## 1 Introduction  
Orthognathic surgery allows broad-spectrum deformity correction involving both aesthetic and functional aspects on the TMJ (temporo-mandibular joint) and on the facial skull district. The type of surgery to be performed depends on the patient's pathology. In 1907, [PERSON] was the first to perform a classification of the dentofacial deformity by dividing the deformity of the jaws into five classes: mandibular prognathism and retrognathism, alveolar mandibular and maxillary protrusion, and open bite [1]. An important aspect that characterized the evolution of the orthognathic surgery consists of the application of plates and screws in terms of rigid or semi-rigid fixation. The use of screws and plates, as a milestone in orthognathic surgery, is easy, rapid, and reliable, and it is demonstrated that it is useful for the patient because it does not imply the intermaximillary fixation that obliges the patients to not open the mouth for long periods with the consequent implications. Orthognathic surgery sometimes appears to be the only way to correct dentofacial deformities; in fact, the orthodontic phase can only act on the mutual position of the teeth but not on the position and the shape of the bones that support them. To make it easier, a virtual assisted approach of the planning phase was demonstrated to have a higher level of accuracy that implies not only a precise analysis of dentofacial deformities but also an accurate preoperative planning [2]. In fact, the success of a surgical intervention is influenced not only by intraoperative techniques but also and above all by a correct and precise planning of the treatment to be implemented [3; 4]. An important instrument to reach a high level of the maxillary position's accuracy and the functional centric occlusion is the anatomical articulator with its face bow transfer [5]; furthermore, preoperative clinical and radiographic assessment is needed to define a correct treatment plan, and surgeons have to manage different types of data and information to model the surgical operations and to create physical mockups of the patients' mouth. The current surgery practice requires the use of an occlusal splint that records the desired position of the dental arches. The key element of the procedure necessary to the success of the surgery resides both in the dental splints recorded in the articulator and in the human surgeon dexterity that, during the surgery, drive the osteotomized segments into the desired position. Segments are fixed in the final position through the use of plates and screws. The patient model surgery is carried on, with the simulated postoperative positioning, to create wafers, which are essential means of transferring the treatment plan into an accurate surgical procedure. The procedure starts with a jaw-print on a deformable model and the creation of the mouth model for recording the original mutual position (between mandible and maxilla) using the face bow. Surgeons are able to reposition the mouth models in the articulator in order to create the splint for recording the final wanted position. In this way, surgeons have a preview of the final occlusion and can define the best surgery strategy to reach the goal for the patient satisfaction. Obviously, surgery has a key role, especially in the correction of deformities relative to the basic bone structures of facial mass; orthodontis usually intervene only on the mutual position of the teeth but not on the position of the bones with a lack of precision under a functional point of view; jaw functionality is also strictly related to facial aesthetic, being an important element for the individual's social relationships. Standard intervention procedures provide manual operations for splint positioning, mandibular dissection, condylar positioning, and plate screwing.