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J Oral Maxillofac Surg66:1895-1900, 2008

Closer Look at the Stability of SurgicallyAssisted Rapid Palatal Expansion

Sylvain Chamberland, DMD, MSc,* and

William R. Proffit, DDS, PhD†

Purpose: To assess the amount of dental and skeletal expansion and stability after surgically assistedrapid maxillary expansion (SARPE).

Patients and Methods: Data from 20 patients enrolled in this prospective study were collected beforetreatment, at maximum expansion, at the removal of the expander 6 months later, before any secondsurgical phase, and at the end of orthodontic treatment, using posteroanterior cephalograms and dentalcasts.

Results: With SARPE, the mean maximum expansion at the first molar was 7.48 � 1.39 mm, and themean relapse during postsurgical orthodontics was 2.22 � 1.39 mm (30%). At maximum, a 3.49 � 1.37mm skeletal expansion was obtained, and this expansion was stable, such that the average net expansionwas 67% skeletal.

Conclusion: Clinicians should anticipate a loss of about one third of the transverse dental expansionobtained with SARPE, although the skeletal expansion is quite stable. The amount of postsurgical relapsewith SARPE appears quite similar to the changes in dental-arch dimensions after nonsurgical rapid palatalexpansion, and also quite similar to dental-arch changes after segmental maxillary osteotomy forexpansion.© 2008 American Association of Oral and Maxillofacial Surgeons

J Oral Maxillofac Surg 66:1895-1900, 2008

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lthough a number of reports on stability after surgi-ally assisted rapid palatal expansion (SARPE) haveeen published, surprisingly little detailed informa-ion exists to document postsurgical changes withhis procedure, and to differentiate between dentalnd skeletal outcomes. This is the case for 2 reasons:ost of the previous studies used only dental casts or

irect measurements of dental-arch dimensions, with-ut the use of posteroanterior cephalograms (P-Aephs) so that skeletal change could be differentiatedrom tooth movement,1-5 and stability was often re-orted from the end of postexpansion orthodonticreatment, and not from the point of maximumxpansion.1-4

*Part-time Clinical Teacher and Lecturer, Faculté de Médecine

entaire, Université Laval; and Private Practice, Quebec City, Que-

ec, Canada.

†Professor, Department of Orthodontics, School of Dentistry,

niversity of North Carolina, Chapel Hill, NC.

Address correspondence and reprint requests to Dr Chamber-

and: 10345 Boulevard de l’Ormiere, Quebec City, Quebec G2B

L2, Canada; e-mail: drsylchamberland@biz.videotron.ca

2008 American Association of Oral and Maxillofacial Surgeons

278-2391/08/6609-0016$34.00/0

aoi:10.1016/j.joms.2008.04.020

1895

More recent papers using pre-expansion and post-xpansion P-A cephs and dental casts have reportedore change than earlier papers. In a series of 14

ases, Byloff and Mossaz observed a mean 8.7-mmxpansion at the first molar, and on average, 36% ofhis expansion (3.1 mm) had relapsed on debonding.6

he skeletal expansion involved 1.3 mm, or 24%, ofhe dental expansion. Berger et al reported an averagef 2.49 mm of skeletal expansion (52% of dentalxpansion).7 Nevertheless, 2 recent systematic re-iews concluded that no good evidence exists for themount of relapse after SARPE.8,9

Our research project sought to provide detailedata for both dental and skeletal stability after SARPE,nd to put outcomes in the context of stability afteronsurgical orthopedic maxillary expansion and ex-ansion with segmental Le Fort I osteotomy.

