Evaluation of Skeletal Stability After Surgical–Orthodontic Correction of Skeletal Open Bite With...

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J Oral Maxillofac Surgxx:xxx, 2010

Evaluation of Skeletal Stability AfterSurgical–Orthodontic Correction ofSkeletal Open Bite With Mandibular

Counterclockwise Rotation UsingModified Inverted L Osteotomy

Zaher Aymach, DDS, DOrtho,* Hitoshi Nei, DDS, PhD,†

Hiroshi Kawamura, DDS, PhD,‡ and Joseph Van Sickels, DDS§

Purpose: To evaluate the surgical–orthodontic stability of treating skeletal open bite patients withmandibular ramus osteotomies using a modified inverted L osteotomy (M-ILO) and counterclockwiserotation of the mandible stabilized with rigid fixation.

Patients and Methods: In a retrospective review, 12 patients with skeletal open bites (8 females, 4males) who received mandibular M-ILO in the period 2004-2007 at Tohoku University Hospital werestudied. Lateral cephalograms were taken immediately before surgery (T1), immediately after surgery(T2), and at 1 yr after surgery (T3). Cephalometric analysis for point B, pogonion, menton, andmandibular plane angle was obtained at the designated time intervals.

Results: Mandibular counterclockwise rotation showed stability for point B, pogonion, and mentonreferred to X-Y coordinate, and for mandibular plane angle. The mean value for each variable wascompared between T2 and T3. No statistically significant change was observed for all variables.

Conclusions: With a well-positioned maxilla, skeletal open bite can be successfully treated usingM-ILO. Mandibular counterclockwise rotation showed stability at 1 yr after surgery.© 2010 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rightsreserved.
J Oral Maxillofac Surg xx:xxx, 2010
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umerous surgical procedures have been proposedo correct a skeletal open bite. Mandibular commonsteotomies include a sagittal split ramus osteotomySSRO), intraoral vertical ramus osteotomy, and in-erted L osteotomy (ILO). These ramus procedures,owever, have not been uniformly successful due to aelapse in both the horizontal and the vertical dimen-ions. Although the potential for relapse of variousandibular ramus osteotomies is a subject of much

ontroversy, factors such as proper surgical tech-ique, rigid fixation, and temporomandibular joint

*PhD candidate, Department of Maxillofacial Surgery, Graduate

chool of Dentistry, Tohoku University, Sendai, Japan.

†Assistant Researcher, Department of Maxillofacial Surgery,

raduate School of Dentistry, Tohoku University, Sendai, Japan.

‡Professor and Chairman, Department of Maxillofacial Surgery,

raduate School of Dentistry, Tohoku University, Sendai, Japan.

§Professor and Assistant Dean, Department of Oral and Maxillo-

acial Surgery, College of Dentistry, the University of Kentucky,

exington, KY.

1

TMJ) were shown to have a great impact on confer-ing stability.1-3 However, much concern of relapseemains when correction of the skeletal open bite isttempted.4,5 For that reason, a maxillary impaction issually recommended because of greater stability.6,7

lthough more stable, a maxillary impaction may notive the best functional or esthetic results for anndividual patient. Therefore, limiting the surgery onhe mandible and closing the open bite with a coun-erclockwise rotation will be required. SSRO, as theost widely used mandibular procedure, was shown

Address correspondence and reprint requests to Dr Aymach:

ohoku University, Graduate School of Dentistry, Department of

axillofacial Surgery, 4-1 Seiryo-machi, Aoba-ku, Sendai 980–8575,

iyagi, Japan; e-mail: [email protected]

2010 American Association of Oral and Maxillofacial Surgeons. Published

y Elsevier Inc. All rights reserved.

278-2391/10/xx0x-0$36.00/0

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2 SKELETAL STABILITY AFTER SURGICAL–ORTHODONTIC CORRECTION OF SKELETAL OPEN BITE

n most recent studies to be a relatively stable proce-ure for counterclockwise rotation when applyingigid fixation and eliminating TMJ pathology.8-11

In our institution, we have used an alternative os-eotomy technique for correcting anterior open bites,imiting the surgery to the mandible. ILO, with a

odification that brings its horizontal osteotomy be-ow the level of mandibular nerve entrance, allowshe distal segment to perform a counterclockwiseotation with the stylomandibular and sphenomandib-lar ligaments preserved and attached to the condylaregment (Figs 1, 2).

The attempt to treat a skeletal open bite using anLO with stable results was originally described byattilo et al in 1985.12 The method was applied as anxtraoral approach with no rigid fixation. Rigid fixa-ion with ILO was described by Van Sickels et al13

sing plates and a transbuccal approach after setting

IGURE 1. Inverted L osteotomy. A, Original design; B, modifiedLO.

