Temporary Implants Research Articles

Fabrication and characterization of new hot extruded ZK60/CNTs+AgNPs nanocomposites for biomedical applications

Magnesium (Mg), with properties such as biodegradability and having a density and elasticity coefficient close to the bones of the body, has attracted a lot of attention as a serious option for orthopedic applications. However, the low compressive strength of Mg compared to the human bone and its weak antibacterial function limit its applications as a substitute for temporary implants to be used under load-bearing conditions. The aim of this paper is to evaluate the synergistic effect of CNTs + AgNPs nanofillers on the in vitro degradation, mechanical and antibacterial behavior of new ZK60/xCNTs + xAgNPs(x: 0, 0.25, 0.5, 1) composites made using semi powder metallurgy, followed by hot extrusion method. The ZK60/0.5CNTs+0.5 AgNPs (CA2) composite boasts a higher ultimate compressive strength (UCS) of 371 ± 15 MPa compared to 297 ± 6 MPa for ZK60 based alloys. The CA2 composite also exhibits a grain size of 9.8 μm and a microhardness of 81 HV.Also, the antibacterial activity assessment demonstrated that adding CNTs + AgNPs hybrid nanofillers to the Mg matrix could notably prevent growing and penetration of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which indicates the synergy between antibacterial mechanisms of CNTs and AgNPs. Cytotoxicity studies confirm that composites with low amounts of CNTs + AgNPs did not show cytotoxic behavior against MG63 cells, although higher loading of CNTs + AgNPs caused toxicity. Also, the examination of osteogenic activity is consistent with other results. In general, according to the results, the potential application of CA2 composite for under load bearing implant application and bone infection treatment is proved.

Magnesium-Titanium Alloys: A Promising Solution for Biodegradable Biomedical Implants.

Magnesium (Mg) has attracted considerable attention as a biodegradable material for medical implants owing to its excellent biocompatibility, mitigating long-term toxicity and stress shielding. Nevertheless, challenges arise from its rapid degradation and low corrosion resistance under physiological conditions. To overcome these challenges, titanium (biocompatibility and corrosion resistance) has been integrated into Mg. The incorporation of titanium significantly improves mechanical and corrosion resistance properties, thereby enhancing performance in biological settings. Mg-Ti alloys are produced through mechanical alloying and spark plasma sintering (SPS). The SPS technique transforms powder mixtures into bulk materials while preserving structural integrity, resulting in enhanced corrosion resistance, particularly Mg80-Ti20 alloy in simulated body fluids. Moreover, Mg-Ti alloy revealed no more toxicity when assessed on pre-osteoblastic cells. Furthermore, the ability of Mg-Ti-based alloy to create composites with polymers such as PLGA (polylactic-co-glycolic acid) widen their biomedical applications by regulating degradation and ensuring pH stability. These alloys promote temporary orthopaedic implants, offering initial load-bearing capacity during the healing process of fractures without requiring a second surgery for removal. To address scalability constraints, further research is necessary to investigate additional consolidation methods beyond SPS. It is essential to evaluate the relationship between corrosion and mechanical loading to confirm their adequacy in physiological environments. This review article highlights the importance of mechanical characterization and corrosion evaluation of Mg-Ti alloys, reinforcing their applicability in fracture fixation and various biomedical implants.

Development of Fe-Mg alloys with intermediate degradation kinetics as potential biodegradable bone implants

This paper reports the production and characterizations of some Fe-xMg (x=3, 5, 7 wt.%) alloys. These Fe-Mg alloys were prepared using the mechanical alloying method followed by low-temperature sintering. The influence of the addition of various Mg contents on the microstructures, hardness, and degradation characteristics of these alloys were examined. The microstructure analyses demonstrated the homogeneous distribution of Fe and Mg in the alloys with a single-phase BCC structure. The inclusion of Mg was found to affect the alloys’ porosity, particle morphology, grain size, formation of corrosion products, and degradation behaviors. The corrosion products obtained from the alloys using the electrochemical and weight loss measurements indicated that their degradation rates (in the range of 3.13–4.7 mm/year) are in-between those of pure Fe and Mg. It was asserted that the Fe-Mg can be an appealing alternative for temporary medical implants. Furthermore, this study may establish an essential foundation for the degradation control of Fe-based implants by including more active elements.

