Effects of Scanning Strategy and Scanner Type on the Accuracy of Intraoral Scans: A New Approach for Assessing the Accuracy of Scanned Data

Purpose This study aimed to determine the most reliable scanning strategy and scanner type, using a new protocol for assessing the accuracy (trueness and precision) of intraoral scan data. Materials and Methods Five different maxillary and mandibular typodont pairs (n = 10) and 2 intraoral scanners were used for the study. A reference scan for each arch was obtained with an industrial scanner. Scanning strategies were classified into 2 continuous methods-continuous scan in horizontal direction (CH group) and continuous scan with vertical rotation in anterior region (CV group)-and 1 segmental method (S group). In the CH group, the scanner head was maintained mostly in a horizontal position. In the CV group, the scanners were rotated 180 degrees around the anterior tooth region to allow smooth scanning through the area. The intraoral scan data were individually superimposed over their corresponding reference scan data. Raw data of the distances between paired surface points were extracted from the superimposed pairs of datasets, with (original distance values) or without consideration (absolute distance values) of the value signs. Trueness values were calculated using absolute distance values, while precision values were obtained from original distance values. Data were analyzed with a 2-way repeated-measures analysis of variance using alpha = 0.05 as the level of significance. Results The CV group produced significantly inferior outcomes compared to the CH and S groups in terms of trueness (p< 0.001, F = 24.67), whereas no significant differences were observed among the 3 scanning strategies with respect to precision (p= 0.451, F = 0.83). Scanner type did not produce significant differences in terms of either trueness (p= 0.058, F = 4.72) or precision (p= 0.742, F = 0.12). Conclusions The segmental approach for scanning the region of interest first and continuous scanning with the scanner head held mostly in a horizontal position are both acceptable as full-arch scanning strategies. However, vertical rotation of intraoral scanners should be minimized.