Purpose: To assess the amount of dental and skeletal expansion and stability after surgically assisted rapid maxillary expansion (SARPE). Patients and Methods: Data from 20 patients enrolled in this prospective study were collected before treatment, at maximum expansion, at the removal of the expander 6 months later, before any second surgical phase, and at the end of orthodontic treatment, using posteroanterior cephalograms and dental casts. Results: With SARPE, the mean maximum expansion at the first molar was 7.48
1.39 mm, and the mean relapse during postsurgical orthodontics was 2.22
1.39 mm (30%). At maximum, a 3.49
1.37 mm skeletal expansion was obtained, and this expansion was stable, such that the average net expansion was 67% skeletal. Conclusion: Clinicians should anticipate a loss of about one third of the transverse dental expansion obtained with SARPE, although the skeletal expansion is quite stable. The amount of postsurgical relapse with SARPE appears quite similar to the changes in dental-arch dimensions after nonsurgical rapid palatal expansion, and also quite similar to dental-arch changes after segmental maxillary osteotomy for expansion.

1. J Oral Maxillofac Surg
66:1895-1900, 2008
Closer Look at the Stability of Surgically
Assisted 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 assisted
rapid maxillary expansion (SARPE).
Patients and Methods: Data from 20 patients enrolled in this prospective study were collected before
treatment, at maximum expansion, at the removal of the expander 6 months later, before any second
surgical phase, and at the end of orthodontic treatment, using posteroanterior cephalograms and dental
casts.
Results: With SARPE, the mean maximum expansion at the first molar was 7.48 1.39 mm, and the
mean relapse during postsurgical orthodontics was 2.22 1.39 mm (30%). At maximum, a 3.49 1.37
mm skeletal expansion was obtained, and this expansion was stable, such that the average net expansion
was 67% skeletal.
Conclusion: Clinicians should anticipate a loss of about one third of the transverse dental expansion
obtained with SARPE, although the skeletal expansion is quite stable. The amount of postsurgical relapse
with SARPE appears quite similar to the changes in dental-arch dimensions after nonsurgical rapid palatal
expansion, and also quite similar to dental-arch changes after segmental maxillary osteotomy for
expansion.
© 2008 American Association of Oral and Maxillofacial Surgeons
J Oral Maxillofac Surg 66:1895-1900, 2008
Although a number of reports on stability after surgi- More recent papers using pre-expansion and post-
cally assisted rapid palatal expansion (SARPE) have expansion P-A cephs and dental casts have reported
been published, surprisingly little detailed informa- more change than earlier papers. In a series of 14
tion exists to document postsurgical changes with cases, Byloff and Mossaz observed a mean 8.7-mm
this procedure, and to differentiate between dental expansion at the first molar, and on average, 36% of
and skeletal outcomes. This is the case for 2 reasons: this expansion (3.1 mm) had relapsed on debonding.6
most of the previous studies used only dental casts or The skeletal expansion involved 1.3 mm, or 24%, of
direct measurements of dental-arch dimensions, with- the dental expansion. Berger et al reported an average
out the use of posteroanterior cephalograms (P-A of 2.49 mm of skeletal expansion (52% of dental
cephs) so that skeletal change could be differentiated expansion).7 Nevertheless, 2 recent systematic re-
views concluded that no good evidence exists for the
from tooth movement,1-5 and stability was often re-
amount of relapse after SARPE.8,9
ported from the end of postexpansion orthodontic
Our research project sought to provide detailed
treatment, and not from the point of maximum
data for both dental and skeletal stability after SARPE,
expansion.1-4
and to put outcomes in the context of stability after
nonsurgical orthopedic maxillary expansion and ex-
*Part-time Clinical Teacher and Lecturer, Faculté de Médecine pansion with segmental Le Fort I osteotomy.
