Accuracy of digital American Board of Orthodontics Discrepancy Index measurements

• We measured ABO discrepancy index (DI) digitally and on plaster casts.
• Total DI scores with OrthoCAD and plaster measurements were similar.
• Total DI score with Ortho Insight 3D was significantly larger than plaster casts.
• With OrthoCAD, only the overjet measurement differed from the plaster casts.
• With Ortho Insight 3D, multiple measurements differed.

IntroductionA digital analysis that is shown to be accurate will ease the demonstration of initial case complexity. To date, no literature exists on the accuracy of the digital American Board of Orthodontics Discrepancy Index (DI) calculations when applied to pretreatment digital models.MethodsPlaster models were obtained from 45 previous patients with varying degrees of malocclusion. Total DI scores and the target disorders were computed manually with a periodontal probe on the original plaster casts (gold standard) and digitally using Ortho Insight 3D (Motion View Software, Hixson, Tenn) and OrthoCAD (Cadent, Carlstadt, NJ). Intrarater and interrater reliabilities were assessed for 15 subjects using the Spearman rho correlation test. Accuracies of the DI scores and target disorders were assessed for all 45 subjects using Wilcoxon signed ranks tests.ResultsIntrarater and interrater reliabilities were high for total DI scores and most target disorders (r > 0.8). No significant difference was found between total DI score when measured with OrthoCAD compared with manual calculations. The total DI scores calculated by Ortho Insight 3D were found to be significantly greater than those by manual calculation by 2.71 points.ConclusionsThe findings indicate that a DI calculated by Ortho Insight 3D may lead the clinician to overestimate case complexity. OrthoCAD's DI module was demonstrated to be a clinically acceptable alternative to manual calculation of the total scores.