Introduction: Titanium and its alloys are being most extensively used for load bearing application due to its corrosion resistance, biocompatibility and mechanical properties. However, stress-shielding effect owing to modulus mismatch between titanium implants and bone leads to bone resorption which is a major setback. Titanium implants with Bone-matching moduli are developed mainly via two routes (a) using metastable β-titanium alloys and (b) porous structures. Surface modification of the developed implants is carried out for better osseointegration.
Current research focuses on the development and characterization of titanium foam, their chemical modification and biological evaluation towards load-bearing application.
Materials and Methods: Titanium foam was developed from Ti6Al4V powders, particle size of 15-45 µm (Good Fellow, U.K.) through powder metallurgy route, without using any space holder particles. Completely dried green samples were sintered at 1400°C under argon atmosphere. Porosity, average pore size, microstructure and mechanical properties were evaluated. Chemical modification of the developed foam was also carried out for improved biocompatibility. In vitro cellular response and in vivo biocompatibility studies in rabbits were also performed.
Results and Discussion: More than 85% porosity with high pore interconnectivity was achieved using this process. Average pore size of the foam was found to be 100-300 µm. Compressive strength, flexural strength and elastic modulus were evaluated as 6.61±0.35 MPa, 6.69±0.84 MPa and 744-984 MPa, respectively. Samples were found to be cytocompatible. Animal study results revealed excellent bone ingrowth within interconnected porous structures.
Conclusion: The compressive strength of the developed foam was closer to cancellous bone. In vitro cytocompatibility study as well as in vivo assessment for critical size defects were also promising, which confirms that the developed foam as well as the process can be used during fabrication of cancellous bone substitute for load bearing applications.
Defence Research and Development Organisation (DRDO), Ministry of Defence, India
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