Dimensional accuracy of impression techniques for the endosteal implants (An in vitro study): Part I

Aims: To detect the most accurate impression materials and technique to transfer single or multiple implants position from the master model to the stone dies by two methods of measurement. Materials and methods: Two master models (Cl III Kennedy with single implant Frialit–2, and Cl II free end saddle with double implants) were fabricated. Four impression techniques were used (direct, and indirect, each with one, and two steps) using condensation, addition (heavy and light consistencies) and addition (medium consistency) silicone impression materials. Five impressions were taken for each technique to produce a total number of 100 stone casts. A mechanical apparatus was carefully designed to allow constant repeatable position of stock impression tray to the master model, and to allow vertical removal of the impression tray that helps to standardize the path of removal. The measurements were performed by using digital caliber and optical micrometer microscope. Results: Showed that the direct (open tray) two steps technique was the accurate technique for transferring implant position to the laboratory cast. The two steps impression technique was the most accurate one than one step. There were no significant differences between single, and double implants. There was significant difference between the two methods of measurements in (Z) axis for both single and double implants case. Conclusion: The direct (open tray), two steps impression technique, and addition impression material is the most accurate technique. The numbers of dental implants had no significant effect on accuracy of stone cast.