Influence of the Metallic Sublayer on Corrosion Resistance in Hanks' Solution of 316L Stainless Steel Coated with Diamond-like Carbon.

The purpose of the study was to ascertain the corrosion resistance in Hanks' solution of Cr-Ni-Mo stainless steel (AISI 316L) coated with diamond-like carbon (DLC) coatings to establish its suitability for biomedical applications, e.g., as temporary implants. The influence of the carbon coating thickness as well as the correlated effect of the metallic sublayer type and defects present in DLC films on corrosion propagation were discussed. The results obtained were compared with findings on the adhesion of DLC to the steel substrate. The synthesis of carbon thin films with Cr and Ti adhesive sublayers was performed using a combined DC and a high-power-impulse vacuum-arc process. Evaluation of the corrosion resistance was carried out by means of potentiodynamic polarisation tests and scanning electron microscopy. Adhesive properties of the sublayer/DLC coating systems were measured using a scratch tester. It was found that systems with Ti sublayers were less susceptible to the corrosion processes, particularly to pitting. The best anti-corrosion properties were obtained by merging Ti with a DLC coating with a thickness equal to 0.5 μm. The protective properties of the Cr/DLC systems were independent of the carbon coating thickness. On the other hand, the DLC coatings with the Cr sublayer showed better adhesion to the substrate.

3D X-ray Tomography Analysis of Mg–Si–Zn Alloys for Biomedical Applications: Elucidating the Morphology of the MgZn Phase

Temporary metal implants, made from materials like titanium (Ti) or stainless steel, can cause metabolic issues, raise toxicity levels within the body, and negatively impact the patient’s long-term health. This necessitates a subsequent operation to extract these implants once the healing process is complete or when they are outgrown by the patient. In contrast, medical devices fabricated from absorbable alloys have the advantage of being biodegradable, allowing them to be naturally absorbed by the body once they have fulfilled their role in facilitating tissue healing. Among the various absorbable alloy systems studied, magnesium (Mg) alloys stand out due to their biocompatibility, mechanical properties, and corrosion behavior. The existing literature on absorbable Mg alloys highlights the effectiveness of silicon (Si) and zinc (Zn) additions in improving mechanical properties and controlling corrosion susceptibility; however, there is a lack of comprehensive quantitative morphological analysis of the intermetallic phases within these alloy systems. The quantification of the complex morphology of intermetallic particles is a challenging task and has significant implications for the micromechanical properties of the alloys. This study, therefore, aims to introduce a robust set of morphometric parameters for evaluating the morphology of intermetallic phases within two as-cast Mg alloys with Si and Zn additions. X-ray Computed Tomography (XCT) was used to capture the 3D tomographic data of the alloys, and a novel pair of morphological parameters (ratio of convex hull to particle volume and convex hull sphericity) was applied to the 3D tomographic data to assess the MgZn phase formed in the two alloys. In addition to the impact of composition, the effect of solidification rate on the morphological parameters was also studied. Furthermore, Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) were employed to gather detailed 2D microstructural and compositional information on the intermetallics. The comprehensive characterization reveals that the morphological complexity and size distribution of the MgZn phase are influenced by both compositional changes and the solidification rate. However, the change in MgZn intermetallic particle morphology with size was found to follow a predictable trend, which was relatively agnostic of the chosen casting conditions.

Controlling Mechanical Properties of Medical-Grade Scaffolds through Electrospinning Parameter Selection.

