Accuracy of six intraoral scanners for scanning complete-arch and 4-unit fixed partial dentures: An in vitro study

Statement of problem. The digital scan accuracy of different intraoral scanners (IOSs) for long-span fixed prosthesis and the effect of the starting quadrant on accuracy is unclear. Purpose. The purpose of this in vitro study was to evaluate the accuracy of 6 IOSs for complete-arch and prepared teeth digitally isolated from the complete-arch and to determine the effect of the starting quadrant on accuracy. Material and methods. A maxillary model containing bilaterally prepared canines, first molar teeth, and edentulous spans between the prepared teeth was used. The model was scanned by using a highly accurate industrial scanner to create a digital reference data set. Six IOSs were evaluated: TRIOS, iTero, Planmeca Emerald, Cerec Omnicam, Primescan, and Virtuo Vivo. The model was scanned 10 times with each IOS by 1 operator according to the protocols described by the manufacturers. Five scans were made starting from the right quadrant (ScanR), followed by 5 scans starting from the left quadrant (ScanL). All data sets were obtained in standard tessellation language (STL) file format and were used to evaluate accuracy (trueness and precision) with a 3D analyzing software program (Geomagic Studio 12; 3D Systems) by using a best-fit alignment. The prepared teeth were digitally isolated from the complete-arch and evaluated with the analyzing software program. The Kruskal-Wallis and Mann-Whitney U statistical tests were used to detect differences for trueness and precision (alpha=.05). Results. Statistically significant differences were found regarding IOSs (P<.003) and scanning sequence (P<.05). The TRIOS showed the best trueness for the complete-arch, but not statistically different from Primescan, Virtuo Vivo, and iTero (P>.003). The lowest median values for precision of the complete-arch were also found using TRIOS, but no significant difference was found among the scanners (P>.003). In terms of trueness and precision, Primescan had the best accuracy for preparations. Emerald showed significant differences depending on the scanning sequence for complete-arch accuracy. ScanR for trueness (P=.021) and ScanL for precision (P=.004) showed improved results. However, Emerald, TRIOS, and Virtuo Vivo showed statistically significant differences in precision of preparations depending on scanning sequence. ScanL deviated less than ScanR when scanned with TRIOS (P=.025) and Emerald (P=.004), and the opposite with Virtuo Vivo (P=.008). In terms of preparations trueness, no significant difference was found between the ScanR and ScanL of any IOS (P>.05). Conclusions. Based on this in vitro study, the accuracy of the complete-arch and prepared teeth differed according to the IOS and scanning sequence.