Accuracy of 12 Intraoral Scanners and Photogrammetric Systems for Full-Arch Edentulous Maxillae: An In Vitro Study

The accuracy of full-arch implant impressions is critical for prosthetic passivity and long-term clinical success. This study compared the trueness and repeatability of twelve digital impression systems (DIS), including nine intraoral scanners (IOS) and three stereophotogrammetric (SPG) systems, for a fully edentulous maxilla restored with eight multi-unit abutments (MUAs). Accuracy was assessed using a coordinate measuring machine-derived reference model and a clinically driven 'worst-MUA' approach, considering the suprastructure as a single functional unit. Trueness and repeatability were evaluated along vertical (Z), horizontal (XY), three-dimensional, and angular dimensions across five repeated acquisitions per system. Significant variability in both trueness and repeatability was observed among DIS. Median trueness deviations ranged from 0.009-0.042 mm (Z), 0.027-0.117 mm (XY), 0.026-0.107 mm (3D), and 0.140°-0.427° (angular). Median repeatability deviations ranged from 0.0014-0.0230 mm (Z), 0.0015-0.0380 mm (XY), 0.0016-0.0372 mm (3D), and 0.0217°-0.1558° (angular). Principal component analysis identified three performance clusters: high-performing systems (Itero Lumina, Imetric 4D, Shining 3D scan, Primescan2), intermediate systems (Shining 3D photogrammetry, Medit i900, Primescan, Panda Eletra, Medit i700, Nobel Fast Map), and low-performing scanners (Trios5, Trios6). Errors were more pronounced at terminal arch positions, on MUAs #1 and #8. These findings highlight the system-dependent nature of digital impression accuracy and demonstrate that several next-generation intraoral scanners achieved accuracy levels comparable to those of photogrammetric systems under the standardized in vitro conditions of this study.