![Selected cut-off points in the coronal plane at: (a) first premolar, (b) second premolar and (c) first molar. -In the axial plane: at the level of the right and left first molar trifurcation for each side (Figure 3). (Maxillary right first molar furcation for the right posterior teeth and the maxillary left first molar furcation for the left posterior teeth) According to Toklu [29].](https://www.researchgate.net/publication/362595430/figure/fig2/AS:11431281080868334@1661433516465/Selected-cut-off-points-in-the-coronal-plane-at-a-first-premolar-b-second-premolar_Q320.jpg)
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Citation: Solano Mendoza, P.;
Aceytuno Poch, P.; Solano Reina, E.;
Solano Mendoza, B. Skeletal,
Dentoalveolar and Dental Changes
after “Mini-Screw Assisted Rapid
Palatal Expansion” Evaluated with
Cone Beam Computed Tomography.
J. Clin. Med. 2022,11, 4652. https://
doi.org/10.3390/jcm11164652
Academic Editors: Letizia Perillo,
Vincenzo Grassia and Fabrizia
d’Apuzzo
Received: 30 June 2022
Accepted: 29 July 2022
Published: 9 August 2022
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4.0/).
Journal of
Clinical Medicine
Article
Skeletal, Dentoalveolar and Dental Changes after “Mini-Screw
Assisted Rapid Palatal Expansion” Evaluated with Cone Beam
Computed Tomography
Patricia Solano Mendoza * , Paula Aceytuno Poch, Enrique Solano Reina and Beatriz Solano Mendoza
Department of Orthodontics and Dentofacial Orthopedics, School of Dentistry, University of Seville,
41009 Sevilla, Spain
*Correspondence: patriciasolano83@hotmail.com
Abstract:
The purpose of this study was to evaluate skeletal, dentoalveolar and dental changes
after Mini-screw Assisted Rapid Palatal Expansion (MARPE) using tooth bone-borne expanders
in adolescent patients after analyzing different craniofacial references by Cone beam computed
tomography (CBCT) and digital model analysis. This prospective, non-controlled intervention study
was conducted on fifteen subjects (mean age 17
±
4 years) with transversal maxillary deficiency.
Pre (T1) and post-expansion (T2) CBCTs and casts were taken to evaluate changes at the premolars
and first molar areas. To compare means between two times, paired samples t- or Wilcoxon test
were used following criteria. Significant skeletal changes were found after treatment for Nasal width
and Maxillary width with means of 2.1 (1.1) mm and 2.5 (1.6) mm (p< 0.00005). Midpalatal suture
showed a tendency of parallel suture opening in the axial and coronal view. For dentoalveolar changes,
a significant but small buccal bone thickness (BBT) reduction was observed in all teeth with a mean
reduction of 0.3 mm for the right and left sides, especially for the distobuccal root of the first molar
on the left side (DBBTL1M) [IC95%: (
−
0.6;
−
0.2); p= 0.001] with 0.4 (0.4) mm. However, a significant
augmentation was observed for the palatal bone thickness (PBT) on the left side. The buccal alveolar
crest (BACL) and dental inclination (DI) showed no significant changes after treatment in all the
evaluated teeth. MARPE using tooth bone-borne appliances can achieve successful skeletal transverse
maxillary expansion in adolescent patients, observing small dentoalveolar changes as buccal bone
thickness (BBT) reduction, which was not clinically detectable. Most maxillary expansions derived
from skeletal expansion, keeping the alveolar bone almost intact with minor buccal dental tipping.
Keywords:
micro implant-assisted rapid palatal expansion; maxillary transverse deficiency; Cone-beam
computed tomography; alveolar bone; midpalatal suture; skeletal expansion; palatal expansion
1. Introduction
Transversal maxillary deficiency (TMD) is a quite common condition that affects
between 8–23% of deciduous and mixed dentitions. However, a lower prevalence has been
reported in adult orthodontic patients [
1
–
4
]. This transverse deficiency [
5
], or maxillary
hypoplasia [
6
], is one of the main problems related to facial growth that should be corrected
as it is diagnosed, with the objective to reestablish a normal transverse skeletal relationship
between maxillary and mandibular basal bones to obtain a stable occlusion [7].
Its etiology is multifactorial, frequently influenced by myofunctional disorders of
the stomatognathic system and generally associated with oral breathing or deleterious
habits such as thumb sucking [
4
,
8
,
9
]. Genetic and hereditary factors are also related, thus
determining the development of maxillary transverse deficiencies. These factors promote
structural changes in the maxilla which will generally lead to posterior crossbite (bilateral
or unilateral), constriction of the nasal cavity and frequent dental crowding [8,10].
