Comparison of different intraoral scanning techniques on the completely edentulous maxilla: An in vitro 3-dimensional comparative analysis

Statement of problem: Information about the accuracy of intraoral scanners for the edentulous maxilla is lacking. Purpose: The purpose of this in vitro study was to compare the accuracy of 3 different intraoral scanner techniques on a completely edentulous maxilla typodont. Material and methods: Two completely edentulous maxillary typodonts with (wrinkled typodont) and without (smooth typodont) palatal rugae were used as reference and were scanned by using an industrial metrological machine to obtain 2 digital reference scans in standard tessellation language (STL) format (dWT and dST). Three different scanning techniques were investigated: in the buccopalatal technique, the buccal vestibule was scanned with a longitudinal movement ending on the palatal vault with a posteroanterior direction; the S-shaped technique was based on an alternate palatobuccal and buccopalatal scan along the ridge; in the palatobuccal technique, the palate was scanned with a circular movement and then with a longitudinal one along the buccal vestibule. Consecutively, 6 types of scans were obtained (n=10), namely wrinkled typodont/buccopalatal technique, wrinkled typodont/S-shaped technique, wrinkled typodont/palatobuccal technique (wrinkled typodont), smooth typodont/buccopalatal technique, smooth typodont/S-shaped technique, and smooth typodont/palatobuccal technique (smooth typodont). Scans in STL format were imported into a dedicated software program, and trueness and precision were evaluated in μm. In addition to descriptive statistics (95% confidence interval), a 2-factor ANOVA on the data ranks, the Kruskal-Wallis, and the Dunn tests were performed to analyze differences among groups (α=.05). Results: Mean values for trueness (95% confidence interval) were wrinkled typodont/buccopalatal technique=48.7 (37.8-59.5); wrinkled typodont/S-shaped technique=65.9 (54.9-77.4); wrinkled typodont/palatobuccal technique=109.7 (96.1-123.4); smooth typodont/buccopalatal technique=48.1 (42.4-53.7); smooth typodont/S-shaped technique=56.4 (43.9-68.9); smooth typodont/palatobuccal technique=61.1 (53.3-69), with statistically significant differences for wrinkled typodont/buccopalatal technique versus wrinkled typodont/palatobuccal technique (P