Influence of Porosity on the Elastic Modulus of Ti-Zr-Ta-Nb Foams with a Low Nb Content

Computational Study of the Influence of α/β-Phase Ratio and Porosity on the Elastic Modulus of Ti-Based Alloy Foams

This work aims to perform a computational analysis on the influence that microstructure and porosity have on the elastic modulus of Ti-6Al-4V foams used in biomedical applications with different α/β-phase ratios. The work is divided into two analyses, first the influence that the α/β-phase ratio has and second the effects that porosity and α/β-phase ratio have on the elastic modulus. Two microstructures were analyzed: equiaxial α-phase grains + intergranular β-phase (microstructure A) and equiaxial β-phase grains + intergranular α-phase (microstructure B). The α/β-phase ratio was variated from 10 to 90% and the porosity from 29 to 56%. The simulations of the elastic modulus were carried out using finite element analysis (FEA) using ANSYS software v19.3. The results were compared with experimental data reported by our group and those found in the literature. The β-phase amount and porosity have a synergic effect on the elastic modulus, for example, when the foam has a porosity of 29 with 0% β-phase, and it has an elastic modulus of ≈55 GPa, but when the β-phase amount increases to 91%, the elastic modulus decreases as low as 38 GPa. The foams with 54% porosity have values smaller than 30 GPa for all the β-phase amounts.

Progress in partially degradable titanium-magnesium composites used as biomedical implants

Titanium-magnesium composites have gained increasing attention as a partially degradable biomaterial recently. The titanium-magnesium composite combines the bioactivity of magnesium and the good mechanical properties of titanium. Here, we discuss the limitations of conventional mechanically alloyed titanium-magnesium alloys for bioimplants, in addition we summarize three suitable methods for the preparation of titanium-magnesium composites for bioimplants by melt: infiltration casting, powder metallurgy and hot rotary swaging, with a description of the advantages and disadvantages of all three methods. The titanium-magnesium composites were comprehensively evaluated in terms of mechanical properties and degradation behavior. The feasibility of titanium-magnesium composites as bio-implants was reviewed. In addition, the possible future development of titanium-magnesium composites was discussed. Thus, this review aims to build a conceptual and practical toolkit for the design of titanium-magnesium composites capable of local biodegradation.

Biomechanical evaluations of the long-term stability of dental implant using finite element modeling method: a systematic review

PURPOSE

The aim of this study is to summarize various biomechanical aspects in evaluating the long-term stability of dental implants based on finite element method (FEM).

MATERIALS AND METHODS

A comprehensive search was performed among published studies over the last 20 years in three databases; PubMed, Scopus, and Google Scholar. The studies are arranged in a comparative table based on their publication date. Also, the variety of modeling is shown in the form of graphs and tables. Various aspects of the studies conducted were discussed here.

RESULTS

By reviewing the titles and abstracts, 9 main categories were extracted and discussed as follows: implant materials, the focus of the study on bone or implant as well as the interface area, type of loading, element shape, parts of the model, boundary conditions, failure criteria, statistical analysis, and experimental tests performed to validate the results. It was found that most of the studied articles contain a model of the jaw bone (cortical and cancellous bone). The material properties were generally derived from the literature. Approximately 43% of the studies attempted to examine the implant and surrounding bone simultaneously. Almost 42% of the studies performed experimental tests to validate the modeling.

CONCLUSION

Based on the results of the studies reviewed, there is no "optimal" design guideline, but more reliable design of implant is possible. This review study can be a starting point for more detailed investigations of dental implant longevity.

Estimate of Coffin–Manson Curve Shift for the Porous Alloy AlSi9Cu3 Based on Numerical Simulations of a Porous Material Carried Out by Using the Taguchi Array

In real engineering applications, machine parts are rarely completely homogeneous; in most cases, there are at least some minor notch effects or even more extensive inhomogeneities, which cause critical local stress concentrations from which fatigue fractures develop. In the present research, a shift of the Coffin–Manson ε_a–N material curve in a structure with random porosity subjected to dynamic LCF loads was studied. This allows the rest of the fatigue life prediction process to remain the same as if it were a homogeneous material. Apart from the cyclic σ–ε curve, which is relatively easy to obtain experimentally, the ε_a–N curve is the second most important curve to describe the correlation between the fatigue life N and the strain level ε_a. Therefore, the correct shift of the ε_a–N curve of the homogeneous material to a position corresponding to the porous state of the material is crucial. We have found that the curve shift can be efficiently performed on the basis of numerical simulations of a combination of five porosity-specific geometric influences and the associated regression analysis. To model the modified synthetic ε_a–N curve, five geometric influences of porosity by X-ray or μ-CT analysis are quantified, and then the porosity-adjusted coefficients of the Coffin–Manson equation are calculated. The proposed approach has been successfully applied to standard specimens with different porosity topography.

Biomedical Ti-Nb-Zr Foams Prepared by Means of Thermal Dealloying Process and Electrochemical Modification

The paper presents results of preparation and modification of Ti20Nb5Zr foams by a thermal dealloying method followed by electrochemical modification. The first step of this study was the preparation of Ti20Nb5Zr30Mg nanopowder using mechanical alloying (MA). The second was forming green compacts by cold pressing and then sintering with magnesium dealloyed from the structure, which resulted in pores formation. The next step was surface modification by electrochemical etching and silver nanoparticle deposition. Porosity, morphology, mechanical properties as well as biocompatibility and antibacterial behavior were investigated. Titanium foam porosity up to approximately 60% and wide pore size distribution were successfully prepared. The new materials have shown positive behavior in the MTT assay as well as antibacterial properties. These results confirmed great potential for thermal dealloying in preparation of porous structures.

A state-of-the-art review of the fabrication and characteristics of titanium and its alloys for biomedical applications

Abstract

Commercially pure titanium and titanium alloys have been among the most commonly used materials for biomedical applications since the 1950s. Due to the excellent mechanical tribological properties, corrosion resistance, biocompatibility, and antibacterial properties of titanium, it is getting much attention as a biomaterial for implants. Furthermore, titanium promotes osseointegration without any additional adhesives by physically bonding with the living bone at the implant site. These properties are crucial for producing high-strength metallic alloys for biomedical applications. Titanium alloys are manufactured into the three types of α, β, and α + β. The scientific and clinical understanding of titanium and its potential applications, especially in the biomedical field, are still in the early stages. This review aims to establish a credible platform for the current and future roles of titanium in biomedicine. We first explore the developmental history of titanium. Then, we review the recent advancement of the utility of titanium in diverse biomedical areas, its functional properties, mechanisms of biocompatibility, host tissue responses, and various relevant antimicrobial strategies. Future research will be directed toward advanced manufacturing technologies, such as powder-based additive manufacturing, electron beam melting and laser melting deposition, as well as analyzing the effects of alloying elements on the biocompatibility, corrosion resistance, and mechanical properties of titanium. Moreover, the role of titania nanotubes in regenerative medicine and nanomedicine applications, such as localized drug delivery system, immunomodulatory agents, antibacterial agents, and hemocompatibility, is investigated, and the paper concludes with the future outlook of titanium alloys as biomaterials.

Graphic abstract