Characteristics of novel Ti-40Nb-xCu alloy and surface treatment with superior antibacterial property and biocompatibility using micro-arc oxidation for dental implants.

Peri-implantitis and insufficient osseointegration are the principal challenges faced by dental implants at present. In order to fabricate dual-function dental implant materials possessing both antibacterial and osteogenic capabilities, this study incorporates the antimicrobial element Cu into the Ti40Nb alloy, developing a novel Ti40Nb-xCu alloy with antibacterial properties. Among them, Ti40Nb3Cu has the best overall performance. Compared to Ti40Nb, the tensile strength increased by 27.97%, reaching 613 MPa. Although the elongation rate has decreased from 23% to 13.5%, the antibacterial rates against S. aureus and P. gingivalis both exceed 85%. Furthermore, the surface of Ti40Nb-xCu alloy was then treated with micro-arc oxidation to enhance its bioactivity, thereby accelerating osseointegration. The results indicated that the MAO treatment retains the antibacterial properties of the Ti40Nb3Cu alloy while significantly promoting bone formation through its introduced porous coating, thus heralding it as a propitious candidate material for dental implant applications.

The Mg doping ZIF-8 loaded with Icariin and its antibacterial and osteogenic performances.

In this study, ICA@Mg-ZIF-8 was synthesized by Mg doping in ZIF-8 and loaded with icariin (ICA). The morphologies and phases were observed and analyzed by SEM, XRD, and the release behaviors of Mg, Zn ions and ICA were tested. Its antibacterial and mineralization performances were evaluated. The results showed that ICA@Mg-ZIF-8 has the same morphology and crystal structure as ZIF-8. ICA@Mg-ZIF-8 showed enhanced antibacterial activity against Escherichia coli and Staphylococcus aureus, and the antibacterial rate was increased to 87.7 % and 64.0 %, respectively. The results of in vitro mineralization showed that ICA@Mg-ZIF-8 presented better osteogenic performance promoting the uniform deposition of more calcium and phosphorus in simulated body fluids compared to ZIF-8.

Evolution of the Strengthening Effects of In Situ TiB Fibers in a Ti Composite with Various Levels of Thermal Processing.

Thermal processing is a useful method for improving the strengthening effects of fibers used to reinforce metal matrix composites (MMCs), but the corresponding models have not been constructed. In this work, a Ti matrix composite (TMC) reinforced by in situ TiB fibers was prepared, then thermal processing was applied to it at different levels of deformation to align the TiB fibers along the loading direction. Changes in the microstructure of the matrix, the orientation and the aspect ratio of the TiB fibers during this process were investigated. It was found that the aspect ratio of TiB fibers decreased sharply after a large amount of deformation. The strengthening effect of TiB fibers in the composite was simulated by strengthening models of the fibers, and the simulated results were verified by the results of tensile tests. The modeled results show that the strengthening factor (C0) of the in situ TiB fibers improved from 0.125 in the as-cast composite to 0.520, 0.688 and 0.858 by the processes with deformation ratios of 0.39, 0.26 and 0.14, respectively. The results of the tensile tests showed that the measured values of C0 gradually deviated from the modeled ones with an increase in the ratio of deformation applied during processing, and the deviation could be interpreted with the strengthening models.

Design and evaluation of a novel biodegradable inferior vena cava filter.

Inferior vena cava filter has been increasingly applied in clinical practice to prevent pulmonary embolism. Nowadays, various complications after implanting conventional filters seriously hinder clinical applications. Therefore, in this paper, a novel biodegradable inferior vena cava filter was designed based on biodegradable materials, which is an hourglass-like filter anchored inside a stent structure fixed by connecting fibers. Firstly, mechanical tests in crimp were performed to study the expansion properties of the filter, showing that the biodegradable inferior vena cava filter could achieve self-expansion easily. Furthermore, the biodegradable inferior vena cava filters and fibers were incubated in phosphate buffer media (pH = 7.4 ± 0.2) at 37°C for six months. Scanning electron microscope micrograph showed that the stents exhibited no significant dimensional and structural changes and had enough radial force to support the vessel. During the degradation period, the results of scanning electron microscope, gel permeation chromatography, differential scanning calorimetry and tensile strength analysis confirmed that the degradation rate of the hourglass-like filter was faster than the connecting fibers, achieving progressive degradation and thus avoiding the polymer fragments from blocking vessel. Cytotoxicity and hemolysis assay demonstrated good biocompatibility of the filter. For 5 mm × 10 mm sized thrombus, in vitro simulated thrombus capture test showed that the mean trapping efficiency of the filter was 90%, which was comparable to traditional inferior vena cava filter. In conclusion, all results exhibited that the as-designed biodegradable inferior vena cava filter has a potential in clinical application for patients who are at temporary high risk of venous thromboembolism.

