Maxillary Deficiency

Chapter

77

 

Maxillary Deficiency: Transverse Plane Discrepancies Rafael E. Alcalde, Dale S. Bloomquist, Don Joondeph

M

odern orthognathic surgery has gone through different para­ digm shifts since its origins. Research and technologic advances have influenced diagnosis, planning, and treatment, which has allowed surgical orthodontics to advance from a skeletal and functional paradigm to a soft tissue and facial esthetics paradigm in the 1990s.1 The latest shift is toward increased efficiency, decreased operating time, and ambulatory procedures that allow lower cost while keeping the highest standards regarding skeletal, functional, and soft tissue esthetic outcomes. Increased efficiency, patient access to care, and affordability can be achieved by avoiding unnecessarily complex surgeries. This, in combination with constant communication between the members of the interdisciplinary team and the use of simple and effective pro­ cedures in office surgical suites or ambulatory surgery centers, will allow us to reduce costly operating room time and minimize the need for prolonged postoperative admission. Discrepancies in the transverse plane are commonly diagnosed as isolated problems or as part of complex dentofacial deformities with a prevalence ranging from 10% to 15% in adolescents and up to 30% in adults.2-5 The most common transverse problems compli­ cating the treatment of patients with dentofacial deformities are transverse maxillary deficiency and transverse mandibular excess. Transverse maxillary excess and transverse mandibular deficiency, though reported, are less frequent. Correction of transverse problems in non-growing patients is a somewhat controversial subject in both the orthodontic and surgi­ cal literature. In patients with maxillary transverse deficiency, con­ ventional orthodontic expansion is limited by the buccal cortical bone of the maxilla and by the lingual bone of the mandible. The orthodontist can compensate in some of these patients by using buccal crown torque in the maxillary posterior dentition or lingual crown torque in the mandible. Frequently, this type of compensation is unstable and may create functional interference.6 Oral and maxillofacial surgeons, in contrast, have traditionally been manag­ ing transverse problems with surgery on the maxilla via either surgi­ cally assisted rapid palatal expansion (SARPE)7-11 or segmental Le Fort I osteotomy.12,13 Use of a midline osteotomy for mandibular constriction has more recently been suggested for patients with wide mandibular arches who are undergoing concomitant bilateral ramus osteotomies. Although research on the results achieved with these surgical procedures has consistently shown acceptable stability on long-term follow-up, most studies are limited by either the number of patients studied or the length of follow-up (or by both).14,15 This chapter emphasizes the diagnosis, indications, biologic foundation, limitations, stability, effects on facial esthetics, and post­ operative care of each treatment alternative for discrepancies in the transverse plane.

640

ETIOPATHOGENESIS The etiology of transverse maxillary and mandibular problems has been related to genetic factors, environmental influences, or a com­ bination of these factors. The most common transverse problems are maxillary deficiency, mandibular excess, or a combination of both. In children, maxillary constriction is manifested as a narrow palatal vault and unilateral or bilateral posterior crossbite. Appro­ priate orthodontic correction of this transverse skeletal discrepancy requires orthopedic maxillary expansion, which is possible only in patients who are still growing. The younger the child, the more effective the skeletal expansion; dental tipping is minimized and sutural distraction histogenesis is maximized. For this reason, ortho­ pedic maxillary expansion is usually accomplished as part of a phase I treatment before puberty. At this stage, maxillary expansion removes the premature contacts that induce lateral functional shifts caused by the transverse discrepancy. When left untreated, these functional shifts can result in progressive and permanent mandibular skeletal asymmetry.6 Rapid palatal expansion with a jackscrew appliance has been used reliably for more than 125 years in skeletally immature indi­ viduals. Even in the current practice of orthodontics, the most com­ monly used fixed expansion orthopedic appliances are tooth borne. Therefore, unwanted dentoalveolar movement should be expected to represent about 50% of the total expansion. This leads to a longterm loss of about 30% of the total arch expansion even after appro­ priate retention, thus confirming the need for overexpansion.16 Multiple studies have reported on the age and process of closure of the mid-palatal suture. Most authors agree that mid-palatal suture growth continues until at least the age of 16 to 18, with a great deal of variation found among individuals. However, difficulty separating the maxillas in postpubertal individuals is not due just to complete fusion of the mid-palatal suture but also to the numerous mechanical interlocking that takes place in the circum-maxillary suture system once the patient stops growing and the sutures become non-functional. Because of these changes in adolescent and older patients, orthope­ dic expansion results in more dentoalveolar than skeletal movement, thereby increasing the risk for excessive dental tipping in the poste­ rior segments, gingival recession, reduced alveolar bone height on the buccal root surfaces, lack of occlusal stability, and eventually relapse.6 Therefore, in mature patients undergoing orthodontic consultation for transverse discrepancies, diagnosis and treatment should be undertaken jointly by the orthodontist and surgeon.

ANATOMY Unilateral and bilateral crossbites, proclined and crowded teeth, narrow and tapered arches with the maxillary alveolar processes tipped outward, arch-length discrepancy, noticeable buccal corridors,

Maxillary Deficiency: Transverse Plane Discrepancies

641

A

Fig. 77-2  n  Facial three-dimensional computed tomography scan displaying the x-, y-, and z-axes. (Courtesy Anatomage, San Jose, CA.)

