Comparison of the accuracy of fixture-level impression making after splinting prosthetic components

Abstract

Considering the effects of different impression-taking techniques on the dimensional accuracy of the final cast and controversies over the best technique in implant dentistry, the present study was undertaken to evaluate the effects of three different open-tray impression techniques on the dimensional accuracy of final casts for implants. A two-piece metallic index was prepared and a patient’s jaw was simulated by placing self-cured acrylic resin in the lower part of the index. Then 2 holes were produced in the acrylic resin at a specific distance from each other, and the analogs were placed in these holes. Three different open-tray impression techniques were evaluated using the upper segment of the index, which mimicked the specific tray. The dimensional accuracy of the casts was evaluated by comparing the distances between the predetermined points on the implant analogs and the positions of the points with similar distances on the master model. A digital caliper (accurate to 0.01 mm) was used to measure the distances. The differences in the measurements on the final casts were analyzed with SPSS 16, using Kruskal-Wallis test. Post hoc Mann-Whitney U test was used for two-by-two comparisons. There was a significant difference between the group in which the analogs and impression copings were not splinted and the group with impression coping splinting without analog splinting and the group with simultaneous splinting of the impression copings and implant analogs, in relation to distances between similar points on the master model. In this context, the second and third techniques better reconstructed the positions of the points. Splinting of impression copings with Duralay acrylic resin prevented the movement of impression copings during the impression-taking procedure and despite an increase in the accuracy of impression taking during splinting of analogs by Duralay acrylic resin, the increase in accuracy was not significant statistically; therefore, splinting of the impression copings without splinting of the analogs is recommended due to an increase in impression-taking accuracy and facilitation of laboratory procedures.