Materials For Bone Implants Research Articles

Influence of scandium on mechanical properties, degradation behavior, and cytocompatibility of Zn-3Cu-0.4Li-xSc alloys for implant applications

Zinc (Zn)-based alloys have emerged as promising new biodegradable materials owing to their moderate corrosion rates and potential biological functionalities. Nevertheless, as-cast pure Zn and its alloys possess low mechanical strength, poor ductility and low hardness, which hinders their biomedical application. In this study, biodegradable Zn-3Cu-0.4Li (ZCL) and ZCL-xSc (x = 0.20, 0.35 and 0.55 wt.%) alloys were fabricated by casting and further hot-rolled (HR), with the aim of acquiring satisfactory mechanical, corrosion and biocompatibility properties for orthopedic implant applications. Results indicated that the mechanical properties of HR ZCL and ZCL-xSc alloys were significantly improved compared to the as-cast alloys. The HR ZCL-0.20Sc alloy showed the best combination of mechanical properties: yield strength of 277 MPa; ultimate tensile strength of 337 MPa; elongation of 40%; and a microhardness of 113 HV. The nanohardness of HR ZCL–xSc alloys increased from 1.64 to 2.43 GPa with increasing Sc content from 0 to 0.55 wt.%. Degradation rates of HR ZCL-xSc alloys gradually increased with increasing Sc content, with the HR ZCL-0.55Sc alloy showing the lowest corrosion resistance and the highest degradation rate of 50.1 μm/y after immersion in Hanks’ balanced salt solution for 30 d. In vitro cytocompatibility assessment using human osteoblast-like SaOS2 cells showed high cell viabilities after 1 d of exposure to undiluted extracts of HR ZCL and ZCL-xSc alloys, and also after 5 d with 50% diluted extracts. Overall, the HR ZCL-0.20Sc alloy has great potential as a biodegradable bone-implant material, due to excellent mechanical, satisfactory corrosion and good biocompatibility properties.

In situ development of a Zn-Mg-Mg2Si alloy for a biodegradable bone implant applications

The microstructure, mechanical properties, corrosion, wear behaviour, and cytocompatibility of in situ Zn−Mg−Mg2Si alloys with different Mg2Si contents were evaluated. By increasing Mg−10Si content, the mechanical strength, hardness, and wear resistance improved while the corrosion rate and cytocompatibility increased and decreased. The Zn−Mg−0.6Mg2Si exhibited the best matching, including a moderate UTS (201 MPa), YS (171 MPa), hardness (100.4 HV), wear loss (0.8 mg), lowest degradation rate (27 μm/y), and highest cell viability (106.6%) among all alloys, showing a preferable candidate as biodegradable bone-implant material.

Development of Ti–26Nb–1.2TiC shape memory composite for biomedical applications

Ti–Nb alloys have great potential in biomedical applications as bone-implant materials due to their low elastic modulus, superelasticity, high corrosion resistance, and good biocompatibility. However, the low yield strength and poor superelasticity of Ti–Nb alloys restrict their practical clinical applications. Here, we report the mechanical properties and superelasticity, corrosion behavior, and biocompatibility of a Ti–26 at.% Nb–1.2 vol.% TiC (Ti–26Nb–1.2TiC) shape memory composite (SMC) prepared by vacuum arc melting and hot rolling. The yield strength, critical stress for inducing martensitic transformation, and elongation of the Ti–26Nb–1.2TiC SMC and a Ti–26Nb alloy were 460 and 337 MPa, 251 and 115 MPa, and 27.2% and 24.1%, respectively. The recovery rate of the SMC under 4% pre-strain reached 91.4%, which was 1.2 times that of the Ti–26Nb. Electrochemical tests in Hanks’ solution revealed that the corrosion current density, passive current density, and corrosion rate of the SMC were lower than those of the Ti–26Nb. Both the Ti–26Nb alloy and Ti–26Nb–1.2TiC SMC showed good cell viability with grade 0 cytotoxicity in relation to MG-63 osteosarcoma cells.