atients and Methods

Twenty patients aged between 15 and 54 years,articipating in a prospective, observational study ofARPE outcomes approved by the Laval Universitythics Committee, received dental casts and P-Aephalograms before SARPE (time-point [T] 1), at theompletion of expansion (T2), at the removal of thexpander approximately 6 months later (T3), before

ny second surgical phase (T4), and at the end of

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rthodontic treatment (T5). All had a transverse dis-repancy of 5 mm or more, and were beyond the levelf maturity at which palatal expansion without sur-ery would be possible (age range, 15 to 54 years).The surgical technique involved essentially all bone

uts required for a Le Fort I osteotomy, and included theeparation of the pterygoid junction and the separationf the midpalatal suture between the incisor roots withthin osteotome.10-13 During surgery, the expansion

evice (Superscrew; Superscrew Superspring Co, High-ood, IL) was activated sufficiently to achieve a 1- to

.5-mm separation of the maxillary central incisors. Allurgery was performed by the same surgeon.

A latency period of 7 days was observed, and thenatients were instructed to activate the screw by 0.25m twice a day. Patients were monitored twice aeek until the planned expansion was achieved, 12

o 20 days later. Brackets were bonded on the maxil-ary teeth 2 months after the expansion had stopped.ctive orthodontic treatment was usually initiated be-

ore SARPE in the mandibular arch, and 2 months afterxpansion had stopped in the maxillary arch. The ex-ansion device was kept in place for approximately 6onths. Following the removal of the expansion device,

o other retention except the main arch wire was usedntil the end of orthodontic treatment.Standardized P-A cephs14 were digitized usinguick Ceph 2000 (Quick Ceph Systems, San Diego,

IGURE 1. Width measurements on P-A cephalometric radio-raphs used in this study. Maxillary (MX) width was measuredetween jugula left (JL) and right (JR), with jugula defined as theoint on the jugal process at the intersection of the outline of theaxillary tuberosity and the zygomatic process. Nasal-cavity (NC)idth was measured between the left and right points at the max-

mum concavity of the piriform rim. Mandibular width was mea-ured between antegonion (AG) left and right.

hamberland and Proffit. Closer Look at SARPE. J Oral Maxillo-ac Surg 2008.

A), and maxillary width changes were evaluated asCf

hanges in distance between the jugula (left andight), and changes in the width of the nasal cavityFig 1). Measurements of dental casts to evaluatehanges in tooth positions were performed at eachime point, using a digital caliper. Intercanine widthsere measured at the cusp tip. The inter-premolar

first and second) widths were measured in the mesialossa, and the intermolar (first and second) widthsere measured in the central fossa.The width of the expansion screw was measured

efore cementation (T1). After removal of the ex-ander (T3), the appliance was poured into labora-ory stone, and the screw width was measured again.he screw width was also measured on the P-A cepht T1 and T2. These measurements were used toalculate the true enlargement factor of the cephalo-ram, which was 4%.The method error was tested on dental casts and P-A

ephs. Every measurement of the dental casts at T5 wasepeated, and every P-A ceph at T5 was retraced. Pear-on correlations indicated a coefficient of fidelity of9.94% for the measurements of dental casts, and of9.90% for the P-A cephs. Statistical significance be-ween baseline and post treatment data collection wasssessed using Student t tests, Wilcoxon rank tests,aired t tests, 1-way analysis of variance, and repeated-easures analysis of variance.

esults

Changes during expansion (T1 to T3), changes afterxpansion (T3 to T5), and net expansion (T1 to T5)re shown in Figure 2. All changes were significantlyifferent from zero (P � .001), except those for the

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1st lower molar

2nd molar

1st molar

2nd premolar

1st premolar

Canine

IGURE 2. Changes in arch width with SARPE. All maxillaryhanges were statistically significantly different from zero; the man-ibular first molar change was not. Blue, changes during expan-ion (T1 to T3). Red, postexpansion changes (T3 to T5). Yellow, netxpansion (T1 to T5).

hamberland and Proffit. Closer Look at SARPE. J Oral Maxillo-ac Surg 2008.

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ower molar (not significant). Note that the amount ofxpansion at the molars was very similar to the ex-ansion at the first premolar (P � .95). This showshe parallelism of the expansion of the posterioreeth.

