title: Dimensional changes of extended-pour alginate impression materials.
abstract: BACKGROUND
  Recently, manufacturers have marketed alginate impression materials, claiming dimensional stability for up to 100 hours to allow shipping to a dental laboratory for digital model fabrication. The purpose of this study was to evaluate the dimensional changes of these newer materials after storage at different temperatures and times.
  
  
  METHODS
  Two extended-pour alginates (claiming 100 hours of accuracy) (Kromopan; Lascod, Florence, Italy; and Triphasix; Parkell, Edgewood, NY), 2 traditional alginates (Jeltrate; Dentsply-Caulk, York, Pa; and Kromatica; Matech, Sylmar, Calif), and 1 vinyl polysiloxane (VP Mix; Henry Schein, Melville, NY) were used to impress a scored aluminum die. The distance between the score lines was measured on the impressions at 10 minutes, 24 hours, and 100 hours after mix, and the percentages of dimensional change were calculated. Temperature effects were studied by storage at cold (-9°C), room (22°C), or hot (46°C) temperatures for 8 hours.
  
  
  RESULTS
  All alginates had statistically significant dimensional changes at 24 and 100 hours (0.69%-6.13%). VP Mix exhibited no statistically significant changes for any storage condition. The Kromopan (100 hour) and Kromatica (traditional) alginates were the most stable (0.85%-2.22% at 100 hours). Triphasix (100 hour) and Jeltrate (traditional) were the least stable (1.53%-4.73% at 100 hours). Cold-temperature storage resulted in the most dimensional changes (1.96%-4.73% at 100 hours). Room-temperature storage resulted in the least dimensional changes (0.97%-1.53% at 100 hours).
  
  
  CONCLUSIONS
  All alginate impression materials in the study had significant changes at 24 and 100 hours in all storage conditions tested.
authors.affiliation: Department of Orthodontics, School of Dental Medicine, University of Colorado, Aurora, CO 80045, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Todd
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Oesterle
authors.forename: Sheldon M
authors.initials: SM
authors.lastname: Newman
authors.forename: W Craig
authors.initials: WC
authors.lastname: Shellhart
mesh_terms: D000464:Alginates; D003760:Dental Impression Materials; D061827:Dimensional Measurement Accuracy; D020724:Elastomers; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D003765:Models, Dental; D013696:Temperature
chemical_list: D000464:Alginates; D003760:Dental Impression Materials; D020724:Elastomers