B Fig. 77-1  n  Clinical intraoral photographs showing tapered dental arches and severe crowding associated with transverse deficiency.

and a deep palate are clinical hallmarks of skeletal transverse maxil­ lary deficiency (Fig. 77-1). Although excessive buccal corridors or negative space, defined as the space between the commissure and the buccal surfaces of the maxillary dentition during a full smile, may be due to a narrow maxilla, it can also be affected by the anteroposterior (AP) and vertical position of the maxilla relative to the lip drape. Crossbites with a wide palatal vault and maxillary alveolar processes tipped inward are commonly seen in patients with dental maxillary deficiency. Posterior crossbites with a threedimensionally well-positioned maxilla, adequate upper incisor display, and the absence of buccal corridors and dental crowding are usually diagnosed as mandibular transverse excess. This is fre­ quently seen in patients with mandibular AP deficiency and con­ firmed when models are positioned in class I occlusion.

DIAGNOSTIC STUDIES Diagnostic studies use standard orthodontic records, which include cephalograms, models, orthodontic setups, and cephalometric analy­ sis. The use of three-dimensional (3D) measurements with cone beam computed tomography (CBCT) is becoming more common and is of specific interest in the diagnosis and treatment planning of patients with transverse discrepancies and facial asymmetry. To make an accurate diagnosis of a transverse discrepancy, the dental and skeletal components of the discrepancy need to be delin­ eated. Models and orthodontic setups have commonly been used to evaluate these discrepancies. The first step includes leveling and alignment of the dentition over the basal bone to determine whether

the discrepancy is an isolated dental problem. This is followed by analysis of models placed in class I canine occlusion to determine whether the transverse problem is absolute or whether it is a relative transverse deficiency or excess secondary to an AP discrepancy. At this point, the presence and severity of the transverse discrep­ ancy at the canine and molar levels must be determined. This is extremely important in establishing which orthodontic or surgical procedure (or both) will be indicated based on the pattern of expan­ sion needed. Ricketts proposed analysis with a transverse plane PA cephalo­ gram to determine the presence of transverse skeletal dysplasia.17 The clinical application of earlier two-dimensional analyses was made difficult by imaging limitations such as the superimposition of anatomic structures, magnification, and the lack of reproducible measurements on PA cephalograms as a result of major changes induced by head positioning, even when standardized techniques were used.18 Adaptation of these and other analyses to the more readily avail­ able CBCT will allow greater accuracy in the diagnosis of these deformities. The third dimension missing from the cephalometric radiograph is the transverse plane or x-axis in the 3D coordinate system. The advent of CBCT and 3D software has made it possible for the orthodontist and surgeon to visualize, evaluate, and simulate hard and soft tissue changes in all three dimensions of the craniofa­ cial structure (Fig. 77-2).18-20

TREATMENT/RECONSTRUCTIVE GOALS • An adequate transverse relationship improves dentofacial esthet­ ics and periodontal health and increases long-term orthodontic stability. Transverse skeletal dysplasia is a risk factor for maxil­ lary buccal gingival recession and periodontal disease. • Improved smile esthetics is the main soft tissue effect of trans­ verse skeletal correction.

642

Current Therapy in Oral and Maxillofacial Surgery

SPECIFIC TREATMENT AND TECHNIQUES LE FORT I SEGMENTAL OSTEOTOMY Background In 1972, Steinhauser reported a one-stage surgical procedure for expansion of the maxilla. The midline split could be performed on the posterior maxilla, anterior maxilla, or total maxilla. He thought widening the total maxilla to be technically difficult, however, because of the need to bone-graft the midline gap. To facilitate the procedure, palatal incisions were added to the buccal approach. Intermaxillary fixation was maintained for 4 to 6 weeks, and a reten­ tion plate was worn for 6 months to assist in stabilization of the transverse repositioning and to aid in consolidation of the bone graft. West and Epker described the application of Schuchardt’s two-stage (1959) and Kufner’s single-stage (1970) posterior maxillary osteoto­ mies for correction of unilateral and bilateral posterior crossbite in patients whose mid-palatal suture was closed. With this technique, maxillary expansion became a one-stage osteotomy that separated the alveolus from the palate. Bell and Turvey reported the results of segmental maxillary surgery performed on 10 patients with a poste­ rior crossbite. Segments were mobilized and positioned into a pre­ operatively determined occlusal relationship with a surgical splint and stabilized with wire fixation and intermaxillary fixation for 6 to 8 weeks. In 1985 in a series of 104 patients undergoing maxillary osteotomy, Turvey pointed out that transverse maxillary deficiency is seldom the only maxillary deformity, and he therefore recom­ mended that a multisegment maxilla be created to correct the hypo­ plastic maxilla in all three planes of space.12,21-23

Technique Before surgery, orthodontic decompensation, leveling, and align­ ment should be achieved. Sufficient room between the dental roots should exist at the planned interdental osteotomy sites to minimize any damage to periodontal tissue. Fabrication of two surgical splints, a palatal splint and an occlu­ sal splint, minimizes intraoperative time. Maxillary segmentation for correction of the transverse deficiency is done on completion of the total maxillary osteotomy and down-fracture. Para-midline sagit­ tal or horseshoe osteotomies are ideal when no changes in the maxil­ lary occlusal plane are needed for the following reasons: • It allows two separate areas of soft tissue expansion in the pos­ terior maxilla to minimize tension, which can prevent expansion or induce relapse. • The lateral palatal soft tissues are thicker, which minimizes the possibility of perforation or rupture of tissue. It improves the anatomy since most of these patients have a deep and narrow palatal vault preoperatively, and the palate will not only be wider but will also become less deep by lowering the central portion. The lateral para-midline osteotomy and interdental cuts can be made with a small side-cutting bur or with a saw. Fine spatula osteotomes are also sometimes used to finish the cuts. In all cases a finger is placed on the palate to decrease the chance of soft tissue damage, as well as to ensure that the osteotomy is completed. Minimal soft tissue dissection at the interdental osteotomy sites is of upmost importance to preserve the blood supply to the dentoal­ veolar structures (Fig. 77-3). The segments are mobilized with finger pressure, and a palatal splint without occlusal coverage is inserted.24 This palatal splint, which is held in place with wires or ball clasps, is constructed with acrylic and abuts the palatal surfaces of the upper teeth. The splint will stabilize the transverse change intra­ operatively, and postoperatively it will be maintained for a period

