stent material properties

The optimization of material properties, surface finish, and stent design is necessary for the develop-ment of stent [19]. Dynamic Mechanical Analysis (DMA) was performed to determine the mechanical properties of the stents. common material format for stents is tubing, a review is conducted to show how tubing attributes influence stent properties and manufacturability. The most common material used in stents is Nitinol, a nickel titanium alloy. Material properties and stent performance:L605s sensitivity to processing parameters has already been described [2]. The mechanical properties of the stents mainly depend on the material, geometry, and medical application of the stent: Mechanical properties material geometry application Mechanical properties = f material geometry application E1 Once we have decided the mechanical properties, we give way to the manufacturing process step. The mechanical properties required for stents include the yield strength (YS), ultimate tensile strength (UTS), elastic modulus or Young’s modulus (YM), and elongation. Suoerelastjcjtv and Shape Memory in Njtjnol Conventional stent materials, like stainless steel or cobalt based alloys, exhibit a distinctly differem elastic deforma­ tion behavior from that of the structW'a1 materials of the By referring the basic stent model with 8 rhombus shape units the stent was mod-elled using SolidWorks. Stent. By referring the basic stent model with 8 rhombus shape units the stent was mod-elled using SolidWorks. Finally, the scientists used the material with the desired properties to make stents, which were tested on rabbits. A small study (NEXT, n=323) with angiographic outcomes, showed that the cobalt–chromium polymer-free sirolimus-eluting stent (Cre8™, Alvimedica, Istanbul, Turkey) offered reduced in-stent late lumen loss at 6 months when compared to a first-generation stainless-steel paclitaxel-eluting PP DES (TAXUS) (0.14 ± 0.36 mm versus 0.34 ± 0.40, p<0.0001 for non-inferiority and … Young’s Modulus is a property that quantifies the resistance of the polymer to deformation prior to the onset of plastic deformation. The composition of the alloy from which one embodiment of the stent is formed is Co-26Cr-6Mo-1Si-1Fe-1Mn-1Ni. Given that the relationship between elastic modulus and strut thickness has been shown to be nonlinear , through careful matching of material properties to stent geometry, a physically attainable elastic modulus may be used to meet the radial stiffness threshold with a … However, a very important material property related to the stent’s mechanical behavior is viscoelasticity. We recommend that you specify the type of contact defined between any 2 contacting bodies modeled in your analysis; e.g., the vessel and outer surface of your stent. Used for the treatment of coronary artery disease, the Absorb stent is gradually resorbed into the vessel wall. The surface properties that are essential to stent performance include electrical charge, texture, and cleanliness. The desired mechanical properties include good radial strength and elastic modulus. The most promising stent for the future is made of biodegradable and non-toxic material. Stent is a tube-like, flexible, and small device. Commonly used rhombus stent design was chosen for this modeling study as shown in Figure 1. The issue of device and material biocompatibility is not unique to stents; it is a grander issue and must be perceived as contextual rather than constitutive. US20020138133A1 US10/150,117 US15011702A US2002138133A1 US 20020138133 A1 US20020138133 A1 US 20020138133A1 US 15011702 A US15011702 A US 15011702A US 2002138133 A1 US2002138133 A The stent is mounted on a … A self-expanding stent formed of helically wound and braided filaments of wrought cobalt, chromium and molybdenum alloy containing less than about five weight percent nickel. In Case 2 and Case 3, the effect of change in yield strength (crimping) is studied. The GPSTM stent is made of Nitinol material… It is interesting to note that many DES essentially employ the same design configuration as their BMS counterparts with a … 646 • Physical Properties of Endovascular Stents May 2000 JVIR Table 1 Combination of Results for Physical Stent Properties Stent Hoop MM' Strength Radial Chronic Stent Stent Stent per Unit Hoop per Unit Resistive Outward Stent Compo-Length Weight Length Strength Mass Force Force Flexibility Radio-Description sition (cm) (g) (glcm) (N/em) (N/gcm) (Nlcm) (N/cm) (1JN) pacity Table 1: Properties of materials used in simulation of femoral artery opening by Nitinol stent. The biomechanics requirements for the stent Among these metallic stent materials, pure Fe and Mg alloys are the two