Development of new titanium implants with longitudinal gradient porosity by space-holder technique

Abstract

Bone replacement with conventional biomate- rials entails a biomechanical incompatibility with respect to highly specialized and anisotropic bone tissue; stiffness mismatch is the most important example of that event, and it is always present in the components of all prosthetic systems for dental and joint replacements. In the case of titanium implants used for those biomedical applications, the main consequence of that mismatch is the bone resorption around the implants due to stress shielding with respect to bone. Bio-inspired design frameworks have opened a broad field of possibilities for new approaches to the stress-shielding phenomenon in bone replacements systems. To that end, conventional and non-conventional powder metallurgy have emerged as the feasible processing techniques for producing porous samples, which can match both complexity and anisotropy of bone tissue. Complete dental restoration is a good example of biomechanical systems with an important change of longitudinal stiffness once the components are implanted; therefore, development of new prosthetics systems with graded porosity for continuous Young's modulus change is required. Samples with longitudinal graded porosity (symmetric and non-symmetric) by space-holder technique were developed, fabricated, and characterized in this work. Main findings indicated that the experimental procedure for space-holder elimination was effective, feasible, and reproducible, with better results for a compaction pressure of 800 MPa with low global NaCl content. Three-layer design (30/40/50) allowed stress shielding to be reduced without any important effect on mechanical strength with respect to the cortical bone.