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British Journal of Oral and Maxillofacial Surgery 48 (2010) 352–355

Available online at www.sciencedirect.com

losure of the anterior open bite using mandibular sagittalplit osteotomy. Bisase ∗, P. Johnson, M. Stacey

oyal Surrey County Hospital, Egerton Road, Guildford, Surrey, GU2 7XX, United Kingdom

ccepted 21 August 2009vailable online 16 September 2009

bstract

nterior open bite is a common problem in orthognathic practice that confers functional and aesthetic handicaps on affected patients. Itsanagement varies, and it is one of the most challenging disorders to treat. The orthodontic and surgical approach to the treatment of skeletal

nterior open bite is still debated, and the results are controversial. The relapse rate is high with all the techniques in current use. The causef relapse is multifactorial and one of the main factors is the type of osteotomy used. Over the last 30 years preference has moved from

andibular sagittal split osteotomy (MSSO) alone, to maxillary procedures only, or to bimaxillary operations, with maxillary procedures

lone being thought to confer the best stability and predictability. The aim of this study was to evaluate the results of correction of anteriorpen bite with the MSSO immediately after operation, and 1 year postoperatively.

2009 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

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eywords: Anterior open bite; Mandibular sagittal split osteotomy; Closure

ntroduction

nterior open bite varies, and is one of the most challengingentofacial deficiencies to treat. The joint orthodontic andrthognathic surgical approach is controversial and resultsan be unpredictable.1 Relapse is multifactorial and cannvolve skeletal and dentoalveolar components. Orthodon-ic treatment involves extrusion of incisors or intrusion of

olars. Dental stability after vertical orthodontic mechanicss unpredictable and is likely to relapse.

Recent reports of intrusion of molars using skeletalnchorage are more encouraging, but to date reported seriesre small.2 One of the main causes of skeletal relapse may be

he type of osteotomy. The type of skeletal fixation may alsoave some influence. Rigid internal fixation confers moretability than intraosseous wire techniques.3–5 Other factors

∗ Corresponding author at: 39 Greenhill Gardens, Merrow, Guildford, GU4HH, United Kingdom. Tel.: +44 7957312298.

E-mail addresses: bbisase@doctors.org.uk (B. Bisase),aul.johnson200@ukonline.co.uk (P. Johnson).

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266-4356/$ – see front matter © 2009 The British Association of Oral and Maxillofaciadoi:10.1016/j.bjoms.2009.08.018

nclude neuromuscular influences on the repositioned jaws.6

arly attempts to close an anterior open bite with mandibularrocedures were mainly segmental,7 but were soon super-eded by posterior impaction of the maxilla at Le Fort I levels this was thought to be more stable.8–10 Proffit et al. classi-ed maxillary impaction as a ‘highly stable’ movement.11

owever, Lo and Shapiro examined the stability of max-llary operations after correction of anterior open bite andound that 25% of 40 patients had no incisal overlap 5 yearsnd 10 months postoperatively.12 Recently, interest has beenekindled in re-establishing a place for mandibular surgerylone.6,13 Anticlockwise rotation of the mandible to close annterior open bite offers certain advantages. In a class II casehere mandibular advancement is also required it is possi-le to limit intervention to a single jaw, thereby avoiding thencreased morbidity associated with a bimaxillary procedure.n addition, the possible adverse aesthetic effects of a max-

llary procedure with posterior impaction can be avoided. Inases with retrogenia, anticlockwise rotation of the mandibleesults in increased prominence of the chin. A genioplastyay thereby be avoided. Oliveira and Bloomquist13 cited an

l Surgeons. Published by Elsevier Ltd. All rights reserved.

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nitial study carried out by Horwitz et al. In a preliminary eval-ation of the long-term stability of mandibular sagittal splitsteotomies (MSSO) to close anterior open bites. They foundhat after 4 years and 6 months only 2/20 cases studied hadelapsed to a point where there was no incisor overlap. To datehere are limited data, but what there are, are encouraging.

