Document Type: Original Article


Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran


Statement of Problems: The aim of impression is accurate registration of the ridge, teeth and surronding tissues. Condensation silicones are impression materials used frequently in fixed prosthesis. These materials have different brand names that makes their selection not easy by the dentists.Purpose: This study was designed to investigate the accuracy of two condensation silicone Impression materials, speedex and Irasil, in putty- wash technique.Materials and methods: In this quazi- experimental study, we designed a laboratory model with 2 metalic dies. One of them had an undercut and was similar to the molar teeth and the other had no undercut and was similar to the premolar teeth. These dies had 3 degrees convergence in walls and were round in cross section. Then impressions were taken with Irasil and Speedex impression materials and the stone models were prepared. Five dimensions of 30 models were measured and compared with laboratory model by the use of T-test.Results: These two.impression materials had a statistically significant effect on the die height without underecut but on other dimensions they had not any statistical significant effect. Die height without undercut was increased with speedex impressions but decreased with Irasil impressions. Die diameter without undercut and the distance between dies were increased with speedex and Irasil impressions.  The die diameter beneath the undercut was increased with speedex but decreased with Irasil impressions. The die height above the undercut was decreased in Irasil and speedex impressions.Conclusion: The usage of Irasil compared n to speedex impression material has a higher effect in only one dimension (die height above undercut) but in other dimensions speedex is better than Irasil.Key words: Dimenstional stability, Silicones, Speedex, Irasil