Comparative Study of the Effect of Storage Environment Temperature on the Accuracy of Hygedent and Chromogel Alginate Impression Materials

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. 

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.

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%).

It seems that the dimensional stability of Hygedent and Chromogel alginates is affected by storage temperature, pouring time, and type of alginate.