Distortion according to the Distance from the Start Point of Scan Using an Intraoral Scanners

Objectives: The purpose of this study was to compare 3-dimensional arch distortion according to the distance from the tooth at the beginning of the scan when a full-arch impression was made by using an intraoral scanner in vitro.
Methods: We used the industrial scanner to digitize the master model for the CAD reference model (CRM). In addition, we digitized the master model by using four intraoral scanners (Trios2, Trios3, CS3500, CS3600) and one dental laboratory scanner (FREEDOM ^H) to make the CAD test model (CTM) (N = 10). Then, the teeth were divided by using inspection software (Geomagic control X), and the steps of overlapping and 3D analysis of CRM and CTM were performed. According to the presence or absence of normal distribution in Root Mean Square (RMS) of all divided teeth, we used Kruskal-Wallis test (α=.05) and post-hoc comparison by using Mann-Whitney U-test and Bonferroni correction Method (α=.005).
Results: The overall RMS value was significantly different for all scanners (P<.001). And the dental laboratory scanner showed the smallest value, the CS3500 showed the largest value. Trios3 showed the best trueness in the teeth where the scan was started. However, the larger the scan range, the less the RMS value difference between Trios3 and CS3500. The RMS values of the dental laboratory scanners showed larger values than the intraoral scanners in the narrow scan range. CS3600 showed a RMS value less than or equal to the dental laboratory scanner at some scan range (#27, #26, #25, #24, #23). But the wider the scan range was, the smaller the RMS values of all the intraoral scanners were.
Conclusions: Full-arch scans are not appropriate for the manufacture of fixed prostheses. However, intraoral scanners are applicable for narrow area scans for single or short span prostheses.