Fig. 77-3  n  Palatal view after maxillary down-fracture with osteotomy cuts in a horseshoe pattern.

of 6 to 10 weeks, at which point it can be replaced by an orthodontic transpalatal appliance. Lack of occlusal coverage allows placement of an occlusal splint for AP and vertical repositioning of the maxilla. The occlusal splint is removed before the patient leaves the operat­ ing room to facilitate oral hygiene and avoid the discomfort that occurs with wiring the classic occlusal splint to the upper dentition. Grafting with autogenous bone, allogeneic bone, or hydroxyapatite, as well as plate and screw fixation across the palatal osteotomy gap, has been described, but there are no adequate data on long-term stability in support of one technique over the other. Finally, the maxilla is put into its normal relationship with the mandible and placed in intermaxillary fixation. The maxilla is pas­ sively repositioned and secured with bone plates and screws, after which the intermaxillary fixation is removed and the occlusion con­ firmed. The soft tissue is closed carefully to minimize shortening of the lip, which often requires the use of an alar base cinch and V-Y closure to maximize paranasal and upper lip esthetics.

Pattern of Expansion The multisegment Le Fort I osteotomy allows repositioning of the maxilla in all three dimensions, and correction of the transverse problem can be performed simultaneously with maxillary AP and vertical repositioning. When a maxilla is widened with the osteo­ tomy made between the central incisors, the segments rotate outward with one or two axes of rotation at the incisal level, and the greatest surgical change occurs at the level of the second molars, which allows more intermolar than intercanine expansion.

Soft Tissue Esthetics Soft tissue changes associated with Le Fort I osteotomies include upturning of the nose, increased exposure of the nares, increased width of the alar cartilage, shortening of the columella, shortening of the upper lip, and possibly loss of exposed vermilion and upper lip curl.25 These changes may be positive or negative, depending on the presurgical facial esthetic characteristics of the patient. In most patients with maxillary hypoplasia, the Le Fort I osteotomy with advancement and inferior repositioning of the maxilla will result in positive changes by improving the acute nasolabial angle and pro­ viding support for the paranasal soft tissues. However, its effects on the facial esthetics of patients with a short upper lip, thin vermilion border, and upturned nasal tip can be disastrous, even when soft tissue closure such as the alar cinch and V-Y closure are used to minimize these potential negative effects.

Maxillary Deficiency: Transverse Plane Discrepancies

Stability Segmental osteotomy for maxillary expansion is at the bottom of the hierarchy of stability as reported by Phillips and co-authors, with a relapse rate of 49% at the second molars and a more clinically significant 29% incidence of crossbite at the end of orthodontic treatment.13 Studies on maxillary expansion using rigid fixation give us a better idea of the stability of this procedure at the present time. To improve transverse stability, it is recommended that expansions greater than 10 mm be avoided and that overexpansion be built into the occlusal splint, which is maintained for 6 to 10 weeks and replaced with a transpalatal arch or any other orthodontic appliance to assist in maintenance of intermolar width during healing and postsurgical orthodontic treatment.

SURGICALLY ASSISTED RAPID PALATAL EXPANSION Background Kole in 1959 was the first to discuss corticotomy for the treatment of adults with maxillary constriction; the lateral maxillary wall was cut 1 cm above the apices, and a palatal incision was used to make a horizontal cut into the maxillary antrum. This was followed by the insertion of a dental-borne expansion device 8 weeks later. In the same year, Converse and Horowitz described three different surgicalorthodontic techniques. 1. Osteotomy through the entire mandibular or maxillary bone thickness 2. Dentoalveolar osteotomy in which the body is left intact but the teeth and their supporting structures are moved segmentally into a planned position 3. Cortical osteotomy or corticotomy to achieve displacement of the dentoalveolar segments more rapidly than with orthodontics alone, especially for maxillary expansion Lines reintroduced corticotomy for adult rapid maxillary expan­ sion in 1975. He reported making lateral incisions at the depth of the vestibule from the canine to the tuberosity and cutting the corti­ cal plate from the piriform aperture to the zygomatic buttress. A palatal incision is made from behind the incisive papilla to the end of the hard palate with a burr. The expansion device is cemented 2 to 3 weeks postoperatively to allow healing and revascularization. This author extended the midline interdental bony cut to the piriform rim instead of using the interdental corticotomy described by Kole. Lines also suggested that because of the short duration and unevent­ ful postoperative course, this procedure can be performed in an outpatient visit with local anesthesia and premedication. From this report two different groups of procedures have developed: SARPE originally and surgically facilitated orthodontic treatment (SFOT) more recently. The latter involves three different techniques that can be used alone or in combination, depending on the correction needed: a corticotomy-facilitated technique (with or without bone grafting), dentoalveolar distraction osteogenesis, and skeletal anchorage devices. SFOT is primarily indicated for dental move­ ment, closure of extraction sites, and opening of implant sites, but it is also used for arch development and correction of dentoalveolar transverse discrepancies. Bell and Epker (1976) reported 15 patients who underwent SARPE under local anesthesia. Lateral maxillary bone cuts, pterygomaxillary disjunction, and interdental midline osteotomy were performed in all patients. Parasagittal palatal oste­ otomies were performed only in those with unilateral posterior crossbite. In the same year Kennedy and colleagues showed in their animal study that lateral maxillary osteotomies are key in achieving maxillary expansion.23,26-30