Dentaire, Université Laval; and Private Practice, Quebec City, Que-
bec, Canada. Patients and Methods
†Professor, Department of Orthodontics, School of Dentistry,
University of North Carolina, Chapel Hill, NC. Twenty patients aged between 15 and 54 years,
Address correspondence and reprint requests to Dr Chamber- participating in a prospective, observational study of
land: 10345 Boulevard de l’Ormiere, Quebec City, Quebec G2B SARPE outcomes approved by the Laval University
3L2, Canada; e-mail: drsylchamberland@biz.videotron.ca Ethics Committee, received dental casts and P-A
© 2008 American Association of Oral and Maxillofacial Surgeons cephalograms before SARPE (time-point [T] 1), at the
0278-2391/08/6609-0016$34.00/0 completion of expansion (T2), at the removal of the
doi:10.1016/j.joms.2008.04.020 expander approximately 6 months later (T3), before
any second surgical phase (T4), and at the end of
1895

2. 1896 CLOSER LOOK AT SARPE
changes in distance between the jugula (left and
right), and changes in the width of the nasal cavity
(Fig 1). Measurements of dental casts to evaluate
changes in tooth positions were performed at each
time point, using a digital caliper. Intercanine widths
were measured at the cusp tip. The inter-premolar
(first and second) widths were measured in the mesial
fossa, and the intermolar (first and second) widths
were measured in the central fossa.
The width of the expansion screw was measured
before cementation (T1). After removal of the ex-
pander (T3), the appliance was poured into labora-
tory stone, and the screw width was measured again.
The screw width was also measured on the P-A ceph
at T1 and T2. These measurements were used to
calculate the true enlargement factor of the cephalo-
gram, which was 4%.
FIGURE 1. Width measurements on P-A cephalometric radio- The method error was tested on dental casts and P-A
graphs used in this study. Maxillary (MX) width was measured cephs. Every measurement of the dental casts at T5 was
between jugula left (JL) and right (JR), with jugula defined as the
point on the jugal process at the intersection of the outline of the repeated, and every P-A ceph at T5 was retraced. Pear-
maxillary tuberosity and the zygomatic process. Nasal-cavity (NC) son correlations indicated a coefficient of fidelity of
width was measured between the left and right points at the max- 99.94% for the measurements of dental casts, and of
imum concavity of the piriform rim. Mandibular width was mea-
sured between antegonion (AG) left and right. 99.90% for the P-A cephs. Statistical significance be-
Chamberland and Proffit. Closer Look at SARPE. J Oral Maxillo-
tween baseline and post treatment data collection was
fac Surg 2008. assessed using Student t tests, Wilcoxon rank tests,
paired t tests, 1-way analysis of variance, and repeated-
measures analysis of variance.
orthodontic treatment (T5). All had a transverse dis-
crepancy of 5 mm or more, and were beyond the level
Results
of maturity at which palatal expansion without sur-
gery would be possible (age range, 15 to 54 years). Changes during expansion (T1 to T3), changes after
The surgical technique involved essentially all bone expansion (T3 to T5), and net expansion (T1 to T5)
cuts required for a Le Fort I osteotomy, and included the are shown in Figure 2. All changes were significantly
separation of the pterygoid junction and the separation different from zero (P .001), except those for the
of the midpalatal suture between the incisor roots with
a thin osteotome.10-13 During surgery, the expansion
device (Superscrew; Superscrew Superspring Co, High-
Canine
wood, IL) was activated sufficiently to achieve a 1- to
1.5-mm separation of the maxillary central incisors. All
1st premolar
surgery was performed by the same surgeon.
A latency period of 7 days was observed, and then
2nd premolar
patients were instructed to activate the screw by 0.25
mm twice a day. Patients were monitored twice a
1st molar
week until the planned expansion was achieved, 12
to 20 days later. Brackets were bonded on the maxil-
2nd molar
lary teeth 2 months after the expansion had stopped.
Active orthodontic treatment was usually initiated be-
1st lower molar
fore SARPE in the mandibular arch, and 2 months after
expansion had stopped in the maxillary arch. The ex- -6 -4 -2 0 2 4 6 8
pansion device was kept in place for approximately 6
months. Following the removal of the expansion device, FIGURE 2. Changes in arch width with SARPE. All maxillary
no other retention except the main arch wire was used changes were statistically significantly different from zero; the man-
dibular first molar change was not. Blue, changes during expan-
until the end of orthodontic treatment. sion (T1 to T3). Red, postexpansion changes (T3 to T5). Yellow, net
Standardized P-A cephs14 were digitized using expansion (T1 to T5).
