3D versus 2D: a more reliable and accurate cephalometric analysis

Aim: 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. Cephalometry is an essential clinical and research tool in orthodontics. It has been used for decades to obtain absolute and relative measures of the craniofacial skeleton. Lateral cephalograms are two-dimensional (2D) radiographs that are used to depict three-dimensional (3D) structures. Consequently, cephalograms have inherent limitations as a result of distortion and differential magnification of the craniofacial complex. This may lead to errors of identification and reduced measurement accuracy. The introduction of maxillofacial Cone Beam (CBCT) has made 3D imaging more readily available for dental applications. Methods: A low-dose CBCT machine was used to acquire the radiographic images in this study of the ten-point 3D cephalometry method. The image quality of CBCT compares favorably to that of multi-slice CT, as it has minimum image noise and a maximum signal-to-noise ratio. 130 patients were selected randomly for the study. They ranged in age from 8 to 42 years; there were 80 females and 50 males. Each patient had already had lateral and posteroanterior cephalograms taken less than 6 months earlier. The cephalometric analysis was performed by three operators repeating the measurements twice (15 days apart) with a calibration meeting. The positions of the maxilla and mandible in 3D space were determined using low-dose CBCT by assigning three reference planes to obtain the (x, y, z) position of each point of the skull relative to point S with coordinates (0, 0, 0), which was automatically determined by the computer as the intersection of the reference planes. The position of the jaws in 3D space was determined by assigning 18 easily identified, repeatable cephalometric point. By analyzing the relationships among the surfaces created and the angular and linear evaluations based on reported criteria, the program automatically detects the expansion of the jaws with very high precision, facial asymmetry in the three spatial planes, the skeletal class, and the anterior vertical dimension. Results: Statistically significant differences were found between angular and linear measurements taken with conventional radiographs and those taken with CBCT (p<0.01). Conclusions: Three-dimensional imaging provides information and images of craniofacial structures free from perspective distortion, with none of the magnification or superimposition associated with 2D images. The 3D cephalometric analysis is easier to interpret than 2D cephalometric analysis (interpolation of cephalometric values on different projections) because it allows movement from a purely mathematical interpretation (evaluation of angles and linear measurements) to a graphical interpretation, with verification of the results using mathematical values (volumetric). Another aid to the clinician is the repeatability and reproducibility of this method, which reduces human error in cephalometric analysis. This method saves time and increases precision, offering a valuable aid to orthodontic diagnosis. This preliminary study expands the landscape of diagnostic methods, allowing for more extensive studies to confirm the clinical effectiveness and validation of the 18-point 3D cephalometric analysis. The value of a 3D image model directly corresponds to the quality of the information, the accurate anatomic data derived, and its collection in a 3D anatomic database. Used appropriately, 3D cephalometrics allows clinicians to analyze, diagnose, plan, and communicate. Treatment changes can then be recommended based on a patient's individual preference within his or her biologic, physiologic, and anatomic limits.