Accuracy of Impressions of Multiple Implants in the Edentulous Arch: A Systematic Review

Purpose: Because there is a paucity of clear-cut evidence regarding which materials and techniques are most accurate for complete-arch, multiple-implant impressions, the current study sought to analyze the data and draw useful conclusions based on the evidence for application in clinical practice. Materials and Methods: Relevant studies published between 1990 and December 2012 were included in the review. The articles were located through PubMed and manually through reviewing references in the literature. Papers examining implant impression accuracy in completely edentulous arches (three or more implants) were included. Clinical case reports, technique articles, abstracts, and review papers were excluded. Results: One of the 34 studies selected for evaluation was clinical; the remaining 33 were in vitro investigations. Ten studies compared polyvinyl siloxane (PVS) and polyether (PE); eight found that these were statistically equal in terms of impression accuracy. The splint effect was examined by 24 studies; 10 failed to observe any differences between splinted and nonsplinted impressions, whereas 7 (> 25%) showed that the splinted technique was better than the nonsplinted technique. Thirteen studies investigated the differences between pickup and transfer impression techniques; six favored pickup over transfer, and five found insignificant differences between the techniques. The effect of nonparallel implants on edentulous multiple-implant impression accuracy was examined by only two studies. Significant differences in accuracy were observed for 15 degrees of angulation. Conclusion: Most of the evidence supports PVS and PE as the most accurate impression materials for edentulous multiple-implant situations, with no clear advantage of either. Conflicting evidence exists regarding the most accurate impression technique (splinted/nonsplinted, pickup/transfer), and no clear recommendation can be made. Inadequate research exists regarding several other factors that might affect edentulous implant impression accuracy. There is a lack of clinical research to support in vitro findings. Keywords: accuracy, closed tray, complete-arch impressions, implant angulation, implant impressions, impression materials, passive fit, impression material