Traditionally, orthopedic rapid maxillary expansion (RME) has been performed to
correct this matter during patient’s growing period showing positive results with a better
J. Clin. Med. 2022,11, 4652. https://doi.org/10.3390/jcm11164652 https://www.mdpi.com/journal/jcm
J. Clin. Med. 2022,11, 4652 2 of 20
prognosis and treatment outcomes at early ages [
5
,
11
–
14
], producing a greater orthopedic
effect in the deciduous and mixed dentition. As the patient grows, progressive calcification,
and craniofacial sutures interdigitation occur, including midpalatal suture closure. Conse-
quently, skeletal expansion becomes a more difficult process due to increased mechanical
resistance [
15
,
16
]. Limited skeletal orthopedic changes have been described after RME
with the use of tooth-borne expanders observing undesirable side effects such as dental
tipping, buccal bone thickness reduction, bone dehiscence and gingival recession in an-
chor teeth [
17
–
22
], limiting this treatment option to incomplete skeletal mature patients,
confirming the importance of early skeletal age treatment [23].
Skeletal support with the use of screws by means of mini-screw assisted rapid palatal
expansion (MARPE) allows for a better distribution of applied forces when the palatal
suture closure is incomplete, thus achieving a greater skeletal effect (orthopedic) by opening
the mid-palatal suture and minimizing secondary effects derived from dentoalveolar
(orthodontic) effects [
24
]. Cone-beam computed tomography (CBCT) images have revealed
a significant increase in the skeletal dimension in adolescent and young adult patients
treated with MARPE [
25
], reducing the aforementioned side effects when the intermaxillary
suture is not completely closed [
26
–
29
], and, therefore, considering MARPE as a proper
treatment option for correcting maxillary transversal discrepancies (MTD) [
30
–
32
] with
potential skeletal effect [
33
,
34
]. Studies show conflicting results regarding the orthopedic
effect MARPE and RME in young adult patients with different types of appliances [35].
Specifically, tooth bone-borne expanders with palatal minis crews and first molar
anchorage have shown effective and positive results for maxillary expansion [
33
,
36
,
37
],
with no risk of periodontal damage.
As studies using computed tomography (CT) report, buccal alveolar bone thinning
after RME in anchored teeth [
20
,
38
], the use of CBCT seems to be fundamental, contributing
to a more complete diagnosis of the transverse dimension [
29
,
39
] providing accurate
tridimensional treatment outcomes evaluations of the maxillofacial complex and their
dentoalveolar response.
This was the main reason that led us to hypothesize that MARPE using tooth bone-
borne expanders could be a safe and effective treatment to correct maxillary transversal dis-
crepancies in adolescent patients with incomplete ossification of the maxillary palatal suture
achieving higher predictable skeletal effects with reduced dentoalveolar
and dental effects.
The purpose of this study is to evaluate skeletal, dentoalveolar and dental changes
after MARPE using tooth bone-borne expanders in patients with incomplete maxillary
palatal suture closure analyzing different craniofacial references by CBCT and digital
model analysis in order to quantify maxillary transverse changes at the three levels after
expansion treatment. Moreover, we tried to show the quantity of skeletal, alveolar and
dental responses to treatment and compare these findings with those that are reported in
the literature.
2. Material and Methods
This prospective, non-controlled intervention study was conducted on patients who
needed maxillary expansion. Patients were recruited from three different centers in the
same city, Seville (Spain): The Department of Orthodontics of the School Dentistry of the
University of Seville, a private dental clinic (COINSOL) and a dental training institute IDEO.
All subjects met the following inclusion criteria: (1) presence of transverse skeletal maxillary
deficiency with or without the presence of posterior crossbite as described by Tamburino
et al. [
40
,
41
], (2) incomplete radiographic ossification of the midpalatal suture according
to Angelieri’s classification [
42
], (3) not having received previous orthodontic treatment,
(4) presence
of first and seconds upper premolars and first upper molars, (5) absence of any
craniofacial irregularities, (6) and any bone defects, or systemic and periodontal disease,
(7) not
being pregnant (8) and having reached prepubertal development with less than
25 years of age. Palatal suture ossification was evaluated following this classification,
categorizing the palatal maturation in five stages (A–E) through its CBCT analysis in an
J. Clin. Med. 2022,11, 4652 3 of 20
axial view. Patients who did not meet the inclusion criteria and those with a portion of the
suture where the fusion had occurred (stage E in accordance with Angelieri’s classification)
and with no low-density spaces along the suture were excluded. Incomplete ossification of
mid palatal suture was blindly evaluated in the initial CBCT (CbctT1) to confirm that the
patient could be included in the study.
All subjects gave their informed consent before taking part in the study. This study was
conducted in accordance with the Declaration of Helsinki, and the protocol was approved
by the Ethics Committee of Vírgen Macarena-Virgen del Rocío University Hospitals in
Seville (238e1b02c492fe6c37e2e9cf37c737297f4cf746).
