title: Dimensional stability of irreversible hydrocolloid impression materials as a function of pouring time: a systematic review.
abstract: BACKGROUND
  Pouring time of irreversible hydrocolloid impressions differs depending on the brand and intended use, either of which may result in variable dimensional stability.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the available literature on dimensional stability of irreversible hydrocolloid impression materials as a function of pouring time and disinfectant solutions used.
  
  
  METHODS
  Three electronic database searches (Medline, PubMed, and EMBASE) were conducted to identify in vitro peer-reviewed studies published in English between the early 1970s and October 2010. Selection criteria included in vitro studies, irreversible hydrocolloid as impression material, and storage time. Heterogeneity in the methodology of the selected studies precluded a meta-analysis.
  
  
  RESULTS
  Of 62 initially selected studies only 18 were included. Traditional irreversible hydrocolloids were generally stable when poured immediately. However, stability decreased as time elapsed. New irreversible hydrocolloid substitutes appear to allow delay in pouring time and repouring of impressions without significant side effects.
  
  
  CONCLUSIONS
  Shorter storage time of irreversible hydrocolloid impressions before pouring is desirable, although this may not be necessary for the extended-pour types. The lack of a standardized technique for studying the effect of storage condition, with or without the use of disinfectants, makes it difficult to make clear recommendations.
authors.affiliation: Department of Dentistry, University of Alberta, Edmonton, Canada. unassar@ualberta.ca
authors.forename: Usama
authors.initials: U
authors.lastname: Nassar
authors.forename: Tehnia
authors.initials: T
authors.lastname: Aziz
authors.forename: Carlos
authors.initials: C
authors.lastname: Flores-Mir
mesh_terms: D000464:Alginates / Q000737:chemistry*; D019551:Dental Disinfectants; D003760:Dental Impression Materials / Q000737:chemistry*; D004356:Drug Storage; D008422:Materials Testing; D013997:Time Factors
chemical_list: D000464:Alginates; D019551:Dental Disinfectants; D003760:Dental Impression Materials