Dimensional accuracy of double poured casts obtained from extended pour alginate impressions: An in vitro study

Background: A new generation of smart alginates have been developed claiming to have good dimensional stability and deformation resistance. However, there is a lack of sufficient scientific evidence in this regard. Aim: This study aims to evaluate the dimensional stability of casts generated from first and second pour of two different types alginate purported to allow multiple pour and remain dimensionally stable after storage. Methodology: Forty impressions were made of a maxillary dentulous model (standard die), using two types of alginate (Hydrogum 5.0, Cavex Colour change). Two sets of casts were generated from 10 impressions of each type of alginate immediately. Ten impressions of each type of alginate were stored wrapped in damp paper towel and stored in zip-locked bags, and two sets of cast were generated after 24 h. Casts were scanned with a three dimensional model scanner and compared with standard die. Results: No significant difference was found between standard die and second poured casts of both alginates after immediate pouring. A significant difference was found between standard die and second poured casts of both alginates after 24 h. However, percentage dimensional change was within clinically acceptable limits. Conclusion: Clinically acceptable casts can be generated by the double pouring of new generation alginates. However, for better results casts should be poured immediately.