The true three-dimensional craniofacial anatomy : 3-D versus 2-D cephalometric analysis

Introduction: The aim of this study was to combine the huge amount of information of low dose Cone Beam CT with a cephalometric simplified protocol thanks to the latest informatics aids. Lateral cephalograms are two-dimensional (2-D) radiographs that are used to represent three-dimensional (3-D) structures. Cephalograms have inherent limitations as a result of distortion, super imposition and differential magnification of the craniofacial complex. This may lead to errors of identification and reduced measurement accuracy. The advantages of CBCT over conventional CT include low radiation exposure, imaging quality improvement, potentially better access, high spatial resolution and lower cost. Patients and methods: This study assessed cephalometric 2D and 3D measurements and the analysis of CBCT cephalograms of the volume and centroid of the maxilla and mandible, in 20 clinical cases. Results: With a few exceptions the linear and angular cephalometric measurements obtained from CBCT and from conventional cephalograms did not differ statistically (P > 0.01). There was a correlation between the variation in the skeletal malocclusion and growth direction of the jaws, and the variation in the spatial position (x, y and z) of the centroids and their volumes (P < 0.01). Conclusion: The 3D cephalometric analysis is easier to interpret than 2D cephalometric analysis. In contrast to those made on projective radiographies, the angular and linear measurements detected on 3D become real, moreover the fewest points to select and the automatic measurements made by the computer drastically reduced human error, for a much more reliable reproducible and repeatable diagnosis.