Special Issue "Ti-Based Biomaterials: Synthesis, Properties and Applications"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Biomaterials".

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editor

Assoc. Prof. Jarosław Jakubowicz
E-Mail Website
Guest Editor
Institute of Materials Science and Engineering, Poznan University of Technology, Poznan, Poland
Interests: nanomaterials, materials synthesis; bulk and porous biomaterials; surface treatment

Special Issue Information

Dear Colleagues,

In the last half century, great attention has been paid to materials that can be used in the human body to prepare parts that replace failed bone structures. Of all materials, Ti-based materials are the most desirable, because they provide an optimum combination of mechanical, chemical and biological properties.

The successful application of Ti biomaterials has been confirmed mainly in dentistry, orthopedics and traumatology. The Ti provides high strength and a relatively low modulus. Ti biocompatibility is practically the highest of all metallic biomaterials, however new solutions are being sought to improve their biocompatibility and osseointegration. Thus, the chemical modification of Ti results in the formation of new alloys (for example low modulus β-type alloys) or composites (for example with hydroxyapatite), which provide new perspectives for Ti biomaterial applications.

Great attention has also been paid to the formation of nanostructures in Ti-based biomaterials, which has leads to extremely good mechanical properties and very good biocompatibility.

The surface treatment applied to Ti-based biomaterials is required to provide fast osseointegration. Oxide, nitride, DLC or hydroxyapatite surface layers are the most desired and surface technology has been extensively investigated. 

Bulk and porous Ti biomaterials, which both have different properties, are used. The introduction of open spaces (voids) into the materials structure is the technological way to reduce the Young’s modulus to a level comparable to human bone.

Over the last years, great attention has been focused on additive technology (3D printing) applied to Ti biomaterials. These processes, such as SLS, SLM or related processes, which use a laser to form the designed chemical composition as well to shape the implant, have gained importance for designing implants for specific patients. The technologies are useful for the formation of bulk, porous as well as gradient biomaterials.

It is my pleasure to invite you to submit a manuscript to this Special Issue that is related to the above topic. Full papers, communications, and reviews are all welcomed.

Assoc. Prof. Jarosław Jakubowicz
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Ti-based alloys and composites
  • Ti-type bionanomaterials
  • Ti bulk and porous biomaterials
  • Ti biomaterials surface modification
  • Ti additive technology
  • Ti new processes
  • Ti biomaterials application

Published Papers (16 papers)

