The purpose of this study is to evaluate validity, reliability and reproducibility of mesiodistal width of tooth and arch length, measured on a digital model obtained via 3-dimensional (3D) model scanner and intraoral scanner compared to a conventional plaster model. Furthermore, the research investigates the validity of space analysis based on various measurements.
A total of 30 patients aged 12 to 18 were eligible for the study. 3 types of models were acquired from each patient: a conventional plaster model (P) obtained with alginate and dental white stone, a model scanned digital model (MSD) obtained by scanning the plaster model via Freedom UHD® model scanner and an intraoral scanned digital model (ISD) obtained by CS3600® intraoral scanner in vivo. The reliability of tooth width and arch length measured in each group was evaluated using Pearson’s correlation coefficient, while the reproducibility was evaluated with intraclass correlation coefficients. The validity was assessed by paired t-test, by comparing differences in various measurements including tooth width, arch length and arch length discrepancy in MSD and ISD, with P group as a control group.
As a result, all measurements of P, MSD and ISD groups showed favorable reliability and reproducibility. Most of measurements for space analysis in MSD group and tooth widths in ISD group also presented a significantly high validity. However, arch length and arch length discrepancy in ISD group presented statistically significant difference between P and ISD group. Arch length was significantly shorter in ISD group, which lead to a decrease in arch length discrepancy. In the meantime, the validity was lower in ISD group compared to MSD group.
Therefore, a clinician should be aware that several significant errors can be found during space analysis and treatment using a digital model obtained with various scanners. Furthermore, an appropriate method of scanning should be opted depending on each circumstance.