**3. Defining treatment objectives**

Therapy planning should be clear and precise and the objectives need to be defined with collaborative partners before a final treatment planning decision:


Starting cases orthodontically and then, if unsuccessful, referring them for surgery often produces compromised results. [5] It is, therefore, important to prioritize problems and think of potential solutions; this way one can define the objectives of each treatment step. The initial treatment plan must be established following a discussion between the different parties responsible for the smooth implementation of the various steps of the treatment plan.In fact, cephalometric and occlusal simulation setup permits the practitioner to project the occlusal dental and facial skeletal result, to ascertain and determine a suitable orthodontic surgical protocol. Those set-up demonstrates the general reharmonization of the teeth, the jaw and the face. It can then be used as a reference instrument in discussions with the surgeon and patient, and can be modified at all times according to the particular needs. The set-up is, and remains, an estimation which supplies simple quantitative proportional and comparative data. We can record all the data in it (Figure 7). [6]

The use of information technology in dental studies and orthodontics in particular, has contributed to the use of set-up scanning. A 3D simulation system has been developed for orthognathic surgery ; it helps integrate the shape data of the teeth, jawbone and face into the same coordinate system on a computer. The movement of bone associated with mandibular osteotomy and the subsequent changes in the facial form can thus be estimat‐ ed preoperatively. [7]

The three-dimensional setups allow orthognathic surgery simulation through:


**2.3. Presurgical skeletal pattern**

138 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**3. Defining treatment objectives**

dentoalveolar system.

record all the data in it (Figure 7). [6]

ed preoperatively. [7]

The influence of the mandibular plane angle on horizontal and vertical skeletal stability has been shown in several studies. [3, 4] High angle patients have a greater risk of relapse after receiving bilateral sagittal split ramus osteotomy than low and normal–angle patients. Patients with a low mandibular plane angle, compared to high and normal angle patients, appear to have a more predictable procedure. Then, patients with a low mandibular plane angle have increased vertical relapse when advancement surgery is indicated; whereas patients with a high mandibular plane angle have more horizontal relapse. [3] Because the muscles of mastication are lengthened in the ramus area, they tend to return to their original positions, rotate the mandible in a clockwise movement, open the bite, and cause relapse. To minimize the risk of relapse, patients should be selected carefully; isolated mandibular advancement or

setback should not be performed for patients with high mandibular plane angles. [3]

**•** Focus of the objective of surgery should center on osteotomy choice and its site;

collaborative partners before a final treatment planning decision:

Therapy planning should be clear and precise and the objectives need to be defined with

**•** Orthodontic objective conditioned by the surgical objective, will consist of determining the necessary strategies to reduce preliminary occlusal obstacles and the rebalancing of the

Starting cases orthodontically and then, if unsuccessful, referring them for surgery often produces compromised results. [5] It is, therefore, important to prioritize problems and think of potential solutions; this way one can define the objectives of each treatment step. The initial treatment plan must be established following a discussion between the different parties responsible for the smooth implementation of the various steps of the treatment plan.In fact, cephalometric and occlusal simulation setup permits the practitioner to project the occlusal dental and facial skeletal result, to ascertain and determine a suitable orthodontic surgical protocol. Those set-up demonstrates the general reharmonization of the teeth, the jaw and the face. It can then be used as a reference instrument in discussions with the surgeon and patient, and can be modified at all times according to the particular needs. The set-up is, and remains, an estimation which supplies simple quantitative proportional and comparative data. We can

The use of information technology in dental studies and orthodontics in particular, has contributed to the use of set-up scanning. A 3D simulation system has been developed for orthognathic surgery ; it helps integrate the shape data of the teeth, jawbone and face into the same coordinate system on a computer. The movement of bone associated with mandibular osteotomy and the subsequent changes in the facial form can thus be estimat‐

The three-dimensional setups allow orthognathic surgery simulation through:

**•** Realization of a morphing orthognathic surgery

**Figure 7. Surgical visual treatment prediction** The presurgical setup can assist surgical diagnosis accurate prediction of the postoperative skeletal, dental and facial profile and has become an essential part of the diagnostic and treatment planning procedure of combined surgical-orthodontic therapy.
