Design, Synthesis, and Preliminary Evaluation for Ti-Mo-Zr-Ta-Si Alloys for Potential Implant Applications

Heat Treatment's Vital Role: Elevating Orthodontic Mini-Implants for Superior Performance and Longevity-Pilot Study

Orthodontic mini-implants are devices used for anchorage in various orthodontic treatments. We conducted a pilot study which aimed to observe preliminary trends regarding the impact of heat treatment on the elastic modulus of Ti6Al4V alloy and stainless steel 316L mini-implants. The initial phase involved testing the impact of heat treatment on the mechanical properties of Ti6Al4V alloy and stainless steel 316L mini-implants.

MATERIAL AND METHODS

Ten self-drilling mini-implants sourced from two distinct manufacturers (Jeil Medical Corporation® and Leone®) with dimensions of 2.0 mm diameter and 10 mm length were tested. They were separated into two material groups: Ti6Al4V and 316L. Using the CETRUMT-2 microtribometer equipment, indentation testing was conducted employing a diamond-tipped Rockwell penetrator at a constant force of 4.5 N.

RESULTS

Slight differences were observed in the elastic modulus of the Ti6Al4V alloy (103.99 GPa) and stainless steel 316L (203.20 GPa) compared to natural bone. The higher elastic moduli of these materials indicate that they are stiffer, which could potentially lead to stress-shielding phenomena and bone resorption. Heat treatment resulted in significant changes in mechanical properties, including elastic modulus reductions of approximately 26.14% for Ti6Al4V and 24.82% for 316L, impacting their performance in orthodontic applications.

CONCLUSION

Understanding the effects of heat treatment on these alloys is crucial for optimizing their biomechanical compatibility and longevity in orthodontic treatment. To fully evaluate the effects of heat treatment on mini-implants and to refine their design and efficacy in clinical practice, further research is needed.

Research Progress of Titanium-Based Alloys for Medical Devices

Biomaterials are currently a unique class of materials that are essential to improving the standard of human life and extending it. In the assent of the appearance of biomaterials that contain non-toxic elements, in this study, we examine a system of Ti25Mo7Zr15TaxSi (x = 0, 0.5, 0.75, 1 wt.%) for future medical applications. The alloys were developed in a vacuum electric arc furnace and then studied from a structural, mechanical and in vivo assessment (on rabbits) perspective. The effect of the silicon addition was clearly seen in both the structural and the mechanical characteristics, standing out as beta alloys with a dendritic structure and lowering the mechanical properties as a result of the silicon addition. In experimental rabbits, the proliferation of mesenchymal stem cells was observed in the periosteum and peri-implant area, differentiating into osteoblasts and then into osteocytes. Osteoclasts were discovered within the cartilaginous islands that provide structural support to newly formed bone, playing a primary role in bone remodeling. The newly formed spongy tissue adhered to the fibrous capsule that surrounds the alloy, ensuring good osseointegration of metallic implants. The overexpression of Osteopontin, Metalloproteinase-2 (also known as gelatinase A), and Metallopeptidase-9 (also known as gelatinase B) underscores the processes of osteogenesis, bone mineralization, and normal bone remodeling.

Microstructural, Mechanical, and Electrochemical Characterization of CrMoNbTiZr High-Entropy Alloy for Biomedical Application

High-entropy alloys (HEA) with superior biocompatibility, high pitting resistance, minimal debris accumulation, and reduced release of metallic ions into surrounding tissues are potential replacements for traditional metallic bio-implants. A novel equiatomic HEA based on biocompatible metals, CrMoNbTiZr, was consolidated by spark plasma sintering (SPS). The relative sintered density of the alloy was about 97% of the theoretical density, indicating the suitability of the SPS technique to produce relatively dense material. The microstructure of the sintered HEA consisted of a BCC matrix and Laves phase, corresponding to the prediction of the thermodynamic CALPHAD simulation. The HEA exhibited a global Vickers microhardness of 531.5 ± 99.7 HV, while the individual BCC and Laves phases had hardness values of 364.6 ± 99.4 and 641.8 ± 63.0 HV, respectively. Its ultimate compressive and compressive yield strengths were 1235.7 ± 42.8 MPa and 1110.8 ± 78.6 MPa, respectively. The elasticity modulus of 34.9 ± 2.9 GPa of the HEA alloy was well within the range of cortical bone and significantly lower than the values reported for commonly used biomaterials made from Ti-based and Cr-Co-based alloys. In addition, the alloy exhibited good resistance to bio-corrosion in PBS and Hanks solutions. The CrMoNbTiZr HEA exhibited an average COF of 0.43 ± 0.06, characterized mainly by abrasive and adhesive wear mechanisms. The CrMoNbTiZr alloy's mechanical, bio-corrosion, and wear resistance properties developed in this study showed a good propensity for application as a biomaterial.

