## 1 Introduction
Additionally, integrating these data with CBCT scans allows for a comprehensive evaluation of skeletal, dento-alveolar, and soft tissue components in a \"real\" 3D digital patient model [9]. Clinically, a dysgnathia may make function difficult but not impossible; thus, considerable effort is required to compensate the anatomical deformity with consequent possible muscular and joint problems [10]. Temporo-mandibular joint (TMJ) disorders' signs and symptoms, such as bruxism, joint deviation during the opening, reduced opening/lateral/protrusive movements, and myofascal pain, were observed in 15.5% of subjects with Class III malocclusion [11]. A surgery treatment is generally planned in severe skeletal malocclusions and orofacial deformities. For instance, among birth defects, the cleft lip and cleft palate require a long-term multidisciplinary treatment in which many reconstructive and/or plastic surgeries are performed [12]. An ideal result of correcting a skeletal malocclusion should consider function, aesthetics, and long-term stability. Indeed, improving aesthetics and function is very important for patient's motivation and life quality. The combination of orthodontic and surgical treatment should be considered for patients who would not have satisfactory aesthetics following orthodontic treatment alone. The orthognathic surgery aims essentially to establish a harmonious profile of the soft tissues in a balanced skeletal framework. Predicting postoperative soft tissue changes is equally crucial as indicating hard tissue displacement; in fact, the extent of the cosmetic change is correlated with the degree of hard tissue repositioning. The management of the relationship between hard and soft tissues may be highly complex due to the morphology, tone, posture, and thickness of the soft tissues, which vary from person to person. Nowadays, the implementation of three-dimensional examinations, such as cone-beam computed tomography (CBCT), provides more accurate assessments [13; 14]. CBCT allows us to perform precise measurements and undertake 3D surgical planning thanks to dedicated software [15; 16]. Three-dimensional-assisted orthognathic surgery, acting on the hard and soft tissues, aims to reposition the maxilla and mandible in order to ensure a marked improvement in facial proportions and balance. Currently, the orthognathic surgical techniques for treating Class III mainly include Le Fort I advancement osteotomy of the maxilla, bilateral sagittal split osteotomy to reduce the mandible length, and genioplasty. During the treatment planning stage, the extraction of the third molars must be considered; this can be performed before orthognathic surgery or at the same time as the surgery. Extraction before the surgery involves a postoperative recovery period of several months. On the contrary, extraction during surgery does not require a significant increase in operating times and does not negatively affect the postoperative course. Nowadays, the sequence of osteectomies is based on preoperative 3D planning and a surgical model. The introduction of virtual treatment planning has been revolutionary in orthognathic surgery [17]. By means of digital approach, it is possible to improve the diagnosis and treatment planning stages thanks to a better visualization of pre-, mid- and postoperative phenotypic changes. Through computer-assisted surgery, it is also possible to plan osteotomies, manufacture accurate surgical guides, and produce intraoperative and final splints [18; 19]. Bilateral sagittal split osteotomy (BSSO) is a surgical procedure primarily used to correct mandibular deficiencies, such as protrusion or retrusion, without addressing other facial skeletal discrepancies. In case of a single jaw repositioning surgery, a final splint is used to guide the occlusion of the repositioned jaw respect to the remaining one. This procedure is commonly indicated for patients with mandibular proganthism and normal values for the maxilla position, following the cephalometric criteria used in orthodontics.