**3. Presurgical orthodontics**

Orthodontic preparation for surgery is different from orthodontic correction alone. Achieve‐ ment of optimal facial esthetics requires integrated cooperation of orthodontists and maxillo‐ facial surgeons. Routine preoperative orthodontics involve dental alignment, incisor decompensation, and arch coordination for the purpose of obtaining maximum intercuspal interdigitation when the jaws are surgically aligned. In short the aims of presurgical treatment are to decompensate lower and upper incisors, level and align both arches and relieve the crowding. In general these corrections will make the malocclusion look worse presurgically, but it will show the true magnitude of the skeletal problem thus allowing an optimal correction at surgery.[6] To sum up, the essential steps in orthodontic preparation for orthognathic surgery are to align the arches individually, achieve compatibility of the arches or arch segments, and establish the proper anteroposterior and vertical position of the incisors.

#### **3.1. Dental alignment**

Dental crowding, spacing, misalignment and rotations of the teeth should be corrected before orthognathic surgery. The key is to get the teeth in proper position and angulation. In this phase of the treatment, extractions might be needed to relieve moderate to severe crowding and make needed space for teeth alignment. Extraction can also help remove dental compen‐ sations. It should be taken into consideration that extraction should be avoided if the space of the jaw permits favorable dental alignment. Incisor inclination, crowding, type of malocclusion and surgical procedure are among the determining factors in deciding which teeth should be extracted.

### **3.2. Decompensation**

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

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

Orthodontic preparation for surgery is different from orthodontic correction alone. Achieve‐ ment of optimal facial esthetics requires integrated cooperation of orthodontists and maxillo‐ facial surgeons. Routine preoperative orthodontics involve dental alignment, incisor decompensation, and arch coordination for the purpose of obtaining maximum intercuspal interdigitation when the jaws are surgically aligned. In short the aims of presurgical treatment are to decompensate lower and upper incisors, level and align both arches and relieve the crowding. In general these corrections will make the malocclusion look worse presurgically, but it will show the true magnitude of the skeletal problem thus allowing an optimal correction at surgery.[6] To sum up, the essential steps in orthodontic preparation for orthognathic surgery are to align the arches individually, achieve compatibility of the arches or arch segments, and establish the proper anteroposterior and vertical position of the incisors.

Dental crowding, spacing, misalignment and rotations of the teeth should be corrected before orthognathic surgery. The key is to get the teeth in proper position and angulation. In this phase of the treatment, extractions might be needed to relieve moderate to severe crowding

(D) a still larger amount that requires surgery as part of the treatment plan.

106 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

segmented.

**3. Presurgical orthodontics**

**3.1. Dental alignment**

Most severe skeletal jaw discrepancies are partly compensated. This natural phenomena called"dentoalveolar compensation" is a system which attempts to maintain normal interarch relationship.[7]

Compensations can be dental or skeletal in nature. Dental compensations can be vertical, transverse and/or sagittal. The factors responsible for dentoalveolar adaptation include: a normal eruptive system, surrounding soft tissue pressures and the influence neighboring and opposing teeth during occlusion. For example in class II skeletal malocclusions the upper anteriors retrocline to compensate for maxillary prognathism and lower incisors procline to compensate for mandibular retrognathism. While in class II skeletal malocclusion the upper anteriors procline to compensate for maxillary retrognathism and lower incisors retrocline to compensate for mandibular prognathism.

In contrast to dental camouflage, in preparation for orthognathic surgery, it is necessary to remove any dental compensations present and to place the teeth in a favorable position with their supporting bone. This is called presurgical decompensation. Presurgical orthodontic decompensation is essential to enable the surgeon to make a considerable amount of surgical correction. Failure to fully remove anterior incisor compensations presurgically will limit the surgical correction, leading to compromised facial esthetics and occlusion. Such anteroposte‐ rior dental decompensation may involve specific extractions, anchorage needs, or use of class II/class III elastics. For example, decompensation of skeletal class II malocclusion will often require the use of class III elastics to upright lower incisors and decompensation of skeletal class III malocclusion necessitates the use of class II elastics to procline lower incisors and establish adequate reverse overjet.

Decompensation accentuates the patient's deformity but is necessary for achievement of normal occlusal relationships when skeletal bones are properly positioned at surgery.