Effects of Silicon Content on the Microstructures and Mechanical Properties of (AlCrTiZrV)-Six-N High-Entropy Alloy Films.

A series of (AlCrTiZrV)-Six-N films with different silicon contents were deposited on monocrystalline silicon substrates by direct-current (DC) magnetron sputtering. The films were characterized by the X-ray diffractometry (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and nano-indentation techniques. The effects of the silicon content on the microstructures and mechanical properties of the films were investigated. The experimental results show that the (AlCrTiZrV)N films grow in columnar grains and present a (200) preferential growth orientation. The addition of the silicon element leads to the disappearance of the (200) peak, and the grain refinement of the (AlCrTiZrV)-Six-N films. Meanwhile, the reticular amorphous phase is formed, thus developing the nanocomposite structure with the nanocrystalline structures encapsulated by the amorphous phase. With the increase of the silicon content, the mechanical properties first increase and then decrease. The maximal hardness and modulus of the film reach 34.3 GPa and 301.5 GPa, respectively, with the silicon content (x) of 8% (volume percent). The strengthening effect of the (AlCrTiZrV)-Six-N film can be mainly attributed to the formation of the nanocomposite structure.

Microstructures, mechanical behavior and strengthening mechanism of TiSiCN nanocomposite films.

Currently, the arguments have existed in the strengthening mechanism and microstructural model of the nanocomposite film due to lack of the convincible experimental evidences. In this investigation, the quarternary TiSiCN nanocomposite films with the different C and Si contents are synthesized by the reactive-magnetron-sputtering technique. The TiSiCN film is characterized as the nanocomposite structure with the TiN nanocrystallites surrounded by the (Si3N4 + C + CNx) interface phase. When the C/Si content ratio is 2:2, the TiSiCN nanocomposite film is remarkably strengthened with the maximal hardness and elastic modulus of 46.1 GPa and 425 GPa, respectively. Meanwhile, the (Si3N4 + C + CNx) interfaces exhibit as a crystallized form, which can coordinate the growth misorientations and maintain the coherently epitaxial growth between the TiN nanocrystallites and interfaces. Through the high-resolution transmission electron microscopy (HRTEM) observations, this investigation firstly provides the direct experimental evidence for the crystallized feature of the interfaces when the TiSiCN nanocomposite film is strengthened, suggesting that the strengthening effect of the TiSiCN nanocomposite film can be attributed to the coherent-interface strengthening mechanism, which is expressed as the "nc-TiN/c-Si3N4/c-C/c-CNx" model.

The mechanical behavior dependence on the TiB whisker realignment during hot-working in titanium matrix composites.

Low-cost TiB whiskers reinforced titanium matrix composite (TMCs) was fabricated with enhanced mechanical performances using in situ technologies and hot working. Morphologies observation indicates that needle-like TiB whiskers with a hexagonal transverse section grow along the [010] direction due to B27 crystal structure and its growth mechanism. Mechanical properties tests show that the mechanical behavior of the TiB whiskers reinforced TMCs is dependent on the deformation amplitudes applied in hot-working. The improvement in yield strength by hot-working is attributed to the TiB whiskers realignment and the refinement of microstructure. Models are constructed to evaluate the realignment of TiB whisker during deformation and the increase in yield strength of the composite at elevated temperatures. These models clarify the alignment effect of TiB whiskers under various deformation amplitudes applied in hot-workings and reveals the yield strength dependence on TiB whiskers orientation.

Improvement of ß-TCP/PLLA biodegradable material by surface modification with stearic acid.

