Proposal for artificial bone formation using powder-layered manufacturing: Porous characteristics of forming bone

In this study, we proposed a powder-layered manufacturing process, which is one technique for rapid prototyping, to produce the desired bone shape for a transplantation from a biomaterial powder. In the experiment, we used conventional inkjet-type equipment and orthopedic filling-paste powder (BIOPEX), of which the main component was alpha-tribasic calcium phosphate, as the forming material. To solidify the powder, we used a sodium chondroitin sulfate + dibasic sodium succinate anhydride aqueous solution-the solvent for mixing powder in clinics-as the binder liquid. In the previous report, we formed a geometric model and living bone to examine the formability of artificial bones, and showed that the formation of artificial bones is possible using this technique. In this paper, we investigated porous characteristics, an important condition for artificial bones. In experiments, we formed cylindrical samples (dimensions:7 mm in diameter, 20 mm in length) by powder-layered manufacturing (PM) and using filling-paste (FP) which is also used in clinical applications. Then we compared the porous characteristics of these samples using mercury porosimetry. The results showed that in the case of PM, porosity was 60%, about three times FP. In addition, we dipped PM samples in water and binder liquid for improving compressive strength by hydration reaction. The compressive strength of two kinds of dipped samples reached about 3 MPa when heated at 90 °C for five hours. Porosity was about 56% when dipped in water, and about 50% when dipped in binder liquid.