643

Key factors to be considered in maxillary expansion include the extent of the arch length discrepancy, arch form, magnitude of the arch deficiency, smile esthetics, and vertical as well as AP position of the maxilla. To determine the target expansion, it is advantageous to decom­ pensate the lower arch by removing the curve of Wilson before proceeding with maxillary expansion or by doing a pretreatment orthodontic setup.

Technique SARPE is usually done before placement of full fixed orthodontic appliances on the upper dentition since in most cases a tooth-borne distraction device is used (Hyrax, Haas, or any other jackscrew device). It is important that the upper molars and bicuspids, which are being used as anchors for the palatal device, be intact and not have recently been subjected to orthodontic forces. This is not neces­ sary if a bone-borne distraction device is used. The palatal expander is fabricated and adapted by the orthodontist before the scheduled procedure, and a trial fitting must be done to avoid difficulty placing the expander during surgery. The procedure is usually done as an outpatient procedure with intravenous sedation or general anesthesia in the office or surgical center. After local anesthetic with epinephrine is infiltrated at the surgical sites, incisions are made bilaterally at the depth of the ves­ tibule from the first molar area to the distal aspect of the canine. The mucoperiosteum is elevated and the maxillary bone exposed from the pterygomaxillary fissure through a subperiosteal tunnel to the piriform aperture. After identifying the infraorbital nerve, an oste­ otomy is performed horizontally at least 5 mm above the apices of the upper teeth from the piriform aperture to the pterygomaxillary fissure. The pterygoid plates are not separated from the maxilla. A single incision is made at the palatal midline, and bilateral muco­ periosteal flaps are elevated to allow parasagittal osteotomies to be performed at each side of the nasal septum to reduce areas of resis­ tance, which can cause unwanted asymmetric maxillary expansion. These osteotomies are usually done with a burr or a saw and they extend from the posterior hard palate to the incisive foramen. Anteriorly, the maxilla is separated by malleting a spatula osteotome between the central incisors at a level below the anterior nasal spine (Fig. 77-4). The surgical sites are irrigated and sutured. After the palatal expander is cemented by the surgeon, the screw is activated imme­ diately just enough to confirm completion of the osteotomies. An anterior nasal package, ice packs, or a pressure bandage can be applied for a day. Antibiotics, analgesic drugs, and an oroantral regimen should be prescribed. Activation of 1 mm/day then starts on postoperative day 3 to reduce the possibility of soft tissue dehiscence.

Pattern of Expansion Maxillary expansion sometimes occurs more at the anterior maxilla than in the molar region. This allows an increase in arch length by creating a midline diastema (Fig. 77-5).

Soft Tissue Esthetics Facial esthetics improves as a result of a widened smile and a reduc­ tion in buccal corridors. Soft tissue changes, similar to those with a multisegment Le Fort I procedure, are related to the extension of soft tissue dissection. The aforementioned technique minimizes soft tissue dissection in the esthetic zone since the vestibular incisions extend only from the first molar to the canine region and the midline dissection is limited to the bony cut site at the lateral aspect of the piriform rim. Palatal incisions and pterygomaxillary disjunctions

Current Therapy in Oral and Maxillofacial Surgery

644

A

A

B B Fig. 77-4  n  A, Frontal view showing osteotomies for surgically assisted rapid palatal expansion. B, Palatal cross section showing bilateral osteotomies at each side of the nasal septum.

have no effect on esthetics as long as maxillary down-fracture is not performed. A factor that needs to be taken into consideration is the potential loss of upper lip support caused by uprighting or retracting the upper incisors as a result of closure of the space following expan­ sion. It is important to exercise good torque control during orthodon­ tic postsurgical closure of the space to maintain upper lip support and lip curl.

Stability Rea and colleagues presented a systematic review of the literature on SARPE done by two examiners through an exhaustive MEDLINE computer search to identify all studies involving maxillary surgery in the English literature from 1970 to 2001.31 A total of 45 of 4,983 studies were identified as human clinical trials reporting SARPE. Five studies met the strict inclusion and exclusion criteria (Box 77-1). All studies were retrospective non-randomized trials without a control group and with sample sizes ranging from 10 to 30 subjects. In all five studies, osteotomies were done at the lateral wall of the maxilla and mid-palate and also included pterygomaxillary release (Table 77-1). Canine and molar expansion was reviewed (Tables 77-2 and 77-3). The mean canine relapse rate was between 8% and 25%, and the mean molar relapse rate was 9% to 22%. SARPE has been found

C Fig. 77-5  n  A, Palatal view showing a narrow maxilla before surgery and orthodontic treatment. B, Maxilla during expansion with the Hyrax device. C, Expanded maxilla after removal of the orthodontic appliances.

to be a relatively simple procedure that produces predictable and stable increases in maxillary width; when overcorrection is consid­ ered, it should not be planned to be more than 25% of the intended expansion.31

MANDIBULAR CONSTRICTION Background Mandibular constriction is a valuable adjunctive surgical procedure for dealing with transverse problems whenever bilateral sagittal osteotomies are to be performed. Although there have been other

