Effect of Scan Calibrator Material on the Accuracy of Calibrated Intraoral Complete-Arch Implant Scans

Scan calibrators (SCs) have been used to correct stitching errors in intraoral complete-arch implant scans. This study aimed to propose a universal SC design and to evaluate the effect of manufacturing material on its accuracy in calibrating complete-arch implant scans.

A universal SC featuring a mid-ridge C-shaped window was designed and evaluated on an edentulous implant model with six screw-retained abutment (SRA)-level scan bodies (SBs). The SC was fabricated from four materials:(1) yellow resin (SC-YR), (2) gray resin (SC-GR), (3) white resin (SC-WR), and (4) titanium alloy (SC-TA). Each SC group was attached to the model and scanned 10 times with an intraoral scanner (IOS). The resulting intraoral scans were calibrated using desktop scans of the SCs as references. A desktop scan of the model served as the overall reference dataset. Each test scan, as well as the reference scan, was processed to contain only six SB-SRA assemblies. The processed test scans were superimposed onto the reference scan by: (1) using all six SBs to evaluate the overall fit, and (2) using the first and second SBs to simulate the virtual Sheffield test. Following superimposition, trueness was evaluated by calculating the linear deviation between the centers of the six SRAs in each test scan and the corresponding centers in the reference scan. Precision was assessed as the deviation between each pair of test scans within the same group.

In the overall fit test, the SC-WR group showed the lowest trueness (31.95 ± 3.93 μm) and precision (39.92 ± 23.34 μm), whereas the SC-YR and SC-TA groups demonstrated the highest accuracy. In the virtual Sheffield test, no statistically significant differences in trueness were observed among the four groups at the distal SRA6 (107.06 μm for SC-YR, 115.24 μm for SC-GR, 104.35 μm for SC-WR, and 81.82 μm for SC-TA), with all values below the clinically acceptable threshold of 150 μm. For precision, the SC-GR group performed worse than the other groups at the distal SRA6; however, all four groups achieved precision values below 150 μm, indicating clinical acceptability.

The proposed SC design, featuring a mid-ridge C-shaped window, offers a universal and accurate approach for calibrating intraoral complete-arch implant scans under in vitro conditions. All four tested SC materials yielded clinically acceptable calibrated scans (linear deviations < 150 μm at all implant sites). Titanium alloy may represent a suitable material for the fabrication of reusable SCs; nevertheless, further in vivo clinical studies are required.