The planning of orthognathic surgery plays a crucial role in the overall success of the surgical treatment for facial skeletal deformities. For many years, two-dimensional (2D) radiographic analysis and model surgery have been the gold standard for this planning process. However, 2D analysis of a complex three-dimensional (3D) structure has inherent limitations. Virtual planning has emerged as a valid alternative, providing more precise 3D information with a much less time-consuming planning process. Over the last 5 years, virtual planning for orthognathic surgery has evolved, particularly in two areas: the transferring method of the virtual plan for orthognathic surgery, and the accuracy assessment of the surgical outcome. The method used to transfer the virtual plan into the operation room directly influences the position of the osteotomized jaws and therefore the outcome of the treatment. Over the years, various transferring systems have been proposed, generally falling into two groups: the splint group, in which intermediate splints are required for positioning the osteotomized jaws; and the splintless group, in which surgical navigation or customized fixation plates are used for the same purpose, without the need for splints. Evidence for the accuracy of virtual plans and of transferring methods is confusing, mainly due to the wide variety of methods used for accuracy analysis. The current evidence shows that a reliable method for accuracy analysis should involve landmark-free and voxel-based registration for calculation of the translation and rotation movements of the osteotomized jaws. For our study, the accuracy of two transfer methods for the virtual surgical plan for orthognathic surgery was investigated. This prospective clinical study was approved by the ethical committee of the Policlinico di Milano, Milan, Italy. All procedures were in accordance with the ethical principles for medical research involving human subjects, adopted by the Helsinki Conference, June 1964, and informed consent was obtained from all participants. The methods of transferring orthognathic surgical plans have evolved as virtual surgical planning has become a new reality. The 3D CAD/CAM splint was the first transferring method introduced together with virtual planning, and has become the most commonly used (Van den Bempt et al., 2018). Over the last few years, a novel approach has been proposed. Combining a surgical guide, this helps the surgeon to determine the exact location and direction of the osteotomy, and a fixation plate. Both transferring systems showed good overall accuracy. The customized fixation plate system was shown to be more accurate than the intermediate CAD/CAM splint for some specific points, and especially along the x-axis. Given the small sample size and the lack of significant studies in area, more investigations are encouraged in order to find a more conclusive answer on the most reliable method for transferring virtual plans.

Regards,
Catherine
Journal Co-Ordinator
Journal of Orthodontics and Endodontics