Electrospinning (ES) is a versatile process mode for creating fibrous materials with various structures that have broad applications ranging from regenerative medicine to tissue engineering and surgical mesh implants. The recent commercialization of this technology for implant use has driven the use of resorbable electrospun products. Resorbable electrospun meshes offer great promise as temporary implants that can utilize the layer upon layer method of additive manufacturing to incorporate porosity as a function of process parameters into a scaffold structure. The interconnected porosity and feature size known to ES have previously been observed to hold great potential for simulating the natural cellular environment of soft tissue. This microstructure, proper degradation kinetics, and mechanical properties combine to provide the design basis for artificial tissue structures that could aid in not only wound healing but also true tissue engineering and regenerative medicine. While current advancement in the field is understood to be limited by material properties, the importance of optimizing mechanical properties with currently available materials should not be overlooked. This work investigated the process parameter effects and interactions that control the structure-property relationship for a range of medical-grade aliphatic polyester materials with a range of intrinsic properties. An ε-caprolactone homopolymer (PCL), l-lactide homopolymer (PLLA), and Lactoflex, a copolymer with intermediate properties relative to the homopolymers, were characterized before, during, and after the additive manufacturing process. The interacting effects of process parameters, distance to collector, and dispensing rate were shown to produce variable-density, nonwoven scaffold structures. The resorbable mesh scaffolds of PLLA, PCL, and Lactoflex demonstrated a broad range of mechanical properties (approximately 1-10 MPa ultimate tensile strength and 5-390 MPa tensile modulus). Postprocessing of scaffolds demonstrated removal of solvents and preservation of micrometer-sized features. Resorbable polymers and electrospinning can produce scaffold materials with excellent features and offer tremendous potential in the field of implantable resorbable devices.

Effect of Stainless Steel Substrate Preparation on the Adhesion Strength and Morphology of Electrophoretically Deposited Sodium Alginate Coatings

In this study, the influence of various mechanical and chemical surface treatments on the adhesion strength and surface properties of sodium alginate coatings electrophoretically deposited (EPD) on 316L stainless steel substrates was investigated. XPS and TEM results revealed the presence of oxide layers containing elements from the substrates, with thicknesses varying from 1 to 45 nm, depending on the treatment used. Most substrates exhibited high roughness and hydrophilic properties (CA with water 62.8–82.6 deg). Sodium alginate coatings with uniform morphology were deposited with the same process parameters, i.e., 5 V and 300 s. The surface topography of the coatings was closely related to that of the substrate on which they were deposited. All coatings exhibited higher hydrophilicity (CA with water 29.5–49.7 deg) compared to the substrates (CA with water 62.8–82.6 deg). The coatings on the etched and anodized substrates demonstrated the highest adhesion strength (class 4B), attributed to the very low oxide layer thickness and the specific substrate surface topography. Mechanical interlocking was identified as the primary adhesion mechanism for these coatings. This work provides insight into optimizing surface treatments for improved adhesion of sodium alginate coatings to stainless steel substrates widely used for temporary bone implants. The results obtained will also be helpful in providing high adhesion of sodium alginate-based composite coatings to steel substrates.

Pain intensity and opioid consumption after temporary and permanent peripheral nerve stimulation: a 2-year multicenter analysis

ObjectivePeripheral nerve stimulation (PNS) is an emerging neuromodulation modality, yet there remains limited data highlighting its long-term effectiveness. The objective of this study was to report real-world data on pain...

Structure and Selected Properties of SnO2 Thin Films.

Magnesium and its alloys are attractive temporary implants due to their biocompatibility and biodegradability. Moreover, Mg has good mechanical and osteoinductive properties. But magnesium and Mg alloys have one significant disadvantage: poor corrosion resistance in a physiological environment. Hence, a deposition of various layers on the surface of Mg alloys seems to be a good idea. The purpose of the article is to analyze the structure and morphology of two MgCa2Zn1 and MgCa2Zn1Gd3 alloys coated by SnO2 ALD (atomic layer deposition) films of various thickness. The studies were performed using scanning electron microscopy (SEM), X-ray fluorescence (XRF), and an X-ray diffractometer. The corrosion activity of the thin films and substrate alloys in a chloride-rich Ringer's solution at 37 °C was also observed. The corrosion tests that include electrochemical, immersion measurements, and electrochemical impedance spectroscopy (EIS) were evaluated. The results indicated that SnO2 had a heterogeneous crystal structure. The surfaces of the thin films were rough with visible pores. The corrosion resistance of SnO2 measured in all corrosion tests was higher for the thicker films. The observations of corrosion products after immersion tests indicated that they were lamellar-shaped and mainly contained Mg, O, Ca, and Cl in a lower concentration.

