Dimensional stability of irreversible hydrocolloid impression material.

Abstract A total of 200 alginate impressions were made from a standard metal model that was grooved at four points to provide precise sites for making buccolingual and mesiodistal measurements to determine dimensional stability. Each of four commercially available alginate impression materials was subjected to five different storage methods prior to pouring in an effort to determine which impression material and storage method produced the most accurate casts. Ten casts were produced from each material-method combination. Means and standard deviations were computed from the buccolingual and mesiodistal measurements of each group of ten casts. These measurements were then compared to the same measurements of the standard model. An analysis of variance and the Duncan Multirange Test were used to determine total error, taking into account each alginate material, each storage method, and the interaction between the two. The immediate-pour technique produced the most accurate casts, and Product B was the material of choice with this method. Product C and Product D were more accurate over-all than Product A and Product B with all storage methods. The accuracy of Product B diminished most rapidly when this material was subjected to any method of storage. The 24-hour storage in a wet paper towel with refrigeration was the least desirable method of storage.