Maxillary Deficiency: Transverse Plane Discrepancies TABLE 77-1  STUDY Pogrel, 1992

645

Included Studies PATIENTS 12

AGE (YR) 16-32

GENDER M: 4/F: 8

FOLLOW-UP (MO) 12

OSTEOTOMIES Bilateral zygomatic buttress, mid-palate

Bays, 1992

19

15-40

M: 3/F: 16

12-48

Bilateral zygomatic buttress, mid-palate

Stromberg, 1995

20

18-59

M: 11/F: 9

12-42

Bilateral zygomatic buttress, palate × 2

Northway, 1997

23

16-38

M: 6/F: 17

12

Bilateral zygomatic buttress, palate × 2

Berger, 1998

28

13-35

M: 12/F: 16

12

Bilateral zygomatic buttress, mid-palate pterygoid release

TABLE 77-2 

Results of Canine Data PATIENTS 12

EXPANSION (MM) N/A

Bays, 1992

19

Stromberg, 1995

TABLE 77-3  RELAPSE (MM) N/A

STUDY Pogrel, 1992

4.5 ± 3.28

*0.39 ± 0.79

20

5.0 ± 2.2

Northway, 1997

23

Berger, 1998 Weighted total

STUDY Pogrel, 1992

PATIENTS 12

EXPANSION (MM) 7.5

RELAPSE (MM) 0.88 ± 0.48

Bays, 1992

19

5.28 ± 2.68

*0.45 ± 0.69

*0.76 ± 0.95

Stromberg, 1995

20

8.3 ± 2.6

*1.2 ± 1.3

3.74 ± 0.45

0.41 ± 0.5

Northway, 1997

23

4.16 ± 0.96

0.35 ± 0.6

28

4.84 ± 0.89

1.12 ± 0.77

Berger, 1998

28

5.78 ± 1.03

90

3.99 ± 2.08

*0.48 ± 1.26 (8%-25%)

Weighted total

90

6.11 ± 2.64

*No relapse.

BOX 77-1 

Results of Molar Data

1.01+/−0.56 *0.78 ± 1.1 (9%-22%)

*No relapse.

Inclusion and Exclusion Criteria for Surgically Assisted Rapid Palatal Expansion

Inclusion Criteria • Human clinical trials • Sample size of 10 or more patients • Expansion and relapse measured on study models • Tooth-borne appliance • At least 12-month follow-up after surgically assisted rapid palatal expansion Exclusion Criteria • Non-surgical maxillary expansion • Clinical trials using segmental Le Fort I expansion • Patients with cleft lip and palate • Patients with craniofacial syndrome

reviews of symphyseal ostectomies, the first known discussion of midline osteotomy was published in 1976. This initial report was included in a description of the surgical techniques used in a patient in whom widening of the mandible was necessary. However, the technique was described in more detail by Brusati and co-authors, who reported use of this osteotomy for mandibular constriction. Alexander and associates were the first to describe stabilization of the mandibular midline osteotomy with rigid internal fixation. This article reviewed stability with a single plate placed across the osteotomy.14,15,32 Mandibular midline osteotomy is generally indicated in patients who require a mandibular ramus osteotomy and have no other

maxillary discrepancy. It is much easier to treat the transverse problem with a simple mandibular midline osteotomy, thereby avoiding a segmental Le Fort I osteotomy. This frequently occurs in patients with mandibular retrognathia who began treatment with a normal molar buccal overjet, and because they have a tapered arch form or a severe AP discrepancy, a transverse deficiency develops secondary to the mandibular advancement. Traditionally, orthodon­ tists have compensated in adults by altering the axial inclinations of the molars and, less often, by bodily moving the teeth. Either type of dental movement can be a problem when advancing the mandible. Tipping the maxillary posterior teeth buccally or the mandibular teeth lingually can result in cusp interference for the surgeon. This problem can be compounded by instability caused by the orthodon­ tist’s attempts at narrowing the posterior mandibular arch or expand­ ing the posterior maxillary arch. If no attempt is made at correcting this kind of transverse discrepancy before surgery, the surgeon has three treatment options besides performing a mandibular midline osteotomy: adding a maxillary segmental osteotomy with expansion, performing SARPE, or leaving the patient with a posterior crossbite or an end-to-end cusp relationship. One of the biggest advantages of mandibular midline osteotomy for constriction is that the decision to surgically correct a transverse discrepancy can be deferred to presurgical evaluation when the dentition is fully decompensated. In addition, mandibular constric­ tion can be added to the treatment plan with almost no impact on the patient because of the minimal additional surgical time and cost. Use of the mandibular midline osteotomy saves the patient from needing to undergo maxillary surgery, as well as significantly reduces surgical costs. Finally, less time is required by the orthodontist in attempting to compensate for any transverse dis­ crepancies that may exist between the maxilla and the mandible (Fig. 77-6).33

646

Current Therapy in Oral and Maxillofacial Surgery

A

B

C

D

E

F

G

H

Fig. 77-6  n  Initial models (A to C) and a lateral cephalogram (D) show class II malocclusion. Presurgical models (E to G) and a lateral cephalogram (H) show increased overjet after extraction of the lower first bicuspids and closure of the space to maximize mandibular advancement.

