3D Cephalometrics in orthognathic surgery

Aim: The aim of this study is to underline the importance of the application of 3D imaging using Cone Beam CT to improve diagnosis and treatment planning. 3D versus 2D cepalometrics has been evaluated to better understand normal and abnormal growth, development and morphogenesis of the head and face. Materials and Methods: 200 patients were selected randomly for the study. 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. To obtain a reference system that is repeatable and is not influenced by changes in the positions of cranial points due to growth, the best solution in terms of simplicity and precision is to use three reference planes, defined using three points: the sella (S), nasion (N), and basion (Ba). The three planes are the mid-sagittal plane passing through S-N-Ba, the mid-axial plane passing through S-N and perpendicular to the mid-sagittal plane, and the coronal plane passing through S and perpendicular to the other two planes. The intersection of these three planes defines the reference point S (0, 0, 0). These planes are repeatable and specific for each patient. Were assessed 18 cephalometric landmarks, 10 mid-points and 8 lateral points; 36 measurments on the three reference planes. Results: Statistically significant differences were found between cephalometric angular and linear measurements taken with conventional radiographs vs those taken with CBCT (p<0.01). In contrast to those on radiographs, the angular and linear measurements three-dimensionally detected, become real, moreover the selection of fewer points and the automatic measurements made by the computer reduced human error, for a much more reliable and repeatable diagnosis. (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. This method saves time and increases precision, offering a valuable aid to orthodontic-surgical diagnosis. The value of a 3D image model directly corresponds to the quality of the information.