3ymach et al. Skeletal Stability After Surgical–Orthodontic Cor-ection of Skeletal Open Bite. J Oral Maxillofac Surg 2010.

ack mandibular prognathism. McMillan et al14 men-ioned the use of ILO as a surgical option for mandib-lar advancement, particularly where the risk of man-ibular nerve injury is unacceptable. Later on, Muto etl15 described a design for ILO that provides goodisibility, greater bony overlap, and rigid fixation toorrect mandibular prognathism. Although thesetudies allowed more applicability for ILO to treat aariety of deformity patterns, most of them had notvaluated skeletal stability after application. To date,here is no work investigating the skeletal stability ofpen bite skeletal deformities treated by ILO with an

ntraoral approach and rigid fixation.The purpose of this study was to evaluate the skel-

tal stability after correction of skeletal open bite byandibular counterclockwise rotation using a modi-

ed intraoral inverted L osteotomy (M-ILO) with rigidxation (Fig 3).

atients and Methods

This retrospective study is exempted from IRBpproval of the human studies committee. Thetudy included 12 patients (8 females, 4 males) withkeletal open bite who had undergone mandibular-ILO at Tohoku University Hospital between 2004

nd 2007. The group’s mean age was 24 yr, 8 mo,anging from 18 to 39 yr (Table 1). Patients for thistudy met the following inclusion criteria: 1) all had

lack of anterior teeth overlap with a skeletalattern of open bite (Go-Me-SN � 33°� 3 upper

acial height [UFH]/lower facial height [LFH] index0.8 � 0.05, Go angle � 134° � 6, Y-axis angle �

0° � 5); 2) the mean ANB was 0.9 � 3 includingkeletal Class I, and Class II and III tendency pat-erns; 3) all the maxillas were confirmed to be wellositioned by clinical and cephalometric examina-ions and none were actively growing at the time ofurgery; 4) all received preoperative and postoper-tive orthodontic treatment; 5) all were operatedn by 1 surgeon using a single jaw procedure (M-LO); and, finally, 6) fixation with a titanium lock-ng miniplate was performed without bone graft-ng. Individuals with craniofacial anomalies,symmetries, syndromes, or history of trauma werexcluded from the study.

SURGICAL TECHNIQUE OF M-ILO

Preoperatively, the anatomy of the mandibular ra-us area, the mandibular foramen, and canal positionas evaluated using digital orthopantomographs and

omputed tomography.

INCISION

After local anesthetic and epinephrine injection, a
0-mm-long incision is made starting approximately

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AYMACH ET AL 3

5 mm proximal to the mandibular second molar andxtending down to the periosteum. A mucoperiostealap is then elevated proximally and laterally to ex-ose the anterior, lateral, and partially medial ramusspects.

VERTICAL OSTEOTOMY

By using an oscillating saw, the osteotomy runsertically 5 to 7 mm anterior to the ramus posteriororder and moves steadily downward to meet the

ower border just anterior to the mandibular angle

IGURE 2. Drawings illustrate different osteotomy lines with relaSRO; B, Original ILO; C, Modified ILO.

ymach et al. Skeletal Stability After Surgical–Orthodontic Corre

Fig 4 displays a model simulation). t

HORIZONTAL OSTEOTOMY

By using a reciprocating saw, the osteotomy cutsorizontally below the level of mandibular foramen. Ittarts posteriorly by cutting through the outer cortexn the area where the nerve course passes throughntil the osteotomy is 7 mm from the ramus anteriororder to include the inner cortex and complete thesteotomy.

SPLITTING

Splitting progresses with an osteotome placed in

stylomandibular and sphenomandibular ligaments. A, Original

f Skeletal Open Bite. J Oral Maxillofac Surg 2010.

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orted with an additional curved osteotome placed inhe vertical cut to help split the rest of the horizontalsteotomy, particularly the area near the mandibularerve entrance.

FIXATION

After maxillomandibular fixation, condyles are seatednd intersegmental bony prematurities are reduced.hen, fixation takes place at the ramus anterior aspectsing an L-shaped titanium locking miniplate withonocortical screws. Maxillomandibular fixation is then

eleased and replaced with light elastic.

ephalometric Landmarksnd Analysis

Cephalometric radiographs were obtained at theeeth in centric occlusion, with the lips relaxed andhe head in a natural position, and assessed at the

IGURE 3. A representative tracing displays mandibular counter-lockwise rotation after M-ILO. (Dotted line), initial; (solid line), follow-ng rotation; (blue circle), the center of rotation; (arrow), the direction.

ymach et al. Skeletal Stability After Surgical–Orthodontic Correc-ion of Skeletal Open Bite. J Oral Maxillofac Surg 2010.

