Papers by Author: György Ring

Abstract: The clinical results of drug eluting stents [DESs] depend on the type of the coating, the coating technology and the dosage and efficiency of the drug. The current study shows our examinations on drug eluting stents. Different types of commercially available coronary stents were investigated. Various methods were used for these experiments, for example optical microscopy, confocal fluorescent microscopy, scanning electron microscopy and EDS analysis. The properties characterizing applicability of drug eluting stents and the changing of the coatings during expansion are shown.

Abstract: Stents are special metallic or polymer endoprostheses of meshed structure and tube shape. Their function is to prevent restenosis in the arteries. Stents can be coated or uncoated. In the expanded part of the artery the chance of restenosis is bigger even without a stent so it is practical to coat the stents. The aim of this work is to present the results of the coating experiments made on the coronary stents. Three types of commercially available polyurethanes were used for these experiments. The coatings were produced by a dipping method. Electro-polished and non-electro-polished metallic sheets and stents were used for these experiments. Contact angle measurements were done to examine the wetting properties of the three different polyurethane coatings. The quality and the changing of the coatings were examined by different methods (stereomicroscope, scanning electron microscope and energy dispersive spectrometry).

Abstract: In our study we summarise the materials and manufacturing technologies of coronary stents used nowadays. Different testing methods for stent’s features are presented and main expansion features such as recoil and foreshortening are determined. The most frequent failures caused by the expansion of the coronary stents are also shown.

Abstract: In this study the main properties of coated coronary stents are shown, such as recoil, foreshortening, surface features and failures and the expansion properties. The types and the effects of active and passive coatings are introduced. The results of our examinations with different coated coronary stents are shown as well. The quality and the changing of the coatings were examined by different methods (stereomicroscopy, atomic force microscopy, scanning electron microscopy and EDS analysis).

Abstract: The role of the stents is to prevent restenosis. The rapid growth of stents’ application in the treatment of cardiovascular diseases resulted in the unique development of these implants. This is mainly due to the effective clinical trials, the success of which determined the use of these endoprostheses. In this study the surface properties of the coronary stents were described by using different methods (stereomicroscopy, scanning electron microscopy and energy dispersive analysis) before and after balloon expansion. Furthermore, the most frequent failures caused by the expansion were introduced. For investigating fatigue properties two high cycle fatigue test equipments were used: the first one simulates the bending stress, and the second one simulates the effect of the pulsating mechanical strain. Surface features of the stents were examined after the fatigue tests as well: macroscopic damages were not originated on the stents, and the implants were not broken down. Only small traces of fatigue occurred on the surface, which became rough; and slip lines and grain boundaries were outlined.

Abstract: The main goal of the present study was to determine the surface features, surface failures and fatigue properties of coated coronary stents. The quality and the changing of the coatings were examined by different methods. In this paper, the results of the examinations with different coated coronary stents are introduced and the results of the coating experiments are shown as well.