Development and mechanical characterization of hydroxyapatite micro/macro-porous scaffolds by an innovative gel-casting process

An innovative gel-casting process was developed in order to obtain micro and macro porous hydroxyapatite (Ca10(PO4)6(OH)2, HA) scaffolds to be used in regenerative medicine for bone tissue reconstruction. The micro-porous materials were prepared using HA suspensions having different solid loadings (in the range of 55-60 wt %) and gelling agent contents (in the range of 0.3-0.75 wt %). After the set-up of the operative parameters, macro-porous components were also prepared by using commercial polyethylene spheres (PE), sieved in the range 355 - 420 m, as a fugitive agent, added to the ceramic suspensions before casting. The PE amount was fixed for obtaining a porosity of 60 vol.% in the fired materials. The mechanical investigation was carried out on both dense and porous samples. The compressive tests, 4-point bending tests and micro-hardness measurements were performed in order to determine Young’s modulus, compressive strength, ultimate tensile stress and fracture toughness. Good correlations between mechanical properties were found. The results obtained for micro and macro-pororous specimens were related with a model based on the ideal cell. An extensive microstructural characterization was carried out by SEM and coupled to mechanical data in view of the validation of modelling tools based on DIB-FEA (digital image based finite element analysis) procedures.