The amount of skeletal expansion with SARPE andts stability are shown in Figure 3. Almost all theelapse was dental, rather than skeletal. The skeletalxpansion measured at both the jugula and the nasalavity was quite stable, and the percentage of expan-ion because of skeletal change increased from 47% to8% as dental relapse occurred. At time of expansion,ll patients were expanded 2 mm beyond the ex-ected final position, and despite the dental relapse,one of the patients showed posterior crossbite at thend of treatment.Of 20 subjects, 8 underwent second-stage maxillary

urgery for anteroposterior or vertical repositioning,nd 5 underwent mandibular advancement only.here was no significant effect of phase 2 surgery on

ransverse relapses.

iscussion

COMPARISON TO OTHER STUDIES OF SARPE

The mean expansion at the first molar observed in

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IGURE 3. Changes over time after SARPE in dental and skeletalimensions, and in percentage of expansion that was skeletal.ote that almost all relapse was dental, rather than skeletal. Re-eated-measures analysis of variance confirmed a significant rela-

ionship between amount of relapse and time elapsed after surgery.lue line with squares indicates expansion at first molar. Red line withiamonds indicates percentage of expansion that was skeletal at each

ime point. Green line with Xs indicates maxillary skeletal expansiont jugula. Magenta line with triangles indicates expansion acrossasal cavity.

hamberland and Proffit. Closer Look at SARPE. J Oral Maxillo-ac Surg 2008.

he SARPE group was similar to that in previous stud- r

es using a comparable research design. The 30%elapse is less than the 36% relapse reported by Byloffnd Mossaz.6 Post-treatment retention is likely to ben important factor in any study of stability.15 In ourtudy, the expander was left in place for 6 monthsstandard deviation, 5.98 � 0.72 months) after thexpansion had stopped, whereas Byloff and Mossaz6

eft the distractor in for 3 months, and then used aemovable retainer for 3 months. The 30% relapse isigher than that reported by Berger et al7 and Pogrelt al.5 Both of those studies used 12 months of follow-p, rather than the end of orthodontic treatment, asheir endpoint. The relapse we found is considerablyigher than in reports from earlier studies that re-orted changes from the end of treatment, and not

rom the point of maximal expansion.1-4

The amount of dental versus skeletal expansionbserved in our SARPE patients, and in other stud-

es6,7,16 using P-A cephs, is larger than clinicians oftenxpect. Immediately after maximum expansion,bout half the expansion (47%) was skeletal, as showny a widening of the maxilla and nasal cavity, andbout half the expansion (53%) was dental. The skel-tal expansion with SARPE was quite stable: the re-apse was almost totally attributable to lingual move-

ent of the posterior teeth. It was recommendedreviously that a 2-mm expansion beyond the desiredesult should be performed. Because a mean relapsef about 30% at the first molars can be expected, weoncur that a 2-mm excess expansion is indicated inARPE patients with a typical expansion of 7 to 8 mmt the first molar. This is needed to compensate foruccal tipping of the entire posterior segment duringxpansion. Interestingly, there is no correlation be-ween the amount of expansion and the amount ofelapse at the first molar (r � 0.01).

The width of the midline diastema at the maximumxpansion point (T2) is highly correlated with therst molar expansion (r � 0.69). This indicates thathe development of a diastema is a predictor thatdequate molar expansion is occurring.

