title: Aging assessment by dynamic mechanical analysis of in vivo encrusted polymeric urinary stents.
abstract: OBJECTIVE
  To investigate the viscoelastic properties of plastic pigtail stents after removal from patients using the method of dynamic mechanical analysis (DMA).
  
  
  METHODS
  Dynamic mechanical analysis was performed in 12 polymeric pigtail stents left indwelling for various periods of time (0-120 days). The encrustations were characterized by infrared spectroscopy, and their morphology was observed using scanning electron microscopy.
  
  
  RESULTS
  Softening and stiffening behavior was observed. Stiffening was found specifically in the stents with heavy mineral deposits.
  
  
  CONCLUSIONS
  Material degradation becomes obvious after certain periods of time. The effect of stent degradation appeared in two forms: softening of the stent polymer, possibly through interaction with urine, and stiffening of the stent secondary to the formation of various insoluble mineral deposits covered by layers of organic matrix.
authors.affiliation: Department of Materials Science, University of Patras, Patras, Greece.
authors.forename: D E
authors.initials: DE
authors.lastname: Mouzakis
authors.forename: N
authors.initials: N
authors.lastname: Bouropoulos
authors.forename: G
authors.initials: G
authors.lastname: Bithelis
authors.forename: E
authors.initials: E
authors.lastname: Liatsikos
mesh_terms: D001672:Biocompatible Materials; D004867:Equipment Design; D006801:Humans; D066298:In Vitro Techniques; D019563:Mechanics; D008855:Microscopy, Electron, Scanning; D011108:Polymers; D017550:Spectroscopy, Fourier Transform Infrared; D015607:Stents; D014514:Ureteral Calculi / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D001672:Biocompatible Materials; D011108:Polymers