To evaluate and compare the time dependent dimensional accuracy of polyvinyl siloxane impressions.

A brass master die containing two identical posts simulating two complete crown tapered abutment preparation was served as a standardized master model. Impressions were made with polyvinyl siloxane materials (monophase and regular body) using a brass made custom tray. The impressions were poured at intervals of 75 min, 24 hours, 48 hours and 1 week, Interabutment and intraabutment distance were measured in the recovered stone dies using a profile projector with an accuracy of 0.001mm.

Results of this study indicated that the casts made were dimensionally accurate and the polyvinyl siloxane silicones are dimensionally stable impressions for one week period.

Delayed pouring of the impressions at four different time periods did not significantly affect the accuracy of the casts produced.