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Title: Multi-scale mechanical investigation of stainless steel and cobalt-chromium stents
Authors: Kapnisis, Konstantinos 
Constantinides, Georgios 
Georgiou, Harry 
Cristea, Daniel 
Gabor, Camelia 
Munteanu, Daniel 
Brott, Brigitta C. 
Anderson, Peter G. 
Lemons, Jack E. 
Anayiotos, Andreas 
Major Field of Science: Engineering and Technology
Field Category: Materials Engineering
Keywords: Fracture;In-stent restenosis (ISR);Mechanical properties;Nanoindentation;Stents
Issue Date: 1-Dec-2014
Source: Journal of the Mechanical Behavior of Biomedical Materials, 2014, vol. 40, pp. 240-251
Volume: 40
Start page: 240
End page: 251
Journal: Journal of the Mechanical Behavior of Biomedical Materials 
Abstract: In-stent restenosis (ISR) remains a significant limitation despite the considerable previous clinical and investigative emphasis on the problem. Complications arising from the interaction of stent materials with the surrounding vessel wall as well as from the mechanical forces developing after implantation, play an important role in the development of ISR. To investigate the relation between mechanical factors and stent structural integrity, and to identify any structural weakness points on the geometry of commercially available Stainless Steel and Cobalt-Chromium stents, accelerated pulsatile durability tests were carried out in a simulated physiological environment. Potential spatial variations in the mechanical properties on stent struts and their role in the observed premature failures of the stent devices during operation were also examined. Fretting wear and fatigue-induced fractures were found on stent surfaces after exposure to cyclic loading similar to that arising in vivo. Nanoindentation studies performed on various locations along the stent struts have shown that the hardness of specific stent locations significantly increases after mechanical expansion. The increase in hardness was associated with a reduction of the material's ability to dissipate energy in plastic deformations, therefore an increased vulnerability to fracture and fatigue. We conclude that the locations of fatigue fractures in stent struts are controlled not only by the geometrically-driven stress concentrations developing during cyclic loading but also by the local material mechanical changes that are imparted on various parts of the stent during the deployment process.
ISSN: 1751-6161
DOI: 10.1016/j.jmbbm.2014.09.010
Rights: © Elsevier
Type: Article
Affiliation : Cyprus University of Technology 
Transilvania University of Brasov 
University of Alabama at Birmingham 
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