Comparison of Bolton analysis and tooth size measurements obtained using conventional and three-dimensional orthodontic models

OBJECTIVES The aim of this study was to compare the accuracy, reproducibility, efficacy and effectiveness of measurements obtained using digital models with those obtained using plaster models. MATERIALS AND METHODS A total of 20 digital models were produced by the Ortho Three-dimensional Models (O3DM) Laboratory and their software (O3DM version 2) was used to obtain measurements. Identical plaster models were used to obtain measurements of teeth with a vernier caliper. The maximum mesiodistal width of each study model, from first molar to first molar, was measured. All measurements were repeated at least 1 month later by the same operator for both digital and manual methods. The data were analyzed using Cronbach α, Wilcoxon signed rank test and the McNemar test. RESULTS Cronbach α value of the data at T1 and T2 for 6 anterior and 12 overall teeth measured using the two methods was very close to the ideal value of 1, indicating high intra-observer reliability. The Wilcoxon signed rank test showed statistically significant differences between the two methods (P = 0.000, P < 0.001). The measurements obtained using the digital models were lower than those obtained using the plaster models. No statistically significant differences were found between the two methods for anterior Bolton discrepancies (P = 0.375) or overall Bolton discrepancies (P = 0.00). Paired comparisons of repeated measurements for Bolton ratios showed no statistically significant differences for anterior or overall Bolton discrepancies (P = 0.688 and P = 0.375, respectively). CONCLUSIONS Use of O3DM software is an acceptable alternative to the traditional vernier caliper method in orthodontic practice.