Controlling sintering temperature for biphasic calcium phosphate scaffolds using submicron hydroxyapatite slurries for LCD 3D printing

Liquid crystal display (LCD)-based 3D printing, a precise and surface-smooth technology, has found widespread use in dentistry due to its exceptional precision and surface quality. This research endeavors to create a scaffold through 3D printing using bone graft materials, specifically addressing the challenge of molding bone graft powders to fit defect areas in dental surgery. Our approach involved developing biphasic calcium phosphate (BCP) scaffolds by regulating the sintering temperature of an HA-based green body. Initially, by using wet ball mill technology, HA slurries with 30 %, 40 %, and 50 % HA content by weight were prepared and exhibited viscosities below 0.15 Pa s. Subsequently, these slurries were 3D printed via an LCD-based VP printer. The utilization of submicron-sized HA particles played a critical role in maintaining slurry stability and preventing sedimentation during the printing process. We investigated sintering temperatures of 1100 °C, 1200 °C, and 1300 °C, discovering that submicron-sized HA particles enabled precise alignment of the decomposition temperature with the typical HA sintering range. Consequently, we achieved the production of BCP scaffolds with adjustable properties by tuning the sintering temperature. Subsequent analysis delved into scaffold shrinkage, mechanical characteristics, degradation behavior, and biological responses. Among the sintered scaffolds, the 50 % HA slurry printed and sintered at 1200 °C exhibited the highest compressive strength. The cell viabilities of these sintered scaffolds consistently met the ISO 10993-5 standard, affirming their biocompatibility. Moreover, the biological responses of MG63 cells demonstrated that the sintered scaffolds not only exhibited cytocompatibility but also facilitated strong cell attachment and proliferation. Furthermore, scaffolds sintered at 1300 °C containing TCP showed the formation of a layer of HA with plate-like structures due to ion-induced precipitation, indicating their bioactivity. In conclusion, this study highlights the promising potential of LCD-based VP 3D printing technology for ceramic slurries, with clear implications for clinical applications in bone tissue engineering.