Effects of surgically assisted rapid maxillary expansion on mandibular position: a three-dimensional study
Oliveira et al. Progress in Orthodontics
Effects of surgically assisted rapid maxillary expansion on mandibular position: a three- dimensional study
Talles Fernando Medeiros Oliveira 0 3
Valfrido Antônio Pereira-Filho 2
Mario Francisco Real Gabrielli 2
Eduardo Sanches Gonçales 1
Ary Santos-Pinto 0 3
0 Department of Orthodontics, School of Dentistry, São Paulo State University (UNESP) , Rua Humaitá, 1680 , Centro , Araraquara, São Paulo 14801-903 , Brazil
1 Department of Stomatology, School of Dentistry, São Paulo University , Bauru, São Paulo , Brazil
2 Department of Oral and Maxillofacial Surgery, School of Dentistry, São Paulo State University (UNESP) , Araraquara, São Paulo , Brazil
3 Department of Orthodontics, School of Dentistry, São Paulo State University (UNESP) , Rua Humaitá, 1680 , Centro , Araraquara, São Paulo 14801-903 , Brazil
Background: This study aimed to evaluate three-dimensional changes in mandibular position after surgically assisted rapid maxillary expansion (SARME). Methods: A retrospective study was carried out with tomographic records of 30 adult patients with maxillary transverse deficiency who underwent SARME. Cone beam computed tomography scans were obtained preoperatively (T1), after expansion (T2) and 6 months after expansion (T3). Mandibular landmarks were measured with respect to axial, sagittal, and coronal planes. Repeated measures ANOVA was used for statistical analysis. Results: Clockwise rotation and lateral displacement of the mandible were observed immediately after SARME. However, mandibular displacements tended to return close to their initial values at T3. Conclusions: Clockwise rotation and lateral shift of the mandible are transient effects of SARME.
Malocclusion; Palatal expansion technique; Cone beam computed tomography
Surgically assisted rapid maxillary expansion (SARME)
has been widely used to treat the maxillary transverse
deficiency in adult patients [
]. The main effects of
SARME occur transversally; however, skeletal changes in
sagittal and vertical planes as a result of expansion have
also been reported in the literature [
1, 3, 4, 6, 7
Despite the effectiveness of expansion in the
treatment of maxillary transverse deficiencies, the possibility
of causing adverse changes in patient’s profile as a
result of mandibular displacement still causes concern
in the indication of this procedure, mainly in
hyperdivergent patients [
]. The clockwise rotation of the
mandible has been reported as one of the main effects of
SARME on the mandibular positioning; however, there
is no consensus about the extent and stability of these
4, 6, 9, 10
A possible explanation for mandibular rotation after
SARME is the occlusal change due to extrusion and
tipping of maxillary segments and cuspal interferences
as result of expansion . Previous studies that assessed
changes in mandibular position after SARME have
limitations since the cephalometric analysis used does not
allow the three-dimensional evaluation of the
mandibular positioning, consequently lateral displacement of the
mandible due to expansion cannot be assessed. The use
of cone beam computed tomography (CBCT) has
advantages because it allows three-dimensional assessment of
bilateral structures without superimposition and with
minimal distortion [
This study aimed to evaluate the three-dimensional
changes in mandibular positioning after SARME.
This retrospective study assessed the CBCT records of 30
adult patients (mean age, 27.5 years; range 18.7–39.7 years;
19 females and 11 males) with maxillary transverse
deficiency greater than 5 mm and unilateral or bilateral
posterior crossbite. Patients with cleft lip and palate or
congenital craniofacial syndromes were excluded. This
study was approved by the Ethics Committee of the
Araraquara School of Dentistry, UNESP, (protocol
Surgery and treatment protocol
Surgery was carried out under general anesthesia in
hospital environment by two surgeons (V.A.P-F. and
E.S.G.). SARME was performed with Subtotal LeFort I
osteotomy, midpalatal suture separation, and
pterygomaxillary disjunction. Patients were treated with Hyrax
type appliance and activation rate of one quarter turn
(0.2 mm) three times a day until the crossbite
correction. The appliance activation was initiated 7 days
postoperatively. After achieving the intended expansion of
the maxilla width, the appliance was blocked and left in
place for about 4 months. Afterward, it was removed
and replaced by a transpalatal arch.