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Research

Open AccessArticle
Investigation of Copper Alloying in a TNTZ-Cux Alloy
Materials 2019, 12(22), 3691; https://doi.org/10.3390/ma12223691 - 08 Nov 2019
Abstract
Alloying copper into pure titanium has recently allowed the development of antibacterial alloys. The alloying of biocompatible elements (Nb, Ta and Zr) into pure titanium has also achieved higher strengths for a new alloy of Ti-1.6 wt.% Nb-10 wt.% Ta-1.7 wt.% Zr (TNTZ), [...] Read more.
Alloying copper into pure titanium has recently allowed the development of antibacterial alloys. The alloying of biocompatible elements (Nb, Ta and Zr) into pure titanium has also achieved higher strengths for a new alloy of Ti-1.6 wt.% Nb-10 wt.% Ta-1.7 wt.% Zr (TNTZ), where strength was closer to Ti-6Al-4V and higher than grade 4 titanium. In the present study, as a first step towards development of a novel antibacterial material with higher strength, the existing TNTZ was alloyed with copper to investigate the resultant microstructural changes and properties. The initial design and modelling of the alloy system was performed using the calculation of phase diagrams (CALPHAD) methods, to predict the phase transformations in the alloy. Following predictions, the alloys were produced using arc melting with appropriate heat treatments. The alloys were characterized using energy dispersive X-ray spectroscopy in scanning transmission electron microscopy (STEM-EDS) with transmission Kikuchi diffraction (TKD). The manufactured alloys had a three-phased crystal structure that was found in the alloys with 3 wt.% Cu and higher, in line with the modelled alloy predictions. The phases included the α-Ti (HCP-Ti) with some Ta present in the crystal, Ti2Cu, and a bright phase with Ti, Cu and Ta in the crystal. The Ti2Cu crystals tended to precipitate in the grain boundaries of the α-Ti phase and bright phase. The hardness of the alloys increased with increased Cu addition, as did the presence of the Ti2Cu phase. Further studies to optimize the alloy could result in a suitable material for dental implants. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Effect of Thermomechanical Treatments on the Phases, Microstructure, Microhardness and Young’s Modulus of Ti-25Ta-Zr Alloys
Materials 2019, 12(19), 3210; https://doi.org/10.3390/ma12193210 - 30 Sep 2019
Abstract
Titanium and its alloys currently are used as implants, possessing excellent mechanical properties (more suited than stainless steel and Co-Cr alloys), good corrosion resistance and good biocompatibility. The titanium alloy used for most biomedical applications is Ti-6Al-4V, however, studies showed that vanadium and [...] Read more.
Titanium and its alloys currently are used as implants, possessing excellent mechanical properties (more suited than stainless steel and Co-Cr alloys), good corrosion resistance and good biocompatibility. The titanium alloy used for most biomedical applications is Ti-6Al-4V, however, studies showed that vanadium and aluminum cause allergic reactions in human tissues and neurological disorders. New titanium alloys without the presence of these elements are being studied. The objective of this study was to analyze the influence of thermomechanical treatments, such as hot-rolling, annealing and solution treatment in the structure, microstructure and mechanical properties of the Ti-25Ta-Zr ternary alloy system. The structural and microstructural analyses were performed using X-ray diffraction, as well as optical, scanning and transmission electron microscopy. The mechanical properties were analyzed using microhardness and Young’s modulus measurements. The results showed that the structure of the materials and the mechanical properties are influenced by the different thermal treatments: rapid cooling treatments (hot-rolling and solubilization) induced the formation of α” and β phases, while the treatments with slow cooling (annealing) induced the formation of martensite phases. Alloys in the hot-rolled and solubilized conditions have better mechanical properties results, such as low elastic modulus, due to retention of the β phase in these alloys. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Characterization and Mechanical Proprieties of New TiMo Alloys Used for Medical Applications
Materials 2019, 12(18), 2973; https://doi.org/10.3390/ma12182973 - 13 Sep 2019
Cited by 2
Abstract
Ti-based alloys are accessible for use in the human body due to their good mechanical properties, corrosion resistance, and biocompatibilities. These main properties of alloys are important criteria for choosing biomedical implants for human bones or for other kinds of applications in general [...] Read more.
