Comparison of the Dimensional Changes of Ariadent and Bayer Alginate Impression Materials (Invitro)

: Dimensional changes of impression materials cause distortion of the cast with negative impact on the outcomes of prosthodontics treatments. There is less evidence about accuracy of the domestic alginate impression materials.The aim of this study was to compare the dimensional changes of Ariadent and Bayer alginate impression materials. Materials and Methods In this experimental study, seventeen casts were made from master model by a cast metallic special tray, using Ariadent (case) and Bayer (control) alginates. Small and large diameter, height and distance of two dies were measured by a digital measuring instruments. Data were collected and analyzed by Paired T –Test, and MannWhittney for the two groups and master model. The difference between the size of small and large diameter, height, and distance of centers of two dies made from Bayer alginate was 209.2 ± 185.6, 345.5 ± 230.7, 219.9 ± 213.1. and 328± 478.7 and for the Ariadent alginate was 198.3 ± 215.5, 342.8± 227.3, 336.7± 280.9, and 281.9± 336.7 microns respectively. These differences were significant with respect to master model (P<0.0005). The changes of measured dimensions within two groups were not significant statistically (P <0.5). Both impression materials have significant dimensional changes which can not be used in fixed prosthodontics; however they can be used in removable prosthodontics with adherence to the principles of standard guidelines.