Technique The surgical technique for mandibular narrowing is always done in conjunction with mandibular bilateral sagittal split osteotomies. The midline cut is made after the sagittal splits are completed, and the mandible is placed in intermaxillary fixation with an occlusal splint. Fixing the occlusion at this time stabilizes the mandible during the osteotomy. A 1.5-cm incision is made below the attached tissue but generally not into the lip. A sagittal saw is used to make a bicortical

cut from the inferior border of the mandible to a point midway between the apices of the central incisors. The cut is then continued only through the buccal cortex up to the attached gingiva. A fine osteotome is twisted in the cut to achieve final splitting of the man­ dible. Based on postoperative peri-apical films, this last fracture line travels up the periodontal ligament space of one of the incisors. The two mandibular body segments are then fully seated into the surgical splint, and the intermaxillary fixation is tightened. A four-hole 2-mm

Maxillary Deficiency: Transverse Plane Discrepancies

I

J

K

L

647

Fig. 77-6, cont’d  n  I to K, Final models and a lateral cephalogram (L) after mandibular advancement combined with mandibular constriction.

plate is contoured to fit passively across the osteotomy site and secured with bicortical screws. The use of bicortical screws was driven by some early problems with unexpected transverse relapse in patients with relatively small constrictions measuring 4 to 6 mm. Rigid fixation of the bilateral sagittal split is then completed, and the intermaxillary wires are removed to check the occlusion. Two plates are rarely used for fixation of the midline osteotomy—when correction of a large transverse discrepancy (8 to 10 mm) is required or there is “soft bone” with minimal cortical thickness. The orth­ odontic arch wire is not cut at the midline during this procedure because we have found that continuity of the wire adds to the stabil­ ity of the osteotomy. This technique is completely different from mandibular intercanine narrowing with midline ostectomy in that removal of symphyseal bone is not necessary (Fig. 77-7).

Pattern of Expansion The amount of mandibular constriction has been shown to be statis­ tically significant and occurs progressively from the anterior to the posterior aspect of the arch. There is minimal change in intercanine width, with most of the constriction taking place across the second molars.34

Fig. 77-7  n  Bilateral sagittal split and midline osteotomies.

Soft Tissue Esthetics The transverse soft tissue response is 60% of the narrowing at the posterior mandible; however, these changes are not noticed by patients since they are minimal and their perception is distracted by the more noticeable AP and vertical changes associated with the mandibular advancement.35

Stability The orthodontist can aid stability by not trying to make any signifi­ cant transverse corrections other than uprighting the molars and reducing the curve of Wilson before surgery. Finally, it has been found that large rectangular arch wires have sufficient memory that

if not narrowed just before surgery, they will cause dental and pos­ sibly skeletal relapse of the transverse correction. The orthodontist will usually schedule an appointment with the patient 1 to 2 days before surgery to place surgical hooks on the arch wire, as well as to narrow the arch wire the amount of the anticipated constriction. In this short time before surgery, no significant dental movement takes place that will cause difficulty fitting the surgical splint at the time of surgery. It needs to be emphasized that as in all surgeries to correct transverse discrepancies, close cooperation with the

648

Current Therapy in Oral and Maxillofacial Surgery

A

B

Fig. 77-8  n  A, Condylar rotation during mandibular advancement caused by lateral displacement of the proximal segment. B, Example of how mandibular constriction reduces condylar rotation induced by mandibular advancement.

orthodontist is essential to minimize relapse. If the orthodontist attempts to correct the transverse discrepancy in adult patients before surgery, there is a poor chance of a long-term successful result because of the instability of the dental compensations. The best results are achieved when the orthodontist uprights the posterior teeth before surgery by removing the curve of Wilson. It has been determined that there is minor lingual torquing of the mandibular posterior segments during the midline osteotomy. This effect, when added to lingual crown torquing caused by the orthodontic mechan­ ics, can result in an unstable correction. It has been reported that narrowing the mandible more than 10 mm at the second molars results in instability. Although two plates have been used in these situations, significant relapse has occurred. In his master’s thesis, Pitts investigated the stability of mandi­ bular constriction with the use of plaster casts.34 His study group had undergone surgery at least 5 years earlier, and he noted a small but statistically significant 0.6-mm relapse at the second molars; however, there were no instances of crossbite at follow-up. Other than the study by Alexander and associates,15 a significant difficulty in any of the maxillary or mandibular research has been reliance on measuring the transverse corrections with plaster models. Obviously, any changes in torque made by the orthodontic appli­ ances after surgery can affect these results. Probably, the best way to assess the stability of any type of transverse correction would be evaluation of posterior occlusion after there has been a sufficient time during which no orthodontic appliances or retainers have been used. Five years after orthodontic treatment, no statistically significant relapse was found from the canines through the first molars, but there was a relapse of 0.6 mm in second molar width as mentioned earlier. Although this relapse was statistically significant, the author concluded that the small amount of change was not clinically significant, especially in the absence of crossbite or end-to-end occlusion at the end of orthodontic treatment and at the 5-year follow-up.15,34

Effects on the Temporomandibular Joint Patient self-reports designed to elicit information about temp­ oromandibular joint function 3 to 4 years after treatment in a study by Joondeph and Bloomquist showed no significant differences when comparing patients who underwent midline constriction with mandibular advancement with those who underwent mandi­ bular advancement alone.33 Long-term patient examination also found no differences between the two groups in the extent of maximum opening and range of motion, both of which were within normal limits. It is not surprising that patients undergoing midline constriction do not have a higher likelihood of temporomandibular dysfunction. A study comparing submentovertex radiographs to measure condylar rotation and lateral movement in 20 consecutive patients showed that mandibular advancement and constriction actually resulted in less change in condylar angulation and width, especially at the medial pole, as a result of surgery than did man­ dibular advancement alone. The subjective reports of temporoman­ dibular joint symptoms from both groups of patients were not significantly different. Joondeph and Bloomquist’s findings from evaluating the effects of sagittal split alone on the temporomandibu­ lar joint were similar to what has been reported by other authors (Fig. 77-8).35

Periodontal Effects In 5-year postsurgical periodontal evaluations of both the midline osteotomy site and the mandibular anterior incision site, no differ­ ences were found in pocket depth, attachment loss, or recession when compared with other mandibular anterior sites in the same patient.

