The role of orthognathic surgery in the correction of dento-skeletal dysmorphies, whether they are Class II or Class III or asymmetries, is to improve both the function and aesthetic appearance of thepatient. Both aspects are equally important to achieve optimal results.

When the surgeon plans the surgery, he or she must therefore take into account the effects that bone displacements will have at the level of the soft tissues directly involved in the surgery, such as the maxilla and mandible. Traditionally, such surgery consists of an orthodontic presurgical phase1,2

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The role of orthognathic surgery in the correction of dento-skeletal dysmorphies, whether they are Class II or Class III or asymmetries, is to improve both the function and cosmetic appearance of the patient. Both aspects are equally important to achieve optimal results.

When the surgeon plans the surgery, he or she must therefore take into account the effects that bone displacements will have at the level of the soft tissues directly involved in the surgery, such as the maxilla and mandible. Traditionally, such surgery consists of an orthodontic presurgical phase1,2

.

The current knowledge of facial aesthetics and its changes consequent to orthognathic surgery is given by studies mainly carried out in 2-dimensions, performed using radiographs (teleradiographs of the skull in PA and LL) and standard photographic material, on which two-dimensional cephalometric and anthropometric studies have been performed. A first fragility, related to less realism, lies in the fact that these represent objects in 2-dimensions when the human body is a structure in 3-dimensions, as well as the chiurgy that is going to be performed and the resulting changes are in the 3-dimensions of space. A second lesser precision of this method of records acquisition is the substantial impossibility of obtaining comparable material in the preoperative and postoperative periods, due to the understandable difficulty of homogeneous acquisition of the records themselves: photographs and radiographs . Recent advances in technology have generated a wide variety of 3-D methods that allow acquisition in the 3-dimensions of space of both surface structures and skeletal bases. These methods include: digital stereophotogrammetry, CT, MRI, and ECO-3D.

This new knowledge has then enabled 3D studies that were previously done in 2D: cephalometry, morphological analysis of the face

. To date, commercially available simulation software manages to be fairly accurate with regard to hard tissues (bone, teeth), but not reliable enough with regard to simulation of soft tissues overlying skeletal bases and consensual motion in the face of facial hard tissue surgery, as they do not take into account the biomechanical variety of individual soft tissue components

Inclusion Criteria:

• Patients undergoing orthognathic surgery and preoperative radiographic study with CBCT and MRI
• Patients with age > or = 18 years old
• Obtaining informed consent
• Patients with preoperative teleradiography and orthopantomography

Exclusion Criteria:

• patients with cleft lip-palate, facial malformations and/or syndromes (syndromes with involvement of the cephalic extremity, such as sd of Apert. Cropuzon, Ofeiffer, Treacher Collins)
• patients who have undergone application of Medpor prostheses or who have undergone ancillary procedures (lipofilling, fillers, volumetric facial augmentations with insertion of polyethylene ketone prostheses)

Verranno arruolati 10 pazienti retrospettivamente. Per ogni paziente verranno effettuate 27 simulazioni virtuali variando le proprietà biomeccaniche delle singole parti. I dati verranno perciò analizzati su 270 interventi virtuali. Le 27 simulazioni procapite vengono determinate in base al range di variazione che in fase iniziale si decide di dare ai vari parametri biomeccanici presi in considerazione per ogni componente del modello (tessuti molli, muscoli, osso)14

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Un campione di 270 simulazione, consente di avere un intervallo di confidenza di 7.85 e un livello di confidenza del 99%. La tabella di seguito dimostra i valori massimi e minimi dati ai singoli muscoli per quanto riguarda il modulo di Young o modulo di elasticità.