orthodontic objectives in orthognathic surgery

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Roy Sabri, DDS, MS1

ORTHODONTIC OBJECTIVES IN ORTHOGNATHIC SURGERY: STATE OF THE ART TODAY In treating jaw discrepancies, camouflage and surgery have different treatment modalities, often involving opposite orthodontic mechanics and different extraction decisions. Pretreatment identification of surgical patients is therefore essential. Esthetics, function, stability, and treatment time have to be considered and patients provided the information they need to be part of the decision-making process. The goal of presurgical orthodontics is to position the teeth, allowing an optimal skeletal correction at surgery. While intra-arch alignment is similar to conventional orthodontics, leveling is not carried out automatically in surgical patients. In open-bite cases, steps within the arches are an indication for segmental surgery. Orthodontic leveling will be limited to the segments, and segments will be leveled with differential intrusion at surgery. In deep-bite/short-face cases, leveling a severe curve of Spee should be done after the occlusion is unlocked by surgery. Anteroposteriorly, dental compensations are removed by ideally positioning the teeth relative to their apical bases. This will make the malocclusion look worse presurgically, but it will unravel the true magnitude of the skeletal problem, thus allowing an optimal correction at surgery. It is important to recognize if a transverse problem is skeletal or dental in nature and if the correction should be done orthodontically, by segmental surgery, or by surgically assisted palatal expansion. No orthodontic expansion should be done presurgically in a patient who will have surgical expansion. Any tooth movement with relapse potential should be avoided presurgically. Postsurgical orthodontics will bring teeth into position and proper intercuspation within a reasonable time period. World J Orthod 2006;7:177–191.

n the or thodontic specialty, there seems to be a shift toward a more adult patient population. In the 1970s, only 5% of orthodontic patients were adults; today, about 1 in 4 or 5 patients fall into that category. 1 As a result, a larger number of patients are undergoing surgical treatment.

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1Clinical

Associate, Division of Orthodontics and Dentofacial Orthopedics, American University of Beirut Medical Center, Beirut, Lebanon.

CORRESPONDENCE Dr Roy Sabri PO Box: 16-6006 Beirut, Lebanon E-mail: [email protected]

HISTORICAL DEVELOPMENT IN ORTHOGNATHIC SURGERY Orthognathic surgery began a century ago with the treatment of mandibular prognathism. 2 For almost 50 years, skeletal Class III patients were treated by mandibular body osteotomies with an external approach. Today, studies have shown that isolated mandibular setbacks are used in fewer than 10% of the 177

COPYRIGHT © 2005 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

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patients, in favor of maxillary and doublejaw surgery.3 In 1957, the introduction of the sagittal split ramus osteotomy by Trauner and Obwegeser 4 marked the beginning of the modern era in orthognathic surgery. This intraoral approach allowed for both setting back or advancing the mandible with the same bone cuts. It also provided good control of condylar position and a broad postsurgical medullar bone interface compatible with transoral rigid fixation. In the 70s, Bell and Epker5 and Wolford6 developed maxillary surgery, which was pioneered earlier in Europe to treat traumatic and gunshot wounds during both World Wars. René LeFort noted midface fractures at sites of weakness, which logically became sites for osteotomy cuts.7 Today, with the LeFort I downfracture technique, the clinician can easily advance or retract the maxilla, with the latter being more difficult. This relative difficulty is overcome by retracting the anterior segment only, after premolar extraction. Clinicians can move up the maxilla and, with autorotation of the mandible, successfully correct skeletal open bites and long-face syndromes. The maxilla also can be moved down, with less predictability. A joint mandibular ramus surgery is advisable to allow the mandible to move down at the chin only, increasing the mandibular plane angle and opening the gonial angle, rather than rotating at the condyle, as in long-face syndrome cases. 8 Lengthening the ramus by moving the mandible down at the gonial angle is unstable, even in long faces with a short ramus, because it stretches the muscles of mastication. Transversely, the maxilla can be expanded in the course of a 2- or 3-piece LeFort technique or expanded independently with surgically assisted rapid palatal expansion. 9,10 The amount of maxillary constriction is less than the range of expansion. The mandible can also be expanded today with distraction osteogenesis 11 and constricted with bone and sometimes tooth removal. Subapical dentoalveolar osteotomies started with Kole12 in the anterior mandible in 1959. Today, segmental surgery is possible in all dentoalveolar segments and