The purpose of this study was to evaluate our results oforrection of anterior open bite using the MSSO with rigidnternal fixation immediately postoperatively and 1 year later.

atients and methods

e made a retrospective review of records of 12 adult patientsonsecutively treated for anterior skeletal open bite withSSO. All procedures were done by a single surgeon usingunsuck and Dalpont modifications. The inclusion criteria

or analysis were: complete clinical records for a minimumf 1 year (including lateral cephalometry and study models);nd rigid internal bicortical screw fixation on each side.

Data collected included patients’ age, sex, and preoper-tive malocclusion pattern including the degree of anteriorpen bite. The procedure, specific pattern of fixation, andny immediate complications were also recorded.

Exclusion criteria were: patients who sucked their thumbshen this was regarded as the cause of the anterior open bite;atients in whom the tongue was thought to be a contributoryactor because of its size; and conditions that affected theemporomandibular joint (TMJ).

Data were recorded from preoperative and postop-rative records. These included clinical documentationnd cephalometry immediately postoperatively, at the firstollow-up appointment (1–2 weeks), and at 1 year.

esults (Table 1)

ifteen patients were identified, but 3 were excluded becauseecords were incomplete (n = 2) and one had possible ongoingondylar resorption that had been suspected preoperatively.

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able 1esults.

ase no. Skeletalpattern

Maxillomandibularangle (◦)

Anterior openbite (mm)

Fix(2.

1 III 47 5 3/32 III 33 4 3/33 II 32 2 3/34 II 35 2 3/35 II 42 4 3/36 II 43 4 3/37 I 33 2 3/38 I 44 5 3/39 II 34 4 4/50 II 30 2 3/31 II 40 2 3/32 II 39 4 3/3

xillofacial Surgery 48 (2010) 352–355 353

welve cases met the criteria, of which 4 were male and 8ere female, and mean age at operation 19 (range 15–25)ears. Patients presented with skeletal tendencies towardslass II in 8/12 cases and towards class III in 2. The meanaxillomandibular angle was 37.6◦ with a range of 30–47◦.Vertical anterior open bite was 2 mm in 5/12, 4 mm in

/12, and 5 mm in 2. Eleven of the 12 cases were fixed withmm × 2.0 mm titanium bicortical positional screws on each

ide, and 1 with 4 screws on one side and 5 on the other usinghe same system. This case required removal of wisdom teetht the same time.

All 12 cases had class I incisal relations (overbite 1–2 mm)t the end of the operation, and at the first surgical review(1–2eeks postoperatively).At 1 year, 10/12 presented with a stable class I incisal rela-

ion similar to the immediate postoperative measurements.wo of the 12 cases presented with an edge-to-edge incisorelation. There was no relapse of anterior open bite, and noases of condylar resorption at 1 year.

Although there are too few patients in each group for sta-istical analysis of the correlation of the maxillomandibularngle and relapse of anterior open bite, it is noteworthy thathe cases with higher angles (43–47◦, cases 1, 6 and 8, Table 1)ach had a relapse of 1 mm at 1 year.

iscussion

he main indication for treatment of an anterior open bitey posterior maxillary impaction is the presence of poste-ior maxillary vertical maxillary excess, which is common.bout a third of patients who present with orthognathic con-

erns have vertical maxillary excess. It is also reported thatbout 60% of patients with it also have an open bite, or aendency to an open bite.14 It follows that many patients whore operated on to correct anterior open bites may require

axillary surgery. Where the vertical and anterior–posterior

osition of the maxilla is within reasonable limits there isess of an indication to operate on the maxilla, except whent is thought to be the most stable technique to close an ante-

ation screws0) L/R

Overbite after operation (mm)

Immediately At 1–2 weeks At 12 months

1 1 01 1 12 2 11 1 12 2 21 1 01 1 12 2 11 1 12 2 21 1 12 2 1

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54 B. Bisase et al. / British Journal of Oral

ior open bite. Although many studies have reported bettertability with a maxillary procedure, the patients are hetero-eneous and include those with appreciable vertical maxillaryiscrepancies.15,16 Few compare or report on cases where theaxilla was in a favourable position without a posterior verti-

al maxillary extension. The height of the mandibular ramusnd the clinical state of the condyles are factors only recentlymphasised as useful contributors to aiding the decision abouthe choice of procedure.6 Patients with a short mandibu-ar ramus, normal condyles, no sign of ongoing resorption,nd a well positioned maxilla (no posterior maxillary excess)ould lend themselves to an MSSO alone as the proceduref choice.

