Comparative evaluation of the dimensional accuracy of three different irreversible hydrocolloid impression materials at different storage periods - an invitro study

Purpose: The purpose of the study was to compare the dimensional stability of three different alginate impression materials at three different storage periods. Materials and Methods: A brass model representing maxillary edentulous ridge was used as a master model in this study. Three customised abutments A,B,C were CAD/CAM machined to simulate full veneer preparation. They were positioned on the master model one in the anterior region and two in the posterior region on either side of the ridge. The centre of the cross hair reference lines made on the occlusal surfaces of abutments was used for measuring linear dimensional changes. A total of 90 impressions of the master model was made by all three irreversible hydrocolloids and stored in three different storage period of 30 minutes, 12 hours and 24 hours. The casts were poured after three storage period with type IV gypsum product and the inter abutment distance between the abutments were measured with the electronic vernier caliper. Results: ANOVA analysis showed no significant differences (p< .05) at 30 minutes storage period between all three alginates and a very high significant difference (p< .001) at 12 and 24 hours storage periods. Conclusion: The dimensional accuracy of the improvised alginates Cavex CA37 and Neocolloid were greater than the conventional Algitex in delayed pouring of the cast.