Preparation and analysis of pure and surface modified nanohydroxyapatite derived from eggshells and its in-vitro studies for bone graft applications

The need and significance for quality bone graft substitute increases due to the worldwide increment in the health problems such as osteoporosis, accidental loss and teeth decay etc. Nowadays, nanohydroxyapatite and its polymeric composites are effectively used as bone grafts and dentin. In this work, nanohydroxyapatite (nHAp) and surface-modified nanohydroxyapatite were synthesized through the precipitation method using bio-wastes (eggshells) as a Calcium precursor. The polymers Polyethylene glycol (PEG) and polyvinyl acrylate (PVA) were used as surface modifiers to control the particle size. The prepared samples were analyzed through X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Differential Thermal Analysis (TG-DTA), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HR-TEM) and X-ray Photoelectronic Spectroscopy (XPS). Also, the samples were subjected to simulated body fluid analysis, antimicrobial and hemolytic assay to analyze the apatite forming ability and hemolytic nature. The XRD, SEM and HR-TEM results show the crystallite and particle sizes are about 41 nm, 57 nm and 66.6 nm (rod-shaped) respectively. While the EDAX spectra show the presence of Calcium, Phosphate, Oxygen and Sodium in the prepared sample. However, the FT-IR spectra confirm the presence of OH, PO43−, and CO32− functional groups in the sample. The thermogram depicts the stability of nHAp/PVA composite is better than nHAp without polymer. This study reports that reprocessing of eggshells to nHAp and its composites paves the way to recover the ecosphere and the obtained value-added product, which may use in making a promising material for bone implants, dental fillers and coatings at low cost.

Magnesium-based alloys with adapted interfaces for bone implants and tissue engineering.

Magnesium and its alloys are one of the most used materials for bone implants and tissue engineering. They are characterized by numerous advantages such as biodegradability, high biocompatibility and mechanical properties with values close to the human bone. Unfortunately, the implant surface must be adequately tuned, or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological media. This article reviews the clinical challenges related to bone repair and regeneration, classifying bone defects and presenting some of the most used and modern therapies for bone injuries, such as Ilizarov or Masquelet techniques or stem cell treatments. The implant interface challenges are related to new bone formation and fracture healing, implant degradation and hydrogen release. A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitro and in vivo tests correlated with material properties' characterization. Mg-based trauma implants such as plates and screws, intramedullary nails, Herbert screws, spine cages, rings for joint treatment and regenerative scaffolds are presented, taking into consideration their manufacturing technology, the implant geometrical dimensions and shape, the type of in vivo or in vitro studies and fracture localization. Modern technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications, physical deposition and chemical conversion coatings. The last part of the article provides some recommendations from a translational perspective, identifies the challenges associated with Mg-based implants and presents some future opportunities. This review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

Microstructural, electrical and mechanical characterizations of green-synthesized biocompatible calcium phosphate nanocomposites with morphological hierarchy

The present work reports the development of novel ternary silver-silver phosphate-biphasic calcium phosphate nanocomposites by plant-extract mediated hydrothermal route. Unique epitaxial morphological growth of the Ag–Ag3PO4 core-shell structure influences the internal grain-grain boundary arrangement. The green-assisted development of the constituent phases helps significant biocompatibility enhancement (∼89–93% for 50 μg/mL; 72 h). Hence long-term bone-replacement purposes and polar fluid osmosis are favorable due to higher cell attachment on the rough surface of the mesoporous nanocomposites. The heterogeneous attachment between the three phases creates defect states indicating intense interfacial polarization, as elucidated by the dielectric spectroscopic studies. The surface charge essential for bone regeneration is likely to be developed. Besides, the porous nanocomposite compacts exhibit superior phase-composition-dependent mechanical (Hardness ∼1.3 GPa; load 4.9 N) and dielectric properties (permittivity ∼1.2 × 103; 200 Hz, 613 K) helping in conduction through bones. Thus the green-synthesized ternary nanocomposites exhibit the essential aspects of a promising bone-implant material.

