In spite of best available impression materials and advanced techniques, we still come across imperfect fit of a dental prosthesis. Selection of impression material is based on the results from the research carried out, hence the accuracy of this research needs to be at the topmost priority, hence a proper research model and methodology has to be followed. The purpose of this paper was to highlight on technique and the device made to meet these requirements.
An in vitro study was done to evaluate the linear dimensional accuracy of commercially available polyvinyl siloxanes of varying viscosities using different impression techniques. A standardized experimental procedure is required to provide identical direction of insertion and removal of the trays that contained the impression material. An impression tray positioning device has been designed and machined in an attempt to meet these requirements.
It was found that putty-wash 2-step techniques with controlled bulk in stock tray found to be as accurate as multiple-mix technique, utilizing heavy viscosity and low viscosity combination in a custom tray and single-mix technique, utilizing medium viscosity in a custom tray.