Even when skeletal expansion is obtained, the loworrelation between skeletal changes and dentalhanges (r � 0.36) confirms that the maxillary seg-ents often do not expand symmetrically. Instead,

ome rotation occurs, with the teeth expanding moreidely than the bone above, as explained by Byloff

nd Mossaz,6 and as demonstrated by Chung andoldman.17 This rotation of the maxillary segments orlveolar bending explains why the skeletal change athe maximal expansion point is only 47% of the dentalxpansion (Fig 3). Hence, the horizontal portion ofhe screw should be more than 3 mm away from thealatal mucosa, to avoid impingement.Interestingly, this study did not confirm previous

eports of a hinge-type expansion with SARPE, with

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ore expansion anteriorly than posteriorly (Fig 2).his suggests that changes in recent years in theurgical procedure for SARPE, which now includesurgical release of the pterygoid junction, may allow aimilar anterior and posterior expansion. The in-reased rigidity of the Superscrew, and its placementore in line with the first molars, may also have

ontributed to the more parallel expansion.18

STABILITY COMPARED WITH NONSURGICAL RAPIDPALATAL EXPANSION

In prepubertal children and adolescents, loss ofbout one third of the maximum expansion across therst molars occurs after nonsurgical rapid palatal ex-ansion.15,19-23 The P-A cephs in patients with palatal

mplants who underwent maxillary expansion demon-trated that approximately 50% of the expansionchieved by rapid palatal expansion (RPE) in childrenas skeletal, and the remainder was dentoalveolar.24,25

Handelman et al22 compared expansion with non-urgical RPE in younger versus older patients, andstimated that skeletal expansion was only 18% inheir adult group, compared with 56% for youngeratients. Baccetti et al19 showed that only 0.9 mm ofkeletal expansion is achieved in RPE patients treateduring or after their peak in skeletal maturation,hereas 3 mm of skeletal expansion was obtained ingroup treated before the peak of skeletal matura-

ion. It is clear that with RPE, the nature of expan-ion shifts from skeletal to dentoalveolar in maturendividuals who are candidates for SARPE. Whenhanges largely involve tooth movement throughhe alveolar housing, it has been shown to be det-imental periodontally.1,26

Our data show a mean 3.47 mm of skeletal expan-ion, which is 68% of the mean dental expansion5.12 mm). Although the amount of relapse in dentalrch widths with SARPE is about the same as withonsurgical RPE in younger patients, there is a differ-nce: with SARPE, the skeletal change is much more

Table 1. RELAPSE BETWEEN MAXIMUM EXPANSION A

Variable

SARPE

n Mean SD % Relap

anine 19 �2.65 1.95 48irst premolar 16 �1.85 2.04 25econd premolar 20 �2.14 2.48 27irst molar 20 �2.22 1.69 30econd molar 18 �4.42 1.80 59

OTE. Variation of n is explained by the fact that someasurements is reduced for those teeth.Abbreviations: NS, no significance; SARPE, surgically assi

hamberland and Proffit. Closer Look at SARPE. J Oral Maxillof

table than with RPE. t

STABILITY COMPARED WITHSEGMENTAL OSTEOTOMY

The best data for stability after transverse expan-ion with segmental Le Fort I osteotomy were re-orted for 42 patients by Phillips et al27 in 1992.omparisons of earlier studies of SARPE stability with

his data set have provided the basis for recommend-ng SARPE as a first stage of treatment, when reposi-ioning of the maxilla in all three dimensions islanned.Stability data for the 12 subjects in Phillips et al27

ho showed expansion equivalent to that of ourARPE patients are shown in Table 1 and Figure 4.he mean relapse across the first molars was greater

or the Le Fort I group, but the difference was nottatistically significant, whereas the mean relapsecross the canines was greater for the SARPE group,nd was significant. The greater change at the caninesor the SARPE group almost surely reflects toothovement generated by the finishing arch wires.ather than mean changes, Figure 4 shows the num-er of patients with SARPE and Le Fort I expansion,ith changes of specific magnitudes across the firstolars and first premolars. The similarity of distribu-

ions is apparent.

