Editorial

4 pages, 165 KiB

Open AccessEditorial

Biodegradable Metals

by Eli Aghion

Metals 2018, 8(10), 804; https://doi.org/10.3390/met8100804 - 08 Oct 2018

Cited by 331 | Viewed by 3804

Over the last two decades, significant scientific efforts have been devoted to developing
biodegradable metal implants for orthopedic and cardiovascular applications, mainly due to their
improved mechanical properties compared to those of biodegradable polymers [...] Full article

(This article belongs to the Special Issue Biodegradable Metals)

Research

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15 pages, 7506 KiB

Open AccessFeature PaperArticle

The Suitability of Zn–1.3%Fe Alloy as a Biodegradable Implant Material

by Alon Kafri, Shira Ovadia, Jeremy Goldman, Jaroslaw Drelich and Eli Aghion

Metals 2018, 8(3), 153; https://doi.org/10.3390/met8030153 - 28 Feb 2018

Cited by 71 | Viewed by 6780

Abstract

Efforts to develop metallic zinc for biodegradable implants have significantly advanced following an earlier focus on magnesium (Mg) and iron (Fe). Mg and Fe base alloys experience an accelerated corrosion rate and harmful corrosion products, respectively. The corrosion rate of pure Zn, however, [...] Read more.

Efforts to develop metallic zinc for biodegradable implants have significantly advanced following an earlier focus on magnesium (Mg) and iron (Fe). Mg and Fe base alloys experience an accelerated corrosion rate and harmful corrosion products, respectively. The corrosion rate of pure Zn, however, may need to be modified from its reported ~20 µm/year penetration rate, depending upon the intended application. The present study aimed at evaluating the possibility of using Fe as a relatively cathodic biocompatible alloying element in zinc that can tune the implant degradation rate via microgalvanic effects. The selected Zn–1.3wt %Fe alloy composition produced by gravity casting was examined in vitro and in vivo. The in vitro examination included immersion tests, potentiodynamic polarization and impedance spectroscopy, all in a simulated physiological environment (phosphate-buffered saline, PBS) at 37 °C. For the in vivo study, two cylindrical disks (seven millimeters diameter and two millimeters height) were implanted into the back midline of male Wister rats. The rats were examined post implantation in terms of weight gain and hematological characteristics, including red blood cell (RBC), hemoglobin (HGB) and white blood cell (WBC) levels. Following retrieval, specimens were examined for corrosion rate measurements and histological analysis of subcutaneous tissue in the implant vicinity. In vivo analysis demonstrated that the Zn–1.3%Fe implant avoided harmful systemic effects. The in vivo and in vitro results indicate that the Zn–1.3%Fe alloy corrosion rate is significantly increased compared to pure zinc. The relatively increased degradation of Zn–1.3%Fe was mainly related to microgalvanic effects produced by a secondary Zn₁₁Fe phase. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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14433 KiB

Open AccessArticle

Development of a Novel Degradation-Controlled Magnesium-Based Regeneration Membrane for Future Guided Bone Regeneration (GBR) Therapy

by Da-Jun Lin, Fei-Yi Hung, Hung-Pang Lee and Ming-Long Yeh

Metals 2017, 7(11), 481; https://doi.org/10.3390/met7110481 - 06 Nov 2017

Cited by 14 | Viewed by 6091

Abstract

This study aimed to develop and evaluate the ECO-friendly Mg-5Zn-0.5Zr (ECO505) alloy for application in dental-guided bone regeneration (GBR). The microstructure and surface properties of biomedical Mg materials greatly influence anti-corrosion performance and biocompatibility. Accordingly, for the purpose of microstructure and surface modification, [...] Read more.

This study aimed to develop and evaluate the ECO-friendly Mg-5Zn-0.5Zr (ECO505) alloy for application in dental-guided bone regeneration (GBR). The microstructure and surface properties of biomedical Mg materials greatly influence anti-corrosion performance and biocompatibility. Accordingly, for the purpose of microstructure and surface modification, heat treatments and surface coatings were chosen to provide varied functional characteristics. We developed and integrated both an optimized solution heat-treatment condition and surface fluoride coating technique to fabricate a Mg-based regeneration membrane. The heat-treated Mg regeneration membrane (ARRm-H380) and duplex-treated regeneration membrane group (ARRm-H380-F24 h) were thoroughly investigated to characterize the mechanical properties, as well as the in vitro corrosion and in vivo degradation behaviors. Significant enhancement in ductility and corrosion resistance for the ARRm-H380 was obtained through the optimized solid-solution heat treatment; meanwhile, the corrosion resistance of ARRm-H380-F24 h showed further improvement, resulting in superior substrate integrity. In addition, the ARRm-H380 provided the proper amount of Mg-ion concentration to accelerate bone growth in the early stage (more than 80% new bone formation). From a specific biomedical application point of view, these research results point out a successful manufacturing route and suggest that the heat treatment and duplex treatment could be employed to offer custom functional regeneration membranes for different clinical patients. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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10157 KiB