An initial sample of 19 patients meeting the established inclusion criteria were se-
lected. Four patients were not included in the analysis: two patients due to incomplete
radiographic registers, one patient used other orthodontic appliance at the same time and
one patient had a different screw positioning. The final sample consisted of 15 patients
between 13 and 24 years of age (mean age: 17.0
±
4.0), with transverse maxillary skeletal
compression (mean:5.4 ±2.1 mm) who completed maxillary expansion (Table 1).
Table 1.
Sample age and maxillary compression distribution. Appliance’s activation time. Age
(years), Maxillar compression (mm), Appliance activation time (days).
N Min Max Mean
Difference (SD)
IC 95%
Mean Median Median
(P25;P75 )
IC95%
Median
Age 15 13.0 24.0 17.0 (4.0) 15.0;19.0 16.0
(14.0;20.0)
16.0; 21.0
Maxillary compression 15 2.5 8.7 5.4 (2.1) 4.2; 6.5 5.1 (3.7;7.5) 3.8; 7.5
Appliance activation time 15 10.0 35.0 22.0 (8.0) 17.0; 26.0 20.0
(15.0;30.0)
15.0; 30.0
2.1. Methodology
Patients were treated by MARPE with a tooth-bone born expander using the MSE
(maxillary skeletal expander designed by Dr. Moon from the University of UCLA) adapted
to individual maxillary expansion requirements [
43
,
44
]. Four stainless steel arms of 1.5 mm
in diameter emerged from a central main screw: two anterior arms extended symmetrically
towards the palatal aspect of the first upper premolars near the most cervical part of the
tooth (without support), and two posterior arms extended the palatal aspect of the first
molars, which remained fixed to the bands placed on the first molars. A 0.7 mm thick steel
lateral arm was connected to the expander’s front arms (Figure 1).
Figure 1. Tooth-bone-borne expander appliance.
Every device was adapted individually for each patient in the same laboratory through
an initial impression with the bands positioned on the upper first molars.
J. Clin. Med. 2022,11, 4652 4 of 20
The central screw expander had four holes of 1.8 mm in diameter for the retention and
insertion of each mini screw of 1.74 mm in diameter and 9, 11 and 13 mm in length which
were used for bone anchoring. Anterior and posterior mini-screws were positioned at the
level the first premolar and the first molar, respectively (BMK micro-screws model ACR of
Medical Resources). To ensure a bicortical anchorage, palatal gingiva thickness, bone height
and distance between the expander and palatal gingiva were considered [
45
]. The central
screw expander length was selected based on the patient’s maxillary expansion needs to
correct the transversal deficiency (8, 10 or 12 mm). The maxillary compression or maxillary
transversal deficiency was calculated considering the difference between the mandibular
and maxillary widths determined by the arch relationship according to Cantarella 2017 [
44
].
Expander placement and the first activation were performed in the same appointment,
following the describe protocol suggested by Bruneto [
8
] according to patients age. The
expander was activated by 1 turn per day (0.26 mm/turn) with subsequent biweekly visits
until full expansion was achieved [
8
]. The total maxillary expansion was completed when
the palatal cusp tips of the maxillary first molars were in contact with the corresponding
buccal cusp tips of the mandibular first molars.
The same experienced examiner was present in the 3 centers (BSM) for the recruitment
of patients enrolled in the study, confirming incomplete ossification of midpalatal suture
and supervised successive visits until the expansion was completed, from February 2020 to
December 2022 [
46
,
47
]. Radiographic CBCT (Cbct) and cast (Model) recordings were col-
lected at two times: T1 (prior to expander placement) and T2 (immediately after maxillary
expansion had been completed). The expander was removed before CbctT2 and ModelT2
to prevent image distortions, and immediately placed back without miniscrews, blocking it
with ligature leaving the expansion device for a 6-month retention period. The patient’s
skeletal maturation was assessed via the cervical vertebral maturation index (CVM) in the
initial teleradiograph (CbctT1) in accordance with Bacetti’s classification and stratified in
6 stages from CVM I-VI [
48
,
49
] base of the presence or absence of concavity in the lower
border of the body of C2, C3 and C4 and the body shape of C3 and C4.
Once the treatment was completed, all measurements were performed by two blinded,
calibrated examiners. Radiographic measurements (PSM) and digital cast measurements
(PAP) were performed, evaluating intraexaminer reproducibility. Skeletal and sutural
maturation were assessed (PSM) from CbctT1 in accordance with the previously describe
classifications [
42
,
48
,
49
]. Intraexaminer reproducibility was analyzed by using randomly se-
lected patients. In order to assure a reliable reproducibility and blindness, each patient was
assigned a unique code and measurements were recorded twice and spaced 1 week apart.
