Two/Tridimensional Accuracy of Casts After Different Impression Techniques-pouring Moments

Objectives: The aim of this study was to investigate two- and tridimensional accuracy of gypsum casts after different impression techniques, die stones and pouring moments.
Methods: A master model with full-crown preparations on teeth #14, 16, 21 and 25 was molded with standardized stock trays and a condensation silicone indicated for immediate and/or late pourings (Speedex-Coltene; putty and wash materials) by means of two techniques (n=10): (1) one-step and (2) two-step: relief obtained with poly(vinyl chloride) (PVC) film. Following impressions, castings (n=10) were performed after 30 min, 3 days or 7 days using a synthetic Type 4 dental die stone (GC FujiRock EP; GC America inc.), or a zero expansion Type 4 dental die stone (Zero Stone; Dentona). For the 2D and 3D dimensional analyses, the gypsum casts were digitalized with an optical scanner device (R700 - 3ShapeA/S). After that, the respective images were managed using the software Rhinoceros^® (version 5.3.2 for Mac), with which was possible to analyze the images concerning the following variables or each tooth: area, volume and declination to Baseline in axes X, Y and Z. Considering the results of Shapiro-Wilk and Levene tests, data were submitted to 3-way ANOVAs. When applicable, Tukey HSD post-hoc test was applied (α=.05).
Results: Irrespective of the dependent variables (area, volume, axes X, Y and Z) and the studied teeth, no significant differences were observed for the interactions among the independent variables (technique, die stone or pouring time; p>.05). Generally, the same behavior was observed when these variables were individually analyzed.
Conclusions: Overall, two- and tridimensional accuracy of gypsum casts were not affected by the one- or two-step impression techniques, die stones and pouring moments.