RESUMEN
One of the most important problems in disinfecting alginate impressions is the dimensional changes caused by hydrocolloid nature of alginate. The aim of this study was to determine and compare the dimensional changes of two irreversible hydrocolloid impression materials [Iralgin -Alginoplast] disinfected by immersion in sodium hypochlorite solution. One metal model consisting of one platform and two partial conical dies was made and 80 impressions were then prepared using two kinds of alginate impressions materials. The impressions were divided into four groups. In groups 1 and 3, impressions were first rinsed for 15 seconds and immersed in 0.525% sodium hypochlorite solution and finally were poured by type 111 dental stone. In groups 2 and 4, impressions made by these two materials were only rinsed by tap water for 15 seconds and kept in 10% moisture for another 10 minutes and then were poured by type III dental stone. Different dimensions of samples in four groups were measured by digital caliper and compared using variance analysis and Duncan tests. Diameters, heights and outer distances of all samples showed significant differences with the metal model [P=0.049], however; inner distances did not have any significant difference [P=0.269]. Moreover, significant differences, in diameter and height, were found between case and control groups. In all four groups, diameters and outer distances increased and heights decreased compared to the metal model which are in agreement with the similar studies. All such changes were estimated less in Iralgin than Alginoplast