Evaluation Of The Reliability And Reproducibility Of Bolton Ratios Using Intraoral Scanner, Model Scanner, And Plaster Models

Abstract

Background: Advances in digital technologies have enabled multiple methods for measuring tooth size ratios; therefore, this study compared the reliability of manual, intraoral scanner, and model scanner techniques in determining anterior and overall Bolton ratios. Materials and Methods: Thirty-six female subjects aged 18–25 years were included. Plaster models were obtained using silicone impressions for manual measurements. Intraoral digital models were created with an intraoral scanner, and additional digital models were produced by scanning plaster casts with a model scanner. Anterior and overall Bolton ratios were measured on all three model types by two observers. Intra- and inter-observer reliability were assessed using intraclass correlation coefficients (ICCs). Bland–Altman analyses evaluated systematic and random errors, and repeated measures ANOVA tested differences between measurement methods. Results: Intra-observer reliability was highest for manual anterior measurements (ICC=0.914), followed by the model scanner (ICC=0.867), with intraoral scans showing lower consistency (ICC=0.826). Inter-observer agreement was lower across all methods, especially for intraoral scans. Bland–Altman analysis revealed the largest bias and widest limits of agreement in intraoral anterior measurements. Anterior Bolton ratios differed significantly between methods (p<0.001), with intraoral scans overestimating by 5–7 percentage points; overall Bolton ratios did not differ significantly (p=0.601). Conclusions: Manual and model scanner measurements provided comparable, reliable results for anterior Bolton analysis, whereas intraoral scanning showed greater variability and overestimation. For accurate assessment of anterior tooth size discrepancies, manual or model-based methods are preferable. Overall Bolton ratios can be reliably evaluated with any of the three methods.

Keywords

• Bolton ratio
• intraoral scanner
• model scanner
• plaster model

Supporting Institution

This study was supported by the Hacettepe University Scientific Research Projects Coordination Unit (Project number TAY-2023-20694).

Ethical Statement

The study protocol was approved by the Clinical Research Ethics Committee of Hacettepe University (Approval No: KA-22051).

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