Stone casts were digitally scanned with Itero
®
Element 2 Scanner (Tel Aviv-Yafo, Israel)
and analyzed for measurements with OrthoCAD
®
software (OrthoCAD iCast Orthodontic
3D Digital Modeling Study of Align Technology, Inc., IL, USA) to evaluate changes at the
following levels: first and second premolar and first molar (1PM, 2PM, 1M): (1) Palatal
Gingival Width (PGW): distance from the palatal gingival margin of the tooth of interest to
its contralateral, (2) Palatal Cusp Width (PCW): distance from the palatal cusp of the tooth
of interest to its contralateral, (3) right and left Clinical Coronal Height (CCH) to evaluate
gingival margin position changes: distance from the center of the gingival margin to the
buccal cusp for the premolars and to the center of the crown in the buccal aspect for the
first molar.
CBCT scan images were obtained with i-CAT
®
Kavo 1723 flat panel model for IDEO
and COINSOL patients, and with Planmeca Promax
®
3D Sirona (Finlandia, Helsinki) for
Dental School patients. For i-CAT
®
Kavo: 37 mA, 120 kV and 26 s scan time were set
for T1 and T2. Voxel size of 0.2 mm. for both exposure times and a field of view of
16 ×13 cm
FOV (cervical included). PlanMeca Promax 3D from Sirona system used same
parameters for two evaluation periods T1 and T2, being: 14 mA, 90 KV, with a 12 s exposure
time, 0.2 Vox and 8
×
8 FOV. Anatomage in Vivo 5,3. i-CAT
®
Kavo software was used to
perform all radiographic measurements with a 1:1 scale, slice thickness 0.5 mm. All CBCT
volume images were reoriented prior to radiographic measurements considering three-
J. Clin. Med. 2022,11, 4652 5 of 20
dimensional reference planes for craniofacial structures orientation and to standardize
linear measurements in the sagittal section (y-plan), axial section (x-plane) and coronal
section (z-plan):
a. Radiographs orientation: In the axial section (x-plane), the mid-palatine suture was
used. In the midsagittal section (y-plane), the horizontal palatal plane was the selected ref-
erence, considering the anterior and posterior nasal spine. In the coronal section (
z-plane
),
the image was oriented perpendicular to the patient’s midsagittal plane tangent to the most
inferior level of nasal floor [50].
b. Cuts standardization: Points were established in the coronal, axial and sagittal
plane at selected teeth: first and second premolars and first molar (1 PM, 2 PM, 1 M) in
line with previous validated cut Standardization and radiographic measurement method
described by Podesser [50] on CT, and by Christie [51] and Toklu [29] on CBCT.
–
In the coronal plane: For the first premolar and the first molar: cuts were made at the
most anterior section where the crown and palatal root can be seen at their greatest
length. For the second premolar: in the most anterior section showing maximum
length of its root (Figure 2).
Figure 2.
Selected cut-off points in the coronal plane at: (
a
) first premolar, (
b
) second premolar and
(c) first molar.
–
In the axial plane: at the level of the right and left first molar trifurcation for each side
(Figure 3). (Maxillary right first molar furcation for the right posterior teeth and the
maxillary left first molar furcation for the left posterior teeth) According to Toklu [
29
].
Figure 3.
Cut in the axial plane for buccal and palatal bone thickness (BBT and PBT) measurements.
Radiographic changes were evaluated at selected teeth for the following variables:
(1) Skeletal changes:
Nasal width, maxillary width, palatal suture opening, sutural expansion,
J. Clin. Med. 2022,11, 4652 6 of 20
nasal floor, palatal floor, (2)
Dentoalveolar changes
:buccal maxillary width and palatal maxillary
width, on left (L) and right (R) side of the upper arch: buccal bone thickness,palatal bone
thickness and buccal alveolar bone crest Level, (3) Dental changes:dental inclination (Table 2).
Table 2.
Description of radiographic CBCT measurements performed with
In vivo
software program.
Standardized coronal and axial sections for radiographic measurements of first and second premolars,
and first molars.
Nasal width (NW)
Distance between right and left most lateral point of the nasal
cavity in the coronal section at the level of first molar where
total length of palatal root and crown are visualized.
Maxillary width
(MW)
Distance between the lowest point of lateral right and left
contour concavities of the maxillary bone, on a coronal
section, at the level of first molar where total length of palatal
root and crown are visualized.
Palatal suture
opening (SO)
Distance between the external right and left maxilla edges in
the axial view generating a slice in the horizontal plane,
allowing a good visualization of the midpalatal suture at first
and second premolar, and first molar. The edges were
identified with a small point on an axial cross-sectional slice at
the level of the first molar trifurcation.
J. Clin. Med. 2022,11, 4652 7 of 20
Table 2. Cont.
Buccal maxillary
width (BMW)
Distance between right and left most prominent point of the
buccal bone crest in first and second premolar, and first molar,
in the first anterior coronal cut described for each tooth.
Palatal maxillary
width (PMW)
Distance between right and left most prominent point of
palatal bone crest in first and second premolar, and first molar,
in the first anterior coronal slice as describe for each tooth. At
the level of the buccal maxillary width.
