Effect of a stackable scanning guide, intraoral scanner type, and operator on the accuracy of maxillary full-arch implant scans: An in vitro study

PURPOSE: To evaluate how a stackable scanning guide, scanner type, and operator influence the accuracy of maxillary full-arch implant scans. METHODS: A maxillary edentulous model with four implants was digitized with an industrial scanner (reference model) and scanned using 2 intraoral scanners (Primescan (PS) and Trios 4 (T4)), without (NG) and with a stackable scanning guide (SG), by two independent operators (n = 7). In addition, a conventional open-tray impressions (CNV) were made. Accuracy was assessed superimposing and assessing the 3D, angular, and interimplant distance deviations. RESULTS: Impression type affected all 3D, angular, and 2D distance deviation outcomes, while operator influence was minimal (ICC 0-4%). CNV showed the greatest deviations. The scanning guide improved 3D accuracy in a position-dependent manner, with the greatest benefits observed at specific implant sites, particularly at distal positions, with deviations ranked CNV > T4 > PS. PS and T4 performed similarly without the guide, and having the guide a limited influence on angular and interimplant distance outcomes. CONCLUSIONS: Digital implant scans were more accurate than conventional open-tray impressions for maxillary full-arch implant scans. The use of a stackable scanning guide improved scan trueness in a position-dependent manner, with scanner type influencing deviation patterns; Trios 4 demonstrated more consistent accuracy across implant positions, operator influence was minimal. CLINICAL SIGNIFICANCE: A stackable scanning guide can improve full-arch digital implant scan accuracy by providing stable reference landmarks and potentially reducing stitching errors, particularly at distal implant sites.