Accuracy of CBCT Panoramic Images in Projection of Tooth Angulations

Objectives: The first purpose was to assess the accuracy of panoramic-like images derived from the Newtom CBCT unit in the projection of mesiodistal tooth angulations. The second purpose was to compare the projected mesiodistal tooth angulations when orienting the panoramic-like image on three different planes: parallel to the occlusal plane, tilted 10° up and 10° down from the occlusal plane.

Methods: A plastic typodont with 28 teeth in ideal occlusion was fixed in position to a dry human skull for imaging. ‘True' angular measurements were calculated using a coordinate measuring machine and compared to the corresponding measurement derived from the CBCT panoramic-like image. To look for a statistically significant difference between the “true” mesiodistal tooth angulations and those measured from the Newtom panoramic-like images a MANOVA using the LSD test for pairwise comparisons was used. The teeth were analyzed both individually and grouped into sextants.

Results: There was a statistically significant difference between the true and panoramic-like image mesiodistal angular projections for all teeth, with the greatest average difference being 3.675° for maxillary left lateral incisor. Statistically significant differences were also found in mesiodistal root angulations between CBCT panoramic-like images that were oriented 10° above the occlusal plane and both 10° below the occlusal plane and on the occlusal plane. The greatest average difference was 3.03°, which was found in the maxillary anterior sextant.

Conclusion: Used properly, the CBCT panoramic-like image can be a useful tool for the evaluation of mesiodistal root angulations. If a tolerance limit of 2.5° is applied, only the mesiodistal angulation of 22 on the CBCT panoramic-like image would be considered to differ from the true angulation, as it would surpass that tolerance limit by 1.175°. If a limit of 5° is applied, the projections of all mesiodistal root angulations are within the tolerance limits.