Digital light processing of high-strength hydroxyapatite ceramics: Role of particle size and printing parameters on microstructural defects and mechanical properties

Dense hydroxyapatite (HA) bars were fabricated using digital light processing. The roles of HA median particle size (MPS), curing depth-to-layer thickness ratio (CD/LT), and debinding process on the printing/debinding flaws and flexural strength of the sintered parts were investigated. Commercial HA was milled for different times to provide powders with an MPS ranging from 0.3 to 2.7 mu m. Thermal debinding led to delamination and vertical cracks, which decreased with increasing MPS; the minimum value required to fabricate specimens with appre-ciable flexural strength was 0.9 mu m. At a given MPS (2.7 mu m), the CD/LT varied between 1.4 and 3.3, indicating a progressive disappearance of the above major flaws. Finally, the positive effect of water debinding prior to thermal debinding on reducing crack formation was demonstrated. After optimisation, the bars achieved a flexural strength greater than 100 MPa, which is the highest value among dense HA fabricated using lithography -based techniques.

Automated summary

Dense hydroxyapatite bars were produced using digital light processing. The effects of HA particle size, curing depth-to-layer thickness ratio, and debinding process on printing/debinding flaws and flexural strength were studied. Optimized bars achieved a flexural strength exceeding 100 MPa, the highest obtained through lithography-based techniques for dense HA fabrication.