Evaluating the Effect of Different Impression Techniques and Splinting Methods on the Dimensional Accuracy of Multiple Implant Impressions: An in vitro Study

Abstract

This study was done to determine more accurate impression technique and splinting method for multiple implant impressions in edentulous patients. A prefabricated maxillary reference model was taken on which four implants were placed parallel to each other using vertical milling machine. Forty custom trays having different tray designs were fabricated using autopolymeri-zing acrylic resin on the stone cast obtained from the reference model. A total of 40 samples (n = 40) were divided into five groups, in which group I included casts obtained from impressions made with closed-tray technique, group II: open-tray impression technique, group III: open-tray impressions splinted with acrylic, group IV: open-tray impressions splinted with light cure material, and group V acted as a control group (reference model). Casts obtained were poured with dental stone. The interimplant distances were checked using coordinate measuring machine to evaluate the three-dimensional (3D) positional accuracy in X, Y, and Z axes. Casts obtained from impressions made with closed-tray technique showed highest mean deviation from the reference model while those obtained from open-tray splinted with light cure showed the least deviation. The casts obtained from open-tray nonsplinted and open-tray acrylic splinted showed intermediate mean deviations. The casts obtained from open-tray impression technique were more accurate as compared with the closed-tray technique. Among splinting, the impressions obtained from light cure splinting showed more accuracy than the impressions obtained from acrylic splinting. The accuracy of the multiple implant impression is influenced by the type of impression material used which ultimately leads to an accurate cast on which precisely fitting prosthesis is fabricated. Several factors including material accuracy, time span before the impression is poured, and extent of intraoral undercuts are to be kept in mind while choosing an impression material.