metals that have been used for making biodegradable coronary stents 6. A stent is not just a stent: stent construction and design do matter in its clinical performance, Singapore Medical Journal. In many circumstances a combination of one or … As previously stated, a material used to make a stent must be formable (i.e., have sufficient ductility and weldability to be formed into the appropriate final stent shape), and yet needs to provide good mechanical properties in the finished stent to hold the lumen open. Epub 2016 May 13. Indeed, it is difficult to design a stent that satisfies the best conditions for all objective functions. Materials and methods: We analyzed the radial resistive force, the chronic outward force, as well as the crush resistance of seven stent models [Zilver Vena (Cook, Bjaeverskov, Denmark), Sinus Venous, Sinus Obliquus and Sinus XL Flex (Optimed, Ettlingen, … In Case 3, the material property (σy=45 Mpa) at 45σ C (crimping temperature) However, the mechanical properties of zinc cannot meet the performance requirements of stent material which severely limit its application. Stent design affects many properties of the stent, such as elastic recoil and rigidity—two undesirable stent characteristics. Entire stent geometry. Utilization of an appropriate stent for treatment is pivotal; however, until today, mechanical properties of venous stents remain unknown. Nitinol 55 and Nitinol 60.It exhibits the shape memory effect and superelasticity at different temperatures. ¼0.0109830MPa. Acid pickling was done as a pre-annealing step to remove the debris and slag material attached to the stent after laser cutting. Among degradable metal cardiac stent materials, zinc has great biocompatibility and corrosion properties, which make it become the most potential stent material. contemporary stents in an effort to prevent restenosis [18]. Nitinol tubing is commonly used in catheters, stents, and superelastic needles. Nickel titanium, also known as Nitinol, is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages.Different alloys are named according to the weight percentage of nickel, e.g. The changes in the material properties of the FGM stent over it length is corresponding to change in its composition which is described by equation (1). DOI: 10.1016/j.scient.2012.10.024 Flexibility can be improved by decreasing the thickness of the material. Objective To analyze the mechanical properties of stent retrievers, their behavior during retrieval, and interaction with different clots and to identify device features that might correlate with … 3. The study of the material and the geometrical properties of the stent can provide useful indications on its performance and on its interaction with the target vessel. Depending on the time of occurrence, ST can be classified into four types: acute, sub-acute, late and very late. Min Ji Kim,1 Moon Young Hwang,1 JiHeung Kim,2 and Dong June Chung 1. Among these metallic stent materials, pure Fe and Mg alloys are the two metals that have been used for making biodegradable coronary stents6. Acute ST occurs between 0 and 24 h following stent … Stents are made-up of metals such as cobalt chromium, stainless steel, and nitinol. Clinical outcomes and material properties of in situ fenestration of endovascular stent grafts. For example, strut pitch and strut size can be modified to adjust the flow reduction effects, but these changes also affect the mechanical properties of the stent, such as radial stiffness or longitudinal flexibility. NiTi shape memory alloy is a temperature sensitive material with non-linear mechanical properties and good biocompatibility, which can be used for medical devices such as stent, catheter guide wire and orthodontic wire. In the current investigation, annealing was employed as a means to improve the mechanical performance of 316LVM coronary stents. While there is little information associating urethral stent type with outcomes after hypospadias surgery, material properties may account for findings of prior studies. It is also an opportunity to tailor these properties to stent design in order to optimize the device performance. It is also an opportunity to tailor these properties to stent design in order to optimize the device performance. used without any improvement of the material; this is essential in order to identify the stent fractures earlier through X-ray. Depending on the time of occurrence, ST can be classified into four types: acute, sub-acute, late and very late. The majority of nitinol stents are of the self-expanding type basing on the superelasticity. This parameter primarily affects the mechanical stability of the stent material over time, and therefore, its ability to withstand external forces for a long duration, as described by creep resistance or stress relaxation . pact on the design and material properties of stents. 