Effect of Storage Conditions on Alginate Impressions' Dimensional Stability

Objectives: The accuracy of alginate impression material is one of its most desired properties. Thus storage of the impression before pouring the cast is a crucial factor for dimensional accuracy. The aim of this study was to determine the best storage condition and the best alginate material to be used for the dimensional accuracy of impressions. Methods: In order to evaluate the dimensional changes, the alginate impressions were made using two different impression materials with different setting times (Orthoprint Alginate, Zhermack Spa, Badia Polesine, Italy [1min 5s], Plastalgin, Septodont, Cedex, France [2min 15s]).The impressions were stored in different storage conditions (1- stored in open air, 2- stored in humid environment in sealed plastic bag, 3- wrapped with wet towel) for different time periods (0min, 15min, 30min, 60min). The dimensional changes for 6 dimensions were compared with an upper jaw master model with 16, 13, 23, 26 numbered teeth without any undercuts. The measurements were performed with a 3-D measurement device. Results: One way ANOVA, Least Significant Difference (LSD) and Univariate ANOVA tests were used for statitical analyses (p≤0,05). According to the results of the study 1- the material with shortest setting time and 2- the impressions stored in humid environment in sealed plastic bags, showed better dimensional stability. Statistically significant changes were observed in some dimensions even after storage for 15min. Conclusion: Although using the material with shortest setting time and storing the impressions in humid environment in sealed plastic bag are better options, alginate impressions should be poured as soon as possible to improve dimesional stability.