Buccal bone
thickness (BBT)
Distance from the external border of the buccal cortical plate
to the center of buccal aspect of first and second premolar root,
and from the external border of buccal cortical plate to the
center of the messiobuccal and distobuccal root of first molar,
in an axial section parallel to the palatal plane, at the level of
the first molar right (R) and left (L) trifurcation for each side.
J. Clin. Med. 2022,11, 4652 8 of 20
Table 2. Cont.
Palatal bone
thickness (PBT)
Distance from the external border of palatal cortical plate to
the center of palatal aspect of first and second premolar root,
and first molar palatal root, in an axial section parallel to
palatal plane, at the level of the first molar right (R) and left
(L) trifurcation for each side.
Buccal alveolar bone
crest level (BACL)
Distance from the tip of buccal cusp to the buccal bone crest of
first and second premolar, and from the mesiobuccal cusp of
first molar crown, to the buccal bone crest in the first anterior
coronal cut describe for each tooth, on the right (R) and
left (L) side.
Dental inclination
(INCL)
Angle formed by the intersection of two tangents that passed
through the buccal and palatal cusps of the first and second
premolars of both contralateral teeth, and through the
messiobuccal and palatal cusp of the first molar, in the
coronal section.
J. Clin. Med. 2022,11, 4652 9 of 20
Midpalatal suture expansion was also assessed in the coronal view, measured in the
middle of the palate as sutural expansion (SEM), and at the level of nasal and palatal floor on
a coronal cross-sectional slice through the center of the first molar, by connecting the right
and left external edges of the suture according to the previous method used by Ngan [34].
(Table 3). The suture external edges were verified in the axial cross-sectional slice for each
tested position.
Table 3.
Evaluation of the suture opening pattern in the coronal section and midpalatal suture
expansion at the nasal and palatal floor levels.
Nasal Floor
(NF)
Distance from right and left external edges of the palatine suture at
the level of the nasal floor in the coronal view. On a coronal
cross-sectional slice through the center of the first molar. The suture
external edges were verified in the axial cross-sectional slice.
Palatal Floor
(PF)
Distance from right and left external edges of the palatine suture at
the level of the palatal floor. On a coronal cross-sectional slice
through the center of the first molar. The suture external edges
were verified in the axial cross-sectional slice.
The skeletal expansion was calculated by the radiographic analysis of: Sutural expan-
sion (SEM), intermolar width (IMW), and palatal maxillary width (PMW) in compliance with
the method proposed by Ngan et al. 2018 [34] (Table 4).
Total expansion (TE) included the skeletal (separation of two maxillary halves at the
midpalatal suture) and dentoalveolar expansion (alveolar bone bending and dental tipping).
A mathematical equation was used to calculate the skeletal and dentoalveolar components
of the Total expansion: TE = Skeletal (orthopedic) expansion: Midpalatal sutural separation
+ dentoalveolar (orthodontic) expansion (alveolar bone bending + dental tipping). Total
expansion was defined as the change between the two time periods (T2–T1) in (1) Intermolar
width, distance between the palatal cusp tip of the right and left first molars measured
in a coronal cross-sectional slice through the midportion of the first molar. (2) Sutural
expansion in the middle of the palate on the same coronal cross-sectional slice and (3) palatal
maxillary width, measured at the first molar’s furcation on the same coronal cross-sectional
slice (Table 4). From the dentoalveolar expansion: Alveolar bone bending, and dental
inclination were also determined for each patient. Alveolar bone bending was defined as
any additional palatal alveolar expansion achieved apart from the sutural separation and
was calculated by subtracting Sutural Expansion (SEM) from the change (T2–T1) in palatal
maxillary width (PMW). Dental inclination was computed by subtracting sutural expansion
and the calculated alveolar bone bending from total expansion [34].
J. Clin. Med. 2022,11, 4652 10 of 20
Table 4.
Radiographic CBCT measurements to quantify skeletal, dentoalveolar and dental expansion.
Sutural expansion, intermolar width and palatal maxillary width (SEM, IMW and PMW) were
measured at first molar and quantified on the same coronal cross-sectional slice.
Sutural expansion
(SEM)
The sutural expansion in the middle of the palate.
Distance between the left and right external border
of the palatal aspect of the maxilla, in the middle of
the palate between the palatine bone and the nasal
floor, on a coronal cross-sectional slice at first molar.
Through the midportion of the first molar.
J. Clin. Med. 2022, 11, x FOR PEER REVIEW 11 of 22
Palatal Floor
(PF)
Distance from right and left external edges of the
palatine suture at the level of the palatal floor. On a
coronal cross-sectional slice through the center of the
first molar. The suture external edges were verified
in the axial cross-sectional slice.
The skeletal expansion was calculated by the radiographic analysis of: Sutural
expansion (SEM), intermolar width (IMW), and palatal maxillary width (PMW) in compliance
with the method proposed by Ngan et al. 2018 [34] (Table 4).