Effect of Si Contents on the Properties of Ti15Mo7ZrxSi Alloys

The main purpose of this research is to evaluate the mechanical characteristics and biocompatibility of two novel titanium alloys, Ti15Mo7ZrxSi (x = 0, 0.5, 0.75, 1). These samples had already undergone grinding, polishing, cutting, and chipping. Electrochemical, metallographic, three-point bending, and microhardness studies were conducted on the studied materials to determine their corrosion behavior, microstructure, Young's modulus, and hardness. The first investigations revealed that both samples had biphasic and dendritic structures, elastic moduli that were between the highest and minimum values achieved by around 20 GPa, and favorable behavior when in contact with physiological fluids at ambient temperature. Ti15Mo7Zr0.5Si and Ti15Mo7Zr0.75Si, the research samples, had greater corrosion potentials, reduced corrosion rates, and therefore higher corrosion resistance, as well as modulus of elasticity values that were comparable to and closer to those of human bone. The results of this investigation indicate that both alloys exhibit favorable corrosion behavior, great biocompatibility, Young's modulus results lower than those of conventional alloys used in biomedical implants, and hardness values higher than commercially pure titanium.

A Comprehensive Review of the Current Research Status of Biodegradable Zinc Alloys and Composites for Biomedical Applications

Zinc (Zn)-based biodegradable materials show moderate degradation rates in comparison with other biodegradable materials (Fe and Mg). Biocompatibility and non-toxicity also make them a viable option for implant applications. Furthermore, Pure Zn has poor mechanical behavior, with a tensile strength of around 100-150 MPa and an elongation of 0.3-2%, which is far from reaching the strength required as an orthopedic implant material (tensile strength is more than 300 MPa, elongation more than 15%). Alloy and composite fabrication have proven to be excellent ways to improve the mechanical performance of Zn. Therefore, their alloys and composites have emerged as an innovative category of biodegradable materials. This paper summarizes the most important recent research results on the mechanical and biological characteristics of biodegradable Zn-based implants for orthopedic applications and the most commonly added components in Zn alloys and composites.

Tensile Deformation and Fracture of Unreinforced AZ91 and Reinforced AZ91-C at Temperatures up to 300 °C

Magnesium alloys are still attractive materials for applications that necessitate light weight due to their low density, moderate strength, and good corrosion resistance. AZ91 is one of the widely applied magnesium alloys due to its very good castability and strength. However, one of the drawbacks of magnesium alloys is the low elastic modulus. So, reinforcing AZ91 with carbon short fibers with the aim of further increasing the strength and improving the elastic modulus is investigated in this study. Squeeze cast AZ91-23 vol.% carbon short carbon (AZ91-C) and the unreinforced AZ91 are deeply examined by tensile testing at different temperatures (20, 100, 150, 200, 250, and 300 °C). Tensile stress-strain curves are measured and the tensile parameters (yield stress, ultimate tensile strength and strain) are defined and presented against the test temperature. Yield stress of AZ91 at 20 °C (109 MPa) is doubled (226 MPa) in the reinforced AZ91-C. Yield stress is found to slightly decrease with increasing the test temperature. Ultimate tensile strength of AZ91 at 20 °C (198 MPa) is increased (262 MPa) in the reinforced AZ91-C. The improvement of the ultimate tensile strength due to reinforcing increases with increasing the test temperature. Flow curves are determined and described by a modified Mecking-Kocks relationship and the flow parameters are determined and described as a function of the test temperature. Microstructure investigation was undertaken of the fractured tensile specimens at the grain boundaries rich in eutectic structure formed at the grain boundaries. Mixed brittle/ductile fracture mode is detected on the fracture surface of unreinforced AZ91, while the SEM investigations show matrix/carbon fiber detachment and fiber fracture as main fracture modes.

