Evaluation of fit accuracy of computer-aided design/computer-aided manufacturing crowns fabricated by three different digital impression techniques using cone-beam computerized tomography

Abstract

Purpose: The aim of this in vitro study was to evaluate the fit accuracy of computer-aided design (CAD)/computer-aided manufacturing lithium disilicate full contour crowns fabricated by three different digital impression techniques. Materials and Methods: An acrylic upper first molar was prepared to receive a full ceramic crown and used to fabricate ten ceramic master dies using lost wax and heat press techniques. Each ceramic die was seated in a typodont model and ten polyvinyl siloxane impressions were made for the dies and neighboring teeth to fabricate ten stone casts. Three groups of lithium disilicate crowns ( n = 10) were fabricated; Group E: Crowns were fabricated by scanning the ten stone casts with in Eos X5 extraoral scanner. Group O: Crowns were fabricated by powder-free scanning of the ten ceramic dies in their typodont models with CEREC Omnicam. Group B: Crowns were fabricated by CEREC Bluecam optical impressions of the ceramic dies in their typodont models after titanium dioxide powder application. All the specimens were milled from IPS e-max CAD blanks. Each crown was evaluated on its die for fit accuracy using computerized cone-beam tomography at seventy measuring points. The variability among the three groups was evaluated using one-way ANOVA test at P Results: No statistically significant difference was found among the three groups for overall results at ( P = 0.658), whereas Group E showed significantly better marginal fit with a mean value of 76 ± 39.0 μm at P = 0.047. Conclusions: All tested digital impression techniques showed clinically acceptable accuracy and extraoral scanning significantly enhanced the marginal fit.