Dimensional Accuracy of Polyvinyl Siloxane Impression Materials Considering Impression Techniques– A Literature Review

Objectives Impression accuracy is the main determinant of the fit, form and function of prosthetic restorations. Polyvinyl siloxane (PVS) is the material of choice in most clinical situations. The purpose of this paper is to provide an up-to-date review of scientific articles which discuss the dimensional accuracy of PVS impression material using various impression techniques, tray types and spacers. Besides, the procedure, advantages and disadvantages of commonly used impression techniques, technique modifications and innovations are also reviewed. Method An electronic search of scientific papers from 1990 to 2018 was carried out using MEDLINE and Google Scholar databases using the search terms “accuracy and polyvinyl siloxane and impression technique” and “accuracy and addition silicone and impression technique”. Results Searching the key words yielded a total of 312 articles. By application of inclusion and exclusion criteria, the obtained results were further reduced to 35 citations. Conclusion Impression technique is a critical variable in the accuracy of PVS impressions. Dual-phase 2-step technique with 1 to 2 mm space for the light body is proven to be highly accurate and is still considered as the standard technique. The use of 2-step technique without providing a space for the wash material is rejected by the literature. Triple-phase 2-step techniques including “matrix impression system” have also functioned well and even superior to traditional dual-phase 2-step technique. Papers suggest that custom trays do not significantly improve the accuracy of impressions and rigid stock trays are suitable alternatives.