Analysis of Degradation Products of Biodegradable ZnMgY Alloy

Biodegradable metallic materials are increasingly gaining ground in medical applications. Zn-based alloys show a degradation rate between those recorded for Mg-based materials with the fastest degradation rate and Fe-based materials with the slowest degradation rate. From the perspective of medical complications, it is essential to understand the size and nature of the degradation products developed from biodegradable materials, as well as the stage at which these residues are eliminated from the body. This paper presents investigations conducted on the corrosion/degradation products of an experimental material (ZnMgY alloy in cast and homogenized state) after immersion tests in three physiological solutions (Dulbecco's, Ringer's and simulated body fluid (SBF)). Scanning electron microscopy (SEM) was used to highlight the macroscopic and microscopic aspects of corrosion products and their effects on the surface. An X-ray energy dispersive detector (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) provided general information about the compounds based on their non-metallic character. The pH of the electrolyte solution was recorded for 72 h during immersion. The pH variation of the solution confirmed the main reactions proposed for the corrosion of ZnMg. The agglomerations of corrosion products were on the micrometer scale, mainly oxides, hydroxides and carbonates or phosphates. The corrosion effects on the surface were homogeneously spread, with a tendency to connect and form cracks or larger corrosion zones, transforming the pitting corrosion pattern into a generalized one. It was noticed that the alloy's microstructure strongly influences the corrosion characteristics.

Biodegradable Cements for Bone Regeneration

Bone cements such as polymethyl methacrylate and calcium phosphates have been widely used for the reconstruction of bone. Despite their remarkable clinical success, the low degradation rate of these materials hampers a broader clinical use. Matching the degradation rate of the materials with neo bone formation remains a challenge for bone-repairing materials. Moreover, questions such as the mechanism of degradation and how the composition of the materials contribute to the degradation property remain unanswered. Therefore, the review provides an overview of currently used biodegradable bone cements such as calcium phosphates (CaP), calcium sulfates and organic-inorganic composites. The possible degradation mechanism and clinical performance of the biodegradable cements are summarized. This paper reviews up-to-date research and applications of biodegradable cements, hoping to provide researchers in the field with inspirations and references.

Antimicrobial Properties of TiNbSn Alloys Anodized in a Sulfuric Acid Electrolyte

TiNbSn alloy is a high-performance titanium alloy which is biosafe, strong, and has a low Young's modulus. TiNbSn alloy has been clinically applied as a material for orthopedic prosthesis. Anodized TiNbSn alloys with acetic and sulfuric acid electrolytes have excellent biocompatibility for osseointegration. Herein, TiNbSn alloy was anodized in a sulfuric acid electrolyte to determine the antimicrobial activity. The photocatalytic activities of the anodic oxide alloys were investigated based on their electronic band structure and crystallinity. In addition, the cytotoxicity of the anodized TiNbSn alloy was evaluated using cell lines of the osteoblast and fibroblast lineages. The antimicrobial activity of the anodic oxide alloy was assessed according to the ISO 27447 using methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli. The anodic oxide comprised rutile and anatase titanium dioxide (TiO₂) and exhibited a porous microstructure. A well-crystallized rutile TiO₂ phase was observed in the anodized TiNbSn alloy. The methylene blue degradation tests under ultraviolet illumination exhibited photocatalytic activity. In antimicrobial tests, the anodized TiNbSn alloy exhibited robust antimicrobial activities under ultraviolet illumination for all bacterial species, regardless of drug resistance. Therefore, the anodized TiNbSn alloy can be used as a functional biomaterial with low Young's modulus and excellent antimicrobial activity.

Phase Equilibria of the Ti-Nb-Mn Ternary System at 1173K, 1273K and 1373K

Phase equilibria in the Ti-Nb-Mn ternary system at 1173K, 1273K and 1373K were studied through the equilibrated alloy method by using scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) techniques. A new stable ternary phase K was confirmed and the composition was around Ti50Nb7Mn43. A wide-range continuous solid solution phase (Ti,Nb)Mn2 with the C14 Laves structure had been found at these temperatures due to the same phase structures of TiMn2 and NbMn2 phases. The solubility of Nb in TiMn4, αTiMn and βTiMn intermetallic compounds was determined. Based on the experimental results and reasonable extrapolations, the isothermal sections of Ti-Nb-Mn ternary system at 1173K, 1273K and 1373K were constructed.

