Dimensional stability of elastomeric impression materials: a critical review of the literature

The aim of the present paper was to review the literature concerning the dimensional stability of dental elastomeric impression materials, to support recommendations to control the variables that influence the accuracy of these materials. An electronic search of the Scopus and PubMed databases was performed in November 2010. Articles were selected according to the following inclusion criteria: investigation of the dimensional stability of dental elastomers, an experimental study, sample size reported, laboratory tests described, and published in an English language peer-reviewed journal. The search resulted in 47 articles published between 1958 and 2008; of these, 24 were selected for inclusion in the present study. Great variability was discovered in the experimental methodologies used, such as different working times, temperatures and storage mediums for the impressions, impression techniques, material thicknesses, tray types, and methods of evaluation. Despite the lack of standardization among the studies, this review supports the following recommendations to control the dimensional stability: impressions should be stored at temperatures between 21 +/- 2 degrees C; polyether impressions should be stored in an environment with a relative humidity below 50%; time until pouring has been settled for each elastomer material.