2. 2016 Jul;64(1):244-50. doi: 10.1016/j.jvs.2016.03.445. The stent-grafts are inserted into arteries to help to keep them open so that blood can flow properly. stainless steel 316L (the most common stent material) and high entropy alloy properties as the material properties for the 3D stent model. Seven mechanical properties were studied by mathematical modeling with determination of: (1) stent deployment pressure, (2) the intrinsic elastic recoil of the material used, (3) the resistance of the stent to external compressive forces, (4) the stent foreshortening, (5) the stent coverage area, (6) the stent flexibility, and (7) the stress maps. Introduction Despite the prevalence of hypospadias surgery and the near ubiquitous use of postoperative urethral stents, there has been no evaluation of the material properties of commonly used choices. Constitutive Materials Over the last few years, engineers and scientists have Surface characteristics of a stent material, which influence thrombosis and neointimal hyperplasia, include surface energy, surface texture, surface potential, and the stability of the surface oxide layer [20, 21 ]. Studies with drug-eluting stents revealed their good biocompatibility properties and that drug-eluting capacity can be safely added to urethral stents. 1. In Case 1 and Case 2, the effect of the decrease in modulus is compared. Three ideal sample stent types with different cell configurations were manufactured. Material and surface (texture) Stent materials and surface are relevant to in-stent re-stenosis. This study investigates the effectiveness and applicability of magnesium as a novel biodegradable ureteral stent material that has inherent antimicrobial properties. Production material of stents are wires or laser-cut tubes. Stent is a tube-like, flexible, and small device. Stent is either made from polymer or metal. Stents are made-up of metals such as cobalt chromium, stainless steel, and nitinol Nowadays, cobalt-chromium is being used as stent material as it triggers activation of coagulation, platelets, endothelial cell dysfunction, and leukocytes Hence, these drawbacks limit the use of polymers in stents. @article{osti_901533, title = {On the Mechanical Properties and Microstructure of Nitinol forBiomedical Stent Applications}, author = {Robertson, Scott W.}, abstractNote = {This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents. The surface properties that are essential to stent performance include electrical charge, texture, and cleanliness. [3] D. R. McClean and N. Eigler, (2002) Stent design: Im-plications for restenosis, MedReviews, LLC. The current generation of stent materials tends to trigger various adverse reactions such as inflammation, fibrosis, thrombosis, and infection. Most of these issues arise due to interface problems between the stent surface and its immediate environment. Where f is an arbitrary material property, D is the distance from the middle, l is the length of the stent, and n is the heteroge-neous index. this study to set up the material properties. There are some properties This higher density makes it possible to design a thin-strut stent … The data are based on the Auricchio model [5,11,22,24]. Boundary conditions and meshing FE model must be replaced by the actual boundary condition to ensure its practicality for the stent. 2.3. J Vasc Surg. tents are narrow tubes. The optimization of material properties, surface finish, and stent design is necessary for the development of stent . Stents Chemical Compounds The self-expanding stents had a radial resistive force between 0.39 NIcOl (Wallstent) and 1.7 Nlcm (Smart). Storage modulus and loss modulus are dynamic mechanical properties used to characterize From: Advances in 3D Textiles, 2015. of stents. Thus, PEEK 450G is a better material for coronary stent implants. Accurate design of the stent shape should be performed in order to limit the room temperature strain imparted to the alloy during stent expansion. The alloy used in the Driver stent is approximately Table 2. Acute ST occurs between 0 and 24 h following stent … Fingerprint Dive into the research topics of 'Multi-objective optimisation of material properties and strut geometry for poly(L-lactic acid) coronary stents using response surface methodology'. the other end. Crossref Google Scholar Interest- Some of these properties are not possessed by other materials currently used to manufacture stents. It is interesting to note that many DES essentially employ the same design configuration as their BMS