improvement in instrumentation allows for precise bony cuts, minimizing damage to teeth and periodontal structures. It is also possible to move the chin in all directions to enhance the final esthetic outcome. The 1990s witnessed the routine use of rigid fixation, which helped increase stability, precision, patient comfort, and patient acceptance of surgical treatment, mainly by eliminating intermaxillary fixation. Due to the many long-term studies available, a hierarchy of stability for the different surgical procedures has been established.13 It is now known that both jaws contribute to the problem in most dentofacial deformities.14 Setting back the mandible only in a Class III patient with a double jaw contribution would lead to an increased nasolabial angle and a short throat length; advancing the maxilla only would also lead to compromised facial esthetics, with biprotrusion and too much widening of the nose (Fig 1). Double-jaw surgery is more commonly and easily done today. However, to get both optimal occlusion and facial esthetics, and avoid correcting one at the expense of the other, presurgical orthodontic preparation becomes crucial. Advances in orthodontics include bonding material; improvement in appliance design, size, and esthetic appearance with ceramic brackets and lingual appliances; wire technology with fewer appointments and better patient comfort and skeletal anchorage. In addition, the acceptance of orthodontic treatment by adults has greatly improved, thanks in part to the media showing movie stars wearing orthodontic appliances.

TREATMENT OF JAW DISCREPANCIES: CAMOUFLAGE VERSUS SURGERY There are 2 treatment alternatives for nongrowing patients with skeletal involvement: (1) orthodontic repositioning of the teeth to camouflage the underlying skeletal discrepancy; or (2) surgical repositioning of the jaws at fault. Even though treatment goals for the 2 treatment options

178 COPYRIGHT © 2005 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART OF THIS ARTICLE MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

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Fig 1 Extraoral and intraoral photographs of a Class III patient before (a,c) and after orthodontic treatment and double-jaw surgery (b,d).

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are the same, namely normal occlusion, improved facial and dental esthetics, and long-term stability, the treatment modalities are different. In camouflage treatment, usually in mild to moderate jaw discrepancies, conventional orthodontics will bring maxillary and mandibular teeth together in occlusion, while in surgical repositioning, teeth will be positioned relative to their bony base, which means, in many situations, farther from each other presurgically. Extraction decisions for camouflage will be different from, if not opposite to, extractions for surgery. A Class II Division 1 malocclusion treated with mandibular advancement might necessitate mandibular first premolar extraction to decompensate (upright) the mandibular incisors, allowing an optimal surgical correction, whereas maxillary first premolars will need to be extracted for overjet correction if the same case were to be treated by camouflage. The same applies in a Class III malocclusion, where the classical extraction pattern (maxillary second and mandibular first premolars) will be reversed and substituted by extraction of the maxillary first and mandibular second premolars or no extractions in the mandibular arch, if such a case were to be treated surgically. It is therefore erro-

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neous to start a case orthodontically and refer the patient to the surgeon if treatment is unsuccessful. In 1985, Proffit and Ackerman15 presented the concept of 3 envelopes of discrepancies: what can be corrected by orthodontic treatment alone, through orthodontic treatment with growth, and through surgical treatment. These are guidelines based on occlusal factors that do not take into account factors such as facial esthetics, the patient’s primary complaint, and patient motivation. Some authors have attempted to establish threshold values for pretreatment identification of patients for whom surgery is indicated.16–23 However, proper selection of patients remains neither simple nor straightforward. Even though long-term studies have shown that patients’ perceptions of outcome were highly positive in both the orthodontic and the surgical groups, no attempt should be made to treat a patient nonsurgically because of his apprehension toward surgery or for reasons like avoiding the increased cost and risk of surgery. 22 Rather, patients should be provided the information they need and involved in the mode-of-treatment decision.21–23


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RATIONALE FOR SURGERY

Treatment time considerations

There are esthetic, functional, stability, and treatment time considerations that will make surgery the treatment of choice even for cases of malocclusion manageable by orthodontics alone.24

With a combined orthognathic approach, overall treatment time is usually shorter. For example, in a Class II Division 1 malocclusion with a prognathic maxilla, space closure after premolar extraction is almost spontaneous with segmental surgery and would take 6 to 8 months with conventional orthodontics alone. The same applies if the Class II Division 1 is due to a retruded mandible; reducing the overjet is much faster with mandibular advancement than with orthodontic space closure after maxillary first premolar extraction.