Quick Ceph 2000 (Quick Ceph Systems, San Diego, Chamberland and Proffit. Closer Look at SARPE. J Oral Maxillo-
CA), and maxillary width changes were evaluated as fac Surg 2008.

3. CHAMBERLAND AND PROFFIT 1897
ies using a comparable research design. The 30%
relapse is less than the 36% relapse reported by Byloff
7.00
68
70
and Mossaz.6 Post-treatment retention is likely to be
an important factor in any study of stability.15 In our
6.00 60
study, the expander was left in place for 6 months
52
(standard deviation, 5.98 0.72 months) after the
5.00 50
47 expansion had stopped, whereas Byloff and Mossaz6
46
left the distractor in for 3 months, and then used a
4.00 40
removable retainer for 3 months. The 30% relapse is
higher than that reported by Berger et al7 and Pogrel
3.00 30
et al.5 Both of those studies used 12 months of follow-
up, rather than the end of orthodontic treatment, as
2.00 20
their endpoint. The relapse we found is considerably
higher than in reports from earlier studies that re-
1.00 10
ported changes from the end of treatment, and not
from the point of maximal expansion.1-4
0.00 0
0.42 7.87 14.4 20.7
The amount of dental versus skeletal expansion
observed in our SARPE patients, and in other stud-
FIGURE 3. Changes over time after SARPE in dental and skeletal ies6,7,16 using P-A cephs, is larger than clinicians often
dimensions, and in percentage of expansion that was skeletal. expect. Immediately after maximum expansion,
Note that almost all relapse was dental, rather than skeletal. Re- about half the expansion (47%) was skeletal, as shown
peated-measures analysis of variance confirmed a significant rela-
tionship between amount of relapse and time elapsed after surgery. by a widening of the maxilla and nasal cavity, and
Blue line with squares indicates expansion at first molar. Red line with about half the expansion (53%) was dental. The skel-
diamonds indicates percentage of expansion that was skeletal at each etal expansion with SARPE was quite stable: the re-
time point. Green line with Xs indicates maxillary skeletal expansion
at jugula. Magenta line with triangles indicates expansion across lapse was almost totally attributable to lingual move-
nasal cavity. ment of the posterior teeth. It was recommended
Chamberland and Proffit. Closer Look at SARPE. J Oral Maxillo- previously that a 2-mm expansion beyond the desired
fac Surg 2008. result should be performed. Because a mean relapse
of about 30% at the first molars can be expected, we
lower molar (not significant). Note that the amount of concur that a 2-mm excess expansion is indicated in
expansion at the molars was very similar to the ex- SARPE patients with a typical expansion of 7 to 8 mm
pansion at the first premolar (P .95). This shows at the first molar. This is needed to compensate for
the parallelism of the expansion of the posterior buccal tipping of the entire posterior segment during
teeth. expansion. Interestingly, there is no correlation be-
The amount of skeletal expansion with SARPE and tween the amount of expansion and the amount of
its stability are shown in Figure 3. Almost all the relapse at the first molar (r 0.01).
relapse was dental, rather than skeletal. The skeletal The width of the midline diastema at the maximum
expansion measured at both the jugula and the nasal expansion point (T2) is highly correlated with the
cavity was quite stable, and the percentage of expan- first molar expansion (r 0.69). This indicates that
sion because of skeletal change increased from 47% to the development of a diastema is a predictor that
68% as dental relapse occurred. At time of expansion, adequate molar expansion is occurring.
all patients were expanded 2 mm beyond the ex- Even when skeletal expansion is obtained, the low
pected final position, and despite the dental relapse, correlation between skeletal changes and dental
none of the patients showed posterior crossbite at the changes (r 0.36) confirms that the maxillary seg-
end of treatment. ments often do not expand symmetrically. Instead,
Of 20 subjects, 8 underwent second-stage maxillary some rotation occurs, with the teeth expanding more
surgery for anteroposterior or vertical repositioning, widely than the bone above, as explained by Byloff
and 5 underwent mandibular advancement only. and Mossaz,6 and as demonstrated by Chung and
There was no significant effect of phase 2 surgery on Goldman.17 This rotation of the maxillary segments or
transverse relapses. alveolar bending explains why the skeletal change at
the maximal expansion point is only 47% of the dental
Discussion expansion (Fig 3). Hence, the horizontal portion of
the screw should be more than 3 mm away from the
COMPARISON TO OTHER STUDIES OF SARPE palatal mucosa, to avoid impingement.