Development of biodegradable in situ Zn-Mg2Sn composites for bone-implant applications

Biodegradable in situ Zn-xMg2Sn composites were prepared via alloying with different Mg2Sn contents and hot-rolling for bone-implant applications. The results indicate that the hot-rolled composites showed increased mechanical strength, hardness, wear resistance, and decreased corrosion rates with increasing Mg2Sn content. Zn-7.5Mg2Sn exhibited the best mechanical property matching, including an ultimate tensile strength of 240.2 MPa, yield strength of 222.0 MPa, elongation of 16.8 %, and hardness of 93.8 HV. Zn-10Mg2Sn showed the lowest degradation rate (22.7 μm/y) among all hot-rolled composites. Furthermore, a 12.5 % concentration of Zn-7.5Mg2Sn extract showed no cytotoxicity toward 3 T3 cells. Overall, the Zn-7.5Mg2Sn composite is proposed as a promising candidate for biodegradable bone-implant material.

Polyether Ether Ketone Coated with Ultra-Thin Films of Titanium Oxide and Zirconium Oxide Fabricated by DC Magnetron Sputtering for Biomedical Application.

Recently, polyether ether ketone has raised increasing interest in research and industry as an alternative material for bone implants. This polymer also has some shortcomings, as it is bioinert and its surface is relatively hydrophobic, causing poor cell adhesion and therefore slow integration with bone tissue. In order to improve biocompatibility, the surface of polyether ether ketone-based implants should be modified. Therefore, polished disc-shaped polyether ether ketone samples were surface-modified by direct current magnetron sputtering with ultrathin titanium and zirconium coatings (thickness < 100 nm). The investigation results show a uniform distribution of both types of coatings on the sample surfaces, where the coatings mostly consist of titanium dioxide and zirconium dioxide. Differential scanning calorimetry revealed that the crystalline structure of the polyether ether ketone substrates was not changed by the coating deposition. Both coatings are amorphous, as shown by X-ray diffraction investigations. The roughness of both coating types increases with increasing coating thickness, which is beneficial for cell colonization. The coatings presented and investigated in this study improve wettability, increasing surface energies, in particular the polar component of the surface energies, which, in turn, are important for cell adhesion.

Biodegradable Zn–Dy binary alloys with high strength, ductility, cytocompatibility, and antibacterial ability for bone-implant applications

The unique combination of biodegradability, biocompatibility, and functionality of zinc (Zn)-based alloys makes them highly desirable for a wide range of medical applications. However, a long-standing problem associated with this family of biodegradable alloys in the as-cast state is their limited mechanical strength and slow degradation rate. Here we report the development of Zn-xDy (x = 1, 3, and 5 wt.%) alloys with high strength, ductility, cytocompatibility, antibacterial ability, and appropriate degradation rate for biodegradable bone-implant applications. Our results indicate that the mechanical properties of Zn–xDy alloys were effectively improved with increasing Dy addition and hot-rolling due to the second-phase strengthening. The hot-rolled (HR) Zn–3Dy alloy showed the best combined mechanical performance with an ultimate tensile strength of 270.5 MPa, a yield strength of 214.8 MPa, an elongation of 55.1%, and Brinell hardness of 75.9 HB. The corrosion and degradation rates of HR Zn–xDy alloys in Hanks’ solution gradually increased with increasing Dy addition due to the intensification of galvanic corrosion. The HR Zn–3Dy alloy showed high antibacterial ability against S. aureus and cytocompatibility toward MC3T3-E1 cells among all the HR alloys. Overall, the HR Zn–3Dy alloy can be considered a promising biodegradable material for bone implants. Statement of significanceThis work reports on Zn–xDy (x = 1, 3, and 5%) alloys fabricated by Dy alloying followed by hot-rolling for biodegradable bone-implant applications. Our findings demonstrate that the hot-rolled (HR) Zn–3Dy alloy showed the best combined mechanical performance with an ultimate tensile strength of 270.5 MPa, a yield strength of 214.8 MPa, an elongation of 55.1%, and Brinell hardness of 75.9 HB. The corrosion and degradation rates of HR Zn–xDy alloys in Hanks’ solution gradually increased with increasing Dy addition due to the intensification of galvanic corrosion. Furthermore, the HR Zn–3Dy alloy showed greater antibacterial ability against S. aureus and the best cytocompatibility toward MC3T3-E1 cells among all the HR alloys.