counterparts with a drug-loaded … Together they form a unique fingerprint. In this study, a new design method of BPS was proposed based on the force analysis of supporting rings and bridges during stent implantation, and a novel BPS called open C -shaped stent (OCS) with superior comprehensive mechanical properties was developed accordingly. Commonly used rhombus stent design was chosen for this modeling study as shown in Figure 1. factors for ISR has been recognized, such as stent material and geometry, lesion and stent length, stent number, diabetes and female sex [19]. Our study sets out to close this gap with an evaluation and comparison of the material properties of four urethral stents commonly used after hypospadias surgery. The von-mises stress of PEEK 450G is superior in both plaque and non-plaque regions and also flexible to expand. The flexible balloon-expandable stents showed pushability values between 0.13/N (AVE Bridge) and 0.20/N (Perflex). The ideal stent material The ideal stent material is fully corrosion resistant, vascular compatible, fatigue resistant, and … Three polymer stent material properties are listed as Case 1, Case 2, and Case 3 in Table 3. Stent retrievers are accepted as the most effective devices for intracranial thrombectomy. This paper gives a brief review of ureteral stent materials and summarizes the advantages and disadvantages of these materials and then dis - cusses the design of ureteral stents and some novel technologies. 2. Accurate design of the stent shape should be performed in order to limit the room temperature strain imparted to the alloy during stent expansion. FEA is used for evaluation of the stent acute performance and for prediction of the stent long-term fatigue life. Download as PDF. Bioabsorbable magnesium alloys are a promising solution for adverse effects of long-term usage of stents. Non-uniform stent expansion increases vascular injury and in-stent re-stenosis 31. Background: Biodegradable polymeric stents represent a competitive approach to permanent and absorbable metallic stents for vascular applications. through a computational approach that optimises material properties and stent geometry. However, the function and the properties of the materials themselves have rarely been inves-tigated. 2. Despite major challenges resulting from the mechanical properties of polymeric biomaterials, these stent concepts gain their attraction from their intrinsic potential for controlled biodegradation and facile drug incorporation. To achieve reasonable scaffolding, it is recommended that the mechanical properties are close to those of 316L stainless steel, which is the standard vascular stent material. In the present study the stent material was found to increase and both indomethacin-releasing stent material and indomethacin to decrease the production of inflammatory mediators. Nevertheless, some devices use 300 series stainless steel, and the Powerlink (Endologix, Irvine, USA) uses a … Sadrnezhaad, Effects of Material Properties on Mechanical Performance of Nitinol Stent Designed for Femoral Artery: Finite Element Analysis, Scientia Iranica B 19(6) (2012)1564-1571. 11 Thus, stent geometry, material, and coatings can affect thrombogenicity, and it is incumbent on us to define when and how. In colorectal surgery, the material is used in devices for reconnecting the intestine after removing the pathology. The Nitinol material, unique stent design and proprietary manufacturing processes of the Portico valve provide specific stent properties that allow the valve to be fully resheathed and recaptured* during the TAVI procedure, if necessary, and also enable the valve to be efficiently prepped and loaded at room temperature. As for the material, the SMA is a nickel-titanium alloy (nitinol), ... For more information about the material properties and parameters for each phase, refer to the documentation for the Shape Memory Alloy Self-Expanding Stent example. factors for ISR has been recognized, such as stent material and geometry, lesion and stent length, stent number, diabetes and female sex [19]. Biomechanics, by its characteristic multi-disciplinary approach, may provide the right key to investigate these devices . - "Effects of material properties on mechanical performance of Nitinol stent designed for femoral artery: Finite element analysis" Equiatomic NiTi, also known as nitinol, has a great potential for use as a biomaterial as compared to other conventional materials due to its shape memory and In theory, bioresorbable stents made from biocorrodible metals are able to have thinner struts and lower profile compared to polymeric scaffolds (17). The techniques require the stent to have good