Table 4. Radiographic CBCT measurements to quantify skeletal, dentoalveolar and dental
expansion. Sutural expansion, intermolar width and palatal maxillary width (SEM, IMW and PMW)
were measured at first molar and quantified on the same coronal cross-sectional slice.
Sutural expansion (SEM)
The sutural expansion
in the middle of the
palate. Distance
between the left and
right external border
of the palatal aspect
of the maxilla, in the
middle of the palate
between the palatine
bone and the nasal
floor, on a coronal
cross-sectional slice at
first molar
. Through the
midportion of the
first molar.
Intermolar width (IMW)
Distance between
right and left tip of
palatal cusp of first
molars in a coronal
cross-sectional slice
through the center of
first molar.
Palatal maxillary width
(PMW)
Distance between the
right and left external
border of the palatal
maxillary bone, on a
coronal cross-
sectional slice at first
molar. Through the
midportion of the
first molar.
Intermolar width
(IMW)
Distance between right and left tip of palatal cusp of
first molars in a coronal cross-sectional slice through
the midportion of first molar.
Palatal maxillary
width (PMW)
Distance between the right and left external border
of the palatal maxillary bone, on a coronal
cross-sectional slice at first molar. Through the
midportion of the first molar.
2.2. Statistical Analysis
The statistical analyses were performed with the Statistical Package, using SPSS 26.0
software for Windows (SPSS Inc. Chicago, IL, USA). For quantitative variables, those
that presented a symmetric distribution, were presented as means and standard deviation
(SD) and those that presented a very asymmetric distribution, as median and interquartile
range (P
25
, P
75
) and frequency and percentages for the categorical variables. The 95%
CIs have been calculated for all the statistics obtained. To assess changes after MARPE
maxillary expansion at two evaluation moments, the Student’s t-test was performed for
paired data once the randomness and normality requirements had been confirmed. In
cases of not meeting the normality requirement (Shapiro–Wilks test), the non-parametric test
(Wilcoxon test) was applied. To compare the means between two independent groups, the
Student’s t-test was performed for independent data once the requirements of randomness,
normality (Shapiro Wilks test) and equality of variance (Levene’s t) had been confirmed. If
said requirements were not met, the Student’s t-test was performed for independent data
with Welch’s correction. If the normality requirements were not met, a non-parametric test
(Mann–Whitney U) was applied. Significance of the results was evaluated at the level of
alpha < 0.05.
Based on the observed effect sizes, experimental statistical power analyses were
conducted to determine the power of the study. The sample size was calculated to detect
any clinically relevant differences in the reduction in buccal wall thickness of 0.5 mm after
expansion [
20
,
29
]. Being the standard deviation of the differences 0.62, considering an
alpha error of 0.05 and a power of 85%, the minimum number of subjects to be included
in the study was 14 patients. ICCs assessment for intraexaminer reproducibility ranged
between 0.85 and 0.98 for radiographic and cast measurement showing an important level
of repeatability for all measurements.
3. Results
ICC were greater than 0.90 for most of the variables and greater than 0.83 for the second
left premolar’s clinical crown height, the first premolar’s palatal maxillary width, the first
premolar’s suture opening, the second right premolar’s buccal bone thickness, the first left
molar’s buccal bone thickness and the second left premolar’s buccal bone thickness.
The initial maxillary transversal deficiency ranged from 2.5 to 8.7 mm with a mean of
5.4 (2.1) mm. The mean amount of screw expansion was 6.8 mm (1.8), ranging from
3.4 mm
to 9.4 mm, with a mean of 22 (8.0) days, 95% CI: (17.0, 26.0). Sutural stage maturation
evaluation according to Angelieri’s classification [
42
] confirming all sutures were not
completely ossified before maxillary expansion: 86.7% [95% CI: (86.7; 93.3) of the sample
(n = 13) presented midpalatal suture stages type C and 6.7% (n = 1) stage type B and D.
J. Clin. Med. 2022,11, 4652 11 of 20
Regarding skeletal maturation (CVM) according to Baccetti [
48
,
49
], most patients presented
stages IV and V with a distribution of 46.7% (n = 7) and 40% (n = 6), respectively, and 13.3%
stage III (Table 5).
Table 5. Sample sex, cross bite, skeletal maturation and palatal sutural stage distribution.
N
Number (%) 95% CI
Sex Male 3 (20) 6.0; 44.4
Female 12 (80) 55.6; 94.0
Cross Bite Absence 3 (20) 6.0; 44.4
Bilateral 12 (80) 56.6; 94.0
Skeletal maturation Stage I 0 (0) 0.0; 21.8
Stage II 0 (0) 0.0; 21.8
Stage III 2 (13.3) 2.9; 36.3
Stage IV 7 (46.7) 23.9; 70.6
Stage V 6 (40.0) 18.8; 64.7
Stage VI 0 (0) 0.0; 21.8
Palatal Sutural Stage Stage A 0 (0) 0.0; 21.8
Stage B 1 (6.7) 0.7; 27.2
Stage C 13 (86.7) 63.7; 97.1
Stage D 1 (6.7) 0.7; 27.2
Stage E 0 (0) 0.0;21.8
3.1. Radiographic Measurements
CBCTs performed at the two evaluation times were needed to analyzed all eval-
uated parameters and existing changes after treatment at the skeletal, dentoalveolar
and dental level.
