Statement of problem: Measuring both the trueness and precision of an intraoral scanner (IOS) will provide a thorough understanding of its accuracy.

Purpose: The purpose of this in vitro study was to measure the complete-arch trueness and precision of 3 commercially available intraoral scanners equipped with the latest software version and compare them by using a laboratory scanner as reference.

Material and methods: Nineteen maxillary and 19 mandibular completely dentate stone casts previously acquired from 19 patients by using a polyvinyl siloxane (PVS) dual mix impression and stock trays were scanned with 3 intraoral scanners (TRIOS 3; 3Shape A/S, i500; Medit, and Emerald; Planmeca) using their latest software versions. The same casts were also scanned with a laboratory scanner (E3; 3Shape A/S) that served as the reference scanner. Files were exported in standard tessellation language (STL) format and inserted into a metrology 3D mesh comparison software program (CloudCompare).

Results: In terms of trueness, a significant difference was found among the scanners (F (2.37)=239.7, P<.001). Planmeca Emerald had significantly lower trueness values than either the Medit i500 (P<.001) or the 3Shape A/S TRIOS 3 (P<.001). No significant difference in trueness was found between the Medit i500 and the 3Shape A/S TRIOS 3 scanner (P=.365). In terms of precision, a significant difference was found among the scanners (F (2.89)=301.2, P<.001). The 3Shape A/S TRIOS 3 scanner was significantly more precise than the other scanners (P<.001 for both the Medit i500 and Planmeca Emerald). The Planmeca scanner was significantly more precise than the Medit i500 scanner (P<.001). Concerning the ability of the scanners to reproduce the files of the reference scanner without overestimation or underestimation, the Medit i500 produced files that significantly underestimated the reference scanner's files (t (37)=-12.4, P<.001). The other scanners did not significantly either underestimate or overestimate the files of the standard (t (37)=-1.91, P=.062 for the TRIOS 3 and t (37)=1.64, P=.101 for the Planmeca) CONCLUSIONS: With regard to completely dentate arch trueness, the Planmeca Emerald IOS had statistically lower trueness. With regard to complete dentate arch precision, the 3Shape A/S TRIOS 3 IOS was the statistically more precise scanner. With regard to reference scanner file estimation, the Medit i500 IOS produced files that significantly underestimated the reference scanner files. All 3 tested scanners exhibited a completely dentate arch average accuracy below 100 μm in vitro.