The significance of thermomechanical processing on the cellular response of biomedical Co-Cr-Mo alloys.

Strengthening of biomedical Co-Cr-Mo alloys has been explored via thermomechanical processing for enhancing the durability of their biomedical applications. However, the effects of cold and hot deformation on the cellular activity continue to be unclear. In this study, we prepared Co-Cr-Mo alloy rods via cold swaging and hot-caliber rolling and studied the relationship between the microstructure and cellular response of pre-osteoblasts.

Favorable modulation of osteoblast cellular activity on Zr-modified Co-Cr-Mo alloy: The significant impact of zirconium on cell-substrate interactions.

Cobalt-chromium-molybdenum alloys exhibit good mechanical properties (yield strength: ~530 MPa, ultimate tensile strength: ~1114 MPa, elongation-to-failure: ~47.3%, and modulus: ~227 GPa) and corrosion resistance. In recent years, from the perspective of osseointegration, they are considered to be lower in rank in comparison to the widely used titanium alloys.

Tuning strain-induced γ-to-ε martensitic transformation of biomedical Co-Cr-Mo alloys by introducing parent phase lattice defects.

In this study, we examined the effect of pre-existing dislocation structures in a face-centered cubic γ-phase on strain-induced martensitic transformation (SIMT) to produce a hexagonal close-packed ε-phase in a hot-rolled biomedical Co-Cr-Mo alloy. The as-rolled microstructure was characterized by numerous dislocations as well as stacking faults and deformation twins. SIMT occurred just after macroscopic yielding in tensile deformation.

Impact of minor alloying with C and Si on the precipitation behavior and mechanical properties of N-doped Co-Cr alloy dental castings.

The addition of carbon and silicon as minor alloying elements was examined as a means to improve the mechanical properties of novel nitrogen-doped Co-Cr-based alloy dental castings. Samples of Co-32Cr-9W-Si-0.25N-C (mass%) alloys were prepared using a dental-casting machine.

Effect of nitrogen on the microstructure and mechanical properties of Co-33Cr-9W alloys prepared by dental casting.

The effect of nitrogen concentration on the mechanical properties of Co-33Cr-9W alloy dental castings fabricated using the "high-Cr and high-N" concept was investigated. Microstructural analysis was performed on the alloys, and findings were discussed in relation to the mechanical properties. Owing to their high nitrogen concentrations (0.

Stacking-fault strengthening of biomedical Co-Cr-Mo alloy via multipass thermomechanical processing.

The strengthening of metallic biomaterials, such as Co-Cr-Mo and titanium alloys, is of crucial importance to the improvement of the durability of orthopedic implants. In the present study, we successfully developed a face-centered cubic (fcc) Co-Cr-Mo alloy with an extremely high yield strength (1400 MPa) and good ductility (12%) by multipass hot-rolling, which is suitable for industrial production, and examined the relevant strengthening mechanisms. Using an X-ray diffraction line-profile analysis, we revealed that a substantial increase in the number of stacking faults (SFs) in the fcc γ-matrix occurred at a greater height reduction (r), while physical modeling demonstrated that the contribution of the accumulated SFs (i.

Development of microstructure and mechanical properties during annealing of a cold-swaged Co-Cr-Mo alloy rod.

In this study, we investigated the evolution of the microstructure and mechanical properties during annealing of a cold-swaged Ni-free Co-Cr-Mo alloy for biomedical applications. A Co-28Cr-6Mo-0.14N-0.

Characterisation of nanoscale carbide precipitation in as-cast Co-Cr-W-based dental alloys.

Carbide precipitation in biomedical Co-Cr alloys significantly influences the performance in terms of mechanical properties and corrosion resistance. In this study, we examined the carbide precipitation associated with local solute partitioning in as-cast Co-Cr-W-based dental alloys at the micro- and nano-scale. Co-28Cr-9W-1Si (mass%) alloys with carbon concentrations ranging from 0.

Manufacturing of high-strength Ni-free Co-Cr-Mo alloy rods via cold swaging.

The strengthening of biomedical metallic materials is crucial to increasing component durability in biomedical applications. In this study, we employ cold swaging as a strengthening method for Ni-free Co-Cr-Mo alloy rods and examine its effect on the resultant microstructures and mechanical properties. N is added to the alloy to improve the cold deformability, and a maximum reduction in area (r) of 42.

Preventing high-temperature oxidation of Co-Cr-based dental alloys by boron doping.

