Objectives: This study was conducted to assess and compare the effect of storage time on the dimensional stability of extended-pour alginates and polyether impression materials.
Materials and Methods: This study was applied on Kennedy class II mod 1 mandibular educational model. Impressions of the model were made using Hydrogum 5 (extended pour alginate) and Impregum polyether material. Four groups were defined according to the impression material and the pouring time: Group I: Impressions were made using extended pour alginate and were poured after one day. Group II: Impressions were made using polyether impression material and were poured after one day. Group III: Impressions were made using extended pour alginate and were poured after five days. Group IV: Impressions were made using polyether impression material and were poured after five days. For each group, ten different impressions were prepared. The impressions were poured to create the casts that were digitally scanned. A 3D data analyzing software was used to evaluate the presence of discrepancies between the original cast and the experimental casts.
Results: Group III showed the highest value 0.91±0.07, regarding average deviation from the defined horizontal plane in the reference cast, followed by group I 0.05±0.037, and group IV 0.25±0.019 while group II showed the lowest value 0.02±0.012. Kruskal Wallis test showed significant difference between the studied groups and Mann Whitney test with Bonferrioni correction showed statistically significant difference between Group III with group II and group IV.
Conclusion: Under appropriate storage conditions, polyether impression material poured after one day produced the most dimensionally accurate casts however, extended pour alginates attained clinically acceptable range of dimensional accuracy