Fabrication of osteoconductive Ca3–xM2x(PO4)2 (M = Na, K) calcium phosphate bioceramics by stereolithographic 3D printing

Osteoconductive ceramic implants based on Ca3–xM2x(PO4)2 (M = Na, K) double phosphates and having the Kelvin structure, tailored macropore size (in the range 50–750 μm), and a total porosity of 70–80% have been produced by stereolithographic 3D printing. We demonstrate that, to maintain the initial geometry of a model and reach sufficiently high strength characteristics of macroporous ceramics (compressive strength up to 9 MPa and fracture toughness up to 0.7 MPa m1/2), the polymer component should be removed under specially tailored heat treatment conditions. Based on our results on polymer matrix destruction kinetics, we have found heat treatment conditions that ensure a polymer removal rate no higher than 0.1 wt%/min and allow one to avoid implant cracking during the firing process.