CLINICAL IMPLICATIONS

These data do not support the conclusion of earliertudies of SARPE that this procedure produces moretable expansion than do segmental osteotomies. Ourata are quite compatible, however, with data fromther studies of SARPE that used both P-A cephs andeasurements of dental casts, and found significantostsurgical changes.It seems clear at this point that relapse in the

mount of arch-width increase produced by SARPE isomparable to the relapse with other expansion pro-edures. Our data show that with SARPE, the relapses almost entirely dental, so that at the end of treat-

ent, there is a net skeletal expansion of 67% of the

) END OF TREATMENT (T5)

Le Fort I Control Group

Significancen Mean SD % Relapse

12 �0.74 1.84 32 P � .059 �1.32 1.67 33 NS

11 �2.06 1.45 39 NS12 �3.06 1.31 42 NS

8 �3.69 1.08 40 NS

ents underwent extraction of teeth, so that number of

pid palatal expansion; SD, standard deviation.

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atients, the expectation is that 50% of the totalhange will be skeletal. No data from sequential P-Aephs exist for Le Fort I expansion.The clinical results involving our SARPE patients,

one of whom showed posterior crossbite at the endf treatment despite their dental relapse, support theoutine use of a 2-mm overexpansion during treat-ent. In the Le Fort I patients reported by Philips

t al,27 overexpansion was not performed. Given theimilarity of relapse in intermolar width between theARPE and Le Fort I patients, it appears that routineverexpansion should also be part of the protocol for

First Molar

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IGURE 4. Percentage of patients with major relapse (�3 mm),oderate relapse (1 to 3 mm), minimal change (–1 to 1 mm), andost-treatment expansion. A, After SARPE (first molars, n � 20; firstremolars, n �16). B, After Le Fort I segmental osteotomy (firstolars, n � 12; first premolars, n � 9). Variation of n is explainedy the fact that some patients underwent extraction of teeth, so that

he number of measurements is reduced for those teeth.

hamberland and Proffit. Closer Look at SARPE. J Oral Maxillo-ac Surg 2008.

xpansion with osteotomy. With SARPE, space for the

lignment of crowded maxillary incisors can be pro-ided by maxillary expansion rather than premolarxtraction. Thus decisions about extraction should beostponed until after the expander is removed.The similar stabilities of transverse expansion of the

ental arches with SARPE and segmental Le Fort Isteotomies provide some insight into the choiceetween procedures. In our view, when only a trans-erse change is needed, SARPE would be the treat-ent of choice. When a second phase of maxillary

urgery to reposition the maxilla vertically or antero-osteriorly is required, the routine performance of areliminary SARPE procedure to obtain better trans-erse stability does not appear to be warranted.28 Anxceptionally narrow maxilla that requires major ex-ansion across the posterior teeth may be an excep-ion.29 Perhaps a current consensus view would statehat the decision for a 2-stage versus 1-stage Le Fort Iurgery should be based not on the stability of trans-erse expansion, but on the risk and morbidity of 2urgeries versus the risk and morbidity of 1-stage,ultisegmented Le Fort I for large expansion alongith vertical or anteroposterior changes.In conclusion, our findings are that:

1) Skeletal expansion with SARPE involves abouthalf the total intermolar expansion at the maxi-mum expansion point. From that point, dentalrelapse occurs, but the skeletal expansion isstable, so that at the end of treatment, about twothirds of the net expansion is skeletal.

2) The transverse stability of SARPE is not signifi-cantly greater than that of segmental Le Fort Iosteotomy, bringing into question the routine useof 2-stage surgery as a way to improve transversestability in patients who require widening andanteroposterior or vertical repositioning of themaxilla.

cknowledgments

We thank Jean-Paul Goulet, DDS, MSD, FRCD(C), and Andréournier, DMD, for their direction and co-direction of this Master’segree project, Dany Morais, DMD, FRCD(C), Oral and Maxillofa-ial Surgeon, for careful surgical treatment, and Gaetan Daigle,Stat, for statistical consultation and statistical analysis. This projectas supported in part by grant DE-05221 from the National Insti-

ute of Dental and Craniofacial Research of the National Institutesf Health (Bethesda, MD).

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1900 CLOSER LOOK AT SARPE

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