Quantitative Imaging of Magnesium Biodegradation by 3D X‐Ray Ptychography and Electron Microscopy

AbstractMagnesium‐based alloys are excellent materials for temporary medical implants, but understanding and controlling their corrosion performance is crucial. Most nanoscale corrosion studies focus on the surface, providing only 2D information. In contrast, macro‐ and microscale X‐ray tomography offers representative volume information, which is, however, comparatively low in resolution and rather qualitative. Here a new mesoscale approach overcomes these drawbacks and bridges the scale gap by combining 3D measurements using ptychographic X‐ray computed tomography (PXCT) with electron microscopy. This combination allows to observe the corrosion progress non‐destructively in 3D and provides high‐resolution chemical information on the corrosion products. A medical Mg–Zn–Ca alloy is used and compared the same sample in the pristine and corroded states. With PXCT an isotropic resolution of 85 and 123 nm is achieved for the pristine and corroded states respectively, which enables to distinguish nanoscale Mg2Ca precipitates from the matrix. The corroded state in best approximation to the in situ conditions is imaged and reveals the complexity of corrosion products. The results illustrate that the corrosion‐layer is dense and defect‐free, and the corrosion of the material is grain‐orientation sensitive. The developed workflow can advance research on bioactive materials and corrosion‐sensitive functional materials.

Development of corrosion-resistant and bioactive ceramic-polymer hybrid coating over Zn-1Mg biodegradable implant material

Zn is an excellent choice for temporary orthopaedic implants since its degradation rate is better than Mg- or Fe-based biodegradable metals and closely matches the healing pace of fractured bones. The current work focuses on modifying the Zn-1Mg surface to slow its corrosion, synchronising it even more closely with patients' recovery phases while enhancing its surface bioactivity for seamless osteointegration. An oxide coating with porous morphology was initially created on Zn-1Mg through plasma electrolytic oxidation (PEO). Subsequently, the PEO-coating pores were sealed with a polymer matrix of polycaprolactone (PCL) to improve corrosion resistance. Finally, PEO-pores were filled with hydroxyapatite (HA) incorporated PCL to enhance corrosion resistance further and impart bioactivity. Raman and X-ray diffraction (XRD) analysis revealed that the phases in the coatings are mainly ZnO, HA, and polymer PCL. Field emission scanning electron microscopy (FESEM) images revealed the porous nature of the PEO coatings, and the PEO coatings with polymer top coats showcased the sealing of the PEO pores. Energy dispersive spectroscopy (EDS) spectra confirmed the species from HA and PCL on the surface of PEO-coated Zn-1Mg. The coatings PEO and PEO with polymer top coating transformed the hydrophobic Zn-1Mg surface into a hydrophilic one, optimising surface roughness for cell adhesion and nutrient absorption. The ceramic oxide layer introduced by the PEO-coating significantly enhanced corrosion resistance, a benefit further amplified by post-processing with the PCL-based matrix. The inclusion of HA into PCL transformed the coated sample into a highly bioactive surface. Consequently, the HA-incorporated PCL top-coated PEO sample displayed superior cell attachment and viability. These findings indicate that ceramic-polymer hybrid coating filled with HA (the inorganic component found in bone) is an optimal choice for temporary orthopaedic implant scenarios.

Design and fabrication of durable poly(3-hydroxybutyrate) (PHB) coating with high adhesion and desirable anti-corrosion performance on Mg alloy for bio-application