Esthetic considerations Surgery should be considered whenever a satisfactory alignment of teeth is possible only at the expense of worsening overall facial esthetics. For example, retracting maxillary incisors to a retruded mandible after maxillary first premolar extraction is possible and will correct an overjet. However, this orthodontic approach will have an adverse effect on the patient’s profile because of considerable retraction of the upper lip and an increase of the nasolabial angle. Soft tissue limitations should be considered and maxillary incisors should not be retracted to the point that the inclination of the upper lip becomes negative to a true vertical line25 (Fig 2).

Functional considerations A unilateral crossbite due to a functional shift is easily manageable orthodontically, whereas surgery will be necessary in the presence of an underlying mandibular asymmetry; the more severe the skeletal problem, the more unlikely a nonsurgical approach can achieve normal occlusion and optimal function.

Stability considerations Skeletal open bites and long-face syndromes have been historically difficult problems to treat before the advent of maxillary surgery. Dental correction of an open bite due to a posterior vertical maxillary excess may be possible in the short term, but will be unstable in the long term. Furthermore, dental extrusion of maxillary incisors in a skeletal open bite may also create an excessive display of gingiva, which is considered unesthetic.

PRESURGICAL ORTHODONTIC PREPARATION The goal of presurgical orthodontics is to position the teeth so that an optimal skeletal correction can be performed at surgery. Intra-arch alignment and transverse discrepancies should be addressed so that arch compatibility can be achieved after surgery. Incisors are the surgeon’s guide to anteroposterior jaw positioning, and their vertical position prior to surgery will determine postsurgical lower facial height. In the planning process for surgical-orthodontic treatment, it is therefore important to decide: (1) where to place the teeth anteroposteriorly, vertically, and transversally; and (2) how to position these teeth or tooth segments, surgically or orthodontically, to maximize the speed and efficacy of treatment. No attempt should be made to perfectly level arches and reach an ideal intercuspation on presurgical working casts; rather, the orthodontist should take full advantage of the unlocked occlusion after surgery to more efficiently complete tooth detailing in all dimensions.26

Intra-arch alignment The first step in presurgical orthodontics is to align the arches and/or arch segments and make them compatible. These initial intra-arch objectives are the same in combined orthognathic and conven-


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Fig 2 Extraoral and intraoral photographs of a skeletal Class II patient before orthodontic treatment (a,d), in retention (b,e), and 8 years postretention (c,f).

Fig 3 Intraoral photographs of presurgical maxillary intra-arch alignment in a unilateral cleft lip and palate patient.

tional orthodontics. The decisions for extraction of compromised teeth, the recuperation of impacted teeth, the correction of rotations, crowding, arch length discrepancies, and the overall alignment of teeth are all carried out systematically at this point (Fig 3). Tooth-size discrepancies should also be identified and eliminated. 27,28 Once accomplished, these

intra-arch objectives will allow proper dental interdigitation after surgery. Whenever segmental surgery is planned, root divergence adjacent to the osteotomy cuts is done from the initial archwire and monitored with periapical radiographs. This will avoid root trauma, gingival recession, and possible ankylosis after surgery.27


