title: Encrustation of a metal alloy urinary stent: a mechanistic investigation.
abstract: METHODS
  A section of a metal stent consisting mainly of tantalum coated partially by strongly adhering calcium oxalate monohydrate (COM) crystals was immersed in supersaturated solutions prepared from calcium chloride and sodium oxalate at 37 degrees C and ionic strength 0.15 M in NaCl. Abstract
  
  
  OBJECTIVE
  To investigate the kinetics of encrustation of a metall alloy urinary stent system in vitro by calcium oxalate and characterize the crystals forming from solutions supersaturated with respect to all calcium oxalate hydrates.
  
  
  RESULTS
  The COM-coated stent mineralized upon immersion in the supersaturated solutions. The process was monitored with a calcium ion-selective electrode and the rates were measured at conditions of sustained solution supersaturation. COM crystals formed on the stent and the rate of COM crystal growth yielded a second-order dependence on the solution supersaturation.
  
  
  CONCLUSIONS
  The deposition of COM crystals on the metal stents coated partially with COM crystals by adhesive forces was found to be most important for the acceleration of the encrustation process. The dependence of the rates on the solution supersaturation suggested absence of secondary nucleation and a surface-controlled process for the encrustation process.
authors.affiliation: Department of Urology and Radiology, Medical School University of Patras, Patras, Greece.
authors.forename: G A
authors.initials: GA
authors.lastname: Barbalias
authors.forename: C
authors.initials: C
authors.lastname: Bouropoulos
authors.forename: N V
authors.initials: NV
authors.lastname: Vagenas
authors.forename: N
authors.initials: N
authors.lastname: Bouropoulos
authors.forename: D
authors.initials: D
authors.lastname: Siablis
authors.forename: E N
authors.initials: EN
authors.lastname: Liatsikos
authors.forename: D
authors.initials: D
authors.lastname: Karnabatidis
authors.forename: P G
authors.initials: PG
authors.lastname: Koutsoukos
mesh_terms: D000497:Alloys; D001672:Biocompatible Materials; D002129:Calcium Oxalate; D003460:Crystallization; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D011475:Prosthesis Failure; D015607:Stents
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; D002129:Calcium Oxalate