Effect of Different Storage Times on Dimensional Stability of Casts Made of Two Alginates: Tropicalgin and Chromogel

Dimensional stability of alginate impression materials is affected by several factors such as storage time, storage conditions and type of the impression material. This study was conducted to assess the effect of storage time on dimensional stability of two different alginates: Tropicalgin and Chromogel.
In this experimental study, impressions were made of a master model with four metal cones on the occlusal surfaces of lower first premolars and third molars on both sides (teeth #1, #5, #12 and #16). The Impressions were divided into five groups in terms of the storage time in wet paper towels within a closed plastic bag before pouring the casts (15 min, 30 min, 60 min, 120 min and 24 h). For each group, 20 impressions and a total of 100 impressions were made. The impressions were poured with type III stone (Parsdental, Iran). Six dimensions (D1 to D6) between 4 cones were considered as the gold standard in order to compare with the same dimensions on the stone casts. Distances were measured by a digital caliper and data were statistically analyzed by MANOVA and one-sample t-test.
Dimensional changes increased over time for both alginates except for one sample (Tropicalgin at 30-min interval for D1, p value = 0.4). There were significant differences between the two materials at all the time intervals except for the first fifteen minutes. Dimensional changes were within the clinically acceptable limits (a change of 1.5% relative to the master model) up to 120 min for both alginates.
The dimensional stability of Tropicalgin and Chromogel alginate impression materials was affected by storage time before pouring in stone and the material type.