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Leveling and vertical incisor position Leveling and arch alignment are usually done systematically as a 1-step procedure in conventional orthodontics. This routine procedure cannot be applied to surgical cases because arch leveling, which is done by a combination of dental extrusion and intrusion, will achieve different vertical tooth movements in different malocclusions. For example, in an anterior open-bite/long-face case, leveling will tend to extrude anterior teeth, while in a deep-bite/short-face case, leveling will tend to intrude anterior teeth because strong musculature will fight posterior tooth extrusion. As mentioned earlier, incisors are the surgeon’s guide to jaw positioning and their vertical position at the time of surgery will determine postsurgical vertical lower facial height. If incisors are intruded presurgically in the deepbite/short-face case, facial height will not be increased by surger y. The same applies for the open-bite/long-face case, where incisor extrusion will decrease the dental open bite before surgery but will interfere with optimal correction of the vertical excess at surgery. Furthermore, the dental relapse potential built in with systematic leveling will lead to postsurgical partial recurrence of the open bite or deep bite. As a general rule, any tooth movement with a relapse potential should be avoided presurgically.28 Presurgical leveling in open-bite cases. In planning presurgical orthodontic preparation for an open-bite case, it is important to identify which group of teeth is at fault. In a patient with a gingival smile that is more excessive posteriorly than anteriorly, the presence of 2 vertical discrepancies or steps within the maxillary arch is an indication for segmental surgery. The open bite will be corrected by differential surgical intrusion of the posterior and anterior segments and closing rotation of the mandible. Thus, orthodontic leveling will be limited to the segments and the segments will be leveled at surgery. This will allow a correction of the increased vertical facial height at surgery and will eliminate the tendency for posttreatment dental relapse

(Fig 4). In the presence of a flat curve of Spee initially, with no vertical discrepancies within the arch, leveling can be done conventionally with a continuous archwire. The open bite will be corrected by a 1-piece LeFort osteotomy with more impaction posteriorly than anteriorly (Fig 5). This posterior impaction will have an uprighting effect on the incisors that should be accounted for. Presurgical leveling in deep-bite cases. In a deep bite, the decision to level by intrusion of incisors or extrusion of posterior teeth depends on the initial facial height. If the anterior lower facial height is short and the distance between the mandibular incisor edge and the chin is normal, then leveling by extrusion of posterior teeth is indicated, so that the chin will move down at surgery.29 Presurgical leveling would have to overcome the heavy biting forces often associated with a deep bite. Rather, a curve of Spee is left in all archwires, including the surgical stabilizing wire. Mandibular advancement surgery is going to create a lateral open bite, with tooth contacts only on anterior and posterior teeth. Now that the occlusion is unlocked by surgery, extrusion of posterior teeth is facilitated by the absence of tooth contacts and is done with flat archwires and lateral box elastics (Fig 6). If incisors are intruded presurgically in a deep-bite/low-angle case, surgery will tend to move the mandible upward at the chin and downward at the gonial angle, due to the pivot effect. This increase in posterior facial height will elongate the muscles of mastication and is unstable. Instead, when incisors are not intruded presurgically in the deepbite/short-face patient, surgery will move the chin down, thus introducing an opening mandibular rotation, which tends to be more stable than straightforward or closing rotations30 (Figs 6c and 7). Conversely, if the anterior lower facial height is excessive, an accentuated mandibular curve of Spee should be leveled presurgically by intrusion of the anterior segment or leveled surgically with a subapical osteotomy after segmental orthodontic leveling. A joint maxillary surgery will often be needed to avoid downward movement at the gonial angle.


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Fig 4 Extraoral and intraoral photographs, tracing and visual treatment objective (VTO), and cast surgery of an open-bite patient before (a, c to g), presurgical sectional orthodontics (h), and after 3-piece maxillary LeFort I osteotomy, sagittal split mandibular ramus osteotomy, mandibular anterior subapical osteotomy and genioplasty (b,i).

Anteroposterior incisor position During surgery, jaws and dentoalveolar segments are mobilized until teeth are brought together. Just as the vertical presurgical position of the incisors determines postsurgical facial height, it is the anteroposterior position of the incisors that will determine how much the maxillary and/or the mandibular jaw can be repositioned anteroposteriorly during surgery.29 In a severe skeletal dysplasia, teeth try to maintain some occlusal contacts compensating for the skeletal problem in all 3 planes of space, particularly anteroposteriorly. For instance, in a skeletal Class II malocclusion, the maxillary

incisors are often uprighted, while the mandibular incisors are proclined. The dental overjet is not indicative of the real amount of the underlying skeletal discrepancy. Likewise, Class III malocclusions often tend to exhibit proclined maxillary incisors and uprighted or lingually inclined mandibular incisors. While these dental compensations are maintained or increased in orthodontic camouflage to reach good dental interdigitation, the opposite is done in surgical treatment. Presurgical orthodontics will remove dental compensations by positioning the teeth ideally relative to their apical bases. This dental “decompensation” will make the malocclusion look worse presurgically, but will unravel the true magnitude 183


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Fig 5 Extraoral photographs pretreatment (a,b); posttreatment (c,d). Intraoral photographs before (e to g), presurgical (h to j), and after 1-piece maxillary LeFort I osteotomy with posterior impaction, sagittal split mandibular ramus osteotomy, and genioplasty (k to m). Superimposition tracing (n).