There have been few publications about mandibularurgery alone, with the few studies published including sam-le sizes of only 15–30.13,17 This may reflect the limitedumber of cases that are appropriate for such a procedure,r may reflect the blanket treatment selected by many, basedn the heterogeneous case-mix previously analysed, whichuggests universally more stability with maxillary surgery.

The former explanation is exemplified by the small num-er of cases in our series, as only a few met the inclusionriteria. Our results suggest that in selected cases mandibularurgery alone is appropriate and allows a stable result.

Studies that describe or compare mandibular anticlock-ise rotational movements alone do not clarify the techniquef sagittal split osteotomy, and whether this was conventionalr modified. In particular, with reference to the posteriorxtension of the cut in the medial ramus, ensuring a split thatllows part of the medial pterygoid to remain attached to theroximal segment and to stripping of the pterygomassetericling, medial pterygoid, and stylomandibular ligament fromhe distal segment.6 These manoeuvres during a modifiededial ramus osteotomy (“short split technique”)8 reduce

he risk that the medial pterygoid muscle may contribute toorces that encourage relapse when closing an anterior openite with the mandible. Other factors thought to contributeo relapse (but to a lesser degree) are the stretching of non-

uscular soft tissue and neuromuscular activity. Both factorsre thought to adapt early postoperatively rather than causeelapse.

Various studies have suggested that rigid fixation confersreater stability than other methods in the closure of anteriorpen bite.18 Most of these data, however, relate to fixationith wire compared with mini-plates. It has been suggested

hat rigid fixation using positional screws in the closure ofn anterior open bite may confer better surgical stability thanemirigid mini-plates, and was therefore the preferred methodsed by the surgeon in this series.13,15,18,19

Although maxillary osteotomy is done regularly withew complications, morbidity still exists and can be life-hreatening, in particular bleeding. In practice some patients

ho need closure of an anterior open bite may also require

n increased prominence of the chin. This would necessitatedvancement genioplasty if the correction of the anterior openite was to be achieved by maxillary surgery only. Anticlock-

xillofacial Surgery 48 (2010) 352–355

ise rotation of the mandible has the aesthetic advantagef addressing this deficit, and avoids the risks and morbid-ty associated to advancement genioplasty as an additionalrocedure. Bimaxillary surgery, although advocated in thelosure of anterior open bite, may present a higher risk oforbidity than either maxillary or mandibular surgery alone.ublished evidence has recognised the risks of relapse with

his procedure11,16 and means that care must be taken in cal-ulating the definite need for double jaw surgery to optimiseisk/benefit for the patient. We suggest that patients whoeet similar inclusion and exclusion criteria to those thate studied should be considered for correction by mandibu-

ar surgery alone to minimise such risks. Although there areew published reports, a growing numbers of surgeons arettempting and reporting this technique to close anterior openite.6,13,17

The limitations in this study included the difficultyf obtaining complete information about the degree ofrthodontic preoperative decompensation, in particular wors-ning the overbite, and also limitations related to sample sizend short follow-up (which should ideally be 2 and 5 years).hese aspects will be addressed in a future prospective study.

onclusion

ur results suggest that the results following the closure ofnterior open bites by mandibular anti-clockwise rotation aret least as stable as AOB’s closed by maxillary impaction.e suggest that consideration should be given to the use ofmandibular procedure alone in the presence of certain con-itions such as the existence of a normal maxilla, in Class IIases where mandibular advancement is also required and theresence of retrogenia where mandibular rotation can obviatehe need for a genioplasty.

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