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

Abstract

Bone replacement with conventional biomaterials 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.

Characterization and Monitoring of Titanium Bone Implants with Impedance Spectroscopy

“…Different studies on titanium implants have shown that at least a 100 µm average pore size is necessary to mark and guide the cellular response to produce and synthetize bone matrix [8,[24][25][26]. Porous titanium parts manufactured with 50% vol.…”

Use of Impedance Spectroscopy for the Characterization of In-Vitro Osteoblast Cell Response in Porous Titanium Bone Implants

“…The large and irregular pores compromise the fatigue behavior of the implant as well as corrosion resistance, due to porosity [27,28]. However, at least a 100 µm average pore size [26,[29][30][31] is required to guide the cellular response and synthesis bone matrix. This bone in growth through the pores also promotes long term stability and implant osseointegration.…”

Open Celled Porous Titanium

“…This might be of a great benefit in some biomedical implants such as intramedullary rod or hip stem. [145] Other techniques have also been used to produce porous Ti with a gradient porosity such as the space holder technique [146] and metal injection molding in combination with a space holder. [147] Examples of Biomedical products making use of AM technology are shown in Figure 17 and…”