Table 1. BASIC PATIENT DATA

Case Number Diagnoses Age (yr)

1 Skeletal Class I 282 Skeletal Class I 393 Skeletal Class I 194 Skeletal Class III 205 Skeletal Class III 226 Skeletal Class III 257 Skeletal Class III 188 Skeletal Class III 299 Skeletal Class III 30

10 Skeletal Class II 2111 Skeletal Class II 2312 Skeletal Class II 24

ymach et al. Skeletal Stability After Surgical–Orthodontic Correction o

IGURE 4. Model simulation of M-ILO with fixation technique. A,ingual view with relation to mandibular nerve entrance; B, anterior viewfixation plates).

ymach et al. Skeletal Stability After Surgical–Orthodontic Correction of

Gender ANB (°) Overjet (mm) Overbite (mm)

F 2 1.5 �3F 3 2.5 �1.5F 3 3 �5M 0 �1 �3.5M �2 �2.5 �5F 0 0 �2F �4 0 �0.5M �3 �3 �4.5F �2 �4 �3F 4 3 �1F 5 4 �4M 4.5 3.5 �3.5


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ollowing 3 intervals: before surgery (T1), immedi-tely after surgery (T2), and at 1 yr after surgery (T3).he following cephalometric points were identified:idpoint of sella (S), nasion (N), orbital (Or), porion

P), point (B), pogonion (Pog), menton (Me), andonion dash (Go=) (Tables 2 and 3). For analysis, the-Y coordinate axis was constructed. This coordinateystem has its origin at Pog and its X axis is parallel tohe Frankfort plane. The vertical line was perpendic-lar to this line through Pog as the Y vertical axis (Fig). A 0.3-mm pencil was used to minimize errors in

ocating cephalometric landmarks on tracing paper.hese serial cephalograms were identified twice by

he same examiner, and, if the difference between thevalues of any point or angle exceeded 0.5 mm or 1°,

espectively, the point or angle was registered a thirdime. The third registration was compared with thethers. The mean value was taken from the 2 closestalues, while the outlier was excluded from the data.racing replication was a good means to reduce theias of identification of cephalometric points.Lateral cephalometric tracings were superimposed

o calculate surgical changes right after surgery (T2-1) and at 1 yr after surgery (T3-T2). Changes in the

Table 2. CEPHALOMETRIC LANDMARKS WITH THEIR DE

Point

� Nasion The most anterior point of the fronr � Orbital The lowest point of the bony orbit

outline is considered)� Porion The top of the external auditory m� Midpoint of sella The center of sella turcica� Point B The deepest point on the outer con

and pogonionogonion The most anterior point of the bonenton The most inferior point of the outlio= � Gonion dash The most posterio-inferior point on

osteotomy line


Table 3. DEFINITION OF LINEAR PLANESAND ANGLES

Plane/Angle Definition

N Anterior cranial baselineH Frankfort horizontal plane, drawn from

the point orbital to porion-B Line joining nasion and point B-Pog Line joining nasion and pogoniono=-Me Mandibular plane

Go=-Me-SN) This angle is constructed from SN andthe intersection of the mandibularplane line Go=-Me

ymach et al. Skeletal Stability After Surgical–Orthodontic Cor-ection of Skeletal Open Bite. J Oral Maxillofac Surg 2010.

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osition of the landmarks were noted relative to theoordinate system X-Y.

esults

The mean values of the variables at (T1), (T2), andT3) are presented in Tables 4 and 5. The meanhanges that occurred after surgery (T3-T2) were�0.4 mm vertical, 0.2 mm horizontal) for pogonion,�0.3 mm vertical, 0.1 mm horizontal) for menton,�0.8 vertical mm, 0.4 mm horizontal) for point B,

ONS

Definition

l suture in the midsagittal planeorbital rims overlapped, the lowest point on the average

f the mandibular alveolar process between infradental

in the midsagittal planethe symphysis in the midsagittal planeandibular lower border just anterior to the designated


IGURE 5. Cephalometric landmarks, linear and angular mea-urements used in this study.