Ti-based alloys are accessible for use in the human body due to their good mechanical properties, corrosion resistance, and biocompatibilities. These main properties of alloys are important criteria for choosing biomedical implants for human bones or for other kinds of applications in general medicine. This paper presents a comparison of four new Ti-based alloys desired to satisfy various requirements for biomedical implants. The materials were prepared with recipes for two new system alloys, TiMoZrTa (TMZT) and TiMoSi (TMS), alloys with nontoxic elements. The presented research contains microstructure images, indentation tests, Vickers hardness, XRD, and corrosion resistance, showing better characteristics than most commercial products used as implants (Young’s modulus closer to the human bone). Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Formation and Properties of Biomedical Ti-Ta Foams Prepared from Nanoprecursors by Thermal Dealloying Process
Materials 2019, 12(17), 2668; https://doi.org/10.3390/ma12172668 - 22 Aug 2019
Abstract
The paper presents a promising method of preparation of titanium-based foams by the thermal dealloying method. The first step of this study was the Ti-Ta-Mg based nanopowder preparation using the mechanical alloying (MA) process performed at room temperature. The next step was forming [...] Read more.
The paper presents a promising method of preparation of titanium-based foams by the thermal dealloying method. The first step of this study was the Ti-Ta-Mg based nanopowder preparation using the mechanical alloying (MA) process performed at room temperature. The next step was forming the green compacts by cold pressing and then sintering with magnesium dealloying from the titanium-based alloy structure. The mechanism of the porous structure formation was based on the removal of magnesium from the titanium alloy at a temperature higher than the boiling point of magnesium (1090 °C). The influence of the Mg content on the formation of the porous Ti-30Ta foam has been investigated. The sintering stage was performed in vacuum. During the dealloying process, the magnesium atoms diffuse from the middle to the surface of the sample and combine to form vapors and then evaporate leaving pores surrounded by the metallic scaffold. The porosity, the mechanical properties as well as biocompatibility have been investigated. The titanium-based foam of high porosity (up to 76%) and the pore size distribution from nano- to micro-scale have been successfully prepared. For the medical applications, the Ti-Ta metallic foams have shown a positive behavior in the MTT test. The as-shown results clearly exhibit a great potential for thermal dealloying in the preparation of porous structures. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Effectiveness of Surface Treatment with Amine Plasma for Improving the Biocompatibility of Maxillofacial Plates
Materials 2019, 12(16), 2581; https://doi.org/10.3390/ma12162581 - 13 Aug 2019
Cited by 1
Abstract
To date, no products have been presented for the surface treatment of metal plates used for repairing maxillofacial defects caused by trauma. Plasma surface treatment is a useful technique for chemically modifying the surfaces of biomaterials. Amine plasma-polymerization is an efficient way to [...] Read more.
To date, no products have been presented for the surface treatment of metal plates used for repairing maxillofacial defects caused by trauma. Plasma surface treatment is a useful technique for chemically modifying the surfaces of biomaterials. Amine plasma-polymerization is an efficient way to prepare bioactive thin film polymers terminated with nitrogen-containing functional groups. The purpose of this study was to investigate the improvement in biocompatibility of titanium (Ti) plates treated with amine plasma-polymerization, and analyze their surfaces characteristics. To compare biocompatibility levels, in vitro test and animal study were performed using an amine plasma-polymerized Ti plate and an untreated Ti plate. After amine plasma-polymerization, the hydrophilicity of the Ti surface was remarkably improved. Biocompatibility was also improved for the Ti plates treated with amine plasma. The clinical application of this technique will not only shorten the time required for osseointegration, but will also improve the regeneration of bone. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessFeature PaperArticle
Mechanical Alloying and Electrical Current-Assisted Sintering Adopted for In Situ Ti-TiB Metal Matrix Composite Processing
Materials 2019, 12(4), 653; https://doi.org/10.3390/ma12040653 - 21 Feb 2019
Abstract
In this work, mechanical alloying and electrical current-assisted sintering was adopted for in situ metal matrix composite material processing. Applied at the initial powder stage, mechanical alloying enables a homogeneous distribution of the starting elements in the proposed precursor powder blends. The accompanying [...] Read more.