### **3.3. Arch coordination**

Arch coordination refers to coordinating the widths of the dental arches so that there is a normal transvers relationship following sagittal jaw movements. Coordination often involves arch expansion, arch contraction, and occlusal plane leveling and alignment. Orthodontic expansion or contraction to coordinate the upper and the lower arches should be carried out prior to the surgical procedure in order to provide correct post-operative occlusal interdigita‐ tion. Poor arch coordination, particularly in the transverse or vertical plane, will restrict or destabilize jaw movements at the time of surgery and compromise postsurgical stability.

### **3.4. Presurgical orthodontics objectives in the transverse plane**

Ideally, the width of maxilla should be slightly more than the mandible in order to produce normal buccal overjet. Transverse discrepancy happens when there is a defect in the widths of the arches. The maxilla is more commonly affected in this discrepancy which can be either unilateral or bilateral. This discrepancy is often combined with sagittal or vertical problems.

Pre-surgical orthodontic treatment consideration of transverse discrepancy:

**i.** The problem is the skeletal or dental

Dental discrepancies are usually treated by means of buccal tipping of the posterior teeth while skeletal discrepancies are corrected by bodily movement of the posterior teeth. If the posterior teeth are tipped lingually, presurgical orthodontic expansion (buccal tipping) should be used; however, the tipping should not exceed 4 to 6 mm total. Bodily movement of the posterior teeth should be done by means of segmental osteotomy, without the need for orthodontic expansion.

**ii.** Is the problem relative or absolute

Articulation of the casts into a class I occlusion allows the clinician to easily distinguish between relative and absolute maxillary constriction. If the occlusion is proper when the casts are brought into class I canine relationship the discrepancy is relative; otherwise, if a crossbite still exists, then the discrepancy is absolute. Absolute skeletal transverse discrepancy requires planning for segmental osteotomies or surgically assisted rapid palatal expansion (SARPE).[5]

SARPE technique is used in cases with a severe discrepancy or when the transverse defect of the maxillary bone is an isolated skeletal anomaly. While, segmental maxillary osteotomy is used for more modest defects (up to 7 mm) or when the transverse deficit is one of a number of maxillary skeletal deficits, including sagittal and vertical defects that would require surgical attention.[8]

#### **3.5. Presurgical orthodontics objectives in the vertical plane**

#### *3.5.1. Open bite cases*

Treatment of anterior open bite has always been a great challenge in orthodontics. Extrusion of anterior teeth and orthognathic surgery are among the possible options for treatment of open bite in non-growing patients. However, dental extrusion of skeletal open bite will be unstable in the long run. Furthermore, it may also create an excessive display of gingiva. Unaesthetic results and lack of stability of dental correction make surgery the treatment of choice for skeletal open bite cases. One of the chief considerations for treatment of these patients is the choice between one piece or segmented maxillary osteotomy. The decision for or against segmentation is made based on the patient's baseline skeletal deformity. These patients generally have an excessive curve of Spee in the upper jaw which is an indication of skeletal problem rather than a dental one. The severity of the curve of Spee indicates the need for segmental osteotomy. In other words, the more severe the curve of Spee, the more obvious the need for segmental osteotomy. When surgical segments are planned, the orthodontist's role is to level presurgically within the segments but not across the osteotomy sites and to make sure that there is enough space between the roots of the involved teeth to allow inter‐ dental osteotomies.

Pre-surgical orthodontic treatment considerations in open bite cases:


**3.4. Presurgical orthodontics objectives in the transverse plane**

**i.** The problem is the skeletal or dental

108 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**ii.** Is the problem relative or absolute

**3.5. Presurgical orthodontics objectives in the vertical plane**

expansion.

attention.[8]

*3.5.1. Open bite cases*

Pre-surgical orthodontic treatment consideration of transverse discrepancy:

Ideally, the width of maxilla should be slightly more than the mandible in order to produce normal buccal overjet. Transverse discrepancy happens when there is a defect in the widths of the arches. The maxilla is more commonly affected in this discrepancy which can be either unilateral or bilateral. This discrepancy is often combined with sagittal or vertical problems.