Surface modification of zirconium alloy implants by collagen encapsulated strontium ranelate@PCN-224 coating to improve biocompatibility and promote osseointegration

Implant materials were extensively used in bone fracture and replacement therapies. However, implants gradually loosen and eventually fail over time. Therefore, the bone integration ability of bone-implant materials needs further study. There are many methods and materials for enhancing osseointegration properties of Zr alloy by surface loading of osteogenic drugs. Compared with the traditional porous drug loading materials (such as zeolite and molecular sieve), the metal-organic framework (MOFs) materials have the advantages of large specific surface area, easy adjustment of pore structure, more active adsorption sites and large adsorption capacity, so they had a wide range of applications in adsorption separation and controlled drug release. In this paper, the metal-organic skeleton PCN-224 with large porosity and specific surface area was synthesized by hydrothermal reaction with H2TCPP and zirconium salt as raw materials. In order to understand the microstructure and physical and chemical properties of the materials and explore their adsorption mechanism, the prepared materials were characterized by XRD, SEM, TEM, FTIR, TG-RSC, surface area analyzer and BET. The particle size of the synthesized PCN-224 was 209.67 ± 25.24nm. The surface area analyzer (BET) showed that the specific surface area of PCN-224 was 735.96cm3g-1, the pore size was 2.18 ± 0.12 nm, and the maximum pore volume was 1.47 cm3g−1nm−1. By comparing the changes of SEM, EDS and XRD before and after PCN-224 was immersed in strontium ranelate solution, the results show that strontium ranelate has been successfully loaded into the pore structure of PCN-224 without destroying the original crystal structure of PCN-224, and its adsorption process conforms to pseudo-second-order kinetics. The maximum adsorption capacity of SR was up to 112.67 ± 2.14 mg g−1. The SR@PCN-224 was mixed with type I collagen and adhered to the anodized Zr alloy surface with a crosslinking agent. The sustained release performance of coated strontium ranelate showed that the complete release time was 13 days. In vitro biological experiments confirmed that Zr-Col-SR@PCN-224 coating could promote osteoblast proliferation and osteogenic differentiation. Metal-organic frame materials loaded with osteogenic drugs can improve the osseointegration performance of bone-implant materials, providing a novel idea and strategy for improving the osseointegration performance of bone implant materials.

New synthetic PEKK/bioceramic hybrids and their surface sulfonation counterparts have increased cellular osteogenic capacity and promoted osseointegration

PEKK has good biocompatibility as an implantable material, but its mechanical properties and osseointegration are not satisfied enough. Aluminum oxide (Al2O3) is highly wear-resistant, while hydroxyapatite (HA) is a biologically active. However all previous biocomposites made via mechanical mixing of these two bioceramic materials have not been able to meet clinical standards. The aim of this work is to resolve these problems by using newly synthesized bioceramic hybrids. In vitro and in vivo experiments have demonstrated that these new biomaterials have significantly improved biocompatibility and biomechanical properties when compared to neat PEKK. Surface sulfonation of the hybrids also leads to further improvements of these two properties. S-PEKK/Al2O3 and S-PEKK/HA promote MC3T3-E1 adhesion. PEKK/HA and S-PEKK/HA significantly promote cell proliferation by upregulating both mRNA and protein levels of cell cycle genes to facilitate cells shift from G0/G1 phase to S phase. PEKK/HA hybrids and S-PEKK/Al2O3 promote cell differentiation by upregulating the expression of osteogenic differentiation genes and proteins. PEKK/HA, S-PEKK/Al2O3 and S-PEKK/HA are able to strongly bind to the new bone and exhibit good in vivo osseointegration properties. We conclude that PEKK/HA, S-PEKK/Al2O3 and S-PEKK/HA show good osteogenic ability, especially S-PEKK/HA, and could be promising materials for bone implants.