Open AccessArticle

Influence of the Composition of the Hank’s Balanced Salt Solution on the Corrosion Behavior of AZ31 and AZ61 Magnesium Alloys

by Jakub Tkacz, Karolína Slouková, Jozef Minda, Juliána Drábiková, Stanislava Fintová, Pavel Doležal and Jaromír Wasserbauer

Metals 2017, 7(11), 465; https://doi.org/10.3390/met7110465 - 01 Nov 2017

Cited by 37 | Viewed by 6794

Abstract

The electrochemical corrosion characteristics of AZ31 and AZ61 magnesium alloys were analyzed in terms of potentiodynamic tests and electrochemical impedance spectroscopy. The influence of the solution composition and material surface finish was examined also through the analysis of corrosion products created on the [...] Read more.

The electrochemical corrosion characteristics of AZ31 and AZ61 magnesium alloys were analyzed in terms of potentiodynamic tests and electrochemical impedance spectroscopy. The influence of the solution composition and material surface finish was examined also through the analysis of corrosion products created on the samples’ surface after electrochemical measurements in terms of scanning electron microscopy using energy-dispersive spectroscopy. Obtained data revealed the differences in the response of the magnesium alloys to enriched Hank’s Balanced Salt Solution—HBSS+ (with Mg²⁺ and Ca²⁺ ions) and Hank’s Balanced Salt Solution—HBSS (without Mg²⁺ and Ca²⁺ ions). Both examined alloys exhibited better corrosion resistance from the thermodynamic and kinetic point of view in the enriched HBSS+. AZ61 magnesium alloy reached higher values of polarization resistance than AZ31 magnesium alloy in both the used corrosion solutions. Phosphate-based corrosion products were characteristic for the AZ31 and AZ61 alloys tested in the HBSS (without Mg²⁺ and Ca²⁺ ions). The combination of phosphate-based corrosion products and clusters of MgO and Mg(OH)₂ was typical for the surface of samples tested in the enriched HBSS+ (with Mg²⁺ and Ca²⁺ ions). Pitting corrosion attack was observed only in the case of enriched HBSS+. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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7070 KiB

Open AccessArticle

Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications

by Matěj Březina, Jozef Minda, Pavel Doležal, Michaela Krystýnová, Stanislava Fintová, Josef Zapletal, Jaromír Wasserbauer and Petr Ptáček

Metals 2017, 7(11), 461; https://doi.org/10.3390/met7110461 - 31 Oct 2017

Cited by 20 | Viewed by 6895

Abstract

Magnesium with its mechanical properties and nontoxicity is predetermined as a material for biomedical applications; however, its high reactivity is a limiting factor for its usage. Powder metallurgy is one of the promising methods for the enhancement of material mechanical properties and, due [...] Read more.

Magnesium with its mechanical properties and nontoxicity is predetermined as a material for biomedical applications; however, its high reactivity is a limiting factor for its usage. Powder metallurgy is one of the promising methods for the enhancement of material mechanical properties and, due to the introduced plastic deformation, can also have a positive influence on corrosion resistance. Pure magnesium samples were prepared via powder metallurgy. Compacting pressures from 100 MPa to 500 MPa were used for samples’ preparation at room temperature and elevated temperatures. The microstructure of the obtained compacts was analyzed in terms of microscopy. The three-point bendisng test and microhardness testing were adopted to define the compacts’ mechanical properties, discussing the results with respect to fractographic analysis. Electrochemical corrosion properties analyzed with electrochemical impedance spectroscopy carried out in HBSS (Hank’s Balanced Salt Solution) and enriched HBSS were correlated with the metallographic analysis of the corrosion process. Cold compacted materials were very brittle with low strength (up to 50 MPa) and microhardness (up to 50 HV (load: 0.025 kg)) and degraded rapidly in both solutions. Hot pressed materials yielded much higher strength (up to 250 MPa) and microhardness (up to 65 HV (load: 0.025 kg)), and the electrochemical characteristics were significantly better when compared to the cold compacted samples. Temperatures of 300 °C and 400 °C and high compacting pressures from 300 MPa to 500 MPa had a positive influence on material bonding, mechanical and electrochemical properties. A compacting temperature of 500 °C had a detrimental effect on material compaction when using pressure above 200 MPa. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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6178 KiB

Open AccessArticle

Preparation and Characterization of Zinc Materials Prepared by Powder Metallurgy

by Michaela Krystýnová, Pavel Doležal, Stanislava Fintová, Matěj Březina, Josef Zapletal and Jaromír Wasserbauer

Metals 2017, 7(10), 396; https://doi.org/10.3390/met7100396 - 27 Sep 2017

Cited by 25 | Viewed by 8326

Abstract

The use of zinc-based materials as biodegradable materials for medical purposes is offered as a possible alternative to corrosion-less resistant magnesium-based materials. Zinc powders with two different particle sizes (7.5 µm and 150 µm) were processed by the methods of powder metallurgy: cold [...] Read more.

