution. The addition of a food-grade dye to the printing solution can prevent overcuring by adjusting the optical path length of light and regulating the polymerization rate. This work further demonstrates that the addition of dyes can enable high-resolution printing, resulting in the achievement of fine multichannels with a diameter of 200 μm. In vivo animal studies using a rat sciatic nerve gap model show that GelMA/PEGDA-based multichannel NGCs can significantly improve peripheral nerve regeneration, as indicated by improved paw sensory recoveries, increased hindlimb gait function, and muscle fiber regeneration. Furthermore, the mechanical properties, pore size, and biodegradation rate of the hydrogel constituting the NGCs successfully demonstrate the feasibility of hydrogel-based multichannel NGCs for accelerating neurologic recoveries.