stent material properties

13 jun stent material properties

The stent-grafts are inserted into arteries to help to keep them open so that blood can flow properly. 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). - "Effects of material properties on mechanical performance of Nitinol stent designed for femoral artery: Finite element analysis" The self-expanding stents had a radial resistive force between 0.39 NIcOl (Wallstent) and 1.7 Nlcm (Smart). The most common material used in stents is Nitinol, a nickel titanium alloy. Biodegradable and Elastomeric Poly (glycerol sebacate) as a Coating Material for Nitinol Bare Stent. 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. J Vasc Surg. 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. 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. Nevertheless, some devices use 300 series stainless steel, and the Powerlink (Endologix, Irvine, USA) uses a … 3. While there is little information associating urethral stent type with outcomes after hypospadias surgery, material properties may account for findings of prior studies. 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. [27] F. Nematzadeh and S.K. Young’s Modulus is a property that quantifies the resistance of the polymer to deformation prior to the onset of plastic deformation. It is also an opportunity to tailor these properties to stent design in order to optimize the device performance. Used for the treatment of coronary artery disease, the Absorb stent is gradually resorbed into the vessel wall. 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. There are some properties The stents made by laser cutting are tubular meshes. 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 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. This imposes a need for strict control during manufacturing to ensure repeatable properties. Stent. Surface characteristics can be modulated by (electromechanical) polishing, ion implantation or coating. Suitable properties for a stent include easy trackability, ease of delivery, excellent radial strength, and a low recoil. The optimization of material properties, surface finish, and stent design is necessary for the develop-ment of stent [19]. The ideal stent material The ideal stent material is fully corrosion resistant, vascular compatible, fatigue resistant, and … [0009] One property is sometimes achieved at the expense of the other. Bioabsorbable magnesium alloys are a promising solution for adverse effects of long-term usage of stents. Interest- Post annealing operation … 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. Sci. Eng. Design and mechanical properties simulation of fish scale-like intracranial thrombectomy stent - Volume 35 Issue 18 Nitinol tubing is commonly used in catheters, stents, and superelastic needles. stainless steel 316L (the most common stent material) and high entropy alloy properties as the material properties for the 3D stent model. FEA is used for evaluation of the stent acute performance and for prediction of the stent long-term fatigue life. 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. This paper describes the fundamental nitinol properties of shape memory and superelasticity. Abbott Vascular uses stretch blowmolding to enhance the physical properties of polylactic acid (PLA) used in its ground-breaking Absorb bioresorbable vascular stent. The biomechanics requirements for the stent The stent graft is implanted within the abdominal aorta which is the largest artery in the abdominal cavity. In Case 1 and Case 2, the effect of the decrease in modulus is compared. 1. [4] (2004) Stent design properties and deployment ratio in-fluence indexes of wall shear stress: A three-dimensional 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. @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 material property choice of the stents is based on the heat treatment results of the NiTi [30]. 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). C 42 479–88. The table presents the mechanical properties of the materials currently used for stent fabrication. 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. 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 … Commonly used rhombus stent design was chosen for this modeling study as shown in Figure 1. material/design and the mechanisms of thrombotic complications from the pre-clinical, pathologic, and clinical viewpoints. Storage modulus and loss modulus are dynamic mechanical properties used to characterize Along with design, these 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 . of stents. The alloy used in the Driver stent is approximately Table 2. 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. Among degradable metal cardiac stent materials, zinc has great biocompatibility and corrosion properties, which make it become the most potential stent material. 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'. Among these metallic stent materials, pure Fe and Mg alloys are the two metals that have been used for making biodegradable coronary stents6. In colorectal surgery, the material is used in devices for reconnecting the intestine after removing the pathology. These alloys have advantages in terms of large recoverable strain and these alloys can exert continuous force during use. The majority of nitinol stents are of the self-expanding type basing on the superelasticity. Among these metallic stent materials, pure Fe and Mg alloys are the two metals that have been used for making biodegradable coronary stents 6. Non-uniform stent expansion increases vascular injury and in-stent re-stenosis 31. Shape memory alloys remember their shape due to thermoelastic martensitic phase transformation. 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. 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. 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). 