The use of zinc-based materials as biodegradable materials for medical purposes is offered as a possible alternative to corrosion-less resistant magnesium-based materials. Zinc powders with two different particle sizes (7.5 µm and 150 µm) were processed by the methods of powder metallurgy: cold pressing, cold pressing followed by sintering and hot pressing. The microstructure of prepared materials was evaluated in terms of light optical microscopy, and the mechanical properties were analyzed with Vickers microhardness testing and three-point bend testing. Fractographic analysis of broken samples was performed with scanning electron microscopy. Particle size was shown to have a significant effect on compacts mechanical properties. The deformability of 7.5 µm particle size powder was improved by increased temperature during the processing, while in the case of larger powder, no significant influence of temperature was observed. Bending properties of prepared materials were positively influenced by elevated temperature during processing and correspond to the increasing compacting pressures. Better properties were achieved for pure zinc prepared from 150 µm particle size powder compared to materials prepared from 7.5 µm particle size powder. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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4668 KiB

Open AccessFeature PaperArticle

Investigation on Mechanical Behavior of Biodegradable Iron Foams under Different Compression Test Conditions

by Reza Alavi, Adhitya Trenggono, Sébastien Champagne and Hendra Hermawan

Metals 2017, 7(6), 202; https://doi.org/10.3390/met7060202 - 02 Jun 2017

Cited by 37 | Viewed by 7726

Abstract

Biodegradable metal foams have been studied as potential materials for bone scaffolds. Their mechanical properties largely depend on the relative density and micro-structural geometry. In this work, mechanical behavior of iron foams with different cell sizes was investigated under various compression tests in [...] Read more.

Biodegradable metal foams have been studied as potential materials for bone scaffolds. Their mechanical properties largely depend on the relative density and micro-structural geometry. In this work, mechanical behavior of iron foams with different cell sizes was investigated under various compression tests in dry and wet conditions and after subjected to degradation in Hanks’ solution. Statistical analysis was performed using hypothesis and non-parametric tests. The deformation behavior of the foams under compression was also evaluated. Results show that the mechanical properties of the foams under dry compression tests had a “V-type” variation, which is explained as a function of different geometrical properties by using a simple tabular method. The wet environment did not change the compression behavior of the iron foams significantly while degradation decreased the elastic modulus, yield and compression strengths and the energy absorbability of the specimens. The deformation of open cell iron foams under compression is viewed as a complex phenomenon which could be the product of multiple mechanism such as bending, buckling and torsion. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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Review

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14 pages, 1349 KiB

Open AccessReview

Advances and Challenges of Biodegradable Implant Materials with a Focus on Magnesium-Alloys and Bacterial Infections

by Muhammad Imran Rahim, Sami Ullah and Peter P. Mueller

Metals 2018, 8(7), 532; https://doi.org/10.3390/met8070532 - 10 Jul 2018

Cited by 57 | Viewed by 7064

Abstract

Medical implants made of biodegradable materials could be advantageous for temporary applications, such as mechanical support during bone-healing or as vascular stents to keep blood vessels open. After completion of the healing process, the implant would disappear, avoiding long-term side effects or the [...] Read more.

Medical implants made of biodegradable materials could be advantageous for temporary applications, such as mechanical support during bone-healing or as vascular stents to keep blood vessels open. After completion of the healing process, the implant would disappear, avoiding long-term side effects or the need for surgical removal. Various corrodible metal alloys based on magnesium, iron or zinc have been proposed as sturdier and potentially less inflammatory alternatives to degradable organic polymers, in particular for load-bearing applications. Despite the recent introduction of magnesium-based screws, the remaining hurdles to routine clinical applications are still challenging. These include limitations such as mechanical material characteristics or unsuitable corrosion characteristics. In this article, the salient features and clinical prospects of currently-investigated biodegradable implant materials are summarized, with a main focus on magnesium alloys. A mechanism of action for the stimulation of bone growth due to the exertion of mechanical force by magnesium corrosion products is discussed. To explain divergent in vitro and in vivo effects of magnesium, a novel model for bacterial biofilm infections is proposed which predicts crucial consequences for antibacterial implant strategies. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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32 pages, 67645 KiB

Open AccessReview

Biodegradable Metallic Wires in Dental and Orthopedic Applications: A Review

by Mohammad Asgari, Ruiqiang Hang, Chang Wang, Zhentao Yu, Zhiyong Li and Yin Xiao

Metals 2018, 8(4), 212; https://doi.org/10.3390/met8040212 - 26 Mar 2018

Cited by 39 | Viewed by 11551

Abstract

Owing to significant advantages of bioactivity and biodegradability, biodegradable metallic materials such as magnesium, iron, and zinc and their alloys have been widely studied over recent years. Metallic wires with superior tensile strength and proper ductility can be fabricated by a traditional metalworking [...] Read more.

