Background and Aim: Considering the lack of sufficient and even contradictory studies on the effect of temperature-dependent dimensional changes of alginate before pouring, this study aimed to investigate the effect of storage temperature of Hygedent and Chromogel alginate molds on dimensional stability. 
Materials and Methods: In this in-vitro experimental study, dimensional changes of two types of alginate were investigated indirectly by measuring a type III stone cast. Ninety molds of each alginate were obtained from a metal model and stored at 1±4, 1±25, and 1±40°C. The casting was performed 12 minutes, 1 hour, and 4 hours after impression taking. The molds were incubated with an approximate humidity of 100%. The diameter, width, and height of the gypsum casts were measured by a digital caliper with an accuracy of 0.01 mm. Dimensional changes of two alginates in three separate directions were statistically analyzed by three-way analysis of variance (ANOVA) and post-hoc test due to the significant difference.
Results: There was no statistically significant difference in width changes at different temperatures, but regarding the diameter, there was a significant difference between 40°C Chromogel and 25°C Hygedent. Regarding the height, only 40°C Hygedent showed a significant difference at 4 hours compared to 12 minutes (P=0.000, 0.26, and 0.000, respectively). However, no statistically significant difference was observed in other temperatures and times (P>0.05). In most groups, dimensional changes of all samples were not within the clinical standard range (1%).
Conclusion: It seems that the dimensional stability of Hygedent and Chromogel alginates is affected by storage temperature, pouring time, and type of alginate.