Modified Biodegradation Behavior Induced Beneficial Microenvironments for Bone Regeneration by Low Addition of Gadolinium in Zinc.

Zinc (Zn) shows a great potential as a biodegradable material for bone implants after a decade of systematic research and development. However, uncontrollable biodegradation behavior and biphasic dose-response prevent Zn from fulfilling its essential role in facilitating bone regeneration. In this study, the low addition of gadolinium (Gd) modifies the intrinsic microstructure of Zn in terms of grain size distribution, grain boundary misorientation, and texture. Adding Gd refines grain size distribution and creates a stronger basal plane texture in Zn, consequently, changing the current density distribution and reducing the anode dissolution rate during corrosion. As a result, uniform degradation is more predominant in Zn-0.4Gd alloy implant, in comparison to localized degradation in pure Zn implant in bone environments. The modified biodegradation behavior of the Zn-0.4Gd alloy implant induces significantly better new bone formation and osseointegration compared to the pure Zn implant. Therefore, Gd with trace amounts is able to tune the degradation behavior and improve the performance of Zn-based implants in promoting bone regeneration.

Phototethering of Collagen onto Polyetheretherketone Surfaces to Enhance Osteoblastic and Endothelial Performance

Polyetheretherketone (PEEK) is a candidate material for bone implants as an alternative to metals. However, PEEK exhibits poor osseointegration and low endothelial compatibility. This study demonstrates the phototethering of collagen onto PEEK surfaces to facilitate osteoblastic and vascular endothelial performance. In particular, collagen with methacryloyl groups is covalently tethered to the PEEK surface via surface-initiated photopolymerization. This process is simpler than the conventional method of collagen-tethering and can be extended to the surface-patterning treatment of collagen. The collagen is confirmed to be tethered to the PEEK surface using attenuated total reflection Fourier transform infrared measurements, bicinchoninic acid assays, and atomic force microscopic observations. When human bone marrow-derived mesenchymal stem cells (HbmMSCs) are cultured on collagen-tethered PEEK (COL-PEEK) surfaces, the cells favorably adhere and proliferate. After inducing osteogenic differentiation, the cells on the COL-PEEK surfaces show higher expression levels of osteoblast-related genes and mineralization than those on the PEEK surface. Moreover, the tethering of collagen greatly improves endothelial proliferation. The COL-PEEK surfaces promotes endothelial networking in coculture with HbmMSCs. These results suggest that COL-PEEK is highly compatible with both osteoblasts and vascular endothelial cells. COL-PEEK is a promising implant that induces osteogenesis and angiogenesis to repair bone tissues.

Surface modification of polyetheretherketone (PEEK) to enhance osteointegration by grafting strontium Eucommia ulmoides polysaccharides

The complex bone regeneration microenvironment puts high demands on orthopedic implants. The implants are not only desired to satisfy the meeting of the biomechanical properties, but should also possess capabilities to promote osseointegration and bone immune regulation. PEEK is a promising polymeric material for bone implants due to its suitable mechanical properties that well match natural cortical bone tissue. However, its inert biological properties limit its application. As a newly-developed bioactive polysaccharides complex, strontium Eucommia ulmoides polysaccharides (EUP-Sr) has been proved to have capabilities including promoting osteogenesis and regulating bone immunity. In this study, in order to improve the bioactivities of PEEK, we introduce EUP-Sr to the PEEK surface via polydopamine-based coating and form a bioactive PEEK named DPEEK@EUP-Sr. The as-fabricated DPEEK@EUP-Sr was systematically investigated through scanning electron microscopy, X-ray photoelectron spectroscopy, water contact angle analysis to verify the successful introduction of EUP-Sr to PEEK, and in vitro biological experiments including cell proliferation and RT-PCR analysis suggested that the DPEEK@EUP-Sr can effectively promote the proliferation of preosteoblast MC3T3-E1, and exhibit significant anti-inflammation and osteogenesis effects, and so should be beneficial for osteointegration between bone and implants.

