Comparative Study of Dimensional Accuracy in Three Dental Implant Impression Techniques: Open Tray, Closed Tray with Impression Coping, and Snap Cap

Abstract

Several impression techniques have been proposed to result passive fitness between the prosthesis and osseointe-grated implant. The aim of the study was to compare dimensional accuracy of three impression methods: Open tray, closed tray with impression coping, and closed tray with snap cap. In this experimental study, a mandibular acrylic model was prepared with a milling machine to place three holes for dental implant analogs (Dio SM) with the dimension of 3.8 × 10 mm into the intended sites (one in midline and two others on the side at a distance of 10 mm) parallel with each other and perpendicular to the plane. Twenty-seven casts were prepared with impression material of polyvinyl siloxane (PVS) and dental stone type IV and divided into three groups. Implant situations were measured by coordinate measuring machine (CMM) and results were analyzed with Kruskal-Wallis and Mann-Whitney test to perform pairwise comparison among the groups. The mean ΔR values for open tray, closed tray with impression coping, and closed tray with snap cap were respectively, 0.070 ± 0.088, 0.173 ± 0.205, and 0.142 ± 0.044. There were statistically significant differences between open tray and closed tray as well as open tray and snap cap methods (p < 0.05), but there was no statistically significant difference between closed tray and snap cap method (p = 0.1). Regarding the results, open tray impression technique had the highest dimensional accuracy compared with the other two methods. There were no statically significant differences between closed tray with snap cap and closed tray with impression coping technique. Snap cap technique is less time consuming with similar dimensional accuracy in comparison with open tray impression technique.