Influence of scan aid surface color on accuracy of calibrated intraoral scan protocol in complete arch implant digital scans.

Statement of problem: Intraoral scans for complete arch implant-supported prostheses have been considered to lack sufficient accuracy for clinical use. Although various scan aids and techniques have been proposed, their effectiveness is still unclear. However, a calibrated intraoral scanning protocol (CISP) has shown accuracy comparable with that of the conventional splinted open-tray method.

Purpose: The purpose of this in vitro study was to evaluate the impact of scan aid color on the accuracy of the CISP for complete arch implant-supported prostheses.

Material and methods: A maxillary edentulous model with 6 implants and multi-unit abutments was scanned using 3 approaches: intraoral scan (IOS), intraoral scan with scan aid (IOS-SA), and CISP. Scan aids in 3 colors (gray, tan, and white) were applied in the IOS-SA and corresponding CISP groups. In the CISP group, the scans were further calibrated with a desktop scan of the scan aid. Each approach was repeated 10 times, and a desktop scan served as the reference model. The scans were aligned with the reference model using 2 approaches: one assessed the overall fit by aligning all scan bodies, and the other simulated the Sheffield fit test by aligning only the first and second scan bodies (SB1 and SB2) to evaluate passive fit in multiple implant-supported prostheses. Linear deviations from the reference model (trueness) and deviations within each group (precision) were analyzed via Python scripts. The accuracy (trueness and precision) of different approaches was compared using a linear mixed model (α=.05), taking the correlation of 6 SBs within a scan and the correlation between IOS-SA and CISP into account (random effect).

Results: When aligned by all scan bodies, the CISP group exhibited superior trueness and precision compared with the IOS and IOS-SA groups. Furthermore, in the virtual Sheffield fit test, the CISP group achieved the highest levels of precision at SB3 and onward among groups. The CISP using tan-colored scan aids showed the highest trueness and precision among all colors, especially at SB5 and SB6.

Conclusions: The calibrated protocol led to improved trueness and precision over IOS alone and IOS-SA, with the tan-colored CISP providing the best outcomes in the virtual Sheffield fit test.