Skeletal changes: The midpalatal suture was successfully opened showing a significant
change in all patients. Suture opening (SO) in the axial view expressed a similar quantity
at the premolar and molar areas, with a mean of 3.3 (1.3) mm for the first premolars,
2.9 (1.4) mm
for the second premolars and 2.6 (1.3) mm for the first molars, showing a
gradual opening tendency from the anterior to the posterior part with no statistically
significant differences between teeth along the length of the midpalatal suture (Table 6).
Midpalatal suture expansion assessed on the coronal view showed a statistically
significant change (p< 0.000) at the Nasal and Palatal Floor levels after maxillary expansion,
not showing statistically significant differences between them.
Dentoalveolar changes: Statistically significant differences were found after maxillary
expansion for buccal and palatal maxillary width in all analyzed teeth. Regarding buccal
bone thickness (BBT), once the maxillary expansion was completed, all locations showed
similar significant changes with a mean reduction of
−
0.3 mm for both sides (Table 7).
Although these values show statistically significant differences, they are not clinically
relevant. In the palatal aspect, bone thickness (PBT) only showed significant changes on
the left side, on the first premolar and the molar, respectively. The buccal alveolar crest
remained with hardly any changes, not being significant at any locations.
J. Clin. Med. 2022,11, 4652 12 of 20
Table 6.
Comparison of Pre and Posttreatment Skeletal measurements. Skeletal changes comparing
CbcT1-CbcT2 measurements. BMW: Buccal maxillary width. PMW: Palatal maxillary width. NW:
Nasal width. MW: Maxillary width. SO: suture opening. 1PM: first premolar; 2PM: second premolar
and M1: first molar.
T1–T2 N Min Max Mean Difference
(SD) mm
IC95%
Mean
Median
(mm)
Median
(P25; P75 )
IC95%
Median p-Value
NW 15 0.4 4.6 2.1 (1.1) 1.5; 2.7 2.3 1.1; 2.7 1.3; 2.7 0.00005
MW 15 0.4 6.2 2.5 (1.6) 1.6; 3.4 2.1 1.3; 3.8 1.9; 3.8 0.00005
SO1PM 15 1.7 6.0 3.3 (1.3) 2.5; 4.0 2.7 2.4; 4.4 2.4; 4.4 0.00005
SO2PM 15 1.2 6.0 2.9 (1.4) 2.1; 3.6 2.4 1.6; 3.8 1.7; 3.8 0.00005
SO1M 15 1.0 6.0 2.6 (1.3) 1.9; 3.3 2.2 1.8; 3.4 1.8; 3.4 0.00005
NF 15 1.1 4.7 2.4 (1.0) 1.9; 3.0 2.4 1.7; 3.1 1.7; 3.1 0.000
PF 15 1.0 4.5 2.4 (1.0) 1.8; 3.0 2.6 1.6; 3.2 1.8; 3.6 0.000
SEM 15 0.7 4.7 2.7 (1.0) 2.1; 3.1 2.6 1.9; 3.3 2.2; 3.3 0.000
Table 7.
Comparison of Pre and Post treatment Dentoalveolar measurements. Dentoalveolar changes
comparing CbctT1-CbctT2 measurements. BBT: buccal bone thickness. MB: messiobuccal root of first
molar. DB: distobuccal root of first molar. R: right side. L: left side. PBT: Ppalatal bone thickness.
BACL: bone alveolar crest level. 1PM: first premolar; 2PM: second premolar and M1: first molar.
