Bioceramic scaffolds are suitable alternatives for bone regeneration. The main advantage of bioceramic scaffolds is the possibility to tailor their mechanical properties along with their biocompatibility and bioactivity, ensuring a promoted regenerative process. Some inert ceramics like zirconia are capable of withstand high stresses, however its high Young’s modulus compromises the implant stability in the human body. The already published research demonstrated that a smart internal design could modify Young’s modulus to suitable values. The aim of our study was to determine Young’s modulus and characterize the mechanical stability of MSLA-printed zirconia scaffolds with and without calcium-phosphate infiltration mainly in terms of compressive strength, flexural strength, and cycling fatigue.

Zirconia frames were prepared via masked stereolithography (MSLA). The suspension for the MSLA was made at the home institution. After printing the frames were debinded and sintered (1500 °C/2 hours, in air). A set of sintered frames was infiltrated using freeze-casting with calcium phosphate-based suspension. The oriented microstructure of calcium phosphate infiltration was achieved by controlled ice growth in one direction. After freeze-casting frames were sintered (1200 °C/2 hour, in air). The compressive strength of both frames with and without infiltration was determined by the compression test. The three-point bending test defined the bending strength of both types of frames. Additionally, zirconia frames with calcium phosphate-based infiltration were tested in HBSS for cycled fatigue.

MSLA-printed zirconia frames reached the theoretical density of 99.2 %, after sintering. The freeze-cast calcium phosphate-based infiltration resulted in a lamellar system of pores with porosity reaching 70 %, and size of interlamellar spaces being 65 µm. The compressive strength achieved the value of 20 MPa, for both, the frames with and without infiltration. The bending strength of zirconia frames without infiltration resulted in ~138 MPa, with Weibull modulus of 6.73. The bending strength of zirconia frames with infiltration achieved the value ~139 MPa, with Weibull modulus of 4.54. The Young’s modulus was calculated with the value ~ 120 GPa. Cycling fatigue in HBSS showed the increase in bioactivity by the presence of an apatite-like layer, proved by SEM. The additional SEM observation revealed, that the failure during the force loading initiates in the site of small cracks originating from printing and post-processing. The XRD did not reveal any unexpected changes in the phase composition of the proposed frames.

We proved that the MSLA is a suitable technique for the preparation of zirconia frames with decreased Young’s modulus, and it can be easily combined with freeze-casting, to create a scaffold with a hierarchical structure. Furthermore, the mechanical stability testing and Weibull modulus revealed that the secondary thermal treatment can influence the durability of the final scaffold.