Study of the Dimensional Changes in Silicones after Different Impression Techniques

Objectives: the aim of this study was to study dimensional changes between a condensation silicone and an addition silicone, both in heavy and light viscosities, used in different impression techniques. A master die with different axial morphologic characteristics was used. Methods: reproductions of the master die were obtained through a two stage putty/wash impression technique, using metallics relieved copings presenting 2,0mm standardized thickness for the preliminary molding, and by the one stage putty/wash impression technique. The casts made out of type IV plaster stone were measured in a profile projector with 10x amplification, all measurements were compared to the standard cast and submitted to ANOVA at 5% level of significance. Results: two stage putty/wash impression technique originated statistically higher models (p= 0,02) than one stage impressions, independent of the material used; the axial characteristic with 6ºangulation and ‘v’ groove originated statistically narrowest models (p< 0,05), when the two stage impression technique was used; no statistically significant difference was found for measures among the pillars of the plaster models for any studied experimental conditions (p> 0,05). Conclusions: the putty/wash impression technique and axial characteristic with 6ºangulation and ‘v’ groove have changed the dimensions of plaster stone, while no alterations have being observed between studied materials.