A laboratory investigation of the accuracy of two impression techniques for single-tooth implants

Purpose: This laboratory study investigated the accuracy of four implant im pression procedures using two impression techniques and two different mater ials. Materials and Methods: A master model was used to produce 40 differen t stone casts incorporating laboratory implant or abutment analogues from t he different combinations of two impression techniques (the repositioning i mpression coping technique at the implant level and the pickup impression t echnique at the abutment level) and materials (President polyvinyl siloxane and Impregum F polyether). Variations in the resulting working casts were measured using the Reflex Microscope to derive distances and angles from th e three-dimensional coordinates of optical targets that were attached to a lest coping placed on the implant analogue and on a reference device positi oned on the occlusal surfaces of the casts. Results: The results showed gre ater variations in analogue position with the repositioning impression tech nique than with the pickup technique. The rotational errors were large enou gh to be of clinical concern. No significant differences were found between polyvinyl siloxane and polyether impression materials for the two tested t ypes of impression techniques. Conclusion: The repositioning impression tec hnique at the implant level can produce less predictable results than the p ickup technique at the abutment level. The choice of impression material ma de no significant difference.