Scanner type and scan body position effects on the complete‐arch digital implant scan accuracy

Background: Even though there are various brands of intraoral (IOS) and laboratory (LBS) scanners, there is no scanner that is accepted as superior in terms of accuracy for scans of completely edentulous arches and their accuracy in different clinical situations has not been proven yet. Additionally, the effect of scan body position on the accuracy is not well-known. Therefore, the verification of the scan accuracy of different scanners can be clinically beneficial to select the optimal scanner. Aim/Hypothesis: To compare the scans of a recently introduced (Virtuo Vivo, VV-IOS) and a commonly used IOS (TRIOS 3, TS-IOS) to an LBS (Cares 7 SERIES, 7S-LBS) for accuracy (trueness and precision) in a completely edentulous mandibula with 6 implants and to evaluate the effect of scan body position on the accuracy. Materials and Methods: Multi-unit abutments and scanbodies were tightened on a poly(methyl methacrylate) edentulous mandibular model with 6 implants. A master reference model (MRM) stereolithography (STL) file was generated by scanning the model with a blue light high-precision scanner. The model was scanned with 3 different scanners (n = 10); 2 different IOSs and an LBS and converted to STL files. Then, all test scans were superimposed over the MRM (nominal) using the best-fit algorithm. To evaluate the effect of scan body position, scan bodies were labeled 1 through 6 (SB1-SB6) started from the left side of the model to refer implant position. The amount of distance and angular deviations between the identical scan bodies in the experimental scan and the MRM was measured for all scan body positions in each scan for trueness. The degree of variance among groups of experimental scans was calculated for precision (distance and angular deviation). The data were analyzed with ANOVA and Tukey HSD tests (α=.05). Results: For trueness, scanner type (P < 0.001) and scan body position (P < 0.001) had a significant effect on mean distance deviation and a significant interaction was found (P = 0.009). 7S-LBS had the highest (P < 0.001) and TS-IOS had the lowest mean distance deviation (P < 0.001). SB1 (P ≤ 0.001) had significantly higher mean distance deviation than SB2 and SB3. For angular deviation, scanner type (P = 0.041) had significant effect, and significant interaction was found between scanner type and scan body position (P = 0.024). VV-IOS had significantly lower mean angular deviation than TS-IOS (P = 0.031). For all scanners, there was no significant difference between angular deviation of different scan body positions (P ≥ 0.682). For precision, significant difference was only found for distance deviation (P = 0.013) between different scanners. VV-IOS had significantly higher mean distance deviation than 7S-LBS (P = 0.01), whereas there was no significant difference among different scanners (P ≥ 0.839) in terms of angular deviation. Conclusions and Clinical Implications: When both trueness and precision (distance and angular deviations) were considered, one scanner type was not superior to others. Position of the scan body only had a significant effect on distance deviation (trueness). LBS had significantly higher distance deviation than IOSs for trueness, but had significantly lower distance deviation than VV-IOS for precision. For angular deviation, significant difference was found between IOSs in terms of trueness, but there was no difference for precision. Acknowledgements: All other authors have no conflicts of interest to declare. The authors do not have any financial interest in the companies whose materials are included in this article. Keywords: accuracy, scanner, precision, scan body, trueness