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2 Journal of Achievements in Materials and Manufacturing Engineering

2 2010

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Use of coronary stents - material and biophysical conditions

Paszenda Z.

Journal of Achievements in Materials and Manufacturing Engineering

2010

Vol. 43, nr 1

125-135

Purpose: The paper discusses application issues of using the metallic implants for treatment of the cardiovascular diseases. The analysis of the biophysical conditions of the heart – coronary vessels system has been used to distinguish the tissue environment properties which should be compatible with properties of the metal biomaterial and stent’s surface. On this basis the author presented results of experiments concerning the usefulness of the passive-carbon layer for surface treatment of vascular stents made of stainless steel. Design/methodology/approach: In order to determine the usefulness of the layer for implants in cardiology the following tests were carried out on the layer: structure, thickness, corrosion resistance, electrical properties and biocompatibility in experimental animals. The structure and thickness of the layer were tested in high resolution transmission electron microscope. Corrosion resistance was carried out by recording anodic polarization curves. Methodology of measurements took into consideration both implantation conditions and application of vascular stents. In tests concerning electrical properties of the layer, current-potential as well as capacity-potential characteristics were determined. Findings: The passive-carbon layer of nanocrystlline structure and high smoothness created on coronary stents’ surface fully ensures pitting corrosion resistance in both implantation and application conditions. Research limitations/implications: Deposition of the dielectric carbon layer on coronary stents’ made of stainless steel is effective method of reducing reactivity of their surface in blood environment and blood clotting in consequence. Originality/value: The need to determine the correct quality and properties of coronary stents was indicated. The properties refer to stents’ design, physio-chemical properties of the metallic biomaterial and its surface. Keywords: Biomaterials; Cr-Ni-Mo steel; Corrosion resistance; Electrical properties; Coronary stents

Modification of surface films on chromium-nickel-molybdenum steel implants used in orthopaedics and traumatology

Marciniak J.

Journal of Achievements in Materials and Manufacturing Engineering

2010

Vol. 43, nr 1

108-116

Purpose: the paper is to characterize stainless steel of modyfied sufrace as a material used in orthopaedics and traumatology on the example of LCP (Locking Compression Plate) used in long bones treatment. Design/methodology/approach: In order to reach the goal biomechanical analyses, both numerical and experimental, were carried out. The results of the analyses are the basis for selecting geometrical features of a plate stabiliser and biomaterial mechanical properties. The degree of stress and deformation also determines areas where corrosion can start to develop. Chromium-nickel-molybdenum steel widely applied for making implants used in orthopaedics and traumatology was selected for testing implant surface modification. Passive and passive-carbon films were formed on the implants. The structure of the created films was tested together with their susceptibility to deformation and resistance to corrosion. Findings: It was shown that formation of passive-carbon DLC coatings is an effective method of increasing steel resistance to pitting, crevice and stress corrosion and of increasing its biocompatibility. Practical implications: The proposed surface treatment seems to be effective method that allow to reduce the risk of post-surgical complications. The coatings can be formed by using electrolytic polishing and passivation and a final RF PACVD process. Originality/value: The author also presents results of the coating surface topography examination, results of tests on its chemical and phase structure as well as mechanical and physicochemical properties.