Biomedical Co-Cr-based alloys used in dental restorations are usually subjected to high-temperature treatments during manufacturing. Therefore, it is practically essential to characterise and control the oxide films formed on the surfaces of these alloys during heat treatment in terms of material loss, the accuracy of fit, and the aesthetics of dental restorations. In this work, the effects of boron doping on the surface oxide films formed on Ni-free Co-28Cr-9W-1Si (mass%) dental alloys under short-term exposure to high temperatures, which simulate the manufacturing process of porcelain-fused-to-metal (PFM) restorations, were investigated.

Developing high strength and ductility in biomedical Co-Cr cast alloys by simultaneous doping with nitrogen and carbon.

Unlabelled: There is a strong demand for biomedical Co-Cr-based cast alloys with enhanced mechanical properties for use in dental applications. We present a design strategy for development of Co-Cr-based cast alloys with very high strength, comparable to that of wrought Co-Cr alloys, without loss of ductility. The strategy consists of simultaneous doping of nitrogen and carbon, accompanied by increasing of the Cr content to increase the nitrogen solubility.

Cold-rolling behavior of biomedical Ni-free Co-Cr-Mo alloys: Role of strain-induced ε martensite and its intersecting phenomena.

Ni-free Co-Cr-Mo alloys are some of the most difficult-to-work metallic materials used commonly in biomedical applications. Since the difficulty in plastically deforming them limits their use, an in-depth understanding of their plastic deformability is of crucial importance for both academic and practical purposes. In this study, the microstructural evolution of a Co-29Cr-6Mo-0.

Strengthening of biomedical Ni-free Co-Cr-Mo alloy by multipass "low-strain-per-pass" thermomechanical processing.

Unlabelled: Further strengthening of biomedical Co-Cr-Mo alloys is desired, owing to the demand for improvements to their durability in applications such as artificial hip joints, spinal rods, bone plates, and screws. Here, we present a strategy-multipass "low-strain-per-pass" thermomechanical processing-for achieving high-strength biomedical Co-Cr-Mo alloys with sufficient ductility. The process primarily consists of multipass hot deformation, which involves repeated introduction of relatively small amounts of strain to the alloy at elevated temperatures.

Texture evolution and mechanical anisotropy of biomedical hot-rolled Co-Cr-Mo alloy.

Crystallographic textures and their effect on the mechanical anisotropy of a hot-rolled biomedical Co-Cr-Mo alloy were investigated. The hot-rolled Co-28Cr-6Mo-0.13N (mass%) alloy examined here exhibited a monotonic strength increment following hot-rolling reduction, eventually reaching a 0.

Assessment of precipitation behavior in dental castings of a Co-Cr-Mo alloy.

This study investigated solute portioning and precipitation in dental castings of a Co-Cr-Mo alloy and discussed their effects on alloy performance, in particular, the mechanical properties. Samples of a commercial Co-29Cr-6Mo (mass%) alloy were prepared using a dental-casting machine. The precipitates formed owing to the partitioning behaviors of the alloying elements were investigated using scanning electron microscopy, electron backscatter diffraction analysis, electron probe microanalysis, and transmission electron microscopy.

Effect of carbon on the microstructure, mechanical properties and metal ion release of Ni-free Co-Cr-Mo alloys containing nitrogen.

This paper investigated the effect of carbon addition on the microstructure and tensile properties of Ni-free biomedical Co-29Cr-6Mo (mass%) alloys containing 0.2 mass% nitrogen. The release of metal ions by the alloys was preliminarily evaluated in an aqueous solution of 0.

Functions of miR-1 and miR-133a during the postnatal development of masseter and gastrocnemius muscles.

The present study investigated the function of miR-1 and miR-133a during the postnatal development of mouse skeletal muscles. The amounts of miR-1 and miR-133a were measured in mouse masseter and gastrocnemius muscles between 1 and 12 weeks after birth with real-time polymerase chain reaction and those of HDACs, MEF2, MyoD family, MCK, SRF, and Cyclin D1 were measured at 2 and 12 weeks with Western blotting. In both the masseter and gastrocnemius muscles, the amount of miR-1 increased between 1 and 12 weeks, whereas the amount of HADC4 decreased between 2 and 12 weeks.

Analysis of the Fracture Mechanism of Ti-6Al-4V Alloy Rods That Failed Clinically After Spinal Instrumentation Surgery.

Study Design: Retrieval analysis of 2 Ti-6Al-4V alloy rods that fractured after spinal instrumentation surgery.

