Dimensional change of acrylic resin tray materials

Twelve commonly used acrylic resin tray materials were compared for linear curing shrinkage. Three of the 12 were found to expand slightly during the first few hours, which had the effect of reducing the net shrinkage. All trays, however, exhibited shrinkage during the 24-hour test period. Therefore, autopolymerizing acrylic resin tray materials should not be used for an impression the same day that they are made unless the tray is boiled as suggested by Pagniano et al. This agrees with research already completed even though the magnitude of shrinkage was considerably less than that reported in previous studies.