The mean expansion at the first molar observed in Interestingly, this study did not confirm previous
the SARPE group was similar to that in previous stud- reports of a hinge-type expansion with SARPE, with

4. 1898 CLOSER LOOK AT SARPE
Table 1. RELAPSE BETWEEN MAXIMUM EXPANSION AND (T3) END OF TREATMENT (T5)
SARPE Le Fort I Control Group
Variable n Mean SD % Relapse n Mean SD % Relapse Significance
Canine 19 2.65 1.95 48 12 0.74 1.84 32 P .05
First premolar 16 1.85 2.04 25 9 1.32 1.67 33 NS
Second premolar 20 2.14 2.48 27 11 2.06 1.45 39 NS
First molar 20 2.22 1.69 30 12 3.06 1.31 42 NS
Second molar 18 4.42 1.80 59 8 3.69 1.08 40 NS
NOTE. Variation of n is explained by the fact that some patients underwent extraction of teeth, so that number of
measurements is reduced for those teeth.
Abbreviations: NS, no significance; SARPE, surgically assisted rapid palatal expansion; SD, standard deviation.
Chamberland and Proffit. Closer Look at SARPE. J Oral Maxillofac Surg 2008.
more expansion anteriorly than posteriorly (Fig 2). STABILITY COMPARED WITH
This suggests that changes in recent years in the SEGMENTAL OSTEOTOMY
surgical procedure for SARPE, which now includes The best data for stability after transverse expan-
surgical release of the pterygoid junction, may allow a sion with segmental Le Fort I osteotomy were re-
similar anterior and posterior expansion. The in- ported for 42 patients by Phillips et al27 in 1992.
creased rigidity of the Superscrew, and its placement Comparisons of earlier studies of SARPE stability with
more in line with the first molars, may also have this data set have provided the basis for recommend-
contributed to the more parallel expansion.18 ing SARPE as a first stage of treatment, when reposi-
tioning of the maxilla in all three dimensions is
STABILITY COMPARED WITH NONSURGICAL RAPID
planned.
PALATAL EXPANSION
Stability data for the 12 subjects in Phillips et al27
In prepubertal children and adolescents, loss of who showed expansion equivalent to that of our
about one third of the maximum expansion across the SARPE patients are shown in Table 1 and Figure 4.
first molars occurs after nonsurgical rapid palatal ex- The mean relapse across the first molars was greater
pansion.15,19-23 The P-A cephs in patients with palatal for the Le Fort I group, but the difference was not
implants who underwent maxillary expansion demon- statistically significant, whereas the mean relapse
strated that approximately 50% of the expansion across the canines was greater for the SARPE group,
achieved by rapid palatal expansion (RPE) in children and was significant. The greater change at the canines
was skeletal, and the remainder was dentoalveolar.24,25 for the SARPE group almost surely reflects tooth
Handelman et al22 compared expansion with non- movement generated by the finishing arch wires.
surgical RPE in younger versus older patients, and Rather than mean changes, Figure 4 shows the num-
estimated that skeletal expansion was only 18% in ber of patients with SARPE and Le Fort I expansion,
their adult group, compared with 56% for younger with changes of specific magnitudes across the first
patients. Baccetti et al19 showed that only 0.9 mm of molars and first premolars. The similarity of distribu-
skeletal expansion is achieved in RPE patients treated tions is apparent.
during or after their peak in skeletal maturation,
whereas 3 mm of skeletal expansion was obtained in CLINICAL IMPLICATIONS
a group treated before the peak of skeletal matura- These data do not support the conclusion of earlier
tion. It is clear that with RPE, the nature of expan- studies of SARPE that this procedure produces more
sion shifts from skeletal to dentoalveolar in mature stable expansion than do segmental osteotomies. Our
individuals who are candidates for SARPE. When data are quite compatible, however, with data from
changes largely involve tooth movement through other studies of SARPE that used both P-A cephs and
the alveolar housing, it has been shown to be det- measurements of dental casts, and found significant
rimental periodontally.1,26 postsurgical changes.
