Alginate substitute materials are inexpensive polyvinyl siloxane (PVS) impression materials that exhibit better detail reproduction and tear strength than alginate. Alginate substitute materials do show slightly more outgassing and resulting cast porosity than traditional alginates, particularly when they are poured soon after mixing. To reduce cast surface porosity, a minimum pouring delay of 60 minutes is suggested.
SUMMARYObjective: To compare three alginate substitute materials to an alginate impression material for cast surface porosity (outgassing), tear strength, and detail reproduction.Materials and Methods: Detail reproduction tests were performed following American National Standards Institute/American Dental Association (ANSI/ADA) Specification No. 19. To measure tear strength, 12 samples of each material were made using a split mold, placed in a water bath until testing, and loaded in tension until failure at a rate of 500 mm/min using a universal testing machine. For cast surface porosity testing, five impressions of a Teflon mold with each material were placed in a water bath (37.88C) for the in-mouth setting time and poured with vacuum-mixed Silky Rock die stone at 5, 10, 30, and 60 minutes from the start of mixing. The gypsum samples were analyzed with a digital microscope for surface porosity indicative of hydrogen gas release by comparing the surface obtained at each interval with four casts representing no,