To improve the degradation properties of magnesium (Mg) alloy-based temporary implants, a durable polymer coating with high adhesion and desirable anti-corrosion performance is designed in this work. The biodegradable poly(3-hydroxybutyrate) (PHB) with high crystallinity (>60 %) and low glass transition temperature (Tg < 5 °C) is conducted as the protective coating for Mg alloy. The hydrogen evolution rate decreases by 2.56 times with the protection of the PHB coating, while the maximum concentrations (Cmax) of Na+ and Cl− ions penetrated across the PHB film are <0.1 % and 10 % of their total concentrations respectively. Furthermore, a simple approach through the network interdiffusion, hydrogen bonding, and chemical cross-linking is performed to improve the adhesion from 0.19 to 8.36 MPa. The modified PHB coated Mg alloy with a strong interface shows excellent corrosion resistance even after 168 h immersion. The design principle for durable polymer coatings is proposed based on the above results. Moreover, the interfacial bonding is identified by the Density Functional Theory (DFT) computational method. This study demonstrates the prepared PHB coating could act as an ion barrier to supply efficient protection for Mg alloys in vitro and enriches our understanding on the structure-property-performance relationship of polymer coatings.

FeMnCSi alloy for degradable pin implants: Surface and in vitro characterization

Biodegradable metals such iron-based materials, are studied as temporary implants in the orthopedic field due to their adequate mechanical properties, non-toxic degradation products, and the possibility of avoiding a second surgical intervention to remove the device. One strategy to overcome the slow degradation rate of pure Fe is the addition of alloying elements. The aim of this work is to characterize the in vitro behavior of a new FeMnCSi alloy (Fe 26.5Mn 0.5C 1.14Si 0.03P 0.01S), and compare it with the performance of pure iron in simulated body fluid. The alloy performance was characterized in terms of chemical composition, microstructure, hemocompatibility and electrochemical responseIt has been found that FeMnCSi alloy presented a marked and progressive degradation in simulated body fluid after 14 days of immersion, significantly larger than pure Fe. The presence of phosphate-based compounds was confirmed on the surface of the alloy after 1 day of immersion while only after 14 days of immersion was detected on Fe. Additionally, the FeMnCSi alloy demonstrates improved blood compatibility compared to pure iron, indicating its suitability for applications in irrigated areas such as bones.

Biological evaluation of femtosecond-laser-textured Fe–Mn alloys for vascular applications

Biodegradable metals represent a valuable solution for the development of temporary vascular implants. These are expected to dissolve in the body over time, avoiding side effects typical of permanent implants, such as thrombosis, in-stent restenosis and chronic inflammation. Iron (Fe)-based alloys, such as iron–manganese (Mn) alloys, are of particular interest for cardiovascular applications due to their intrinsic properties. However, their degradation behavior and biological performance need to be improved. Femtosecond (fs)-laser-induced surface topography could affect both their degradation and cell–material interaction. In this work, fs-laser-induced patterning was performed on a Fe–Mn20 alloy to tune both the degradation behavior of the material and its interaction with the biological environment for cardiovascular applications. Processing parameters were varied to select an optimized surface morphology, characterized by linear grooves. Profilometric analysis, scanning electron microscopy and degradation rate analysis were performed on the treated samples. Thereafter, endothelial cell viability tests and hemocompatibility assessment were carried out on selected process conditions. The obtained fs-laser-induced linear patterns were demonstrated to decrease the degradation rate and to improve the biological response toward both endothelial cells and blood. These results demonstrate how fs-laser-induced patterning is a promising solution for the development of biodegradable metal-based vascular implants.

Heat Treatment Influence on the Cavitational Erosion Zn-Mg Behavior Used for Biomedical Applications

Recent research in the medical field of temporary implants refers to the development of new biodegradable alloys, which are simultaneously subject to aggressive conditions of pressure fluctuations exerted in blood vessels. Both zinc and magnesium are biocompatible metallic materials, but also biodegradable. The present work approaches a new alloy from the Zn-Mg system, elaborated within the Polytechnic University of Bucharest, on which cavitational erosion tests were performed. It was followed the effect of applying the homogenization heat treatments of cast alloy, at different temperatures and maintenance durations (300°C and 400°C, each with a maintenance of 5h and 10 h) on the behavior at the vibratory cavitation. Finally, the correlation between the parameters of the heat treatment – the structure – behavior at cavitational erosion compared to those of the untreated thermal alloy was determined.