Our data show a mean 3.47 mm of skeletal expan- It seems clear at this point that relapse in the
sion, which is 68% of the mean dental expansion amount of arch-width increase produced by SARPE is
(5.12 mm). Although the amount of relapse in dental comparable to the relapse with other expansion pro-
arch widths with SARPE is about the same as with cedures. Our data show that with SARPE, the relapse
nonsurgical RPE in younger patients, there is a differ- is almost entirely dental, so that at the end of treat-
ence: with SARPE, the skeletal change is much more ment, there is a net skeletal expansion of 67% of the
stable than with RPE. total change. With nonsurgical expansion in growing

5. CHAMBERLAND AND PROFFIT 1899
alignment of crowded maxillary incisors can be pro-
A SARPE: Post-Tx changes
vided by maxillary expansion rather than premolar
60
extraction. Thus decisions about extraction should be
First Molar postponed until after the expander is removed.
50 First Premolar
The similar stabilities of transverse expansion of the
40
dental arches with SARPE and segmental Le Fort I
osteotomies provide some insight into the choice
between procedures. In our view, when only a trans-
30
verse change is needed, SARPE would be the treat-
ment of choice. When a second phase of maxillary
20
surgery to reposition the maxilla vertically or antero-
posteriorly is required, the routine performance of a
10
preliminary SARPE procedure to obtain better trans-
verse stability does not appear to be warranted.28 An
0
>-3 -3 to -1 -1 to 1 1 to 3 exceptionally narrow maxilla that requires major ex-
Relapse (mm) pansion across the posterior teeth may be an excep-
tion.29 Perhaps a current consensus view would state
LeFort 1:Post-Tx Changes
B 70
that the decision for a 2-stage versus 1-stage Le Fort I
surgery should be based not on the stability of trans-
First Molar verse expansion, but on the risk and morbidity of 2
60
First Premolar surgeries versus the risk and morbidity of 1-stage,
multisegmented Le Fort I for large expansion along
50
with vertical or anteroposterior changes.
40
In conclusion, our findings are that:
30 1) Skeletal expansion with SARPE involves about
half the total intermolar expansion at the maxi-
20 mum expansion point. From that point, dental
relapse occurs, but the skeletal expansion is
10 stable, so that at the end of treatment, about two
thirds of the net expansion is skeletal.
0
2) The transverse stability of SARPE is not signifi-
>-3 -3 to -1 -1 to 1 1 to 3
cantly greater than that of segmental Le Fort I
Relapse (mm) osteotomy, bringing into question the routine use
FIGURE 4. Percentage of patients with major relapse ( 3 mm), of 2-stage surgery as a way to improve transverse
moderate relapse (1 to 3 mm), minimal change (–1 to 1 mm), and stability in patients who require widening and
post-treatment expansion. A, After SARPE (first molars, n 20; first
premolars, n 16). B, After Le Fort I segmental osteotomy (first
anteroposterior or vertical repositioning of the
molars, n 12; first premolars, n 9). Variation of n is explained maxilla.
by the fact that some patients underwent extraction of teeth, so that
the number of measurements is reduced for those teeth. Acknowledgments
Chamberland and Proffit. Closer Look at SARPE. J Oral Maxillo- We thank Jean-Paul Goulet, DDS, MSD, FRCD(C), and André
fac Surg 2008. Fournier, DMD, for their direction and co-direction of this Master’s
Degree project, Dany Morais, DMD, FRCD(C), Oral and Maxillofa-
cial Surgeon, for careful surgical treatment, and Gaetan Daigle,
patients, the expectation is that 50% of the total PStat, for statistical consultation and statistical analysis. This project
change will be skeletal. No data from sequential P-A was supported in part by grant DE-05221 from the National Insti-
tute of Dental and Craniofacial Research of the National Institutes
cephs exist for Le Fort I expansion. of Health (Bethesda, MD).
The clinical results involving our SARPE patients,
none of whom showed posterior crossbite at the end
of treatment despite their dental relapse, support the References
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