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Fig 6 Extraoral photographs of a Class II deep bite-low angle patient before (a) and after (b) treatment. Superimposition tracings (c). Presurgical and hand-articulated study casts simulating mandibular advancement (d,e). Intraoral photograph 2 weeks postsurgery (f). Intraoral photographs before (g) and after (h) treatment.

Fig 7 (a) Retrognathic mandible leveled presurgically (solid lines) and after advancement (dotted lines): 1, closing mandibular rotation; 2, increased posterior facial height; 3, no increase in anterior facial height. (b) Same case not leveled presurgically (solid lines) after mandibular advancement (dotted lines): 1, opening mandibular rotation; 2, no increase in posterior facial height (more stable situation); 3, increase in anterior facial height. 1

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Fig 8 Extraoral and intraoral photographs of a Class III patient before treatment (a,d), presurgical (b,e), after orthodontics and double-jaw surgery (c,f), and superimposition tracing (g).

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of the skeletal problem, allowing an optimal correction at the time of surgery, without any limitations or interferences from the occlusion (Fig 8). Failure to fully remove anteroposterior incisor compensations presurgically will limit the surgical correction, leading to compromised facial esthetics and occlusion. Such anteroposterior dental “decompensation” may involve specific extractions and anchorage needs and will often necessitate the use of Class III elastics in Class II cases to upright mandibular incisors and advance maxillary molars into a full Class II occlusion. Conversely, Class II elastics would be used in Class III cases to procline mandibular incisors and establish

adequate reverse overjet. In the presence of minimal attached gingiva or a thin periodontium in the anterior mandibular region, a gingival graft might be indicated before any labial tooth movement to avoid gingival stripping or dehiscence31 (Fig 9). Anterior subapical osteotomies in conjunction with first premolar extractions are often indicated in severe maxillary dentoalveolar protrusion. A setback of the osteotomized anterior segment with a clockwise rotation of more than 10 degrees would cause a marked vertical step between the canines and the second premolars in the stationar y segment32 (Fig 10). To avoid severe steps


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Fig 9 Intraoral photographs of a Class III patient before (a) and after (b) gingival graft in the anterior mandibular region, orthodontics, and mandibular setback.

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Fig 10 A severe clockwise rotation of the osteotomized anterior segment, causing a marked step between the canine and the second premolar.

that can be difficult to level later, a partial surgical setback is done with minimal clockwise rotation of the mobilized segment leaving 2 to 3 mm of extraction space on each side, which will be closed postsurgically with round wires; or proper inclination of the incisors and canines is established presurgically, so that excessive rotation of the anterior segment at surgery can be avoided.29,32

Arch coordination and transverse problems A final objective in presurgical orthodontics is to get reasonable arch compatibility when jaws or dentoalveolar segments are mobilized during surgery. Usually, arch compatibility is achieved spontaneously with the normal progression of coordinated maxillary and mandibular continuous archwires, toward the fulldimension rectangular wires or surgical wires33 (see Fig 5). This will only be possible in the absence of severe transverse problems, such as with cleft lip and palate patients. Transverse problems are often overlooked because posterior dental compensations are less obvious than incisor compensations for anteroposterior skeletal discrepancies. The presence or absence of a posterior crossbite is not

