Accuracy of complete-arch implant digital scans: effect of scanning protocol, number of implants and scan body splinting

Int J Prosthodont. 2022 Oct 21. doi: 10.11607/ijp.7332. Online ahead of print.

Abstract

Purpose: To determine the effects of scanning protocol, number of implants, and implant splinting on the accuracy of digital scanning in the edentulous arch.

Materials and methods: A resin-based model of an edentulous mandible with six implants was scanned with a coordinate measurement machine as a reference and then with two intraoral scanner (IOS) systems (TRIOS 3 and Primescan). Ten scans were taken per IOS in three experiments, and each scan was compared to the reference to evaluate trueness and precision. Analysis involved using engineering software (GOM Inspect) to measure linear and angular discrepancies. In experiment 1, three scanning protocols were compared (linear, zigzag, and half-arch). In experiment 2, three clinical situations were simulated. In experiment 3, the effect of implant splinting with a suture thread was measured. Normal distribution of data was examined with Shapiro-Wilk test. Levene test was used for equality of variance (αα = .05). Statistical differences in distance and angular deviations were analyzed by Student t test or ANOVA with post hoc Tukey test (α = .05).

Results: The best results in terms of trueness and precision were obtained with a linear scanning protocol and six implants: TRIOS 3 = trueness 52 µm/0.42 degrees, precision 40 µm/0.26 degrees; and Primescan = trueness 24 µm/0.28 degrees, precision 18 μm/0.27 degrees. The scanning protocol did not significantly affect distance or angular deviation accuracy. Trueness and precision significantly decreased with four implants using both Primescan and TRIOS 3. Splinting implants negatively affected accuracy with both scanners.

Conclusion: Both IOS systems achieved clinically satisfying accuracy in distance (< 100 μm) and angular (< 0.5 degrees) deviation with six implants and a linear scanning protocol. With four implants, angular deviations sometimes differed between implants within the same digital scan depending on the IOS and the clinical situation.