الفهرس 
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Abstract
This study investigated the dimensional accuracy and surface detail reproduction of three different elastomeric impression materials (VPS, Vinyl siloxanether and Polyether) .The study included the effect of the impression technique either single step or two steps and the effect of the moisture condition on the dimensional accuracy and surface detail reproduction.
In the present investigation, two standardized stainless steel dies were constructed for the dimensional accuracy testing, another two standardized stainless steel discs were constructed for detail reproduction testing. Rigid custom impression trays were used as to minimize the deformation of the impression materials and standardize the forces applied while seating and removing the tray from the die.
A part of the present study was concerned with comparing the dimensional accuracy and detail reproduction of the conventional impression to that of the optical impression.
The length between points X and Y, the width of the finish line at four different points and the height of the die were the selected measures in this study for dimensional accuracy testing on the produced stone dies as to see the effect on the dimensional changes in a vertical and a horizontal plane.
Data were collected from all the tests previously done according to the sample grouping, in the form of tables of means and standard deviations. The collected data were then statistically analyzed.
Data analysis in this study was performed in several steps. Initially, separate analysis was performed with One way Analysis of Variance ANOVA for numerical data followed by t-test to compare between material types as function of impression technique and moisture condition (Dry vs. Moist). Multifactorial Analysis of Variance ANOVA was used to test the effect of the impression technique, the moisture condition and the measuring site within each material on dimensional accuracy. Chi-square test was used for non-numerical data to detect the significance in detail reproduction and presence of voids.
The results of this study revealed that the elastomeric impression materials used exhibited comparable dimensional accuracy with Vinyl siloxanether impression material having best statistically significant results.
The impression technique and the moisture conditions showed statistically non significant effect on the dimensional accuracy of the used impression materials. The detail reproduction showed statistically significant results with the two step impression technique under dry conditions. The optical impression showed reasonable results for dimensional accuracy testing.
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