CBCT scans were acquired preoperatively (T1),
immediately after expansion (T2) and 6 months after expansion
(T3) using an iCAT CBCT scanner (Imaging Sciences
International, Hatfield, PA, USA) set up at 120 kVp,
36 mA, 0.3 mm voxel, and FOV of 17 × 23 cm. The
patients were positioned sitting upright in the natural
head position, and they were instructed to occlude in
maximum habitual intercuspation during the CBCT
scanning. The DICOM files were imported into Dolphin
3D (version 11.5, Dolphin Imaging, Chatsworth, CA,
USA) for further analysis. In order to maintain the same
reference planes in all time points, head orientation of
each data set was standardized using orientation tool in
Dolphin 3D software. The 3D orientation was performed
according to three reference planes obtained from stable
landmarks such as porion, orbitale, and nasion. The
Frankfurt horizontal plane was defined by the right and
left orbitale and the right and left porion landmarks. The
transporionic plane was defined by the right and left
porion landmarks, perpendicular to Frankfurt horizontal
plane. The midsagittal plane was defined as the plane
orthogonal to axial and coronal planes passing through
nasion landmark [
]. Then, the head was moved so that
the previously defined planes were coincident with the
reference planes. The Frankfurt horizontal plane was
oriented to match the axial plane, the transporionic
plane was oriented to match the coronal plane, and the
midsagittal plane was moved to match the sagittal plane
(Fig. 1). Afterward, the mandibular landmarks (Menton,
the right and left condylion and the right and left
gonion) were defined using volume rendering and
multiplanar reconstruction (Fig. 2). In order to assess the
changes in mandibular position at the three time points,
linear and angular measurements were performed
between the mandibular landmarks and the reference
planes (Fig. 3).
Eighteen CBCT images were randomly chosen and
assessed twice by the same calibrated examiner, with a
minimum interval of 30 days. Reliability was confirmed
by the intra-class correlation coefficient (ICC), which
ranged from 0.929 to 0.996. The Shapiro-Wilk test was
used to investigate assumptions of normality.
Longitudinal changes were evaluated using repeated measures
ANOVA, Greenhouse-Geisser corrections were applied
for data that violated sphericity assumptions. In
statistically significant results, the Bonferroni multiple
comparison test was used to assess differences between
time points. Data analysis were performed using SPSS
16.0 (SPSS, Chicago, IL, USA) with a significance level
of 5% (α = 0.05).
The mandible showed a mean lateral displacement of
1.08 mm (SD = 0.93) immediately after SARME.
Twentyone patients showed lateral mandibular displacement
greater than 0.5 mm after expansion. The changes in
mandibular position were assessed according to the side
of the mandibular displacement observed after SARME;
bilateral structures were classified in contralateral or
ipsilateral to the mandibular displacement observed.
Repeated measures ANOVA showed significant changes
over time with respect to axial plane for menton (p < 0.001),
Menton 90.88a 8.77 89.35b 8.79
Different superscript letters show statistically significant differences
T1 preoperatively, T2 immediately after expansion, T3 6 months after expansion, SD standard deviation
and for contralateral gonion (p = 0.025) (Table 1). In
relation to the coronal plane, only the menton
measurement had significant changes (p < 0.001) (Table 2).
However, with respect to the sagittal plane, there were changes
over time for ipsilateral condylion (p = 0.024), contralateral
condylion (p = 0.001), ipsilateral gonion (p = 0.018), and
contralateral gonion (p = 0.029) (Table 3). Measurements
of the mandibular plane angle (FMA) also changed
significantly over the time of this study (p < 0.01) (Table 4).
