"Dentofacial deformity refers to deviations from the norm of facial proportions and tooth ratios of such magnitude as to represent a disability." [1] These conditions afflicted two aspects of the patient's health: the first related to the functions performed by the stomatognathic apparatus (mastication, swallowing, phonation, etc...), the second related to the morphology of the face, which--by virtue of the severe disharmony of its parts--did not fully realize its function as an organ of relationships, leading the patient to high levels of psychological distress.

The nature of the dentofacial deformities was mainly related to skeletal discrepancies between the maxillae, such that the malocclusion could not be resolved by orthodontic treatment alone. The resolution of these conditions required a perfect synergy between orthodontic therapy (aimed at dental alignment of the individual arches) and surgical therapy (aimed at morphological harmonization of the face and obtaining the correct occlusion).

**Orthognathic Surgery**

Orthognathic surgery allows the repositioning of the jaws in all three spatial planes. This procedure is indicated for patients with:

• Class 3 malocclusion, caused by maxillary retrusion, mandibular prognathism, or a combination of the two;
• Class 2 malocclusion, due to mandibular retrusion, with a normally conformed, protruded, or retruded maxilla and/or with excessive verticality;
• Class 1 malocclusion, characterized by consensual bimaxillary retrusion (a condition that may be seen in complex medical issues, such as in OSAS patients);
• Facial asymmetries caused by overgrowth on one side or facial torsion;
• Other malocclusions not correctable with orthodontic treatment alone, such as transversal or dento-alveolar deficits;
• Sequelae from facial trauma.

Orthognathic surgery has progressed rapidly since the 1950s when surgical techniques for treating most malocclusions that could not be resolved through orthodontics alone were first developed.

Subsequent technological advances have simplified the diagnosis of dentofacial deformities in three dimensions: Multislice CT (MSCT), Cone Beam CT (CBCT), Magnetic Resonance Imaging (MRI), stereophotogrammetry, dental arch scanning, software that allows surgical planning and outcome prediction, intraoperative navigation, and CAD-CAM technology. The conventional approach to orthognathic surgery (Orthodontic-first) consists of three phases: pre-surgical orthodontic treatment, the surgical phase, and post-surgical occlusion stabilization (post-surgical orthodontic treatment).

**Orthognathic Surgery and Technology: From 2D Study to 3D** To diagnose dentofacial deformities, the investigators have utilized 3D digital records created through dedicated software or devices. Real data and digital information are combined to simulate the surgical procedure.

**3D Cephalometry** Cephalometry is the method used to analyze the geometry of facial structures. Historically, this method was based on 2D radiology. The use of CT allowed the application of the same geometric criteria to 3D reconstructions of the skull and face. Studies assessing its accuracy showed that this method is comparable to standard 2D cephalometry for known measurements, but it adds a significant amount of new information, particularly regarding the rotational and translational aspects of the jaws and individual teeth.

**3D Surgical Planning** It is now possible to plan surgery using computer-assisted digital methods. The surgical plan can be transferred accurately to the patient through CAD-CAM-manufactured devices. The planning process can simulate both orthodontic and/or surgical treatment.

At the University of Bologna, the investigators have extensive experience with intraoperative navigation guided by 3D virtual simulation, combining navigation and virtual 3D surgery. they also have expertise in producing individualized CAD-CAM synthesis devices. It has been previously demonstrated that virtual orthodontic planning is as reliable as traditional methods using plaster models in orthodontic-only patients.

In fact, incorporating digital orthodontic planning into the orthodontic/surgical workflow is of great importance for the following reasons:

1. Initial treatment prediction to better guide therapeutic choices;
2. Improved communication between orthodontists and surgeons;
3. Enhanced communication with patients, providing an accurate prediction of the treatment plan from the beginning.

Inclusion Criteria:

• Patients with dentoskeletal dysmorphia.
• Patients undergoing orthognathic surgery.
• Patients between 18 and 60 years of age at the time of orthognathic surgery.
• Obtaining informed consent.Inclusion criteria
• Patients with dentoskeletal dysmorphia.
• Patients undergoing orthognathic surgery.
• Patients between 18 and 60 years of age at the time of orthognathic surgery.
• Obtaining informed consent.

Exclusion Criteria:

• Patients who have undergone other facial surgeries during the treatment period.
• Patients who have not followed the data collection phases foreseen in the 3D Study.

All patients operated since January 2015 and who completed the "T2" follow-up by May 30, 2020, at the Maxillofacial Surgery Department (AOU di Bologna), who followed the normal care pathway provided for cases of dentoskeletal dysmorphosis, which consisted of:

T0: Initial 3D study (before the start of orthodontic treatment) T1: Preoperative 3D study (1 month after surgery) T2: Final 3D study (at the end of post-operative orthodontic treatment with the appliance removed)