Accuracy analysis of complete-arch digital scans in edentulous arches when using an auxiliary geometric device

Statement of problem. Obtaining reliable digital scans of edentulous patients is challenging because of the absence of anatomic landmarks/geometric variations along the dental arch. Whether adding an auxiliary geometric device (AGD) will improve scanning is unclear. Purpose. The purpose of this in vitro study was to analyze the accuracy of complete-arch digital scans of completely edentulous arches by placing a consumable AGD. Material and methods. stainless-steel model of the maxilla of a completely edentulous arch with 4 implants was built. The model was scanned using a reference industrial scanner as the control and using 3 intraoral scanners (True Definition [3M ESPE], TRIOS 3 [3Shape A/S], and iTero [Align Technology, Inc]). Each intraoral scanner was used 10 times without the AGD in place and 10 more times with the AGD fixed on the model. Accuracy in terms of trueness and precision was established by comparing 5 reference distances with or without the AGD in place. A software program for analyzing 3D data was used to measure these 5 distances, and a data analysis software program was used for statistical and measurements analysis (alpha=.05). Results. Significant differences (P<.05) were found in all reference distances for trueness and in 4 of the 5 reference distances for precision depending on whether the AGD had been used or not. Without the AGD in place, trueness ranged from 21 +/- 16 mu m in the shortest reference distance to 125 +/- 80 mu m in the largest reference distance. With the AGD in place, trueness ranged from 11 +/- 8 in the shortest reference distance to 64 +/- 51 mu m in the largest reference distance. Precision ranged from 18 +/- 14 mu m in the shortest reference distance to 84 +/- 74 mu m in the largest reference distance without the AGD and from 7 +/- 7 mu m in the shortest to 63 +/- 46 mu m in the largest with it. Conclusion. Complete-arch digital scans of edentulous jaws are more accurate when an AGD is used to resolve the lack of anatomic landmarks. An additional advantage is that the use of the AGD allows for a more fluent scanning process.