Multiple comparison test revealed differences in the
menton measures between T1 and T2 with respect to
the axial plane (1.35 mm) and to the coronal plane
(−1.53 mm), showing downward and backward
movement of this landmark immediately after SARME
(Tables 1 and 2). However, the assessment at T3 revealed
a relapse of these movements (T3-T2, p < 0.05). Similar
changes were found for measures of mandibular plane
angle (FMA), indicating a transitional clockwise rotation
of the mandible after expansion.
Changes in mandibular landmark measures with respect
to sagittal plane confirm the lateral movement of the
mandible immediately after SARME (T2-T1, p < 0.05);
however, no significant change was observed between T2
and T3 neither between T1 and T3 (Table 3).
The possibility of causing adverse changes in patient’s
profile as a result of mandibular displacement still causes
concern in indicating maxillary expansions [
rotation of the mandible with an increase in lower facial
height has been reported as a side effect of SARME [
In fact, our study found a clockwise rotation of the
mandible immediately after SARME. This movement was
represented by an increase in the values of the FMA as well
as downward and backward displacements of the menton.
However, according to our results, the mandibular
rotation seems to be a transient movement as the values
observed 6 months after SARME (T3) tended to return
close to their initial values (T1). Altug-Atac et al. [
Gunbay et al. [
] reported clockwise rotation of the
mandible after SARME whereas Parhiz et al. [
Iodice et al. [
] did not observe significant rotational
movement of the mandible. Methodological differences
among these studies and assessment in different time
points justify the divergence in their findings on
mandibular rotation. The first authors carried out the assessment
after a short period following SARME whereas the other
authors conducted a later evaluation. Our findings agree
with the studies found in the literature since a transient
increase in the mandibular plane angle was observed.
Our findings showed that besides the clockwise
rotation, previously reported in literature, there is also a
lateral displacement of the mandible immediately after
SARME. However, it was not related with the type of
crossbite presented previously. Variations on mandibular
displacement could be observed among the patients,
even in those with unilateral posterior crossbite. The
lack of a pattern for mandibular displacement can be
explained by individual changes in the pattern of
occlusion following the expansion, such as in asymmetric
]. Thus, the direction to which the
mandible will move after SARME becomes unpredictable in
adult patients, in contrast to the correction of postural
asymmetry found in children with functional unilateral
posterior crossbites [
Changes observed in condylion and gonion landmarks
with respect to the sagittal plane occurred because the
analysis was performed considering the mandibular
displacement. So, one would expect an increase in the
distance from the landmarks ipsilateral to mandibular
displacement to the midsagittal plane, as well as a
decrease in the distance from the contralateral structures
to the same plane. Thus, even though an average
displacement of 1.08 mm had been observed in menton
between T1 and T2, it was not possible to predict the
direction of this change since this landmark can move
away or closer to the midsagittal plane as a result of the
mandibular movement after SARME. Despite this
changes occur at T2, there was a tendency to return to
original position 6 months after expansion, so that no
significant difference was observed between T3 and T1.
Additionally, mandibular lateral movements were small
and showed no clinical relevance.
Mandibular movements take place in three
dimensions; thereby, bilateral mandibular structures may show
distinct behaviors during SARME. Such fact was
Different superscript letters show statistically significant differences
FMA mandibular plane angle, T1 preoperatively, T2 immediately after
expansion, T3 6 months after expansion, SD standard deviation
observed in vertical changes of the gonion, which was
significant only to the contralateral side to the
mandibular displacement. This resulted in different values of the
mandibular plane angle between the ipsilateral and
contralateral sides, although both have shown a
This study suggests the presence of mandibular
displacement in most patients after SARME; however, the
direction of this displacement cannot be predicted. Clockwise
rotation and mandibular lateral displacement are
transient effects of SARME.
CBCT: Cone beam computed tomography; SARME: Surgically assisted rapid
TFMO has contributed with acquisition and statistical analysis of data and
drafted the manuscript. VAPF and ESG have undertaken the surgical part of
the study and acquisition of CBCT. MFRG and ASP have contributed to the
design of the study and revised the manuscript. All authors have read and
approved the final manuscript.