Poly-L-lactide (PLLA) is a biodegradable polymer and used widely. Incorporation of beta tricalcium phosphate (ß-TCP) into PLLA can enhance its osteoinductive properties. But the interfacial layer between ß-TCP particles with PLLA matrix is easy to be destroyed due to inferior interfacial compatibility of the organic/inorganic material. In this work, a method of ß-TCP surface modification with stearic acid was investigated to improve the ß-TCP/PLLA biomaterial. The effects of surface modification on the ß-TCP were investigated by FTIR, XPS, TGA and CA. It was found that the stearic acid reacted with ß-TCP and oxhydryl was formed during the surface modification. Hydrophilicity of untreated or modified ß-TCP/PLLA composite was increased by the addition of 10 wt.% ß-TCP, but it decreased as the addition amount increased from 10 wt.% to 20 wt.%. Two models were suggested to describe the effect of ß-TCP concentration on CA of the composites. Mechanical properties of ß-TCP/PLLA composites were tested by bending and tensile tests. Fractures of the composites after mechanical test were observed by SEM. It was found that surface modification with stearic acid improved bending and tensile strengths of the ß-TCP/PLLA composites obviously. The SEM results indicated that surface modification decreased the probability of interface debonding between fillers and matrix under load.

A comparison between a hinged plate and screw system and a conventional tension-band plate and screw system used for correction of an angular deformity of the lower limb: an animal study.

BACKGROUND: The purpose of the animal study is to introduce a newly designed hinged plate and screw system for correction of angular deformities of the lower limbs. The technique was compared with the use of a conventional tension-band plate and screw system. METHODS: This is a randomized controlled animal trial. Eight 3-month-old Bama miniature pigs were used to establish animal models. In each animal, one leg was randomly allocated into study group and another leg into control group. Legs of the study group were corrected with a hinged plate and screw system, and legs of the control group were corrected with a conventional tension-band plate and screw system. The corrective rates of medial slope angle, medial proximal tibial angle, and angle of the two arms of the hinged plate were measured. Residual stress on the implants was also evaluated. A P < 0.05 was statistical significant. RESULTS: At the final measurements of 18 weeks, the mean corrective rates of medial slope angle, medial proximal tibial angle, and angle of the two arms of the study group were 0.71°/week, 0.85°/week, and 2.18°/week, respectively; the data in the control group were 0.84°/week, 0.89°/week, and 2.13°/week, respectively. No significant difference was found between the groups regarding the mean corrective rates of the angles (P < 0.05). The mean residual stress in the study group was 643.35 MPa, and measurement in the control group was 1,273.63 MPa, with a significant difference (P < 0.05). CONCLUSIONS: Compared to the conventional tension-band plate and screw system, the hinged plate and screw system may be more reliable for correction of angular deformities of the lower limb.

Martensitic transformation of FeNi nanofilm induced by interfacial stress generated in FeNi/V nanomultilayered structure.

FeNi/V nanomultilayered films with different V layer thicknesses were synthesized by magnetron sputtering. By adjusting the thickness of the V layer, different interfacial compressive stress were imposed on FeNi layers and the effect of interfacial stress on martensitic transformation of the FeNi film was investigated. Without insertion of V layers, the FeNi film exhibits a face-centered cubic (fcc) structure. With the thickness of V inserted layers up to 1.5 nm, under the coherent growth structure in FeNi/V nanomultilayered films, FeNi layers bear interfacial compressive stress due to the larger lattice parameter relative to V, which induces the martensitic transformation of the FeNi film. As the V layer thickness increases to 2.0 nm, V layers cannot keep the coherent growth structure with FeNi layers, leading to the disappearance of interfacial compressive stress and termination of the martensitic transformation in the FeNi film. The interfacial compressive stress-induced martensitic transformation of the FeNi nanofilm is verified through experiment. The method of imposing and modulating the interfacial stress through the epitaxial growth structure in the nanomultilayered films should be noticed and utilized.

New understanding of hardening mechanism of TiN/SiNx-based nanocomposite films.

In order to clarify the controversies of hardening mechanism for TiN/SiNx-based nanocomposite films, the microstructure and hardness for TiN/SiNx and TiAlN/SiNx nanocomposite films with different Si content were studied. With the increase of Si content, the crystallization degree for two series of films firstly increases and then decreases. The microstructural observations suggest that when SiNx interfacial phase reaches to a proper thickness, it can be crystallized between adjacent TiN or TiAlN nanocrystallites, which can coordinate misorientations between nanocrystallites and grow coherently with them, resulting in blocking of the dislocation motions and hardening of the film. The microstructure of TiN/SiNx-based nanocomposite film can be characterized as the nanocomposite structure with TiN-based nanocrystallites surrounded by crystallized SiNx interfacial phase, which can be denoted by nc-TiN/c-SiNx model ('c' before SiNx means crystallized) and well explain the coexistence between nanocomposite structure and columnar growth structure within the TiN/SiNx-based film.