At present, strong requirements in orthopaedics are still to be met, both in bone and joint substitution and in the repair and regeneration of bone defects. In this framework, tremendous advances in the biomaterials field have been made in the last 50 years where materials intended for biomedical purposes have evolved through three different generations, namely first generation (bioinert materials), second generation (bioactive and biodegradable materials) and third generation (materials designed to stimulate specific responses at the molecular level). In this review, the evolution of different metals, ceramics and polymers most commonly used in orthopaedic applications is discussed, as well as the different approaches used to fulfil the challenges faced by this medical field.

https://royalsocietypublishing.org/doi/pdf/10.1098/rsif.2008.0151

Biomaterials in orthopaedics.

Ti-based alloys are finding ever-increasing applications in biomaterials due to their excellent mechanical, physical and biological performance. Nowdays, low modulus β-type Ti-based alloys are still being developed. Meanwhile, porous Ti-based alloys are being developed as an alternative orthopedic implant material, as they can provide good biological fixation through bone tissue ingrowth into the porous network. This paper focuses on recent developments of biomedical Ti-based alloys. It can be divided into four main sections. The first section focuses on the fundamental requirements titanium biomaterial should fulfill and its market and application prospects. This section is followed by discussing basic phases, alloying elements and mechanical properties of low modulus β-type Ti-based alloys. Thermal treatment, grain size, texture and properties in Ti-based alloys and their limitations are dicussed in the third section. Finally, the fourth section reviews the influence of microstructural configurations on mechanical properties of porous Ti-based alloys and all known methods for fabricating porous Ti-based alloys. This section also reviews prospects and challenges of porous Ti-based alloys, emphasizing their current status, future opportunities and obstacles for expanded applications. Overall, efforts have been made to reveal the latest scenario of bulk and porous Ti-based materials for biomedical applications.

/pdf/new-developments-of-ti-based-alloys-for-biomedical-1vs3nsqg8x.pdf

New Developments of Ti-Based Alloys for Biomedical Applications

Assessing the corrosion of biodegradable magnesium implants: a critical review of current methodologies and their limitations.

Significance of calcium phosphate coatings for the enhancement of new bone osteogenesis – A review ☆

A Review on Biomedical Titanium Alloys: Recent Progress and Prospect

Three-dimensional growth of differentiating MC3T3-E1 pre-osteoblasts on porous titanium scaffolds.

Titanium foam, prepared by using a patented powder-metallurgy–based process involving a powder blend that was molded, foamed, and sintered using a three-step thermal treatment, was deoxidized in a molten CaCl2 bath. The polarization experiments were carried out by cathodically polarizing the foam (working electrode) against a counter (graphite) electrode. Under constant potential (polarization) mode, the dominant mechanism of deoxidation was the ionization of oxygen, present in the foam, and its subsequent discharge, as CO2/CO, at the anode surface. More than ∼85 pct oxygen could be effectively removed by carrying out the electro-deoxidation experiments in fresh and pre-electrolyzed melt(s) at an electrolyte temperature of 950 °C. Scanning electron microscopy–energy dispersive X-ray (SEM-EDX) detection of the deoxidized foams did not show a presence of any inclusion(s) or secondary phase(s).

/pdf/electrochemical-deoxidation-of-titanium-foam-in-molten-22sbt2hswy.pdf

Electrochemical Deoxidation of Titanium Foam in Molten Calcium Chloride

Electrochemical impedance spectroscopy has been revealed to be a useful tool to evaluate the exposed surface area and consequently to evaluate the corrosion behavior of titanium foams intended for biomedical applications.In order to find the most accurate corrosion assessment, a new equivalent circuit involving a porous model in series with a double TiO 2 layer model was proposed to fit the experimental data. Although seldom used in the literature, such technique could be useful for the characterization of porous media. Determining corrosion potentials and current densities, the titanium foams have revealed to be slightly more resistant to corrosion in simulated body fluid solutions at 37°C under static mode (no stress applied to the samples) compared to dense and polished titanium. The best titanium foams exibited penetration rates around 0.07 μm yr - 1 . Cyclic voltammetry experiments have shown that the titanium oxide layer stability was not affected by the fabrication process of the foams.

Surface and Corrosion Electrochemical Characterization of Titanium Foams for Implant Applications

A technique has been recently developed to produce foamed metallic structures from dry powder blends containing a metallic powder, a polymeric binder, and a foaming agent. The blend is molded and heat-treated to foam and consolidate the material. The final properties may be tailored by varying the sintering temperature. Microstructure, chemical composition, and properties of nickel (Ni) foams sintered at different temperature are presented and discussed. The resulting material has an open cell microstructure with three levels of porosity. This structure leads to materials having low density (∼ 90% porosity) and high specific surface area. The specific surface area is reduced and the mechanical strength is increased when the sintering temperature increases.

/pdf/production-of-metallic-foams-having-open-porosity-using-a-15suy3pcxf.pdf

Production of Metallic Foams Having Open Porosity Using a Powder Metallurgy Approach

This article presents the mechanical behavior of porous NiTi in the context of biomedical applications related to bone prostheses To produce the porous metallic material, a novel technique consisting of mixing prealloyed NiTi powder with a polymer powder and a foaming agent has been used This method permits control of the size of pores and the porosity level For the present study, pores similar to those found in bones (400 to 500 μm) were obtained with a total porosity of the specimens varying from 50 to 70 pct The compression mechanical testing carried out on small cylindrical specimens revealed shape memory deformation recovery up to 64 pct, while the superelastic behavior resulted in a reversible deformation up to 77 pct By varying the amount of porosity, it was possible to obtain Young’s moduli in the range of 26 to 46 GPa, which is similar to the modulus of cancellous (spongy) human bone

Maxime Gauthier

Papers

Three-dimensional growth of differentiating MC3T3-E1 pre-osteoblasts on porous titanium scaffolds.

Electrochemical Deoxidation of Titanium Foam in Molten Calcium Chloride

Surface and Corrosion Electrochemical Characterization of Titanium Foams for Implant Applications

Production of Metallic Foams Having Open Porosity Using a Powder Metallurgy Approach

Mechanical and Microstructural Characterization of Porous NiTi Shape Memory Alloys