Transfer accuracy of 3D printed versus CAD/CAM milled surgical guides for temporary orthodontic implants: A preclinical micro CT study

ObjectivesTemporary anchorage devices (TADs) have become an integral part of comprehensive orthodontic treatments. This study evaluated the transfer accuracy of three-dimensional (3D) printed and computer-aided design/computer-aided manufacturing (CAD/CAM) milled surgical guides for orthodontic TADs using micro-computed tomography (CT) imaging in a preclinical trial. MethodsOverall, 30 surgical guides were used to place TADs into typodonts; 3D printing and CAD/CAM milling were used to produce the guides. The virtual target positions of the TADs were compared to the real positions in terms of spatial and angular deviations using digital superimposition. Micro-CT imaging was used to detect the positions. To evaluate reliability, two investigators collected the measurements twice. Intra-rater and inter-rater correlations were tested. ResultsIn total, 60 palatal TADs were evaluated. The mean coronal deviations in the print group ranged from 0.15 ± 0.20 mm to 0.71 ± 0.22 mm, whereas in the mill group, they ranged from 0.09 ± 0.15 mm to 0.83 ± 0.23 mm. At the apical tip, the overall deviations in the print group ranged from 0.14 ± 0.56 mm to 1.27 ± 0.66 mm, whereas in the mill group, they ranged from 0.15 ± 0.57 mm to 1.09 ± 0.44 mm. The mean intra-class and inter-class correlation coefficients ranged from 0.904 to 0.987. No statistically significant differences were found between the groups. ConclusionsCAD/CAM milled guides yielded spatial and angular accuracies comparable to those of 3D printed guides with notable deviations in the vertical positioning of TADs. Clinical significanceDigital planning of orthodontic temporary implants combines clinical predictability and the safety of surrounding tissue. Therefore, the transfer accuracy of the guides is crucial. This preclinical study was the first to evaluate CAD/CAM milling for orthodontic guides and found its accuracy comparable to that of the current "gold standard".

Emergence of rapid solidification microstructure in additive manufacturing of a Magnesium alloy

Abstract Bioresorbable Mg-based alloys with low density, low elastic modulus, and excellent biocompatibility are outstanding candidates for temporary orthopedic implants. Coincidentally, metal additive manufacturing (AM) is disrupting the biomedical sector by providing fast access to patient-customized implants. Due to the high cooling rates associated with fusion-based AM techniques, they are often described as rapid solidification processes. However, conclusive observations or rapid solidification in metal AM — attested by drastic microstructural changes induced by solute trapping, kinetic undercooling, or morphological transitions of the solid-liquid interface — are scarce. Here we study the formation of banded microstructures during laser powder-bed fusion (LPBF) of a biomedical-grade Magnesium-rare earth alloy, combining advanced characterization and state-of-the-art thermal and phase-field modeling. Our experiments unambiguously identify microstructures as the result of an oscillatory banding instability known from other rapid solidification processes. Our simulations confirm that LPBF-relevant solidification conditions strongly promote the development of banded microstructures in a Mg-Nd alloy. Simulations also allow us to peer into the sub-micrometer nanosecond-scale details of the solid-liquid interface evolution giving rise to the distinctive banded patterns. Since rapidly solidified Mg alloys may exhibit significantly different mechanical and corrosion response compared to their cast counterparts, the ability to predict the emergence of rapid solidification microstructures (and to correlate them with local solidification conditions) may open new pathways for the design of bioresorbable orthopedic implants, not only fitted geometrically to each patient, but also optimized with locally-tuned mechanical and corrosion properties.