Ag-Incorporated Polydopamine/Tannic Acid Coating on Titanium With Enhanced Cytocompatible and Antibacterial Properties.

Titanium (Ti) and its alloys are the most commonly used materials for bone implants. However, implant failure often happens due to bacterial infection. Developing antibacterial coatings on Ti implants is an effective strategy. Dopamine and tannic acid were cross-linked to form coating on Ti through Michael addition and Schiff base reaction. In addition, the Ag ions were grafted on the coating by the redox reaction of phenolic hydroxyl groups. Thus, an Ag-incorporated polydopamine/tannic acid coating was prepared on Ti substrate. SEM, EDS, water contact angle, FTIR, and XRD results demonstrated that the coating was formed on Ti successfully. The antibacterial activity of the coating against Gram-negative E. coli was examined, and the cytotoxicity of the coating was investigated by mouse fibroblast cells. The improvement of hydrophilicity, good cytocompatibility, and antibacterial effectiveness indicates that the coating has potential to surface modification of Ti implants.

Impact of gadolinium on mechanical properties, corrosion resistance, and biocompatibility of Zn-1Mg-xGd alloys for biodegradable bone-implant applications

Zinc (Zn) and its alloys are currently regarded as one of the promising families of biodegradable metals for implant applications owing to their suitable biodegradability and biofunctionality. However, the inadequate mechanical properties of as-cast (AC) pure Zn restricted the practical clinical bone-implant applications due to its coarse grain size and hexagon close-packed crystal structure. Here, the impact of gadolinium (Gd) on the mechanical properties, corrosion resistance, hemolysis percentage, anticoagulant activity, and cytotoxicity of AC and hot-rolled (HR) Zn-1Mg-xGd (x = 0.1, 0.2, and 0.3) (wt.%) alloys were investigated for biodegradable bone-implant applications. Tensile testing showed that the HR Zn-1Mg-0.3Gd alloy exhibited the highest tensile strength of 288.1 MPa, tensile yield strength of 250.9 MPa, and elongation of 13.2%. Electrochemical corrosion and immersion tests revealed that the corrosion rates of both AC and HR specimens increased with increasing Gd content in Hanks’ solution, and the HR Zn-1Mg-xGd specimens exhibited higher corrosion rates compared to their AC counterparts. The HR Zn-1Mg-xGd specimens showed an increasing hemolysis percentages and decreasing activated partial thromboplastin time (APTT) values with increasing Gd addition. The alloy extracts of HR samples at ≤ 25% concentration exhibited no cytotoxicity toward MG-63 cells, and the HR Zn-1Mg-0.3Gd alloy displayed the highest cell viability among all three alloy extracts at 12.5% concentration. Overall, the HR Zn-1Mg-0.3Gd can be considered a promising biodegradable implant material for bone-implant materials owing to its high mechanical strength and ductility, suitable degradation rate, and satisfying biocompatibility. Statement of significanceIn this work, Zn-1Mg-xGd (x = 0.1, 0.2, and 0.3 wt.%) alloys were developed by alloying with gadolinium (Gd) and hot-rolling, and their mechanical properties, corrosion behavior, hemolysis percentage, anticoagulant activity, and cytotoxicity were investigated for biodegradable implant application. Our findings demonstrated that the hot-rolled Zn-1Mg-0.3Gd alloy exhibit the highest ultimate tensile strength of 288.1 MPa, yield strength of 250.9 MPa, and elongation of 13.2%. Hot-rolled Zn-1Mg-xGd alloys show slowly increasing hemolysis percentages and decreasing activated partial thromboplastin time (APTT) values with increasing Gd addition. Extracts of hot-rolled Zn-1Mg-xGd alloys at a concentration of ≤ 25% show no cytotoxicity towards MG-63 cells, and Zn-1Mg-0.3Gd exhibit good cytocompatibility among all three alloys at a concentration of 12.5%.

