title: An in vitro study on the dimensional stability of a vinyl polyether silicone impression material over a prolonged storage period.
abstract: BACKGROUND
  A new elastomeric impression material, a vinyl polyether silicone, has been commercially introduced. Its dimensional stability at different pouring times has not been reported.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate the dimensional stability of vinyl polyether silicone (VPES) impressions as a function of delayed-pouring time for up to 2 weeks after performing a recommended clinical disinfection procedure.
  
  
  METHODS
  The 3 medium-body impression materials tested were EXA'lence 370, Imprint 3, and Impregum Penta soft. Impressions of a cylindrical metal model, which served as a control, were made and poured in a Type V stone after being disinfected in 2.5% buffered glutaraldehyde solution. Die diameter and anteroposterior and cross-arch measurements on each cast were made and compared to direct measurements of the control with a digital micrometer. The linear dimensional changes were compared and analyzed by using the Mann-Whitney U test (α=.05).
  
  
  RESULTS
  Considering the absolute values for the mean percentage dimensional change, VPES cast measurements were below 1.0% (P<.001), with the majority being minimal (≤0.34%) at all pour times. Measurements of the casts were larger than those of the control in all but one specimen. The percentage dimensional changes of the individual die diameters were higher than those of the anteroposterior and cross-arch linear measurements. Casts produced from VPES impressions had similar dimensional changes to those of VPS at 1 week of storage and similar changes to those of PE at 2 weeks of storage. The behavior of VPES impressions varied from being the most accurate at immediate-pour to gradually exhibiting higher dimensional changes as time progressed.
  
  
  CONCLUSIONS
  Casts produced from a disinfected regular set VPES (EXA'lence 370 monophase) demonstrated excellent dimensional stability at different pour times and were comparable to the tested VPS and PE impression materials.
authors.affiliation: Department of Dentistry, Faculty of Engineering, University of Alberta, Edmonton, Alberta, Canada. unassar@ualberta.ca
authors.forename: Usama
authors.initials: U
authors.lastname: Nassar
authors.forename: Andrea
authors.initials: A
authors.lastname: Oko
authors.forename: Samer
authors.initials: S
authors.lastname: Adeeb
authors.forename: Marwan
authors.initials: M
authors.lastname: El-Rich
authors.forename: Carlos
authors.initials: C
authors.lastname: Flores-Mir
mesh_terms: D002133:Calcium Sulfate / Q000737:chemistry; D019551:Dental Disinfectants / Q000737:chemistry; D003760:Dental Impression Materials / Q000737:chemistry*; D003761:Dental Impression Technique / Q000295:instrumentation; D003764:Dental Materials / Q000737:chemistry; D004987:Ethers / Q000737:chemistry*; D005976:Glutaral / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D003765:Models, Dental / Q000592:standards; D011145:Polyvinyls / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry; D012828:Silicones / Q000737:chemistry*; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014753:Vinyl Compounds / Q000737:chemistry*
chemical_list: D019551:Dental Disinfectants; D003760:Dental Impression Materials; D003764:Dental Materials; D004987:Ethers; C022821:Impregum; D011145:Polyvinyls; D012117:Resins, Synthetic; D012828:Silicones; D012833:Siloxanes; D014753:Vinyl Compounds; C034183:vinyl polysiloxane; D005976:Glutaral; D002133:Calcium Sulfate