Accuracy of intraoral scanners in different complete arch scan patterns

The accuracy (trueness and precision) of intraoral scanners and complete arch scans remains controversial.The purpose of this in vitro study was to compare the trueness and precision of 3 intraoral scanners with various scan patterns.Four standard metal spheres were installed on a dental maxillary cast according to American National Standard/American Dental Association (ANSI/ADA) specification no. 132. Six distances among the center of spheres were measured with a coordinate measuring machine and used as references. Four different scanning patterns were assigned: zigzag, occlusal-palatal-buccal, occlusal-buccal-palatal, and molar-to-canine. Dental Wings and TRIOS 3 applied to the first 3 scan patterns, while True Definition applied to all patterns (n=30). Six distances in the scan files were also measured and calculated for relative errors of trueness and precision. A ratio less than 0.0025 was considered acceptable and used for binary outcome analysis. Differences among scanners and scan patterns in terms of trueness and precision were analyzed with the chi-squared test, Fisher exact test, and logistic regression (α=.05).The zigzag scan pattern from TRIOS 3 and the occlusal-buccal-palatal pattern from True Definition exhibited 100% acceptable precision. TRIOS 3 revealed the highest number of acceptable trueness values in the occlusal-palatal-buccal scan (88.3%). The scan patterns from Dental Wings and TRIOS 3 were related to the trueness. TRIOS 3 and True Definition were 12.8 and 6.4 times more likely to obtain acceptable trueness than Dental Wings (P<.001). The zigzag scan pattern had the highest chance of obtaining acceptable trueness.The scan patterns influenced the trueness and precision of the intraoral scanners in different ways. For the best trueness, TRIOS 3 should be applied with an occlusal-palatal-buccal scan pattern, Dental Wings should be applied with a zigzag scan pattern, while True Definition can be used with any scan pattern.