Accuracy of a computed tomography scanning procedure to manufacture digital models

Accurate articulation of the digital dental casts is crucial in orthodontic diagnosis and treatment planning. We aimed to determine the accuracy of manufacturing digital dental casts from computed tomography scanning of plaster casts regarding linear dimensions and interarch relationships and to test whether eventual differences in interarch relationships between plaster and digital casts would affect orthodontic diagnostics.

Plaster casts with the wax bites of 2 patients were used to create digital dental casts with a computed tomography scanner. This was repeated 4 times with a 1-week interval. Linear distances were measured on plaster and digital models twice by 2 observers. Next, the 4 digital models of each patient were scored twice by 5 observers for interarch variables.

Digital vs plaster measurements showed high Pearson correlation coefficients (>0.954), whereas the mean difference was small (<0.1 mm) and not significant. The interarch scorings, however, showed significant differences for all variables, except overjet for model 1.

We found substantial interarch inaccuracies of the digital models. These inaccuracies are probably due to a lack of built-in "collision control" in the software and manual articulation of the digital models by a human operator.