radiographic properties for fluoroscopy and good magnetic properties that avoid stent movement, floating, and image artifact during MRI. Biodegradable and Elastomeric Poly (glycerol sebacate) as a Coating Material for Nitinol Bare Stent. Nitinol (nickel~titanium) alloys exhibit a combination of properties which make them particularly suitable for the manufacture of self-expanding stents. Some of these properties are not possessed by other materials currently used to manufacture stents. This imposes a need for strict control during manufacturing to ensure repeatable properties. material/design and the mechanisms of thrombotic complications from the pre-clinical, pathologic, and clinical viewpoints. The strut configuration selected was the closed-cell type, and nitinol was chosen as the material for stent manufacture because the innate characteristics of this material increase stent flexibility. 3. 1Department of Polymer Science and Engineering, Sungkyunkwan University, Suwon 440746, Republic of Korea. Given the superelastic properties of NiTi stent, the used Surface characteristics can be modulated by (electromechanical) polishing, ion implantation or coating. Metal is frequently used as a stent material due to its strength, flexibility, and biocompatibility. Abbott Vascular uses stretch blowmolding to enhance the physical properties of polylactic acid (PLA) used in its ground-breaking Absorb bioresorbable vascular stent. describe the unique material properties ofNitinol and how they relate to the performance characteristics ofNitinol stents. The material properties for the stent designs were assumed to be isotropic and linear elastic. These alloys have advantages in terms of large recoverable strain and these alloys can exert continuous force during use. Stainless steel is very popular for making stents, as it is quite cost effective. Stent materials The stent materials have a great influence on their efficacy, especially their mechanical and physicochemical properties. Along with design, these This article will review the discovery, material properties, processing methods and medical applications of Nitinol, with a special focus on stents for the treatment of arterial diseases, which constitute one of Nitinol’s major uses. Stent is either made from polymer or metal. Background: Angioplasty with stenting is one of the primary treatment for coronary artery disease, hence, performance of the stent is deemed important. The material property choice of the stents is based on the heat treatment results of the NiTi [30]. The tensile properties of the six wrought alloys showed that fracture elongation of the order of 17-20% can be achieved in the most ductile materials. Post annealing operation … Nitinol (nickel~titanium) alloys exhibit a combination of properties which make them particularly suitable for the manufacture of self-expanding stents. This is a major problem of current ureteral stents, which are used clinically to treat the blockage of ureteral canals. Stiffer stents may contribute to decreased postoperative comfort, while a stent that is too soft and extensible may have issues with dislodgement, kinking and breaking. Tensile Testing of Stent Materials Tensile properties of Nitinol can be evaluated using ASTM F2516 “Standard Test Method for Tension Testing of Nickel-Titanium Superelastic Materials”, which specifies a method to understand the upper and lower plateau strengths, tensile strength and elongation of this superelastic material. Suitable stent materials are metals, metal-alloys or polymers. Material properties and stent performance:L605s sensitivity to processing parameters has already been described [2]. Two different temperatures (1000°C and 1150°C) were explored for the thermal processing of the device. Shape memory alloys remember their shape due to thermoelastic martensitic phase transformation. Each of these developments aimed to address a specific failure or cause of morbidity. Schiavone A, Zhao L G and Abdel-Wahab A A 2014 Effects of material, coating, design and plaque composition on stent deployment inside a stenotic artery—finite element simulation Mater. Bioabsorbable stents are the new generation of stents. The tensile properties of the six wrought alloys showed that fracture elongation of the order of 17-20% can be achieved in the most ductile materials. Biodegradable stents, especially those composed of magnesium alloy-based materials, can provide a temporary scaffold that support vessels while naturally resorbing in the body after the targeted vessel heals, thereby preventing the restenosis and late thrombosis issues caused by their metallic predecessors. Although more work is needed to understand the exact deformation