The reliability of cephalometric measurements in orthodontics: Cone beam computed tomography versus two-dimensional cephalograms

 Due to the important role of imaging in the diagnosis and treatment plan in orthodontics, CBCT (Cone Beam Computed Tomography) images because of their three-dimensional nature, can minimize the disadvantages of two-dimensional images such as magnification, distortion, or superimposition. The purpose of this study was to evaluate the accuracy of conventional cephalograms and CBCT scan measurements in linear orthodontic diagnostic measurements.

In the first part, the distances between the 14 anatomical landmarks on the 5 dried human skulls (reference models) identified by metal spheres were measured by a digital caliper. In the next step, CBCT images were scanned from the same reference models. In the second part, radiographic images were taken from 26 patients enrolled according to inclusion and exclusion criteria in three stages, scanning CBCT images, digital LC (Lateral Cephalometric) images from the same CBCT images, manual tracing of digital LC images. Finally, using the obtained data, the accuracy of measurements performed directly on the reference models with CBCT images as well as the CBCT images, digital LC and traced digital LC images of the patients were evaluated together.

The mean of direct measurements on the reference models was not significantly different from the measured values on CBCT images (ρ-value> 0.05). In other words, the measurement of the CBCT images was the same as the reference models. Also, in most cases, linear measurements between the traced LC image with digital LC images and the CBCT of patients were different (ρ-value > 0.05). Meaning traced LC images and digital LC in 8 cases, CBCT and digital LC in 4 cases and finally traced digital LC and CBCT in 5 cases were different.

The present study showed that the accuracy of CBCT image measurements was similar to the direct measurements obtained from the reference models. Also, the accuracy of linear measurements of CBCT images is higher and more reliable than that of digital LC images as well as traced digital LC images.