12 3D printing of a calcium phosphate paste for the production of patient specific bone substitutes
Bone defect is a medical condition greatly impairing patient's functionality and is either caused by trauma, infection or cancer. Its treatment can include bone graft from the patient or another human, or the implantation of a bone substitute. The later can be done by using calcium phosphate cements, which react with water to form a hard and biocompatible material with a chemical composition close to the natural bone.
3D printing is an additive manufacturing technique allowing the creation of personalized objects to fit the patient's bone defect, which is a major criterion for implant success. One of the challenges of 3D printing can be a lack of stability of the material once printed, which -particularly when printing complex shapes- risks leading to a deformation of the structure and an implant not being personalized anymore.
In this study we developed a process using co-extrusion printing of a multicomponent calcium phosphate paste to improve its post-printing and post-processing stability. The co-extruded filaments were composed of a calcium phosphate paste core which was surrounded by a water-ethanol based solvent shell. The printed scaffolds were post-processed using a one hour 134°C steam autoclave cycle to allow simultaneous sterilization and hardening.
Co-extrusion printing led to a significant increase in the post-printing stability of the ink. Compression mechanical tests showed a significant increase in the mechanical properties of the scaffolds both before and after post-processing. Computed tomography observations showed a significant decrease in the number of scaffolds internal defects and cracks after post-processing. This work shows the potential of a process compatible with clinical needs to increase calcium phosphate printing stability and mechanical properties while decreasing structural defect.