Effect of digital workflow on the marginal fit of long-span implant-supported bars for kennedy ii class removable prostheses in vitro

Abstract

Introduction The production procedures, including impressions, introduce errors affecting the passivity of fit. A completely digital workflow is possible nowadays because of the intraoral scanners (IOS). This study aimed to evaluate the effect of the impression technique (conventional versus digital) and the screw tightening sequence on the marginal discrepancy (MD) of implant-supported bars. Methodology This laboratory study was conducted on a simulated Kennedy class II edentulous maxilla with three parallel implants in the edentulous quartile. The closed tray technique with a-silicon (CTM) and the intraoral scanning with the I-Tero™ system (IOS) were compared and three bars were manufactured from each technique. Depending on the screw tightening sequence (A11 and A17) 4 groups were created with 6 samples each. The MD was examined implementing 24 negative replicas, which were sectioned and studied under a stereomicroscope. The Horizontal Discrepancy (BHD), Vertical Discrepancy (BVD) and Conical Discrepancy (BCD) of the bar were calculated on the means of the measurements of the horizontal, the vertical and the conical MD respectively. The descriptive statistics, normality tests, one-way ANOVA (a=.05) and post-hoc Tukey’s tests were run and the graphs were draw with SPSS. Results There was a significant effect (P<.05) of the impression technique combined with the screw tightening sequence on all variables. The post-hoc Tukey’s tests revealed significant differences between all groups except from those of the same impression technique only for the BHD (P<.05). Conclusion In this study all groups resulted in marginal discrepancies. The closed tray impression technique gave better results.