mechanisms, this method offers precise pseudoelastic force tuning for stents by changing the material properties, which, until now has not been possible. Tensile Testing of Stent Materials Tensile properties of Nitinol can be evaluated using ASTM F2516 “Standard Test Method for Tension Testing of Nickel-Titanium Superelastic Materials”, which specifies a method to understand the upper and lower plateau strengths, tensile strength and elongation of this superelastic material. Metallic Stents Since the bare metal stent (BMS) was introduced into the clinical arena in 1994 [1,2], several metal alloys have been applied as platform material for metallic stents. How to improve stent mechanical properties is a key issue for designing biodegradable polymeric stents (BPSs). [27] F. Nematzadeh and S.K. Higher the von-mises stress in stent, the stiffness of the stent being high, but which may damage the coronary artery . [4] (2004) Stent design properties and deployment ratio in-fluence indexes of wall shear stress: A three-dimensional Eng. In the present article, the effects of material properties on mechanical performance of Z shaped nitinol wire stent under crushing test for clinical applications are studied by finite element modelling. Sci. The stents made by laser cutting are tubular meshes. Stents are used to keep blood vessels free from blockage. 11, 12 Previous studies have shown that differences in stent design can have a profound influence on late lumen loss 13 and neointima proliferation, 14 thereby affecting restenosis rates and requirements for post-procedural intervention. Design and mechanical properties simulation of fish scale-like intracranial thrombectomy stent - Volume 35 Issue 18 The stent is sewn onto a woven polyester graft [7]. In this review article, they are discussed, together with the issues they attempted to resolve. The material properties of plaque were adopted from the documented literatures [11], where a third order polyno-mial strain energy density function, with nonzero coefficients C 10 ¼0.04MPa, C 02 ¼0.003MPa, and C 03 ¼0.02976MPa, was used. [0009] One property is sometimes achieved at the expense of the other. Stent is a medical device that can provide scaffolding to organ walls and vessels to keep arteries open. A stent having variable thickness with improved radiopacity, MRI compatibility, radial stiffness, and flexibility and to the method of making such stents. This paper describes the fundamental nitinol properties of shape memory and superelasticity. The Endurant II is made with high-density multifilament polyester graft material and a stent with anchor pins laser-cut from a single piece of nitinol (nickel titanium). stainless steel 316L (the most common stent material) and high entropy alloy properties as the material properties for the 3D stent model. This imposes a need for strict control during manufacturing to ensure repeatable properties. Due to Nitinol's unique properties it has seen a large demand for use in less invasive medical devices. Abstract: Bacterial infection often causes clinical complications and failure of indwelling medical devices. Density Values Material Pounds per Inch3 Cobalt alloy 0.304 316L stainless steel 0.287 • Denser than stainless steel.The cobalt alloy is more dense than 316L stainless steel (see Table 2). The stent graft is implanted within the abdominal aorta which is the largest artery in the abdominal cavity. processed stents were fabricated and evaluated both thermally and mechanically and compared to a base material stent. A stent is a woven, knitted or braided cylindrical mesh structure made of stainless steel, nitrol or chrome-cobalt alloy that is inserted in a diseased or contracted artery or vein to restore a free blood flow by keeping the vessel open. A summary of the mechanical and physical properties of different bioresorbable materials used in the fabrication of BRS and DES are shown in … Forty parametric stent designs were generated: cross-sectional area (post-dilation), fore-shortening, stent-to-artery ratio and radial collapse pressure were evaluated computation-ally using finite element analysis. The table presents the mechanical properties of the materials currently used for stent fabrication. Suitable properties for a stent include easy trackability, ease of delivery, excellent radial strength, and a low recoil. Therefore, from the viewpoint of mechanical properties and visibility on X-ray imaging, metals are the main materials utilized for stents. onV Mises stress mathematical equation was used in The self­ expanding stents had flexibilities between O.13/N (Memotherm) and 0.241N (Symphony). C 42 479–88.

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