In this work, mechanical alloying and electrical current-assisted sintering was adopted for in situ metal matrix composite material processing. Applied at the initial powder stage, mechanical alloying enables a homogeneous distribution of the starting elements in the proposed precursor powder blends. The accompanying precursor preparation and the structurally confirmed size reduction allow obtainment of a nanoscale range for the objects to be sintered. The nano precursors aggregated in the micro-sized particle objects, subjected to electrical current-assisted sintering, characterize the metal matrix composite sinters with high uniformity, proper densification, and compaction response, as well as maintaining a nanoscale whose occurrence was confirmed by the appearance of the highly dispersed reinforcement phase in the examined Ti-TiB material example. The structural analysis of the sinters confirms the metal matrix composite arrangement and provides an additional quantitive data overview for the comparison of the processing conditions. The mechanical alloying examined in this work and the electrical current-assisted sintering approach allow in situ metal matrix composite structures to create their properties by careful control of the processing steps. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Plasma-Induced Crystallization of TiO2 Nanotubes
Materials 2019, 12(4), 626; https://doi.org/10.3390/ma12040626 - 20 Feb 2019
Abstract
Facile crystallization of titanium oxide (TiO2) nanotubes (NTs), synthesized by electrochemical anodization, with low pressure non-thermal oxygen plasma is reported. The influence of plasma processing conditions on TiO2 NTs crystal structure and morphology was examined by X-ray diffraction (XRD) and [...] Read more.
Facile crystallization of titanium oxide (TiO2) nanotubes (NTs), synthesized by electrochemical anodization, with low pressure non-thermal oxygen plasma is reported. The influence of plasma processing conditions on TiO2 NTs crystal structure and morphology was examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the first time we report the transition of amorphous TiO2 NTs to anatase and rutile crystal structures upon treatment with highly reactive oxygen plasma. This crystallization process has a strong advantage over the conventional heat treatments as it enables rapid crystallization of the surface. Thus the crystalline structure of NTs is obtained in a few seconds of treatment and it does not disrupt the NTs’ morphology. Such a crystallization approach is especially suitable for medical applications in which stable crystallized nanotubular morphology is desired. The last part of the study thus deals with in vitro biological response of whole blood to the TiO2 NTs. The results indicate that application of such surfaces for blood connecting devices is prospective, as practically no platelet adhesion or activation on crystallized TiO2 NTs surfaces was observed. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Surface Characteristics and Hydrophobicity of Ni-Ti Alloy through Magnetic Mixed Electrical Discharge Machining
Materials 2019, 12(3), 388; https://doi.org/10.3390/ma12030388 - 26 Jan 2019
Cited by 3
Abstract
Nickel–titanium (Ni-Ti) alloy has been selected as stent material given its good biocompatibility. In this study, experimental research on this material was conducted using magnetic field-assisted electrical discharge machining (EDM). The surface topography of the machined workpiece was analyzed with a scanning electron [...] Read more.
Nickel–titanium (Ni-Ti) alloy has been selected as stent material given its good biocompatibility. In this study, experimental research on this material was conducted using magnetic field-assisted electrical discharge machining (EDM). The surface topography of the machined workpiece was analyzed with a scanning electron microscope (SEM). Hydrophobicity was measured by using an optical contact angle measuring instrument. The roughness values of different positions on the surface were measured using a TR200 roughness instrument. Results showed that the composite structure of solidification bulge–crater–pore–particle can be prepared on the surface of the Ni-Ti alloy through magnetic mixed EDM using suitable processing parameters. Moreover, the contact angle of the surface reaches 138.2°. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Influence of Heat Treatments on Microstructure and Mechanical Properties of Ti–26Nb Alloy Elaborated In Situ by Laser Additive Manufacturing with Ti and Nb Mixed Powder
Materials 2019, 12(1), 61; https://doi.org/10.3390/ma12010061 - 25 Dec 2018
Abstract
In the present work, a Ti–26Nb alloy was elaborated in situ by laser additive manufacturing (LAM) with Ti and Nb mixed powders. The alloys were annealed at temperatures ranging from 650 °C to 925 °C, and the effects of the annealing temperature on [...] Read more.
