Effect of Astringent Products on Accuracy of Polyether Impressions and Plaster Casts

To investigate whether hemostatic agents have any detrimental effects on polyether impressions and plaster casts after a clinically viable cleaning protocol.

A total of 60 human molar teeth were manually standardized, prepared, and subdivided into five groups (G): G0 (control/no contamination); G1 (ViscoStat Clear); G2 (ViscoStat); G3 (Astringedent); and G4 (Astringedent X). Each tooth was contaminated with a hemostatic agent for 3 minutes and cleaned with a 30-second air/water spray. Before and after contamination, an impression was taken and a plaster cast was poured. The impressions and plaster casts of all teeth were scanned using a light scanner. Data were matched using a three-dimensional analysis software that displayed color-coded maps. Means of the maximum positive/negative values and of the mean deviations in each group were calculated and compared. All color-coded maps were interpreted descriptively using the program's color scale, and all impressions and plaster casts were microscopically evaluated.

Values of mean deviations throughout all matched scans showed maximum values ranging from -30.1 to +17.5 μm. None of the groups showed significantly different deviation values or patterns when compared to each other. Impressions showed a thin, discontinuous coating for G2, G3, and G4; no changes were found for plaster casts.

Presented deviations showed the same values and distribution patterns within all groups. A cleaning protocol of 30 seconds of air/water spray is sufficient to remove hemostatic agents, preventing effects to polyether impressions and plaster casts. However, ferric sulfate-containing hemostatic agents left discontinuous coatings on impression surfaces.