الفهرس 
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Abstract
This study was conducted to evaluate and compare surface details reproduction in dry and wet conditions, dimensional accuracy and tear strength of three different types of elastomeric impression materials which were vinyl siloxanether, hydrophilic polyvinyl siloxane (PVS) and polyether (PE).
In the surface details reproduction test, a total of 42 specimens were made which were divided into three groups, 14 specimens for each material, each group was further divided equally into two subgroups according to the conditions in which they were made, one for the dry condition and another for the wet conditions.
All specimens were prepared according to the ADA specification No.19 for elastomeric dental impression materials by using a standardized stainless steel test block with definite ruled lines ranging from 0.300 to 0.020 mm wide. For preparation of the specimens in the dry condition, the test block was first dried with an air spray then each of the tested materials was manipulated and syringed onto the test block in accordance to the manufacturer’s recommendations. The wet condition was achieved by immersing the test block in previously prepared artificial saliva before application of the impression material.
Evaluation of the 0.020 line was done visually by two independent examiners under X10 magnification.
Results have shown that, under dry conditions there were no statistically significant differences when comparing the surface details reproduction readings of vinyl siloxanether, polyvinyl siloxane and polyether, but under wet conditions polyvinyl siloxane showed less detail reproduction than both vinyl siloxanether and polyether.
In dimensional accuracy test, a total of 21 specimens were made which were divided into three groups, 7 specimens for each, according to the type of material used. All specimens were prepared according to the ADA specification No.19 for elastomeric impression materials by using a metal mold which consists of two parts, a ruled block (AA) with three definite lines and two horizontal grooves perpendicular to the main three lines and a mold (BB).
Evaluation of the dimensional accuracy was made after 24 hours of making impression where a single investigator measured the distance between the crosslines on the ruled block to the nearest 0.005 mm by using a Tool Maker’s measuring microscope and recorded as reading (a). Measurement of the distance between the crosslines on the impression was made three times, then the measured lengths were averaged and recorded as reading (b). The dimensional change was calculated according to the ADA specification as follows: a – b / a × 100.