Comparative accuracy of complete-arch intraoral scans using full-scan and segmental-and-merge strategies

Full-arch intraoral scanning often suffers from cumulative stitching errors. Segmental scanning using overlapping segments followed by digital merging has been proposed as a potential solution, but quantitative evidence remains limited. This study aimed to evaluate the accuracy of three intraoral scanning strategies-full-arch, 3-segment merging, and 5-segment merging-in both wired and wireless intraoral scanners (IOSs) using combined linear-distance and surface-based analyses.

A maxillary typodont with three 2-mm metallic reference spheres was scanned using two IOSs (Medit i700 and i700 Wireless). Each scanner acquired 10 full-arch, 3-segment, and 5-segment scans; segmental scans were merged in Exocad. Accuracy was assessed in Geomagic Control X as: (1) trueness and precision of three inter-sphere distances (right molar-incisor, left molar-incisor, inter-molar) and (2) global surface root-mean-square (RMS) deviation and the percentage of points within ± 100 µm. Group differences were analyzed using Kruskal-Wallis and Dwass-Steel-Critchlow-Fligner tests.

Across both IOSs, the 3-segment strategy consistently demonstrated the lowest linear deviation and variability, particularly for the inter-molar distance, while full-arch scans exhibited the greatest errors. Segmental scanning strategies resulted in significantly lower global RMS deviation and higher in-tolerance percentages than full-arch scans (RMS decreased from ~68 - 74 µm to 55 - 60 µm; in-tolerance increased from ~87 - 89% to > 93%). No significant differences in trueness, precision, RMS deviation, or in-tolerance percentage were observed between the wired and wireless scanners.

Segmental-and-merge scanning strategy enhances the accuracy of complete-arch IOS acquisition and is unaffected by wired versus wireless data transmission.