Surface Analysis of Study Models Generated From OrthoCAD and CBCT

Objectives: To determine the accuracy of CBCT-generated digital models as compared to OrthoCAD models for orthodontic diagnosis and treatment planning using surface area analysis.

Methods: 30 maxillary and 30 mandibular paired stereolithography (STL) files obtained from scanned impressions and CBCT images were superimposed using Rapidform software program, using a ‘best-fit’ algorithm and surface-to-surface analysis was performed. The average linear difference between the two files at all points on the surfaces was measured and tolerance levels of 0.25, 0.5, 0.75, 1.0, 1.25, and 1.5 mm were set to determine the surface correlation amount (%) between the two files. Additionally, six linear measurements from predetermined landmarks were also measured and analyzed. Analysis of Variance (ANOVA) for repeated measures was applied to the data from the linear measurements. 

Results: The average maxillary model linear difference was 0.28 to 0.60 mm, whereas the average mandibular model linear difference ranged between 0.34 to 0.61 mm. Greater than 90% surface correlation was obtained on average at 1.00 mm in the maxillary models and at 1.25 mm in the mandibular models. The mean differences obtained from the linear measurements of the maxillary and mandibular models were 0.071 and 0.018 mm, respectively. 

Conclusions:

Surface-to-surface analysis of OrthoCAD and CBCT-generated digital models pointed out to a fair overlap between two protocols. Accuracy of CBCT-generated digital models can be considered adequate for initial diagnosis and treatment planning in orthodontics.