indicative of a transverse problem, particularly when it is associated with severe anteroposterior problems.34 In a severe skeletal Class II malocclusion, a narrow and V-shaped maxillary arch is often associated with a more ovoid mandibular arch. By hand-articulating the study casts into a Class I canine relationship, simulating a mandibular advancement, a bilateral crossbite not existing initially, will appear because the mandibular arch is moved forward into a more constricted area of the maxillary arch. Presurgical orthodontics should, therefore, include expansion of the maxillary arch. This transverse expansion in the absence of a crossbite will lead to a buccal crossbite or Brodie syndrome that will self-correct with mandibular advancement at surgery (Fig 11). On the other hand, a posterior crossbite in a Class III malocclusion might not need to be addressed presurgically because it will self-correct with a mandibular setback, as the mandibular arch is moved to a wider portion of the maxillary arch at surgery or as the maxillary arch is moved into a narrower area of the mandibular arch with a maxillary advancement. Incomplete transverse correction will lead to instability and unsuccessful correction of the malocclusion. It is imperative to recognize a transverse problem 187


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Fig 11 Intraoral photographs of a skeletal Class II patient with severe overjet and V-shaped maxillary arch before treatment (a,b), hand-articulated study casts simulating mandibular advancement leading to a bilateral crossbite (c), intraoral photograph after expansion leading to a reverse bilateral crossbite (d), and after treatment (e,f).

from the beginning. It is also essential to note whether it is skeletal or dental in nature and if the correction is going to be done or thodontically, by segmental surgery, or by surgically assisted palatal expansion. 35 Orthodontic expansion should be done only within the boundaries of the normal orthodontic capability, and while up to a half-cusp crossbite can be left for correction after surgery, skeletal discrepancies should not be masked by compensatory dental movements.33,36 As with the vertical dimension, tooth movements with relapse potential should be avoided before surgery. In cases where maxillary surgery is not considered, a constricted maxillary arch can be corrected separately with surgically assisted rapid maxillary expansion.35 Whenever a 2- or 3-piece maxillar y LeFor t osteotomy is indicated, surgery will resolve the transverse problem and orthodontic treatment will be limited to the segments. No orthodontic expansion should be done presurgically in a patient who will have surgical expansion.33 Finally, arch compatibility in surgical patients cannot be checked clinically; the only reference to whether it has been achieved lies in the articulation of study casts. Once the outcome is satisfactory, the patient is ready for surgery.

PLANNING FOR SURGERY The orthodontist should take progress casts as the patient approaches the end of orthodontic preparation for surgery. Impressions should be taken with the archwires removed to avoid distortion. After the needed final orthodontic adjustments have been made, full-size stabilizing archwires should be placed and kept for 3 to 4 weeks to become passive before presurgical records are taken. These records include panoramic and lateral cephalometric radiographs, study casts, and facial and intraoral photographs. A posteroanterior cephalometric radiograph is also needed in cases of asymmetry and transverse problems. All diagnostic and prediction procedures done initially should now be repeated, with the presurgical records for the final surgical planning. In cases involving maxillary surgery, cephalometric predictions will simulate surgical movements, quantify the autorotation of the mandible, and evaluate the resulting soft tissue profile. Cast surgery is done next and has 2 objectives: (1) to duplicate surgical movements from the prediction tracings and confirm their feasibility for the occlusion; and (2) to fabricate the surgical interocclusal wafer splints to be used dur-


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ing surgery.33,37 A semi-adjustable articulator with a facebow transfer is used whenever a LeFort I osteotomy is planned without mandibular ramus surgery. In such a situation, where the condyle-dentition relationship is preserved during surgery, it is important that the autorotation of the mandible to a new position be simulated as accurately as possible.33 Conversely, if the condyles are to be separated from the dentition by a vertical ramus osteotomy, there is no need to maintain this relationship during cast surgery. Therefore, an arbitrary articulator can be used in cases of mandibular ramus surgery without maxillary surgery. In double-jaw surgery, the mandibular position with the condyles intact will be the guide for repositioning the maxilla before mandibular surgery is performed; therefore, an articulator mounting is required. 33 The maxillary cast will be mobilized first and stabilized on the articulator. A first occlusal splint is made for this position.38,39 The mandibular cast is then mobilized, brought into occlusion with the maxillary cast, and stabilized. A second splint is constructed in this final position. It is important that this final splint be thin, as a thick splint will increase the possibility of error as the mandible rotates into occlusion when the splint is removed. A wire embedded in the lingual acrylic can be used as reinforcement. The splint should not cover the buccal surface of the teeth; this allows visual verification of proper seating at surgery.29 If the surgeon can bring the casts together and easily reproduce the occlusion, a splint is not really necessary. However, in segmental surgery, it ensures accurate performance of the surgical movements and also eliminates the need for the orthodontist to be present during surgery to place a continuous archwire to lock the osteotomized segments. It is imperative that the final presurgical wires be completely passive. This will ensure that there will be no dental changes between the time of the impression and the surgery, which could lead to a poorly fitting splint and errors in the planned surgical moves.27 Some type of attachments may be placed on the archwires or the brackets to facilitate fixation