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. Commonly used rhombus stent design was chosen for this modeling study as shown in Figure 1. The mechanical properties required for stents include the yield strength (YS), ultimate tensile strength (UTS), elastic modulus or Young’s modulus (YM), and elongation. Epub 2016 May 13. Together they form a unique fingerprint. 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. However, the mechanical properties of zinc cannot meet the performance requirements of stent material which severely limit its application. Bioabsorbable stents are the new generation of stents. 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. Background: Biodegradable polymeric stents represent a competitive approach to permanent and absorbable metallic stents for vascular applications. The material properties for the stent designs were assumed to be isotropic and linear elastic. pact on the design and material properties of stents. Material properties and stent performance:L605s sensitivity to processing parameters has already been described [2]. 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. It is also an opportunity to tailor these properties to stent design in order to optimize the device performance. 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. In Case 3, the material property (σy=45 Mpa) at 45σ C (crimping temperature) The GPSTM stent is made of Nitinol material… Acute ST occurs between 0 and 24 h following stent … 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. Stainless steel is very popular for making stents, as it is quite cost effective. 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. The von-mises stress of PEEK 450G is superior in both plaque and non-plaque regions and also flexible to expand. 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. Depending on the time of occurrence, ST can be classified into four types: acute, sub-acute, late and very late. 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. Table 1: Properties of materials used in simulation of femoral artery opening by Nitinol stent. 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. 2.3. However, a very important material property related to the stent’s mechanical behavior is viscoelasticity. Finally, the scientists used the material with the desired properties to make stents, which were tested on rabbits. 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. Utilization of an appropriate stent for treatment is pivotal; however, until today, mechanical properties of venous stents remain unknown. Clinical outcomes and material properties of in situ fenestration of endovascular stent grafts. factors for ISR has been recognized, such as stent material and geometry, lesion and stent length, stent number, diabetes and female sex [19]. Acid pickling was done as a pre-annealing step to remove the debris and slag material attached to the stent after laser cutting. Material properties and stent performance:L605s sensitivity to processing parameters has already been described [2]. 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, … 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. From: Advances in 3D Textiles, 2015. Indeed, it is difficult to design a stent that satisfies the best conditions for all objective functions. Flexibility can be improved by decreasing the thickness of the material. Each of these developments aimed to address a specific failure or cause of morbidity. 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 … A stent is not just a stent: stent construction and design do matter in its clinical performance, Singapore Medical Journal. processed stents were fabricated and evaluated both thermally and mechanically and compared to a base material stent. Stent retrievers are accepted as the most effective devices for intracranial thrombectomy. Entire stent geometry. 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 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 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. The self­ expanding stents had flexibilities between O.13/N (Memotherm) and 0.241N (Symphony). 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. Due to Nitinol's unique properties it has seen a large demand for use in less invasive medical devices. It is interesting to note that many DES essentially employ the same design configuration as their BMS counterparts with a … this study to set up the material properties. Boundary conditions and meshing FE model must be replaced by the actual boundary condition to ensure its practicality for the stent. Stent design affects many properties of the stent, such as elastic recoil and rigidity—two undesirable stent characteristics. Metal is frequently used as a stent material due to its strength, flexibility, and biocompatibility. In this review article, they are discussed, together with the issues they attempted to resolve. contemporary stents in an effort to prevent restenosis [18]. 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. The stent is sewn onto a woven polyester graft [7]. ¼0.0109830MPa. This imposes a need for strict control during manufacturing to ensure repeatable properties. The composition of the alloy from which one embodiment of the stent is formed is Co-26Cr-6Mo-1Si-1Fe-1Mn-1Ni. 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. The surface properties that are essential to stent performance include electrical charge, texture, and cleanliness. Stents are used to keep blood vessels free from blockage. 2016 Jul;64(1):244-50. doi: 10.1016/j.jvs.2016.03.445. [3] D. R. McClean and N. Eigler, (2002) Stent design: Im-plications for restenosis, MedReviews, LLC. Three polymer stent material properties are listed as Case 1, Case 2, and Case 3 in Table 3. 11 Thus, stent geometry, material, and coatings can affect thrombogenicity, and it is incumbent on us to define when and how. A stent having variable thickness with improved radiopacity, MRI compatibility, radial stiffness, and flexibility and to the method of making such stents. Stent is a medical device that can provide scaffolding to organ walls and vessels to keep arteries open. DOI: 10.1016/j.scient.2012.10.024 Crossref Google Scholar Min Ji Kim,1 Moon Young Hwang,1 JiHeung Kim,2 and Dong June Chung 1. 