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 to 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.