before screws and plates placement. Soldered brass spurs in each interproximal area are the preferred mode of attachment, if care is taken not to overheat the wire. Preformed crimp-on hooks can also be placed with special pliers directly over the wire without removing it. This is much easier and faster than soldered spurs. However, these types of hooks are not tight and can slip along the wire during surgery. While crimping, care should be taken to avoid any archwire distortion that might not be noticed if the wire is not removed and will result in a poorly fitting splint at surgery.33

SURGICAL MANAGEMENT AND POSTSURGICAL ORTHODONTICS With rigid fixation techniques, the acrylic splint is ligated to one of the arches at surgery to key the occlusion, and light elastics are used to guide jaw function. A soft diet (ie, milkshakes, yogurt, mashed potatoes) is advised for the first week following surger y. Patients can then advance their diet progressively, determined by comfort level. By 6 to 8 weeks, the jaws should be healed enough for heavy mastication. Healing may not necessarily be faster with rigid fixation, but bony segments are more stable right after surgery, allowing limited early function. This can be assisted by physical therapy, in which patients are advised to gently open and close their mouths within comfortable limits starting 1 week af ter surger y. These exercises are increased over the next 2 weeks to 3 10to 15-minute sessions of opening and closing, as well as lateral movements.29 Patients are usually back to work within 1 week or 10 days after surgery, and most facial edema is gone 2 to 3 weeks postsurgery. It is possible to resume postsurgical orthodontics as early as 2 weeks following surgery with rigid fixation, while 6 to 8 weeks are required with wire osteosynthesis and maxillomandibular fixation. The goal of postsurgical orthodontic treatment is to bring the teeth to welldetailed positions and proper intercuspa189


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tion within a reasonable time (4 to 6 months), taking advantage of the unlocked occlusion following surgery. At the first postsurgical orthodontic appointment, the splint is removed and the stabilizing archwires are replaced with continuous working archwires. A long appointment should be scheduled to allow for repairs, because loose bands or brackets are not uncommon after surgery. It is important that when the splint is removed, the stabilizing archwires be removed at the same time. After splint removal, dental intercuspation might not be perfect, with only 2 or 3 teeth in contact; if the stabilizing archwires that hold the teeth rigidly are left in place, a shift to an undesirable convenience bite with greater intercuspation will result.33 This will complicate orthodontic finishing and could stress osteotomy sites. Rather, teeth should be allowed to settle rapidly to full contact right after splint removal and this is best done on light, undersized round wires, typically 0.016-inch stainless steel assisted by light box elastics. These elastics are not necessarily vertical, but could have an anterior or a posterior vector to support the sagittal correction. They should be worn full-time, including during meals, for the first 4 weeks. This phase should not last more than 6 to 8 weeks. Weekly visits are recommended for better control, allowing the orthodontist to change box elastics into a Class II or Class III direction as needed. If tooth movement is desired on the mandibular arch only, to level a severe curve of Spee, the maxillary stabilizing archwire can be maintained and a mandibular flexible wire can be placed. In segmental surgery, elastics should not be used on sectional archwires because they rapidly distort arch form. A continuous archwire should replace sectioned arches after splint removal. Whenever palatal expansion has been performed during surgery, postsurgical flexible archwires needed for tooth settling cannot prevent transverse relapse. A transpalatal bar or a heavy labial wire (0.036-inch) placed in the headgear tubes can be used for transverse control. If root divergence was performed presurgically, root parallelism should be achieved. By this time, postsurgical orthodontic finishing is much the same as with conventional orthodontics;

there is also nothing specific about retention in surgical patients. The retention appliance is placed depending on the initial malocclusion.

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