Objective To compare the accuracy of mesiodistal tooth angulation measurements by using traditional panoramic radiographs and cone beam CT (CBCT) panoramic images.Methods Plaster models of 15 volunteers with individual normal occlusions were collected. The functional occlusal plane and tooth long axis on the plaster models were marked from the right first molar to the left first molar in the upper and lower dental arches. A radiographic stent,which contains radiopaque markers near the functional occlusal plane and approximating the root axis, was fabricated for each model. Traditional panoramic radiographs and CBCT scan images were obtained from each patient, with the radiographic stent seated on the dentition. A panoramic image reconstruction was made from the CBCT volumetric data by using related software. The CBCT panoramic image data were oriented parallel to the maxillary or mandibular functional occlusal plane containing all the radiopaque markers when measuring the maxillary or mandibular teeth, respectively. The mesiodistal tooth angulations of the plaster model, traditional panoramic radiographs, and CBCT panoramic images were measured and compared. Multivariate analysis of variance and Dunnett-t test were performed to compare the differences among the three methods.Results The difference among the three methods was statistically significant (P=0.00). Significant differences compared with the model measurement were found in two teeth (upper second premolar and lower second premolar) among twelve teeth (P=0.00) in traditional panoramic measurement. CBCT panoramic measurement was not significantly different to model measurement.Conclusion Traditional panoramic radiographs do not provide a more reliable measure of mesiodistal tooth angulation, whereas CBCT panoramic image is an effective tool for evaluating mesiodistaltoothangulation.
