**2. Treatment planning**

Proffit and Ackerman [2] introduced the concept of envelope of discrepancy to graphically illustrate four ranges of correction for any characteristics of malocclusion: (A) an amount that

can be accomplished by orthodontic tooth movement alone; (B) a larger amount that can be accomplished by orthodontic tooth movement aided by absolute anchorage; (C) an additional amount that can be achieved by functional or orthopedic treatment to modify growth;[3-5] and (D) a still larger amount that requires surgery as part of the treatment plan.

People who can potentially benefit from orthognathic surgery include those with jaws that are positioned incorrectly. Orthognathic surgery is also the treatment of choice in patients who have not had the benefit of dentofacial orthopedics for growth guidance, or in cases where the deformity is so severe that orthodontics alone is not enough to correct it. Achieving successful treatment outcomes in these patients requires implementing an effective treatment plan. It should be considered that treatment planning is one of the most important stages because once the treatment is started it is hardly possible to reverse or suspend it. At this stage, the patient should be verified to have no potential of growth. If the patient is still growing he or she should be examined annually until growth is complete. Once facial growth cessation is verified the patient should be referred to a multidisciplinary clinic for joint treatment planning with the maxillofacial surgeon and orthodontist. In the beginning information about patient's general health state and previous diseases is evaluated and if there are no contraindications for surgery and general anesthesia a thorough examination of the face including evaluation of facial and dental photographs, cephalometric radiographs, and dental casts should be done. Subse‐ quently, the orthodontist and maxillofacial surgeon should make a joint decision concerning the treatment approach. One of the aspects for consideration is whether the surgery is required in the mandible, maxilla or both and whether the jaw is to remain in one piece or to be segmented.