Microstructural Features and Microhardness of the Ti-6Al-4V Alloy Synthesized by Additive Plasma Wire Deposition Welding

Wire arc additive manufacturing (AM) is able to replace the traditional manufacturing processes of Ti alloys. At the same time, the common drawback of Ti workpieces produced by AM via wire deposition welding is the formation of a coarse-grained dendritic structure, its strong anisotropy and, consequently, lower strength as compared to a monolithic alloy. In this work, a new method is proposed for the enhancement of the strength properties of the Ti-6Al-4V alloy synthesized by AM via wire deposition welding, which involves the use of a wire with an initial ultrafine-grained (UFG) structure. The UFG wire is characterized by a large number of defects of the crystalline lattice and grain boundaries, which will enable increasing the number of "crystallization centers" of the α-phase, leading to its refinement. The macro- and microstructure, phase composition and microhardness of the Ti-6Al-4V alloy samples were investigated. The microhardness of the alloy produced by layer-by-layer deposition welding using a UFG wire was shown to be on average 20% higher than that of the samples produced by a deposition welding using a conventional wire. The nature of this phenomenon is discussed, as well as the prospects of increasing the mechanical characteristics of Ti alloys produced by additive manufacturing.

Experimental Research on New Developed Titanium Alloys for Biomedical Applications

The mechanical properties and electrochemical behavior of two new titanium alloys, Ti20Mo7Zr and Ti20Mo7Zr0.5Si, are investigated in this paper. The alloys have been manufactured by vacuum arc remelting (VAR) technique and studied to determine their microstructure, corrosion behavior, and mechanical properties. Metallographic observations and quantitative microanalysis by optical microscopy, scanning electron microscopy SEM, and energy dispersive X-rays spectroscopy EDX were performed. Data about the three-point bending test and microhardness are presented. For electrochemical properties, three different environments were used: Ringer solution at 25 °C, Ringer solution at 40 °C simulating fever condition, and 3.5% NaCl solution. Metallographic investigation revealed the biphasic and dendritic structure of both samples when the procedures were performed. Electrochemical testing in body simulation fluid, fever conditions, and saline medium showed that the lower the proportion of silicon in the samples, the higher the corrosion resistance. The formation of a titanium oxide layer on the surface of both samples was noticed using quantitative EDX analysis. The three-point bending test for the two samples revealed that the presence of silicon decreases the modulus of elasticity; the surface of the samples displayed soft and hard phases in the microhardness test. Electrochemical impedance spectroscopy (EIS) measurements were carried out at different potentials, and the obtained spectra exhibit a two-time constant system, attesting double-layer passive film on the samples.

Smart Web Service of Ti-Based Alloy’s Quality Evaluation for Medical Implants Manufacturing

The production of biocompatible medical implants is accompanied by technological and time costs. As a result, to be used in the human body, such a product must be of the highest quality. Assessing the quality of biomedical implants made of titanium alloys is relevant given their impact on the health and life of their wearer. In the case of the production of such implants by additive technologies, an important task is to evaluate the properties of the alloys from which it is made. The modern development of Artificial Intelligence allows replacing traditional assessment methods with machine learning methods for such assessment. Existing machine learning methods demonstrate very low classification accuracy, and existing hybrid systems, although increasing classification accuracy, are not sufficient to apply such schemes in practice. The authors improved the hybrid PNN-SVM system to solve this problem in this paper. It is based on the combining use of PNN, Ito Decomposition, and SVM. The PNN’s summation layer outputs were used as additional attributes to an initial dataset. Ito decomposition was used to nonlinearly model relationships between features of an extended dataset. Further classification is carried out using SVM with a linear kernel. The proposed approach’s modeling is performed based on a real-world dataset using the smart web service designed by the authors. Experimentally found an increase in the classification accuracy by 6% of the proposed system compared to existing ones. It makes it possible to use it in practice. Designed smart web service, in which the authors implemented both improved and existing hybrid classification schemes allows to quickly, easily, and without high qualification of the user to implement and explore in more detail chosen classification scheme when classification tasks in various fields of industry.