Comparing the accuracy of master models based on digital intra-oral scanners with conventional plaster casts

For the fabrication of dental inlays and crowns precise information on patients' teeth morphology is required. Besides the conventional method, where mold materials impressions are prepared, the use of digital scanners is more and more becoming a central part in the nowadays dentistry. The aim of the manuscript is to compare the accuracy of master models based on two intra-oral digital scanners and silicone impressions. A metal cast reference arch model with predefined measurement points was scanned using the Lava™ Chairside Oral Scanner C.O.S. and the iTero™ Intraoral Scanner respectively. These scans were applied for the fabrication of models using rapid prototyping and milling from a proprietary resin. In addition, plaster models were produced using conventional A-silicone impressions. Using a coordinate measuring machine and a micro computed tomography scanner the models were evaluated with micrometer precision. The mean distance deviations from model to model correspond to 112 μm (C.O.S.), 50 μm (iTero™) and 16 μm (gypsum). The results verified the high precision of the conventional technique based on A-silicone impressions and plaster models. The accuracy of the master models obtained on the basis of the digital scans is clinically sufficient to fabricate bridges with up to four units.