Trueness and Precision of Three Novel Scan Body Designs with Horizontal Extensions for Complete-Arch Implant Impressions: A Comparative In Vitro Study with Intraoral Scanning and Photogrammetry Systems

Accurate transfer of implant positions is critical for complete-arch implant-supported rehabilitations, yet intraoral scanning accuracy degrades over long edentulous spans, where errors accumulate. This in vitro study evaluated the trueness and precision of three novel auxiliary scan body designs with two horizontal extensions, additively manufactured by vat photopolymerisation, primarily against original manufacturer scan bodies and secondarily against a partial dentition scanning protocol and three photogrammetry systems (two extraoral, one intraoral). Four implants (Ø 3.8 × 10 mm) were placed in a prefabricated polyurethane edentulous maxillary model; anterior implants were parallel and perpendicular to the occlusal plane, while posterior implants were angled at 30°. Nine groups were assessed: one reference dataset and eight study groups, the latter each comprising 12 repeated scans. Deviations were calculated as differences in inter-implant centre distances (linear, µm) and inter-axis angles (angular, degrees) relative to a laboratory optical scanner. Group differences were significant for all endpoints (p < 0.001). Mean linear deviations ranged from 31 ± 4 µm to 58 ± 18 µm and mean angular deviations from 0.068 ± 0.012° to 0.538 ± 0.250°. No group exceeded the 100 µm mean linear threshold; one photogrammetry system exceeded the 0.40° mean angular threshold. Linear and angular results followed different rankings and should be evaluated separately.