title: A scanning electron microscopic study of biliary stent materials.
abstract: BACKGROUND
  Clogging of biliary stents remains an important problem. In vitro studies have shown less sludge formation in Teflon stents. Recently, clinical studies with Teflon stents have produced contradictory results. The aim of this study was to investigate whether the surface properties of the endoprostheses could explain the variation observed in clinical studies.
  
  
  METHODS
  A total of 9 different types of unused 10F endoprostheses were examined by scanning electron microscopy (SEM): polyethylene Amsterdam-type, polyurethane Amsterdam-type, Teflon Amsterdam-type, Teflon Tannenbaum-type and a Tannenbaum-type stent with a thin stainless steel mesh between inner and outer layers.
  
  
  RESULTS
  All polyethylene stents had a relief with tiny lumps. All Teflon stents had multiple shallow pits and ridges along the entire longitudinal axis. Both Tannenbaum-type stents also had multiple particles protruding into the stent lumen with adjacent holes in the wall of the stent. The polyurethane stent had an extremely smooth surface.
  
  
  CONCLUSIONS
  SEM of Teflon made stents showed a markedly irregular inner surface, which may explain the controversial results of clinical studies. Our results indicate that the inner surface of a new stent should first be evaluated by SEM before clinical trials are initiated.
authors.affiliation: Department of Gastroenterology and Hepatology and Department of Electron Microscopy, Academic Medical Center, University of Amsterdam, The Netherlands.
authors.forename: A M
authors.initials: AM
authors.lastname: van Berkel
authors.forename: J
authors.initials: J
authors.lastname: van Marle
authors.forename: H
authors.initials: H
authors.lastname: van Veen
authors.forename: A K
authors.initials: AK
authors.lastname: Groen
authors.forename: K
authors.initials: K
authors.lastname: Huibregtse
mesh_terms: D002779:Cholestasis / Q000517:prevention & control*; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D020959:Polyethylene; D011138:Polytetrafluoroethylene; D015607:Stents; D013499:Surface Properties
chemical_list: D011138:Polytetrafluoroethylene; D020959:Polyethylene