In the present work, a Ti–26Nb alloy was elaborated in situ by laser additive manufacturing (LAM) with Ti and Nb mixed powders. The alloys were annealed at temperatures ranging from 650 °C to 925 °C, and the effects of the annealing temperature on the microstructure and mechanical properties were investigated. It has been found that the microstructure of the as-deposited alloy obtained in the present conditions is characterized by columnar prior β grains with a relatively strong <001> fiber texture in the build direction. The as-deposited alloy exhibits extremely high strength, and its ultimate tensile strength and yield strength are about 799 MPa and 768 MPa, respectively. The annealing temperature has significant effects on the microstructure and mechanical properties of the alloys. Annealing treatment can promote the dissolution of unmelted Nb particles and eliminate the micro-segregation of Nb at the elliptical-shaped grain boundaries, while increasing the grain size of the alloy. With an increase in annealing temperature, the strength of the alloy decreases but the ductility increases. The alloy annealed at 850 °C exhibits a balance of strength and ductility. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessCommunication
Titanium Plasma-Sprayed Coatings on Polymers for Hard Tissue Applications
Materials 2018, 11(12), 2536; https://doi.org/10.3390/ma11122536 - 13 Dec 2018
Abstract
The paper presents the results of titanium plasma spraying (TPS) on polymer substrates. Polyethylene (PE300), polyamide PA6, and fiber glass-reinforced polyamide (PA6.6-GF30) were used as substrates. The PE300 and PA6.6-GF30 substrates exhibited appropriate behavior during the TPS process, whereas the PA6 substrate did [...] Read more.
The paper presents the results of titanium plasma spraying (TPS) on polymer substrates. Polyethylene (PE300), polyamide PA6, and fiber glass-reinforced polyamide (PA6.6-GF30) were used as substrates. The PE300 and PA6.6-GF30 substrates exhibited appropriate behavior during the TPS process, whereas the PA6 substrate did not “accept” Ti during plasma spraying, and the coating did not form. The TPS coatings exhibited low porosity and high homogeneity, and they had a typical multilayer structure composed of Ti and its oxides. The nanoindentation test showed good mechanical properties of the coatings and demonstrated a hardness and a Young’s modulus of approximately 400 HV and 200 GPa, respectively. The bending test confirmed the good adhesion of the titanium coatings to the polymer substrates. The Ti coatings did not fall off the substrate after its significant bending deformation. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Comprehensive Evaluation of the Properties of Ultrafine to Nanocrystalline Grade 2 Titanium Wires
Materials 2018, 11(12), 2522; https://doi.org/10.3390/ma11122522 - 11 Dec 2018
Abstract
This paper describes the mechanical properties and microstructure of commercially pure titanium (Grade 2) processed with Conform severe plastic deformation (SPD) and rotary swaging techniques. This technology enables ultrafine-grained to nanocrystalline wires to be produced in a continuous process. A comprehensive description is [...] Read more.
This paper describes the mechanical properties and microstructure of commercially pure titanium (Grade 2) processed with Conform severe plastic deformation (SPD) and rotary swaging techniques. This technology enables ultrafine-grained to nanocrystalline wires to be produced in a continuous process. A comprehensive description is given of those properties which should enable straightforward implementation of the material in medical applications. Conform SPD processing has led to a dramatic refinement of the initial microstructure, producing equiaxed grains already in the first pass. The mean grain size in the transverse direction was 320 nm. Further passes did not lead to any additional appreciable grain refinement. The subsequent rotary swaging caused fine grains to become elongated. A single Conform SPD pass and subsequent rotary swaging resulted in an ultimate strength of 1060 MPa and elongation of 12%. The achieved fatigue limit was 396 MPa. This paper describes the production possibilities of ultrafine to nanocrystalline wires made of pure titanium and points out the possibility of serial production, particularly in medical implants. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Bioactive Sphene-Based Ceramic Coatings on cpTi Substrates for Dental Implants: An In Vitro Study
Materials 2018, 11(11), 2234; https://doi.org/10.3390/ma11112234 - 09 Nov 2018
Cited by 5
Abstract
Titanium implant surface modifications have been widely investigated to favor the process of osseointegration. The present work aimed to evaluate the effect of sphene (CaTiSiO5) biocoating, on titanium substrates, on the in vitro osteogenic differentiation of Human Adipose-Derived Stem Cells (hADSCs). [...] Read more.