Objective: To determine the mechanism that underlies fractures of Ti-6Al-4V alloy rods after spinal instrumentation surgery from a materials science viewpoint.

Summary Of Background Data: Rod failures after spinal instrumentation surgery are often reported and many case-based studies have been published.

Influence of carbon addition on mechanical properties and microstructures of Ni-free Co-Cr-W alloys subjected to thermomechanical processing.

We report the effects of carbon concentration on the microstructures and tensile deformation behaviors of thermomechanically processed Ni-free Co-29Cr-9W-1Si-C (mass%) alloys designed for use as disk materials in CAD/CAM dental technology. The alloy specimens, which contained carbon in different concentrations, were prepared by casting and subsequent hot rolling. Overall, the developed Ni-free alloys with added carbon showed an excellent combination of high strength and high ductility.

Effects of carbon concentration on microstructure and mechanical properties of as-cast nickel-free Co-28Cr-9W-based dental alloys.

We determined the effects of carbon concentration on the microstructures and tensile properties of the Ni-free Co-29Cr-9W-1Si-C (mass%) cast alloys used in dental applications. Alloy specimens prepared with carbon concentrations in the range 0.01-0.

Local strain evolution due to athermal γ→ε martensitic transformation in biomedical CoCrMo alloys.

Locally developed strains caused by athermal γ face-centered cubic (fcc)→ε hexagonal close-packed (hcp) martensitic transformation were investigated for the γ matrix of Ni-free Co-29Cr-6Mo (wt%) alloys prepared with or without added nitrogen. Electron-backscatter-diffraction-(EBSD)-based strain analysis revealed that in addition to ε-martensite interiors, the N-free alloy that had a duplex microstructure consisting of the γ matrix and athermal ε-martensite plates showed larger magnitudes of both elastic and plastic strains in the γ phase matrix than the N-doped counterpart that did not have a ε-martensite phase. Transmission electron microscopy (TEM) results indicated that the ε-martensite microplates were aggregates of thin ε-layers, which were formed by three different {111}γ〈112¯〉γ Shockley partial dislocations in accordance with a previously proposed mechanism (Putaux and Chevalier, 1996) that canceled the shear strains of the individual variants.

Effects of nitrogen addition on microstructure and mechanical behavior of biomedical Co-Cr-Mo alloys.

In the present study, the microstructures and tensile deformation behaviors of biomedical Co-29Cr-6Mo (wt%) alloys containing different concentrations of nitrogen (0-0.24wt%) were systematically investigated. As the nitrogen concentration increased, the volume fraction of athermal ε martensite decreased, because nanoprecipitates hindered the formation of stacking faults (SFs) by acting as obstacles to Shockley partial dislocation formation, and athermal ε martensite usually forms through the regular overlapping of SFs.

Nanoarchitectured Co-Cr-Mo orthopedic implant alloys: nitrogen-enhanced nanostructural evolution and its effect on phase stability.

Our previous studies indicate that nitrogen addition suppresses the athermal γ (face-centered cubic, fcc)→ε (hexagonal close-packed, hcp) martensitic transformation of biomedical Co-Cr-Mo alloys and ultimately offers large elongation to failure while maintaining high strength. In the present study, structural evolution and dislocation slip as an elementary process in the martensitic transformation in Co-Cr-Mo alloys were investigated to reveal the origin of their enhanced γ phase stability due to nitrogen addition. Alloy specimens with and without nitrogen addition were prepared.

Seasonal and environmental changes of mycorrhizal associations and heterotrophy levels in mixotrophic Pyrola japonica (Ericaceae) growing under different light environments.

Premise Of The Study: Mixotrophy is a strategy whereby plants acquire carbon both through photosynthesis and heterotrophic exploitation of mycorrhizal fungi. In Euro-American Pyroleae species studied hitherto, heterotrophy levels vary according to species, sites of study, and possibly light conditions. We investigated mycorrhizal association and mixotrophy in the Asiatic forest species Pyrola japonica, and their plasticity under different light conditions.

The effect on intracytoplasmic sperm injection outcome of genotype, male germ cell stage and freeze-thawing in mice.

Background: Intracytoplasmic sperm injection (ICSI) has been widely used to study the mechanisms of mammalian fertilization and to rescue male-factor infertility in humans and animals. However, very few systematic analyses have been conducted to define factors affecting the efficiency of ICSI. In this study, we undertook a large-scale series of ICSI experiments in mice to define the factors that might affect outcomes.