Comparison of Different Intraoral Scanners With Prefabricated Aid on Accuracy and Framework Passive Fit of Digital Complete-Arch Implant Impression: An In Vitro Study.

Objectives: This study aimed to compare the accuracy of digital complete-arch implant impressions with prefabricated aids using three intraoral scanners (IOSs) and explore the correlation between virtual deviation measurement and physical framework misfit.

Materials and methods: Four edentulous maxillary master models with four and six parallel and angular implants were fabricated and scanned by a laboratory scanner as reference scans. Ten scans of each master model were acquired using three IOSs (IOS-T, IOS-M, and IOS-A) with and without prefabricated aids. Trueness and precision of root mean square (RMS) errors were measured. Ten aluminum alloy frameworks were fabricated, and the misfit was measured with a micro-computed tomography scan with one screw tightened.

Results: Trueness and precision showed significant improvement when prefabricated aids were used for all three IOSs (p < 0.010). Median (interquartile range) RMS errors of trueness reduced from 67.5 (30.4) to 61.8 (30.3) μm, from 100.6 (35.4) to 45.9 (15.1) μm, and from 52.7 (33.2) to 41.1 (22.5) μm for scanner IOS-T, IOS-M, and IOS-A, respectively (p < 0.010). The precision of IOS-A and IOS-M was significantly better than IOS-T when using prefabricated aid (p < 0.001). RMS errors and the maximum marginal misfit of the framework were significantly correlated (p < 0.001, R² = 0.845).

Conclusions: With the prefabricated aids, the accuracy of IOSs enhanced significantly in digital complete-arch implant impressions. Three IOSs showed different levels of improvement in accuracy. Virtual RMS errors <62.2 μm could be the clinically acceptable threshold (150 μm) for framework passive fit.