Accuracy of Interproximal Space Measurement Across Different Orthodontic Tooth-Segmentation Programs: A Comparative Clinical Study

This study evaluated reliability and accuracy of interproximal space measurement in two different orthodontic tooth-segmentation programs in comparison with clinical space measurement and assessed the minimum distance threshold ensuring accuracy. From 6586 digital dental models, eligible digital dental images (DDIs) were selected based on anterior spacing, intra-oral scans, and clinical space (CS) measurement in vivo. Interproximal spaces were virtually measured using two programs: semi-automatic (VS_S; Orthoanalyzer®) and full-automatic (VS_F; DentOne®). Accuracy was analyzed against CS as the gold standard, and the minimum distance threshold for reliable measurement was explored. In 85 interproximal spaces from 22 adult patients, both programs showed excellent repeatability (VS_S, ICC=0.922; VS_F, ICC = 0.948). Agreement between VS_S and CS was good (ICC = 0.785 to 0.882), while agreement between VS_F and CS was consistently good (ICC ≈ 0.884). Mean VS values (VS_S, 0.11; VS_F, 0.13 mm) were lower than CS (0.21 mm, p < 0.001). The mean difference was −0.101 to −0.113 mm in VS_S and −0.078 to −0.082 mm in VS_F. The 95% limits of agreement (LoA) for VS_F were narrower compared to VS_S with a higher proportion of measurements falling within the LoA (95.3% vs. 91.8–92.9%). A significant association between space size and measurement accuracy was found in discrete CS intervals, with higher relative measurement accuracy for larger interproximal spaces (all, p < 0.001). This suggests that tooth-segmentation programs showed reliable accuracy in measuring interproximal spaces > 0.20 mm, though with slight underestimation compared to clinical measurements. Clinical assessment could be supplemented to enhance virtual orthodontic planning, particularly for narrow interproximal spaces.