This study was approved by the Ethics Committee of Araraquara School of
Dentistry, under protocol number - CAAE: 14484713.1.0000.5416.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
1. Chung CH , Woo A , Zagarinsky J , Vanarsdall RL , Fonseca RJ . Maxillary sagittal and vertical displacement induced by surgically assisted rapid palatal expansion . Am J Orthod Dentofacial Orthop . 2001 ; 120 : 144 - 8 .
2. Anttila A , Finne K , Keski-Nisula K , et al. Feasibility and long-term stability of surgically assisted rapid maxillary expansion with lateral osteotomy . Eur J Orthod . 2004 ; 26 : 391 - 5 .
3. Lagravere MO , Major PW , Flores-Mir C . Dental and skeletal changes following surgically assisted rapid maxillary expansion . Int J Oral Maxillofac Surg . 2006 ; 35 : 481 - 7 .
4. Parhiz A , Schepers S , Lambrichts I , et al. Lateral cephalometry changes after SARPE . Int J Oral Maxillofac Surg . 2011 ; 40 : 662 - 71 .
5. Prado GP , Furtado F , Aloise AC , et al. Stability of surgically assisted rapid palatal expansion with and without retention analyzed by 3-dimensional imaging . Am J Orthod Dentofacial Orthop . 2014 ; 145 : 610 - 6 .
6. Altug Atac AT , Karasu HA , Aytac D. Surgically assisted rapid maxillary expansion compared with orthopedic rapid maxillary expansion . Angle Orthod . 2006 ; 76 : 353 - 9 .
7. Bretos JL , Pereira MD , Gomes HC , Toyama Hino C , Ferreira LM . Sagittal and vertical maxillary effects after surgically assisted rapid maxillary expansion (SARME) using Haas and Hyrax expanders . J Craniofac Surg . 2007 ; 18 : 1322 - 6 .
8. Lineberger MW , McNamara JA , Baccetti T , Herberger T , Franchi L . Effects of rapid maxillary expansion in hyperdivergent patients . Am J Orthod Dentofacial Orthop . 2012 ; 142 : 60 - 9 .
9. Gunbay T , Akay MC , Gunbay S , et al. Transpalatal distraction using boneborne distractor: clinical observations and dental and skeletal changes . J Oral Maxillofac Surg . 2008 ; 66 : 2503 - 14 .
10. Iodice G , Bocchino T , Casadei M , Baldi D , Robiony M. Evaluations of sagittal and vertical changes induced by surgically assisted rapid palatal expansion . J Craniofac Surg . 2013 ; 24 : 1210 - 4 .
11. Hilgers ML , Scarfe WC , Scheetz JP , Farman AG . Accuracy of linear temporomandibular joint measurements with cone beam computed tomography and digital cephalometric radiography . Am J Orthod Dentofacial Orthop . 2005 ; 128 : 803 - 11 .
12. Ikeda K , Kawamura A . Assessment of optimal condylar position with limited cone-beam computed tomography . Am J Orthod Dentofacial Orthop . 2009 ; 135 : 495 - 501 .
13. Sanders DA , Rigali PH , Neace WP , Uribe F , Nanda R . Skeletal and dental asymmetries in class II subdivision malocclusions using cone-beam computed tomography . Am J Orthod Dentofacial Orthop . 2010 ; 138 ( 542 ): e1 - 20 .
14. Cevidanes L , Oliveira AEF , Motta A , Phillips C , Burke B , Tyndall D. Head orientation in CBCT-generated cephalograms . Angle Orthod . 2009 ; 79 : 971 - 7 .
15. Koudstaal MJ , Smeets JB , Kleinrensink GJ , Schulten AJ , van der Wal KG. Relapse and stability of surgically assisted rapid maxillary expansion: an anatomic biomechanical study . J Oral Maxillofac Surg . 2009 ; 67 : 10 - 4 .
16. Pinto AS , Buschang PH , Throckmorton GS , Chen P . Morphological and positional asymmetries of young children with functional unilateral posterior crossbite . Am J Orthod Dentofacial Orthop . 2001 ; 120 : 513 - 20 .