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nd (�0.56°) for mandibular plane angle (Tables 6nd 7). To determine how significant these changesre, 7 separate t tests were carried out. For each test,he mean value of the variable right after surgery wasompared with its mean value at 1 yr after surgery.here was no statistically significant evidence that theean value of all the variables was altered at least 1 yr

fter surgery (P � .05) (Figs 6, 7).

iscussion

The complex nature of the open bite deformitiesresents a number of problems and options for theurgeon. A major concern continues to be the stabilityf the changes after orthognathic surgery procedureso close an open bite, particularly with a mandibular-ependent surgery. Although some reports men-ioned that closing an open bite or decreasing theandibular plane with SSRO increases the risk of

elapse up to 33%,16-18 recent studies suggest thatolely SSRO applied with some modifications is aelatively stable procedure for correcting open bitesith the presence of rigid fixation and absence of TMJathology.9-11 Such modifications included using ahort sagittal splitting line (Epker-Hunsuck modifica-ion) that can help free the distal segment from thetylomandibular ligament.10 Other suggestions cane to develop a green-stick fracture or osteotomyn the internal ramus aspect belonging to the distalegment, to reduce the tension on the sphenoman-

Table 5. VALUES FOR THE VARIABLE OFMANDIBULAR PLANE ANGLE Go=-Me-SN(°)

Variable

T1 T2 T3

Mean SD Mean SD Mean SD

o=-Me-SN 38.4 3.8 35.6 4.2 36.1 3.7

Table 4. VALUES OF THE SELECTED CEPHALOMETRIC VA

Variable

T1

Mean SD

oint BV 10.8 1.6H �2.9 1.2

ogV 0 0H 0 0eV �8.5 1.4H �4.6 2.3



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ibular ligament, or even to detach the ligamentrom the Lingula.8

The M-ILO, as an alternative osteotomy tech-ique, helps to move the mandible counterclock-ise effectively with little interference from theandibular ligaments and noticeably negating theeed of further stripping on the distal segment afterotation, thus maximizing blood supply to the bonyegments.

Fixation of M-ILO is performed intraorally usingn L-shaped locking miniplate and monocorticalcrews applied on the ramus anterior aspect. Theownward level of the horizontal cut helps in seat-

ng and controlling the condylar segment. Thisbandons the use of condylar positional plates as-ociated with the original ILO that showed a poorontrol over the condylar segment during fixa-ion.13,14 After M-ILO, the patient is kept on a softiet for 4 to 6 weeks and wears light elastics.Nerve damage and numbness after ramus osteoto-ies are considered a critical complication. The orig-

nal ILO is believed to reduce the incidence of neu-

Table 6. VALUES FOR THE SELECTEDCEPHALOMETRIC VARIABLES (mm) OF THESURGICAL MOVEMENT (T2-T1) AND THE CHANGEAFTER SURGERY (T3-T2)

ariable

T2-T1 T3-T2

Mean SD Mean SD

oint BV 4.1 1 �0.8 0.3H �1.8 2.4 0.4 0.4

ogV 4 1 �0.4 0.2H �1 2.4 0.2 0.1eV 3.8 1.1 �0.3 1.6H �0.9 0.2 0.1 0.1

ES FOR THE PATIENTS TREATED WITH M-ILO (mm)

T2 T3

n SD Mean SD

9 2 14.1 25 1.6 �4.8 1.5

1 3.6 12 2.4 �1 2.4

7 1.7 �5 1.76 1.6 �4.5 1.6


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osensory defect.19 This defect, which was attributedo the deep dissection carried on the ramus medialspect,13 showed significant recovery postoperativelyompared with SSRO.19,20 For the M-ILO, there is anncreased risk of injury to the nerve as the lateral hori-ontal osteotomy cuts in the proximity of the nerveourse. Therefore, ascertaining the nerve entranceocation and course via computed tomographiccan, obtaining proper technique skills, and main-aining limited soft tissue dissection on the ramusedial aspect will all have a great impact on reduc-

ng nerve injury. Clinically, our patients operatedith M-ILO were less likely to develop a neurosen-

ory defect, and if developed, more rapidly recov-red than our patients operated with SSRO. Amonghe patients included in this study, only 2 cases showedpartial defect that took no longer than 2 mo to recovern performing the 2-point discrimination test.For any skeletal deformity, skeletal as well as

entoalveolar stability is of high concern for main-aining good results, especially with cases of openite. Thus, observing tongue activity and positionnd obtaining proper anterior teeth overlap orth-dontically are helpful tools in maintaining stableesults.6,21

IGURE 6. Diagram representing the changes immediately afteorizontal values of B, Pog, and Me points.