Obtaining Biocompatible Porous Composite Material Based on Zinc-Modified Hydroxyapatite and Lactide-Glycolide Copolymer

The development of surgery in the field of bone tissue reconstruction provides a stable demand for new materials for implants. Of particular interest are materials based on hydroxyapatite, which are close in chemical composition to the elemental composition and structure of bone and have similar biologically active properties. In this work, the regularities of the formation of new composite materials based on a zinc-modified hydroxyapatite framework coated with a copolymer of lactide and glycolide were revealed for the first time. The aim of this work was to obtain porous composite materials based on zinc-modified hydroxyapatite and a copolymer of lactide and glycolide with properties suitable for use as a material for bone implants. The phase and elemental composition of the composites was studied by infrared spectroscopy, X-ray diffraction, and X-ray spectral microanalysis. Regularities have been established between the surface properties and the composition of materials, as well as their biocompatibility, determined using monocytes isolated from human peripheral blood. The antibacterial activity of the materials against gram-positive and gram-negative bacteria was determined.

High-resolution ex vivo analysis of the degradation and osseointegration of Mg-xGd implant screws in 3D

Biodegradable magnesium (Mg) alloys can revolutionize osteosynthesis, because they have mechanical properties similar to those of the bone, and degrade over time, avoiding the need of removal surgery. However, they are not yet routinely applied because their degradation behavior is not fully understood.In this study we have investigated and quantified the degradation and osseointegration behavior of two biodegradable Mg alloys based on gadolinium (Gd) at high resolution.Mg-5Gd and Mg-10Gd screws were inserted in rat tibia for 4, 8 and 12 weeks. Afterward, the degradation rate and degradation homogeneity, as well as bone-to-implant interface, were studied with synchrotron radiation micro computed tomography and histology. Titanium (Ti) and polyether ether ketone (PEEK) were used as controls material to evaluate osseointegration.Our results showed that Mg-5Gd degraded faster and less homogeneously than Mg-10Gd. Both alloys gradually form a stable degradation layer at the interface and were surrounded by new bone tissue. The results were correlated to in vitro data obtained from the same material and shape. The average bone-to-implant contact of the Mg-xGd implants was comparable to that of Ti and higher than for PEEK. The results suggest that both Mg-xGd alloys are suitable as materials for bone implants.

Effect of Surface Roughness on the Properties of Titanium Materials for Bone Implants

Effect of Surface Roughness on the Properties of Titanium Materials for Bone Implants

Porous Ti6Al4V alloys with high strength-to-modulus ratio fabricated by unidirectional freeze casting of SiC fiber-containing slurry

Porous titanium alloys with high strength-to-modulus ratio are one of the promising materials for bone implants. In the present work, porous Ti6Al4V alloys with SiC fiber bridges and fiber reinforced wall structure were obtained by unidirectional freeze casting of SiC fiber-containing slurry. The effect of SiC fiber content on the pore structure, microstructure, interface and compressive properties was systematically investigated. The formations of fiber bridges and fiber reinforced wall structure were elaborated through analyzing the interaction between fibers and ice front. Addition of SiC fibers has significant effects on the porosity, structural wavelength, and pore morphology of porous alloys. Porosity increases with the increase in fiber content, and pore morphology changes from lamellar to dendritic. Porous Ti6Al4V alloys mainly contain equiaxed α and β phase. Crystalline phases of Ti5Si3 and TiC are present at the interface. Micropores are also observed on the fiber side close to the interface due to the Kirkendall effect. Both Young's modulus and yield stress increase with the increase in SiC fiber content, while they dramatically decrease at higher fiber content of 10 vol%. SiC fiber bridges and fiber reinforced wall structure have synergetic strengthening effects for suppressing buckling deformation of lamellar walls and thus for improving the strength of porous titanium alloys. Porous Ti6Al4V alloys fabricated by 2 vol% SiC fibers possess high porosity of 67% and high strength-to-modulus ratio of 0.027.