A comparison of the precision of three-dimensional images acquired by 2 digital intraoral scanners: effects of tooth irregularity and scanning direction

Objective: The purpose of this study was to compare the precision of threedimensional (3D) images acquired using iTero^&#174 (Align Technology Inc., San Jose, CA, USA) and Trios^&#174 (3Shape Dental Systems, Copenhagen, Denmark) digital intraoral scanners, and to evaluate the effects of the severity of tooth irregularities and scanning sequence on precision. Methods: Dental arch models were fabricated with differing degrees of tooth irregularity and divided into 2 groups based on scanning sequence. To assess their precision, images were superimposed and an optimized superimposition algorithm was employed to measure any 3D deviation. The <i>t</i>-test, paired t-test, and one-way ANOVA were performed (<i>p </i>&lt; 0.05) for statistical analysis. Results: The iTero^&#174 and Trios^&#174 systems showed no statistically significant difference in precision among models with differing degrees of tooth irregularity. However, there were statistically significant differences in the precision of the 2 scanners when the starting points of scanning were different. The iTero&#174 scanner (mean deviation, 29.84 ± 12.08 μm) proved to be less precise than the Trios^&#174scanner (22.17 ± 4.47 μm). Conclusions: The precision of 3D images differed according to the degree of tooth irregularity, scanning sequence, and scanner type. However, from a clinical standpoint, both scanners were highly accurate regardless of the degree of tooth irregularity.[Korean J Orthod 2016;46(1):3-12]