Titanium implant surface modifications have been widely investigated to favor the process of osseointegration. The present work aimed to evaluate the effect of sphene (CaTiSiO5) biocoating, on titanium substrates, on the in vitro osteogenic differentiation of Human Adipose-Derived Stem Cells (hADSCs). Sphene bioceramic coatings were prepared using preceramic polymers and nano-sized active fillers and deposited by spray coating. Scanning Electron Microscopy (SEM) analysis, surface roughness measurements and X-ray diffraction analysis were performed. The chemical stability of the coatings in Tris-HCl solution was investigated. In vitro studies were performed by means of proliferation test of hADSCs seeded on coated and uncoated samples after 21 days. Methyl Thiazolyl-Tetrazolium (MTT) test and immunofluorescent staining with phalloidin confirmed the in vitro biocompatibility of both substrates. In vitro osteogenic differentiation of the cells was evaluated using Alizarin Red S staining and quantification assay and real-time PCR (Polymerase Chain Reaction). When hADSCs were cultured in the presence of Osteogenic Differentiation Medium, a significantly higher accumulation of calcium deposits onto the sphene-coated surfaces than on uncoated controls was detected. Osteogenic differentiation on both samples was confirmed by PCR. The proposed coating seems to be promising for dental and orthopedic implants, in terms of composition and deposition technology. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Comparison of Mechanical Stability of Elastic Titanium, Nickel-Titanium, and Stainless Steel Nails Used in the Fixation of Diaphyseal Long Bone Fractures
Materials 2018, 11(11), 2159; https://doi.org/10.3390/ma11112159 - 01 Nov 2018
Abstract
Elastic nails made of the nickel-titanium shape memory alloy (Nitinol) have been reported to control bone modeling in animal studies. However, the mechanical stability of the Nitinol nail in the fixation of long bone fractures remains unclear. This study compared mechanical stability among [...] Read more.
Elastic nails made of the nickel-titanium shape memory alloy (Nitinol) have been reported to control bone modeling in animal studies. However, the mechanical stability of the Nitinol nail in the fixation of long bone fractures remains unclear. This study compared mechanical stability among nails made of three materials, namely Nitinol, titanium, and stainless steel, in the fixation of long bone fractures. These three materials had identical shapes (arc length: π/2 and radius: 260 mm). A cylindrical sawbone with a 10-mm gap and fixed with two C-shaped elastic nails was used to examine the stability of the nails. A finite element (FE) model was developed based on the sawbone model. The end cap for elastic nails was not used in the sawbone test but was considered based on a constraint equation in FE simulation. The results of stability tests appeared to depend on the presence or absence of the end cap. In the sawbone test, the titanium nail yielded a higher ultimate force against the applied load than did the stainless steel and Nitinol nails before the gap completely closed; the difference in linear stiffness between the nails was nonsignificant. In FE simulation, the titanium nail produced smaller gap shortening than did stainless steel and Nitinol nails without the end cap; the difference in gap shortening between the nails was minor with the end cap. The titanium elastic nail should be a better choice in managing diaphyseal long bone fractures when the end cap is not used. For Nitinol and stainless steel nails, the end cap should be used to stop the nail from dropping out and to stabilize the fractured bone. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Electromagnetic Analysis, Characterization and Discussion of Inductive Transmission Parameters for Titanium Based Housing Materials in Active Medical Implantable Devices
Materials 2018, 11(11), 2089; https://doi.org/10.3390/ma11112089 - 25 Oct 2018
Abstract
The growing demand for active medical implantable devices requires data and or power links between the implant and the outside world. Every implant has to be encapsulated from the body by a specific housing and one of the most common materials used is [...] Read more.