Design multifunctional Mg–Zr coatings regulating Mg alloy bioabsorption

Magnesium (Mg) alloys are widely used for temporary bone implants due to their favorable biodegradability, cytocompatibility, hemocompatibility, and close mechanical properties to bone. However, rapid degradation and inadequate strength limit their applicability. To overcome this, the direct current magnetron sputtering technique is employed for surface coating in Mg-based alloys using various zirconium (Zr) content. This approach presents a promising strategy for simultaneously improving corrosion resistance, maintaining biocompatibility, and enhancing strength without compromising osseointegration. By leveraging Mg's inherent biodegradability, it has the potential to minimize the need for secondary surgeries, thereby reducing costs and resources.This paper is a systematic study aimed at understanding the corrosion mechanisms of Mg–Zr coatings, denoted Mg-xZr (x = 0–5 at.%). Zr-doped coatings exhibited columnar growth leading to denser and refined structures with increasing Zr content. XRD analysis confirmed the presence of the Mg (00.2) basal plane, shifting towards higher angles (1.15°) with 5 at.% Zr doping due to lattice parameter changes (i.e., decrease and increase of “c” and “a” lattice parameters, respectively). Mg–Zr coatings exhibited “liquidphilic” behavior, while Young's modulus retained a steady value around 80 GPa across all samples. However, the hardness has significantly improved across all samples’ coating, reaching the highest value of (2.2 ± 0.3) GPa for 5 at.% Zr. Electrochemical testing in simulated body fluid (SBF) at 37 °C revealed a significant enhancement in corrosion resistance for Mg–Zr coatings containing 1.0–3.4 at.% Zr. Compared with the 5 at.% Zr coating which exhibited a corrosion rate of 32 mm/year, these coatings displayed lower corrosion rates, ranging from 1 to 12 mm/year. This synergistic enhancement in mechanical properties and corrosion resistance, achieved with 2.0–3.4 at.% Zr, suggests potential ability for reducing stress shielding and controlled degradation performance, and consequently, promising functional biodegradable materials for temporary bone implants.

Compression properties of cellular iron lattice structures used to mimic bone characteristics

Recently, cellular materials made by the repetition of unit cells, that is, iron lattices have become appealing to mimic the structure of bone. The aim of the study is to choose the most adequate lattice structures, which have the compressive mechanical properties closer to the ones of bone, in the perspective of their use as temporary implants. Five types of unit cells were selected, such as, cubic (C), truncated octahedron (TO), truncated cubic (TC), rhombicuboctahedron (RCO), and rhombitrucated cuboctahedron (RTCO). The mechanical properties were assessed by numerical simulations with a finite-element analysis. The size effect was studied with the comparison of results among samples with different numbers of unit cells. Simulations covered a wide range of relative densities. Graded dense-in and dense-out configurations were constructed with lattices of types RTCO and TO, being the unit cells, themselves graded. Lattice structures RTCO and TO were found to be stable at every relative density studied, while C, TC and RCO lattices are unstable at low densities. The evaluation of size effects was not conclusive, which could be biased by other factors. The Young's modulus of RTCO and TO lattices enable to reproduce the properties of both trabecular and cortical bone, with an appropriate choice of the relative density. To mimic trabecular bone, only RTCO and TO structures with low relative densities, can be used, while arrangements of C, TC and RCO cells can only replicate the properties of cortical bone. Graded cells may have the same properties as non-graded with lower density.

Retrospective Clinical Analysis of the Effectiveness of Skeletally Anchored Appliances for Maxillary Expansion

(1) Background: Skeletally anchored appliances for maxillary expansion are a less invasive alternative to surgery and are increasingly often selected as a method of treatment. The purpose of this study was to retrospectively evaluate the efficacy of maxillary expansion using distractors supported by temporary orthodontic implants (TOIs) in patients of differing sex and age. (2) Methods: The study group consisted of patients treated with distractors anchored to TOIs between July 2019 and June 2022. The group was divided into adolescent and the adult patients. Effectiveness was evaluated one and two weeks after installation of the distractors and the results were analyzed statistically. (3) Results: In total, 39 patients were treated, of which 21 were women and 18 men, ranging in age from 11 to 42. A group of 8 girls and 9 boys younger than 18 years were included. The presence of diastema at the first follow-up visit was observed in all girls and in 8 of the boys, as well as in 7 women and in none of the men. At the second visit, no diastema was found in one woman, but was noted in 3 men (p = 0.007). At the completion of distraction, diastema was observed in all the girls and in 12 women, as well as in 8 out of 9 boys and in 3 men (p = 0.015). (4) Conclusions: The effectiveness of the distraction procedure in adolescents is positive, regardless of sex. However, in adults, the procedure has limited effectiveness in males.