Effect of restoration span on the accuracy of six intraoral scanners and one dental laboratory scanner evaluated by a virtual-fit method.
OBJECTIVES To evaluate the effect of restoration span on scanner-related restoration fit obtained with six intraoral scanners and one dental laboratory scanner. METHODS A maxillary resin model with eight abutments was scanned with an ATOSQ reference scanner and subsequently with the Aoralscan Elite, Mediti900, Primescan2, R2i3, RunyesV6, and TRIOS6 intraoral scanners, and the AutoScan-DSEXPro(H) laboratory scanner (n=12 per test scanner). Complete-arch, four-unit bridge, and single-unit restorations were digitally designed. The designed restoration meshes were superimposed on the reference scan using a virtual-fit approach. Marginal gap (MG) and absolute marginal discrepancy (AMD) were calculated for each scanner in the metrology software. Statistical analysis was performed using generalized linear mixed models. RESULTS Mean MG ranged from 15-30 µm for single crowns, 16-44 µm for bridges, and 37-91 µm for complete-arch restorations. MG was significantly higher for bridges than for single crowns for all scanners except AutoScan-DSEXPro(H) and Aoralscan Elite. Complete-arch restorations showed significantly higher MG and AMD than bridges for all scanners, although mean MG remained below the clinically derived, model-based threshold of 100 µm. However, several R2i3 and TRIOS6 scans exceeded this MG threshold. Mean AMD exceeded the threshold for RunyesV6, R2i3, and TRIOS6 in complete-arch restorations. CONCLUSIONS Restoration span is a critical determinant of scanning accuracy, particularly when moving from four-unit bridges to complete-arch restorations, even for the laboratory scanner. The virtual-fit method enables robust, clinically interpretable comparison of scanner accuracy across restoration types. CLINICAL SIGNIFICANCE Intraoral scanner selection should consider the intended restoration span. While all evaluated scanners performed well for short-span restorations, only some maintained high accuracy for complete-arch tooth-borne restorations. Because these findings are based on an in vitro study, scanners with lower complete-arch accuracy should be used with caution in clinical practice.