Subtractive manufacturing of customized hydroxyapatite scaffolds for bone regeneration

An approach to the preparation of customized hydroxyapatite scaffolds for bone regeneration based on subtractive manufacturing has been developed. The developed method is intended as a simple alternative to rapid prototyping based on additive manufacturing methods. The method for the preparation of customized scaffolds consists in computer numerical controlled (CNC) milling of porous hydroxyapatite foam. The machinable foam for customized scaffolds was prepared by direct foaming of a colloidal hydroxyapatite suspension and the foam structure was consolidated by the gelcasting method. The optimal foam after sintering reached a high porosity of 83.3% and the cellular-like structure contained spherical pores with an average diameter of 613 µm, which were connected through windows with an average diameter of 161 µm. The compressive strength of the sintered foam reached an average value of 2 MPa. CNC milling was tested at different stages of the production cycle of the porous foam and after the reinforcing of the foam by impregnation. The best results were obtained by milling the foam presintered at 1100 °C. The milling process was demonstrated and scaffold examples were successfully manufactured.