Dimensional Stability of Alginate Impression Materials

Objective: To compare the dimensional stability of a reportedly 100-hour stable alginate impression material (Kromopan-100, Aurum) to a traditional alginate (Jeltrate, Dentsply) impression material.  Methods:  Teeth in a maxillary master arch (Dentoform, Kilgore) were modified using a #56 carbide bur to create boxes as reference points.  The boxes were placed in teeth #5 and 13 to evaluate cross-arch stability and teeth #14 and 15 to evaluate intra-arch stability.  The alginate materials were vacuum-mixed, loaded in a metal tray and placed on the master arch. Thirty impressions were fabricated per alginate type.  Both impression materials were stored according to the manufacturer's instructions. The Jeltrate impressions were wrapped in a wet paper towel soaked with 25 mL of water and the Kromopan-100 impressions were stored unwrapped.  All impressions were stored individually in zip-lock bags for six different storage times: immediate, 24-, 48-, 72-, 96-, and 120-hours.  Each group consisted of 5 samples (n=5).  The impressions were cast in vacuum-mixed dental stone (Die-Keen, Heraeus Kulzer).  The master arch and stone casts were scanned by placing the cusp tips on a flatbed scanner (Scanjet-5590, HP).  Distances were measured on digitized images between the reference points on both the master arch and stone casts using Image J Software (NIH).  Mean distances and percent change from the master cast were determined per directional distance. A three-way ANOVA/Tukey (alpha=0.05) was used to determine differences in the percent change of the stone casts from the master arch (two impression materials, two directions, six storage times). See table.  Results: No significant difference in percent change between the stone casts and the master arch was found based on impression material (p=0.540), direction (p=0.954) or storage time (p=0.115).  Conclusions: The wet-paper-towel-wrapped Jeltrate and the Kromopan-100 impression materials maintained similar dimensional stability over time when stored in zip-lock bags.