POSTOPERATIVE CARE There is no difference in the postoperative care of patients after a normal sagittal split since intermaxillary fixation is not needed. If the orthodontist has not narrowed the mandibular arch wire before surgery, it needs to be done as soon as practical after surgery.

Maxillary Deficiency: Transverse Plane Discrepancies

649

PEARLS AND PITFALLS Discrepancies in maxillo-mandibular width may be manifested as three different patterns. Selection of the surgical procedure for each pattern will be determined by the location (intercanine, intermolar, or both) of the deficiency, the magnitude of the discrepancy, Bolton analysis, the pattern and limits of expansion or constriction, stability, and effects on facial esthetics. Narrow Maxilla with a Normal Mandible • Maxillary intercanine deficiency: SARPE. • Indication: isolated transverse maxillary skeletal deficiencies; if maxillary or mandibular repositioning is needed, a second surgery will be required. Simultaneous anterior or inferior maxillary repositioning (or both) can be achieved by distraction osteogenesis with application of the floating bone concept. • Usually performed before orthodontic decompensation. • Range of expansion of 5 to 15 mm. • Increases arch length for correction of an arch length deficiency with minimal esthetic impact, except for improvement in smile esthetics. Mild increases in alar width may be seen. • Maxillary expansion is the same or larger at the anterior maxilla than at the molar region, thereby creating a maxillary midline diastema. • The limitations of the soft tissue–induced expansion of the multisegment Le Fort I osteotomy do not apply to this technique. • Maxillary intermolar deficiency: segmental Le Fort I. • Indication: maxillary expansion when simultaneous AP or vertical repositioning (or both) is necessary. This procedure can be done alone or combined with mandibular osteotomies. • It is usually performed after orthodontic decompensation of the maxillary arch is completed, which can be challenging, especially in patients with significant dental crowding. • The amount of expansion is usually restricted by the soft tissues at the osteotomy sites. • More posterior than anterior maxillary expansion is achieved since the axis of rotation is at the upper dental midline for a two-piece maxilla. • The Le Fort I procedure has considerable esthetic impact as described previously. • Overcorrection is indicated to compensate for relapse-induced posterior crossbite at the end of treatment. • Pitfall: segmental Le Fort I osteotomies with expansions of up to 15 mm have been reported, but expansions greater than 10 mm at the posterior maxilla may be associated with relapse postoperatively.

Wide Mandible with Normal Maxilla • Mandibular intermolar excess: mandibular constriction. • Indication: mainly for patients with mandibular transverse excess (<10 mm) who have ideal maxillary position and smile esthetics or whose facial esthetics are likely to be negatively affected by the soft tissue changes associated with Le Fort I osteotomy. This technique is commonly used in patients with an absolute transverse discrepancy as a result of mandibular advancement. • The decision to surgically correct a transverse discrepancy can be deferred to the presurgical evaluation when the dentition is fully decompensated. • There are minimal risks and morbidity, which saves the patient from undergoing additional maxillary surgery with increased operating time and cost. • It decreases the transverse mandibular dimensions mainly at the posterior mandible, with the dental midline as the axis of constriction producing negligible soft tissue impact. • Mandibular constriction ranging from 3 to 10 mm has been reported. • Pitfall: although this procedure has excellent long-term stability, relapse has been noted with constrictions greater than 10 mm at the second molars. • Mandibular intercanine excess. • It is rarely treated surgically because it is usually diagnosed as a discrepancy in tooth size and treated orthodontically. Narrow Maxilla with a Wide Mandible (Severe Transverse Maxillomandibular Discrepancy >10 mm) • A combination of the aforementioned techniques is indicated to minimize postoperative relapse. Summary • The sparse literature on surgical correction of transverse discrepancies is a consequence of less than ideal tools to diagnose and evaluate treatment outcomes. Better-designed studies will take place with the development of new 3D imagery. This will then lead to more accurate diagnosis and treatment of dentofacial transverse problems. As presented in this chapter, each treatment option has its indications, and therefore all three procedures should be routine in the practice of any surgeon providing orthognathic surgery.

REFERENCES 1. Sarver DM, Profitt WR, Ackerman JL: Evaluation of facial soft tissues. In Profitt WR, White RP Jr, Sarver DM, editors: Contemporary treatment of dentofacial deformity, St. Louis, 2003, CV Mosby. 2. Kelly JE, Harvey CR: An assessment of the occlusion of the teeth of youths 12-17 years, U.S. Public Health Service Publication No 77:164, Government Printing Office, 1977. 3. McLain JB, Steedle JR, Vig PS: Face height and dental relationships in 1600 children: a survey, J Dent Res 62:308-313, 1983. 4. Bell WH: Surgical correction of dentofacial deformities: new concepts, Philadelphia, 1985, WB Saunders, pp 2-3. 5. Proffit WR, Phillips C, Dann C IV: Who seeks surgical-orthodontic treatment? Int J Adult Orthod Orthognath Surg 3:153-160, 1990.