Dental discrepancies are usually treated by means of buccal tipping of the posterior teeth while skeletal discrepancies are corrected by bodily movement of the posterior teeth. If the posterior teeth are tipped lingually, presurgical orthodontic expansion (buccal tipping) should be used; however, the tipping should not exceed 4 to 6 mm total. Bodily movement of the posterior teeth should be done by means of segmental osteotomy, without the need for orthodontic

Articulation of the casts into a class I occlusion allows the clinician to easily distinguish between relative and absolute maxillary constriction. If the occlusion is proper when the casts are brought into class I canine relationship the discrepancy is relative; otherwise, if a crossbite still exists, then the discrepancy is absolute. Absolute skeletal transverse discrepancy requires planning for segmental osteotomies or surgically assisted rapid palatal expansion (SARPE).[5] SARPE technique is used in cases with a severe discrepancy or when the transverse defect of the maxillary bone is an isolated skeletal anomaly. While, segmental maxillary osteotomy is used for more modest defects (up to 7 mm) or when the transverse deficit is one of a number of maxillary skeletal deficits, including sagittal and vertical defects that would require surgical

Treatment of anterior open bite has always been a great challenge in orthodontics. Extrusion of anterior teeth and orthognathic surgery are among the possible options for treatment of open bite in non-growing patients. However, dental extrusion of skeletal open bite will be unstable in the long run. Furthermore, it may also create an excessive display of gingiva. Unaesthetic results and lack of stability of dental correction make surgery the treatment of choice for skeletal open bite cases. One of the chief considerations for treatment of these patients is the choice between one piece or segmented maxillary osteotomy. The decision for or against segmentation is made based on the patient's baseline skeletal deformity. These patients generally have an excessive curve of Spee in the upper jaw which is an indication of skeletal problem rather than a dental one. The severity of the curve of Spee indicates the need for segmental osteotomy. In other words, the more severe the curve of Spee, the more obvious the need for segmental osteotomy. When surgical segments are planned, the orthodontist's

In the presence of a flat curve of Spee with no vertical discrepancies within the arch, leveling is done with a continuous arch wire and the open bite can be corrected by a 1-piece Lefort I osteotomy. However, if a segmental Le Fort I osteotomy is planned for open bite correction, presurgical dental leveling and alignment should be carried out separately in each segment.

**b.** Leveling the mandibular arch:

Since patients with open bite generally do not have severe reverse curve of Spee in the lower arch, continuous arch wire is used for complete leveling.

#### *3.5.2. Deep bite cases*

In patients with deep bite, there is nearly always an excessive curve of Spee in the lower arch and occasionally a reverse curve in the upper arch. In these cases, the curve of Spee is leveled intruding the incisors or extruding the posterior teeth. The decision to level by intrusion of the incisors or extrusion of the posterior segment depends on the initial facial height of the patients. As a general rule, the shorter the face height, the greater the need for extrusion.

#### **3.6. Presurgical orthodontics objectives in the sagittal plane**

#### *3.6.1. Class II malocclusion*

Skeletal class II malocclusion is naturally compensated to mask the skeletal discrepancy. This natural dental compensation involves retroclination of the upper incisors and proclination of lower incisors. The goals of presurgical orthodontics for these cases involve decompensation of these natural compensations along with alignment of teeth and establishing compatible arch forms.

Orthodontic decompensation of skeletal class II malocclusion cases involve proclining of retroclined upper incisors and uprighting the proclined lower incisors. This decompensation will increase the amount of overjet, which allows the maxillofacial surgeon to carry out maximum mandibular advancement and subsequently establish class I canine relationship after the surgery. (Figure 1)

**Figure 1.** Orthodontic presurgical decompensation of class II malocclusion.

Alignment and leveling and the need for extraction in skeletal class II malocclusion cases depends on the degree of crowding. In crowded cases, extraction of upper second premolars and lower first premolars is a common orthodontic plan in preparation for surgical correction. The extraction of upper second premolars prevent further retroclination of upper incisors and the extraction of lower first premolars facilitate uprighting of lower incisors and subsequently establish enough overjet for surgery. We should bear in mind that extraction space should be closed before surgery

#### *3.6.2. Class III malocclusion*

In skeletal class III malocclusion cases the natural dental compensation involves proclination of the upper incisors and retroclination of lower incisors. Therefore, in these cases, orthodontic decompensation is achieved by uprighting the upper incisors and proclining the lower incisors and thereby increasing the reverse overjet to the maximum which would allow the surgeon to carry out maximum mandibular setback.

Similar to skeletal class II patients, in these cases also the alignment and levelling and the need for extraction depends on the degree of crowding. The usual pattern of extraction in these cases involves the extraction of upper first premolars in order to facilitate the uprighting of upper incisors and extraction of lower second premolars in order to prevent further retroclination of the lower incisors. These extractions also help to establish enough reverse overjet for the surgical procedure. Extraction space should also be closed before surgery. (Figure 2)

**Figure 2.** Orthodontic presurgical decompensation of class III.
