Processing and biocompatibility evaluation of laser processed porous titanium.

The Laser Engineered Net Shaping (LENS) method was used to fabricate porous Ti implants. Porous Ti structures with controlled porosity in the range of 17-58 vol.% and pore size up to 800 microm were produced by controlling LENS parameters, which showed a broad range of mechanical strength of 24-463 MPa and a low Young's modulus of 2.6-44GPa. The effects of porous structure on bone cell responses were evaluated in vitro with human osteoblast cells (OPC1). The results showed that cells spread well on the surface of porous Ti and formed strong local adhesion. MTT assay indicated LENS processed porous Ti provides a preferential surface for bone cell proliferation. Porous Ti samples also stimulated faster OPC1 cell differentiation compared with polished Ti sheet, which could be due to the change in cell morphology within the pores of Ti samples. More extracellular matrix and a higher level of alkaline phosphatase expression were found on the porous samples than on the Ti sheet. This can be beneficial for faster integration of porous implant with host bone tissue. The results obtained also indicated that a critical pore size of 200 microm or higher is needed for cell ingrowth into the pores, below which OPC1 cells bridged the pore surface without any growth in the pores.