Comparing the linear measurements made on digital models obtained with 3shape (TRİOS3) oral scanner and 3shape (R700) model scanner by manuel technique; evaluation of validity, reliability and reproducibility

The aim of our study was to evaluate the validity, reliability and reproducibility of linear measurements made on digital models by comparing them with the gold standard method of manual plaster model measurements. 200 patients were divided into 4 equal groups: finished group and mild, moderate and severe crowding groups. Intraoral scans of patients were performed with 3Shape TRIOS3 (Copenhagen, Denmark) and plaster model scans with 3Shape R700 (Copenhagen, Denmark) devices. With the OrthoAnalzer software on the digital model data and with the digital caliper on the plaster models, 18 linear measurements, Hays-Nance, Bolton and Korkhaus-Schwartz analyses, spee, overjet, overbite, and occlusal height measurements were made. Measurements of 20 patients from each group were repeated 2 weeks later by the same investigator. To evaluate validity, reliability and reproducibility, paired t-test, Cronbach's Alpha and intraclass correlation coefficients were used, respectively. Statistically significant differences were found when digital systems were compared to manual technique in terms of validity. In general, digital model measurements provided smaller values than manual technique. In all groups, more numbers of measurements were found to be similar to gold standard in model scanning compared to intraoral scanning. Although the mean differences were found to be clinically negligible, with almost all of the mean differences being less than 0.5 mm, some of the 18 numbered linear measurements exceeded the 0.5 mm limit. 18 linear measurements showed low, medium and high values in terms of reproducibility and reliability, while reproducibility and reliability were found to be high in other measurements. It was found that the validity of the measurement methods among the groups was not affected by the amount of crowding, while the reproducibility and reliability were higher in the finished group compared to the other groups. Digital model measurements have provided accurate, reliable and reproducible values in the majority of measurements compared to manual technique. 3Shape digital models can be used as an alternative to the gold standard in clinical applications. However, it should be noted that there are measurement parameters that still need to be developed. Key words: Digital model, Plaster model, Reliability, Reproducibility, Validity.