Effect of scan calibrator morphologies on the accuracy of calibrated complete-arch implant intraoral scans: an in vitro study.

OBJECTIVE: To evaluate the effect of four scan calibrator (SC) morphologies on the accuracy of calibrated complete-arch implant intraoral scans. METHODS: A study model featuring six scan bodies (SBs) at the screw-retained abutment (SRA) level was fabricated, and reference data were obtained by scanning the model with an industrial scanner. A universal SC was manufactured in four morphologies: (1) tubular (SC-TU), (2) crumpled (SC-CR), (3) spherical (SC-SP), and (4) polyhedral (SC-PO). Each SC was attached to the model, and the resulting model-SC assembly was scanned ten times (n = 10) using an intraoral scanner (IOS) to obtain uncalibrated scans. These uncalibrated datasets were then calibrated using the corresponding desktop scans of the SCs. Both the uncalibrated and calibrated scans were registered against the reference scan via two alignment strategies: (1) using all SBs to assess the overall fit, and (2) using only the first and second SBs to simulate the Sheffield test. Linear deviations between the central points of SRAs were calculated using a custom Python script. RESULTS: When aligned using all SBs, trueness was comparable among the four SC-assisted groups, whereas the SC-CR group exhibited significantly lower post-calibration precision (40.11 ± 35.21 μm) than the SC-SP (29.63 ± 17.37 μm) and SC-PO (28.08 ± 13.48 μm) groups. In the virtual Sheffield test, the SC-SP (86.30 ± 34.25 µm) group demonstrated significantly higher trueness than the SC-CR group (162.06 ± 62.45 µm) following calibration at the distal SRA6. Furthermore, the SC-PO (66.21 ± 29.96 μm) group exhibited significantly higher post-calibration precision than the other three SC groups at SRA6. CONCLUSIONS: SC morphologies influence the accuracy of calibrated complete-arch implant intraoral scans. SC-PO demonstrated the highest post-calibration precision. CLINICAL SIGNIFICANCE: The proposed SC morphologies, except for SC-CR, may help correct IOS stitching errors. The polyhedral morphology may represent a favorable design choice for SC fabrication.