The growing demand for active medical implantable devices requires data and or power links between the implant and the outside world. Every implant has to be encapsulated from the body by a specific housing and one of the most common materials used is titanium or titanium alloy. Titanium thas the necessary properties in terms of mechanical and chemical stability and biocompatibility. However, its electrical conductivity presents a challenge for the electromagnetic transmission of data and power. The proposed paper presents a fast and practical method to determine the necessary transmission parameters for titanium encapsulated implants. Therefore, the basic transformer-transmission-model is used with measured or calculated key values for the inductances. Those are then expanded with correction factors to determine the behavior with the encapsulation. The correction factors are extracted from finite element method simulations. These also enable the analysis of the magnetic field distribution inside of the housing. The simulated transmission properties are very close to the measured values. Additionally, based on lumped elements and magnetic field distribution, the influential parameters are discussed in the paper. The parameter discussion describes how to enhance the transmitted power, data-rate or distance, or to reduce the size of the necessary coils. Finally, an example application demonstrates the usage of the methods. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Diffusivities and Atomic Mobilities in bcc Ti-Mo-Zr Alloys
Materials 2018, 11(10), 1909; https://doi.org/10.3390/ma11101909 - 08 Oct 2018
Cited by 6
Abstract
β-type (with bcc structure) titanium alloys have been widely used as artificial implants in the medical field due to their favorable properties. Among them, Ti-Mo alloy attracted numerous interests as metallic biomaterials. Understanding of kinetic characteristics of Ti alloys is critical to understand [...] Read more.
β-type (with bcc structure) titanium alloys have been widely used as artificial implants in the medical field due to their favorable properties. Among them, Ti-Mo alloy attracted numerous interests as metallic biomaterials. Understanding of kinetic characteristics of Ti alloys is critical to understand and manipulate the phase transformation and microstructure evolution during homogenization and precipitation. In this work, diffusion couple technique was employed to investigate the diffusion behaviors in bcc Ti-Mo-Zr alloys. The diffusion couples were prepared and annealed at 1373 K for 72 h and 1473 K for 48 h, respectively. The composition-distance profiles were obtained via electron probe micro-analysis (EPMA). The chemical diffusion coefficients and impurity diffusion coefficients were extracted via the Whittle-Green method and Hall method. The obtained diffusion coefficients were assessed to develop a self-consistent atomic mobility database of bcc phase in Ti-Mo-Zr system. The calculated diffusion coefficients were compared with the experimental results. They showed good agreement. Simulations were implemented by Dictra Module in Thermo-Calc software. The predicted composition-distance profiles, inter-diffusion flux, and diffusion paths are consistent with experimental data, confirming the accuracy of the database. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Open AccessArticle
Assay of Secondary Anisotropy in Additively Manufactured Alloys for Dental Applications
Materials 2018, 11(10), 1831; https://doi.org/10.3390/ma11101831 - 26 Sep 2018
Cited by 2
Abstract
Even though additive manufacturing (AM) techniques have been available since the late 1980s, their application in medicine is still striving to gain full acceptance. For the production of dental implants, the use of AM allows to save time and costs, but also to [...] Read more.
Even though additive manufacturing (AM) techniques have been available since the late 1980s, their application in medicine is still striving to gain full acceptance. For the production of dental implants, the use of AM allows to save time and costs, but also to ensure closer dimensional tolerances and higher repeatability, as compared to traditional manual processes. Among the several AM solutions, Laser Powder Bed Fusion (L-PBF) is the most appropriate for the production of metal prostheses. The target of this paper was to investigate the mechanical and microstructural characteristics of Co–Cr–Mo and Ti–6Al–4V alloys processed by L-PBF, with a specific focus on secondary anisotropy that is usually disregarded in the literature. Tensile specimens were built in the EOSINT-M270 machine, along different orientations perpendicular to the growth direction. Density, hardness, and tensile properties were measured and the results combined with microstructural and fractographic examination. For both alloys, the results provided evidence of high strength and hardness, combined with outstanding elongation and full densification. Extremely fine microstructures were observed, sufficient to account for the good mechanical response. Statistical analysis of the mechanical properties allowed to attest the substantial absence of secondary anisotropy. The result was corroborated by the observations of the microstructures and of the failure modes. Overall, the two alloys proved to be high-performing, in very close agreement with the values reported in the datasheets, independently of the build orientation. Full article
(This article belongs to the Special Issue Ti-Based Biomaterials: Synthesis, Properties and Applications)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