Table 7. VALUES OF THE MANDIBULAR PLANEANGLE Go=-Me-SN (°) OF THE SURGICALMOVEMENT (T2-T1) AND THE CHANGE AFTERSURGERY (T3-T2)

Variable

T2-T1 T3-T2

Mean SD Mean SD

o=-Me-SN 3.1 1.5 �0.6 1.2


ymach et al. Skeletal Stability After Surgical–Orthodontic Correction o

Our extended clinical contemplation to M-ILOuggests that for those cases of open bite withevere skeletal pattern or accompanying craniofa-ial anomalies, maxillary posterior impaction maye included in the treatment plan. Moreover, weractice M-ILO for open bites accompanying smallo moderate skeletal sagittal discrepancies that cane fixed without requiring bone grafting because

ntersegmental bony prematurities are often seenarticularly at the posterior area. Therefore, when a

arge amount of advancement will follow closing anpen bite, or in the lack of intersegmental bonyontacts with a gap formed over 5 mm, bone graft-ng (ie, harvested from anterior symphysis cortex)hould be considered. We had not reported a case oflating failure or infection that required early removal orefixation. Regarding the TMJ issue, the initial clinicalata of our patients undergoing M-ILO had not recordeddevelopment of TMJ symptoms, if any, to be consid-

red much more severe than at the time before surgery,lthough further investigation will be required to reachconclusion.Using M-ILO when indicated, limiting surgery to 1

aw will significantly reduce the financial impact tohe patient and can make an orthognathic treatmentlan affordable.With the versatility of ILO application,22 our up-

oming studies will investigate the application of-ILO for lengthening short ramus as in asymmetry

ases or hemifacial microsomia by combining M-LO with SSRO. In addition, this study presents thetability for a short-term follow-up; because of that,

long-term evaluation of our open bite patientsith large sample size is needed.The M-ILO was shown to be a good method for

reating skeletal open bite. It allows mandibular coun-

ry (T2-T1) and at 1 yr after surgery (T3-T2) for the vertical and
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erclockwise rotation and easy fixation with stableesults at 1 yr after surgery.

eferences1. Lai S, Tseng Y, Huang I, et al: Skeletal changes after modified

intraoral vertical ramus osteotomy for correction of mandibularprognathism. J Plast Reconstr Aesthet Surg 60:139, 2007

2. Joss CU, Vassalli IM: Stability after bilateral sagittal split osteot-omy advancement surgery with rigid internal fixation: A sys-tematic review. J Oral Maxillofac Surg 67:301, 2009

3. Joss CU, Vassalli IM: Stability after bilateral sagittal split osteot-omy setback surgery with rigid internal fixation: A systematicreview. J Oral Maxillofac Surg 66:1634, 2008

4. Wriedt S, Buhl V, Al-Nawas B, et al: Combined treatment ofopen bite—Long-term evaluation and relapse factors. J OrofacOrthop 70:318, 2009

5. Epker BN, Fish LC: Surgical-orthodontic correction of open bitedeformity. Am J Orthod 71:278, 1977

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8. Ricard D, Ferri J: Modification of the sagittal split osteotomy ofthe mandibular ramus: Mobilizing vertical osteotomy of theinternal ramus segment. J Oral Maxillofac Surg 67:1691, 2009

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1. Stansbury CD, Evans CA, Miloro M, et al: Stability of open bitecorrection with sagittal split osteotomy and closing rotation of

IGURE 7. Diagram representing the changes immediately after sngle Go=-Me-SN.


the mandible. J Oral Maxillofac Surg 68:149, 2010

2. Dattilo DJ, Braun TW, Sotereanos GC: The inverted L osteot-omy for treatment of skeletal open-bite deformities. J OralMaxillofac Surg 43:440, 1985

3. Van Sickels JE, Tiner BD, Jeter TS: Rigid fixation of the intraoralinverted “L” osteotomy. J Oral Maxillofac Surg 48:894, 1990

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7. Frey DR, Hatch JP, Van Sickels JE, et al: Alteration of themandibular plane during sagittal split advancement: Short- andlong-term stability. Oral Surg Oral Med Oral Pathol Oral RadiolEndod 104:160, 2007

8. Frey DR, Hatch JP, Van Sickels JE, et al: Effects of surgicalmandibular advancement and rotation on signs and symptomsof temporomandibular disorder: A 2-year follow-up study. Am JOrthod Dentofac Orthop 133:490, 2008

9. Naples RJ, Van Sickels JE, Jones DL: Long-term neurosensorydeficits associated with bilateral sagittal split osteotomy versusinverted “L” osteotomy. Oral Surg Oral Med Oral Pathol 77:318,1994

0. Kobayashi A, Yoshimasu H, Kobayashi J, et al: Neurosensoryalteration in the lower lip and chin area after orthognathicsurgery: Bilateral sagittal split osteotomy versus inverted Lramus osteotomy. J Oral Maxillofac Surg 64:778, 2006

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(T2-T1) and at 1 yr after surgery (T3-T2) for the mandibular plane


urgery

lag, 1998, p 191

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