6. Kluemper GT, Spalding PM: Realities of cra­ niofacial growth modification, Atlas Oral Maxillofac Surg Clin North Am 9:23-57, 2001. 7. Bays RA, Greco JM: Surgically assisted rapid palatal expansion: an outpatient technique with long term stability, J Oral Maxillofac Surg 50:110-113, discussion 114-115, 1992. 8. Pogrel MA, Kaban LB, Vargervik K, et al: Surgically assisted rapid maxillary expansion in adults, Int J Adult Orthod Orthognath Surg 7:37-41, 1992. 9. Stromberg C, Holm J: Surgically assisted, rapid maxillary expansion in adults. A retro­ spective long-term follow-up study, J Craniomaxillofac Surg 23:222-227, 1995. 10. Northway WM, Meade JB Jr: Surgically assisted rapid maxillary expansion: a

comparison of technique, response, and stability, Angle Orthod 67:309-320, 1997. 11. Berger JL, Pangrazio-Kulbersh V, Borgula T, et al: Stability of orthopedic and surgically assisted rapid palatal expansion over time, Am J Orthod Dentofacial Orthop 114:638-645. 1998. 12. Turvey TA: Maxillary expansion: a surgical technique based on surgical-orthodontic treat­ ment objectives and anatomical consider­ ations, J Maxillofac Surg 13:51-58, 1985. 13. Phillips C, Medland W, Fields H Jr, et al: Stability of surgical maxillary expansion, Int J Adult Orthodont Orthognath Surg 7:139146, 1992. 14. Brusati R, Sesenna E, Mannucci N, et al: The midline mandibular osteotomy-ostectomy in the correction of dentofacial deformities, Int

650

Current Therapy in Oral and Maxillofacial Surgery

J Adult Orthodon Orthognath Surg 2:37-50, 1987. 15. Alexander CD, Bloomquist DS, Wallen TR: Stability of mandibular constriction with a symphyseal osteotomy, Am J Orthod Dento­ facial Orthop 103:15-23, 1993. 16. Krebs AA: Rapid expansion of midpalatal suture studied by means of fixed appliance: an implant study over a 7 year period. Trans Eur Orthod Soc 40:131-142, 1964. 17. Ricketts RM: Perspectives in the clinical application of cephalometrics, the first fifty years, Angle Orthod 51:115-150, 1981. 18. Ludlow JB, Gubler M, Cevidanes L, et al: Precision of cephalometric landmark identifi­ cation: cone-beam computed tomography vs conventional cephalometric views, Am J Orthod Dentofacial Orthop 136:312.e1312e10, discussion 312-313, 2009. 19. Swennen RJ, Schutyser F: Three-dimensional cephalometry: spiral multi-slice vs. conebeam computed tomography, Am J Orthod Dentofacial Orthop 130:410-416, 2006. 20. Park SH, Yu HS, Kim KD, et al: A proposal for a new analysis of craniofacial morphology by 3-dimensional computed tomography, Am J Orthod Dentofacial Orthop 129:600.e23600.e34. 2006.

21. Steinhauser EW: Midline splitting of the maxilla for correction of malocclusion, J Oral Surg 30:413-422, 1972. 22. West RA, Epker BN: Posterior maxillary surgery: its place in the treatment of dentofa­ cial deformities, J Oral Surg 30:562-563, 1972. 23. Bell WH, Epker BN: Surgical-orthodontic expansion of the maxilla, Am J Orthod 70:517-528, 1976. 24. Reinkingh MR, Rosenberg A: Palatal surgical splint for transverse stability of LeFort I osteotomies: a technical note, Int J Oral Maxillofac Surg 25:105-106, 1996. 25. Betts N, Dowd K: Soft tissue changes associ­ ated with orthognathic surgery, Atlas Oral Maxillofac Surg Clin North Am 8:13-38, 2000. 26. Kole H: Surgical operations on the alveolar ridge to correct occlusal abnormalities, Oral Surg 12:515-529, 1959. 27. Converse JM, Horowitz SL: The surgicalorthodontic approach to the treatment of den­ tofacial deformities, Am J Orthod 55:217-243, 1969. 28. Lines PA: Adult rapid maxillary expansion with corticotomy, Am J Orthod 67:44-56, 1975.

29. Roblee R, Bolding S, Landers J: Surgically facilitated orthodontic therapy: a new tool for optimal interdisciplinary results, Philadelphia, 2009, WB Saunders. 30. Kennedy JE, Bell WH, Kimbrough OL, et al: Osteotomy as an adjunct to rapid maxillary expansion, Am J Orthod 70:123-137, 1976. 31. Rea A, Alcalde RE, Bloomquist D, et al: Systematic review of surgically assisted rapid maxillary expansion, Chicago, September 2002, 84th Annual Meeting of the American Ass­ociation of Oral and Maxillofacial Surgeons. 32. Plumpton S: Surgical correction of unilateral mandibular prognathism by intra-oral ostec­ tomy of the symphysis, Br J Plast Surg 20:7077, 1967. 33. Joondeph D, Bloomquist D: Mandibular midline osteotomy for constriction, Am J Orthod Dentofacial Orthop 126:268-270, 2004. 34. Pitts AL: Mandibular midline osteotomy: stability, periodontal status, TMJ function [master’s thesis], Seattle, 1996, University of Washington. 35. Alcalde RE: Soft tissue changes associated with mandibular constriction with midline osteotomy, J Oral Maxillofac Surg 60:72, 2002.