Abstract
Optimal thickness of impression materials in the custom tray in order to get the most accurate impression. To investigate the effect of different tray spacer thickness on the accuracy and the dimensional stability of impressions made from monophasic condensation silicone, addition silicone and polyether impression materials. Three different types of elastomeric monophasic impression materials were used for making the impression of a master die with tray having tray spacer thickness of 2, 4 and 6 mm. Each type of impression was poured in die stone after 1 h. Each cast was analyzed by a travelling microscope and compared with the master die. The data was tabulated and subjected to statistical evaluation. The results of the study indicated that the impressions made from 2 to 4 mm spaced trays produced more accurate stone casts when compared to 6 mm spaced tray. No statistical significant differences were observed between the accuracy and dimensional stability of the three materials tested. Minimum changes were observed when the cast was poured after 1 h and the tray space was 2 mm for all the materials tested. It is therefore advisable not to exceed tray space of 2 mm.