3. Production material of stents are wires or laser-cut tubes. 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 Stents Chemical Compounds The stent is mounted on a … Dynamic Mechanical Analysis (DMA) was performed to determine the mechanical properties of the stents. Biomechanics, by its characteristic multi-disciplinary approach, may provide the right key to investigate these devices . 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. Depending on the time of occurrence, ST can be classified into four types: acute, sub-acute, late and very late. 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. Hence, these drawbacks limit the use of polymers in stents. used without any improvement of the material; this is essential in order to identify the stent fractures earlier through X-ray. This higher density makes it possible to design a thin-strut stent … 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. 2. Therefore, from the viewpoint of mechanical properties and visibility on X-ray imaging, metals are the main materials utilized for stents. Higher the von-mises stress in stent, the stiffness of the stent being high, but which may damage the coronary artery . describe the unique material properties ofNitinol and how they relate to the performance characteristics ofNitinol stents. Given the superelastic properties of NiTi stent, the used Download as PDF. tents are narrow tubes. Accurate design of the stent shape should be performed in order to limit the room temperature strain imparted to the alloy during stent expansion. through a computational approach that optimises material properties and stent geometry. 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. Thus, PEEK 450G is a better material for coronary stent implants. Background: Angioplasty with stenting is one of the primary treatment for coronary artery disease, hence, performance of the stent is deemed important. Accurate design of the stent shape should be performed in order to limit the room temperature strain imparted to the alloy during stent expansion. Material and surface (texture) Stent materials and surface are relevant to in-stent re-stenosis. In theory, bioresorbable stents made from biocorrodible metals are able to have thinner struts and lower profile compared to polymeric scaffolds (17). 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 ]. Some of these properties are not possessed by other materials currently used to manufacture stents. However, the function and the properties of the materials themselves have rarely been inves-tigated. Nitinol 55 and Nitinol 60.It exhibits the shape memory effect and superelasticity at different temperatures. 2. 2. This is a major problem of current ureteral stents, which are used clinically to treat the blockage of ureteral canals. 1Department of Polymer Science and Engineering, Sungkyunkwan University, Suwon 440746, Republic of Korea. Studies with drug-eluting stents revealed their good biocompatibility properties and that drug-eluting capacity can be safely added to urethral stents. 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. A summary of the mechanical and physical properties of different bioresorbable materials used in the fabrication of BRS and DES are shown in … factors for ISR has been recognized, such as stent material and geometry, lesion and stent length, stent number, diabetes and female sex [19]. Stent materials The stent materials have a great influence on their efficacy, especially their mechanical and physicochemical properties. 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. By referring the basic stent model with 8 rhombus shape units the stent was mod-elled using SolidWorks. The flexible balloon-expandable stents showed pushability values between 0.13/N (AVE Bridge) and 0.20/N (Perflex). It is interesting to note that many DES essentially employ the same design configuration as their BMS counterparts with a drug-loaded … 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. Three ideal sample stent types with different cell configurations were manufactured. Suitable stent materials are metals, metal-alloys or polymers. How to improve stent mechanical properties is a key issue for designing biodegradable polymeric stents (BPSs). Nitinol (nickel~titanium) alloys exhibit a combination of properties which make them particularly suitable for the manufacture of self-expanding stents. 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 … Acute ST occurs between 0 and 24 h following stent … stainless steel 316L (the most common stent material) and high entropy alloy properties as the material properties for the 3D stent model. The data are based on the Auricchio model [5,11,22,24]. 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. 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. 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. Stent is a tube-like, flexible, and small device. common material format for stents is tubing, a review is conducted to show how tubing attributes influence stent properties and manufacturability. onV Mises stress mathematical equation was used in By referring the basic stent model with 8 rhombus shape units the stent was mod-elled using SolidWorks. the other end. 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. The optimization of material properties, surface finish, and stent design is necessary for the development of stent . In many circumstances a combination of one or … 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. This study investigates the effectiveness and applicability of magnesium as a novel biodegradable ureteral stent material that has inherent antimicrobial properties. Stents are made-up of metals such as cobalt chromium, stainless steel, and nitinol. Stent is either made from polymer or metal. Two different temperatures (1000°C and 1150°C) were explored for the thermal processing of the device.

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