Environment to Store Alginate at its Best: An In-vitro Study

Introduction: Irreversible hydrocolloid alginate impressions are among the widely used impression materials in dentistry but they suffer from one major drawback, i.e., dimensional change after setting. Because of clinical limitations, impressions are poured to make cast after a time delay which is so long as compared to the recommended period. This can be reduced by storing the impression material in different storage environments.

Aim: To assess the impact of the storage environment on the dimensional accuracy of alginate impression material.

Materials and Methods: In this in-vitro study, 70 samples were made with chromatic alginate impression material according to the manufacturer’s guidelines and divided into seven groups (Exposed to atmosphere, Airtight container in the refrigerator, 2% NaCl (Sodium Chloride) solution, Air-tight container, Distilled water, 1% K2SO4 (Potassium Sulphate) solution and Mixture of 2% NaCl and 1% K2SO4 Solution). Samples were made with stainless steel die fabricated according to ADA specification 18 and dimensions were noted after 24 hours of storage. Distance between the cross lines was calculated using profile projector. ANOVA Test and Tukey Test were applied to compare the mean dimensional change of seven groups and to compare the difference in mean dimensional change between the groups.

Results: Samples kept in a solution of 1% K2SO4 and 2% NaCl solution had no significant dimensional change (F-value 2026.0, p-value <0.001), whereas samples stored in open-air resulted in the greatest dimensional change (Group 7 > Group 6 > Group 3 > Group 4 > Group 2 > Group 5 > Group 1).

Conclusion: The impressions which are kept in a combined solution of 1% K2SO4 and 2% NaCl have shown the best impact on the dimensional accuracy of alginate impression materials. However, these can also be seen in 1% K2SO4 or in 2% NaCl solutions, respectively.