Assessing the American Board of Orthodontics objective grading system: Digital vs plaster dental casts

Introduction: The purposes of this study were to determine whether the American Board of Orthodontics objective grading system (ABO OGS) can be assessed accurately from digital dental casts and whether there are statistical differences between digital and plaster dental casts in scoring the ABO OGS. Methods: Thirty posttreatment plaster dental casts were selected and scanned by OrthoCAD (Cadent, Carlstadt, NJ) to produce 30 corresponding digital dental casts. The plaster and digital casts were compared by using the criteria of the ABO OGS. Because the data were ordinal, a nonparametic statistical analysis was used. Results: The Wilcoxon test for paired samples showed significant differences between the plaster and digital casts for occlusal contacts, occlusal relationships, and total scores (P <.05). No significant differences were found for alignment, marginal ridges, overjet, and interproximal contacts. Buccolingual inclination was not included in this study because of inability to perform proper measurements with the OrthoCAD program. Mean differences of points deducted ranged from .03 point for marginal ridges to 5.07 points for the total score. The variable with the most points deducted related to occlusal relationships, and the fewest points were deducted for interproximal contacts. Conclusions: Based on this study, the current OrthoCAD program (version 2.2) was not adequate for scoring all parameters as required by the ABO OGS.