  1. Biomechanical Comparison of Elastic Titanium, Nickel-Titanium and Stainless Nails in the Fixation of Diaphyseal Long Bone Fractures

Yen-nien Chen

Background. Elastic nail made up with nickel-titanium shape memory alloy (Nitinol) has been approved to control the bone modeling of the fractured bone in animal studies. However, the mechanical effect of the Nitinol nail in the fixation of diaphyseal long bone fracture is unclear. The objective of this study is to compare the mechanical stability of the Nitinol nail with the currently used titanium and stainless nails in the fixation of diaphyseal long bone fractures.

Methods. Cylinder sawbone with a 10-mm gap and then fixed with two C-shape elastic nails was used to exam its stability with various nail materials. Furthermore, a finite element (FE) model based on the sawbone model was created to compare the gap deformation and contact forces between the nails and the inner aspect of the canal. Three different kinds of materials, namely titanium, Nitinol and stainless, with identical shape (arc lengthπ/2 and radius 260 mm) were used in this study. Axial compression until the gap closed was conducted on the fractured sawbone without the end cap by using the material property testing system, while axial compression and bending test were considered in the FE simulation. Furthermore, the effect of end cap on the nail stability is considered in the FE simulation by a constraint equation in ANSYS Workbench.

Results. The results indicated that the titanium nail yielded a higher resistance force to against the applied load than the stainless and Nitinol nails before the cap totally closed. The FE simulation indicated that the titanium nail yielded higher stability with lesser gap deformation than the stainless and Nitinol nails in axial compression and bending without the end cap. The gap deformation in axial compression and bending was larger in the Nitinol nail than the titanium and stainless nails when the end cap was used, but the difference was minor.

Conclusion. Based on the present results, the titanium elastic nail with C-shape is the first priority in the management of diaphyseal long bone fracture when the end cap is not used. The end cap is suggested to the Nitinol and stainless nails for stopping the nail from dropping and then maintains the gap.

 

  1. The Hydrophobic Surface of NiTi Alloy Prepared by Magnetic Stirring EDM

Li Li

In coronary heart disease (CHD) treatment scheme, intrusive stent is the most effective treatment and the drug eluting stent has good effect. Aiming at the problems of microporous preparation in the current surface microhole drug carrier, the paper puts forward a new process for preparing drug loaded porous on the platform surface by magnetic field assisted EDM. Nickel titanium alloy is chosen as stent material because of its good biocompatibility. The surface topography of the machined workpiece was analyzed by scanning electron microscope (SEM), hydrophobicity was measured by using video optical contact angle measuring instrument, and roughness values of different positions on the surface were measured by using the TR200 roughness instrument. This process prepares multi-scale microporous structure surface, on the other hand improves the biocompatibility of the material surface by modifying the characteristics of the surface. The effect of EDM processing factors on the formation mechanism of micropore structure and surface micro characteristics will be studied deeply in this project.

 

  1. The Process and Clinic Study of LENS Manufacturing of Customized Titanium Implants

Guangbin Zhao, Mian Qin, Yaxiong Liu

State key laboratory for manufacturing system engineering, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, China

LENS manufacturing of porous structure can match the mechanical properties of the replaced bone tissue by adjusting the porosity, and realize the customized outline structure meanwhile. The influence of process parameters of LENS manufacturing on the porosity of porous structure were studied for the establishment of the model design criteria. The method of LENS manufacturing of custom hip prosthesis was studied and two cases successfully used in clinical and have good results.

 

  1. Bioactive Sphene-based Ceramic Coatings on cpTi Substrates for Dental Implants: An In Vitro Study

Stefano Sivolella

Titanium implant surface modifications have been widely investigated in order to favor the process of osseointegration. The present work aimed at evaluating the effect of sphene (CaTiSiO5) biocoating, on titanium substrates, on the in vitro osteogenic differentiation of Human Adipose-Derived Stem Cells (hADSCs). Sphene bioceramic coatings were prepared using preceramic polymers and nano-sized active fillers, and deposited by spray coating. SEM analysis, surface roughness measurements and X-ray diffraction analysis were performed. The chemical stability of the coatings in Tris–HCl solution was investigated. In vitro studies were performed by means of proliferation test of hADSCs seeded on coated and uncoated samples after 21 days. Methyl Thiazolyl-Tetrazolium (MTT) test and immunofluorescent staining with phalloidin confirmed the in vitro biocompatibility of both substrates. In vitro osteogenic differentiation of the cells was evaluated using Alizarin Red S staining and quantification assay and real-time PCR. When hADSCs were cultured in presence of Osteogenic Differentiation Medium, a significantly higher accumulation of calcium deposits onto the sphene-coated surfaces than on uncoated controls was detected. Osteogenic differentiation on both samples was confirmed by PCR. The proposed coating seems to be promising for orthopedic and dental implants, in terms of composition and deposition technology

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