Owing to significant advantages of bioactivity and biodegradability, biodegradable metallic materials such as magnesium, iron, and zinc and their alloys have been widely studied over recent years. Metallic wires with superior tensile strength and proper ductility can be fabricated by a traditional metalworking process (drawing). Drawn biodegradable metallic wires are popular biodegradable materials, which are promising in different clinical applications such as orthopedic fixation, surgical staples, cardiovascular stents, and aneurysm occlusion. This paper presents recent advances associated with the application of biodegradable metallic wires used in dental and orthopedic fields. Furthermore, the effects of some parameters such as the surface modification, alloying elements, and fabrication process affecting the degradation rate as well as biocompatibility, bioactivity, and mechanical stability are reviewed in the most recent works pertaining to these materials. Finally, possible pathways for future studies regarding the production of more efficient biodegradable metallic wires in the regeneration of bone defects are also proposed. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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898 KiB

Open AccessFeature PaperReview

The Biological Responses to Magnesium-Based Biodegradable Medical Devices

by Lumei Liu, Juan Wang, Teal Russell, Jagannathan Sankar and Yeoheung Yun

Metals 2017, 7(11), 514; https://doi.org/10.3390/met7110514 - 21 Nov 2017

Cited by 21 | Viewed by 6118

Abstract

The biocompatibility of Magnesium-based materials (MBMs) is critical to the safety of biodegradable medical devices. As a promising metallic biomaterial for medical devices, the issue of greatest concern is devices’ safety as degrading products are possibly interacting with local tissue during complete degradation. [...] Read more.

The biocompatibility of Magnesium-based materials (MBMs) is critical to the safety of biodegradable medical devices. As a promising metallic biomaterial for medical devices, the issue of greatest concern is devices’ safety as degrading products are possibly interacting with local tissue during complete degradation. The aim of this review is to summarize the biological responses to MBMs at the cellular/molecular level, including cell adhesion, transportation signaling, immune response, and tissue growth during the complex degradation process. We review the influence of MBMs on gene/protein biosynthesis and expression at the site of implantation, as well as throughout the body. This paper provides a systematic review of the cellular/molecular behavior of local tissue on the response to Mg degradation, which may facilitate a better prediction of long-term degradation and the safe use of magnesium-based implants through metal innovation. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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871 KiB

Open AccessReview

The Prospects of Zinc as a Structural Material for Biodegradable Implants—A Review Paper

by Galit Katarivas Levy, Jeremy Goldman and Eli Aghion

Metals 2017, 7(10), 402; https://doi.org/10.3390/met7100402 - 01 Oct 2017

Cited by 237 | Viewed by 13169

Abstract

In the last decade, iron and magnesium, both pure and alloyed, have been extensively studied as potential biodegradable metals for medical applications. However, broad experience with these material systems has uncovered critical limitations in terms of their suitability for clinical applications. Recently, zinc [...] Read more.

In the last decade, iron and magnesium, both pure and alloyed, have been extensively studied as potential biodegradable metals for medical applications. However, broad experience with these material systems has uncovered critical limitations in terms of their suitability for clinical applications. Recently, zinc and zinc-based alloys have been proposed as new additions to the list of degradable metals and as promising alternatives to magnesium and iron. The main byproduct of zinc metal corrosion, Zn²⁺, is highly regulated within physiological systems and plays a critical role in numerous fundamental cellular processes. Zn²⁺ released from an implant may suppress harmful smooth muscle cells and restenosis in arteries, while stimulating beneficial osteogenesis in bone. An important limitation of pure zinc as a potential biodegradable structural support, however, lies in its low strength (σ_UTS ~ 30 MPa) and plasticity (ε < 0.25%) that are insufficient for most medical device applications. Developing high strength and ductility zinc with sufficient hardness, while retaining its biocompatibility, is one of the main goals of metallurgical engineering. This paper will review and compare the biocompatibility, corrosion behavior and mechanical properties of pure zinc, as well as currently researched zinc alloys. Full article

(This article belongs to the Special Issue Biodegradable Metals)

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