Résumé
Condensation silicons are more commonly used in fixed Prosthodontics than other elastomers. The aim of this study was to compare the accuracy and dimensional stability of two condensation silicons: Speedex and Irasil. A metal master model containing two abutments representing two prepared teeth with definite dimensions was prepared and a metal tray was made. 40 impressions were taken [20 of each impression material] and 10 of them were poured with die stone [Prevest] after 30 minutes and the other IC were poured after 120 minutes, according to the manufacturer's instructions. Using a steriomicroscope M6c-l 0 and Digital camera motican-480 the following dimensions were measured three times on the metal and stone models: [1] x = distance between the center of the abutments [2] y1 = height of the abutment with an undercut [3] y2 = height of the abutment without an undercut [4] z1 width of the abutment with an undercut, and [5] z2 = width of the abutment without an undercut. The difference between the dimensions of the main and stone models was assessed, Multivariance and T-tests were used for statistical analysis. There was no significant difference in dimensional stability between groups I and 4 [Speedex, 30' and Speedex, 120'] and between groups 2 and 3 [Irasil, 30'-120']. A significant difference was observed between Speedex and Irasil in both time periods [30 and 120 minutes]. The difference between the die stone and the master model was significant in mesiodistal [x] and buccolingual [H] dimensions for both materials. A significant difference was also found between Irasil and the main model in occlusogingival [y1] and buccolingual [z2] dimensions in both time periods, but Speedex failed to show a significant difference in the same dimensions and time periods. In the y2 dimension in contrast to Irasil, Speedex demonstrated a significant decrease of dimensional stability. Timing did not affect the dimensions of the two impression materials. The mesiodistal dimensions [x] of both Speedex and Irasil increased on the casts. A significant difference was found in dimensional stability between Speedex and Irasil impression materials