Validity, reliability, and reproducibility of linear measurements on digital models obtained from intraoral and cone-beam computed tomography scans of alginate impressions

Abstract

Digital 3-dimensional models are widely used for orthodontic diagnosis. The aim of this study was to assess the validity, reliability, and reproducibility of digital models obtained from the Lava Chairside Oral scanner (3M ESPE, Seefeld, Germany) and cone-beam computed tomography scans of alginate impressions for tooth-width measurements and the Bolton analysis. A digital model, an intraoral scan, and a plaster model were made for each of 22 subjects. Tooth-width measurements on the digital model and the intraoral scan were compared with those on the corresponding plaster models (gold standard). Intraclass correlation coefficients were calculated to determine the interexaminer reliability of the measurements of each method. The anterior and overall Bolton ratios were calculated for each participant and for each method. The paired ttest was used to determine the validity. The scanning time for the intraoral scanner was registered and analyzed. Tooth-width measurements of each tooth on the digital models and the intraoral scans did not differ significantly from those on the plaster models (P>0.05). The overall and anterior Bolton ratios from the 2 types of digital models differed significantly from the gold standard (P<0.05). However, the differences never exceeded 1.5 mm; this could be regarded as clinically insignificant. The scanning times of the intraoral scanner decreased significantly with the number of scans performed. Both intraoral scanning and cone-beam computed tomography scanning of alginate impressions are valid, reliable, and reproducible methods to obtain dental measurements for diagnostic purposes.