T1–T2 N Min Max Mean difference
(SD) mm
IC95%
Mean
Median
(mm)
Median
(P25;P75 )
IC95%
Median p-Value
BMW1PM 15 0.6 7.8 3.7 (2.0) 2.6; 4.8 3.5 2.1; 5.0 2.2; 5.0 0.00005
BMW2PM 15 0.8 14.8 4.1 (3.6) 2.1; 6.1 2.6 2.2; 4.3 2.4; 4.3 0.001
BMW1M 15 1.1 9.7 3.7 (2.1) 2.6; 4.9 3.3 2.6; 4.0 3.1; 4.0 0.001
PMW1PM 15 1.0 8.4 3.7 (1.8) 2.7; 4.7 3.4 2.6; 4.8 2.9; 4.8 0.00005
PMW2PM 15 1.6 7.8 3.2 (1.6) 2.3; 4.1 3.0 2.2; 3.6 2.8; 4.4 0.001
PMW1M 15 −5.6 7.2 2.2 (2.6) 0.7; 3.6 2.3 1.7; 3.0 1.8; 3.0 0.009
BBTR1PM 15 −1.0 0.0 −0.3 (0.3) −0.4; −0.1 −0.2 −0.4; 0.0 −0.2; −0.0 0.003
BBTR2PM 15 −0.4 0.3 −0.1 (0.2) −0.2; −0.0 −0.2 −0.2; −0.0 −0.2; −0.0 0.013
MBBTR1M 15 −0.9 0.0 −0.3 (0.3) −0.5; −0.2 −0.2 −0.6; −0.1 −0.3; −0.1 0.001
DBBTR1M 15 −0.9 0.0 −0.3 (0.3) −0.5; −0.2 −0.3 −0.5; −0.2 −0.4; −0.2 0.00005
BBTL1PM 15 −1.3 −0.2 −0.3 (0.4) −0.6; −0.1 −0.2 −0.5; −0.1 −0.5; −0.1 0.004
BBTL2PM 15 −0.6 0.0 −0.3 (0.2) −0.3; −0.1 −0.3 −0.4; −0.1 −0.3; −0.1 0.00005
MBBTL1M 15 −1.1 0.0 −0.4 (0.4) −0.6; −0.2 −0.3 −0.7; 0.0 −0.6; 0.0 0.003
DBBTL1M 15 −1.5 0.0 −0.4 (0.4) −0.6; −0.2 −0.3 −0.7; −0.1 −0.5; −0.1 0.001
PBTR1PM 15 −1.8 1.1 0.1 (0.7) −0.3; 0.5 0.2 −0.3; −0.4 −0.0; 0.4 0.552
PBTR2PM 15 −0.7 0.8 0.2 (0.4) −0.4; 0.5 0.3 0.0; 0.4 0.0; 0.4 0.09
PBTR1M 15 −0.2 0.9 0.1 (0.3) −0.0; 0.3 0.0 0.0; 0.3 0.0; 0.3 0.073
PBTL1PM 15 −0.4 0.6 0.2 (0.2) 0.0; 0.3 0.2 0.1; 0.3 0.1; 0.3 0.013
PBTL2PM 15 −0.3 0.5 0.1 (0.2) 0.0; 0.3 0.2 0.1; 0.3 0.1; 0.3 0.012
PBTL1M 15 −0.1 0.5 0.2 (0.2) 0.1; 0.3 0.1 0.0; 0.4 0.1; 0.4 0.003
BACLR1PM
15 −2.3 0.7 −0.1 (0.7) −0.5; 0.3 0.0 −0.2; 0.2 0.0; 0.3 0.448
BACLR2PM
15 −1.1 0.5 −0.1 (0.5) −0.4; 0.2 0.0 −0.4; 0.2 −0.1; 0.2 0.420
BACLR1M 15 −2.2 1.0 −0.0 (0.8) −0.5; 0.5 0.2 −0.6; 0.6 −0.2; 0.6 0.493
BACLL1PM
15 −1.2 0.3 −0.2 (0.4) −0.4; 0.0 0.0 −0.2; 0.1 −0.0; 0.1 0.012
BACLL2PM
15 −1.6 0.7 −0.2 (0.5) −0.5; 0.1 −0.1 −0.6; 0.1 −0.5; 0.1 0.145
BACLL1M 15 −0.4 1.5 0.2(0.6) −0.1; 0.5 0.1 −0.1; 0.4 −0.1; 0.4 0.144
Dental changes: Dental inclination did not show significant variation after treatment
being minimal on all the evaluated teeth. The reduction in the measured angle shows a
tendency to positive tipping, slightly increasing from the first molar to the first premolar
(Table 8).
J. Clin. Med. 2022,11, 4652 13 of 20
Table 8.
Comparison of Pre and Post treatment Dental inclination measurements. Dental inclination
changes after maxillary expansion comparing CbctT1-CbctT2 measurements. INCL: inclination. 1PM:
first premolar; 2PM: second premolar and M1: first molar.
T1–T2 N Min Max Mean Difference
(SD) mm
IC 95%
Mean
Median
mm
Median
(P25;P75 )
IC95%
Median p-Value
INCL1PM
15 −33.6 22.4 −1.6 (15.9) −10.4; 7.3 −0.2 −13.2; 8.6 −2.0; 8.6 0.71
INCL2PM
15 −22.5 32.3 −2.0 (15.6) −10.6; 6.7 −5.7 −14.0; 6.0 −12.9; 6.0 0.62
INCL1M 15 −15.3 21.7 −3.3 (9.4) −8.5; 1.9 −3.7 −10.0; −1.3 −8.0; −1.3 0.200
3.2. Cast Measurements
Palatal gingival widths and palatal cusp widths showed significant changes in all the
teeth after MARPE. Regarding the height of the clinical crown (CCH), significant minor
changes were observed only on the left side, with a mean change of 0.2 (0.2) mm, 0.1 (0.2)
mm and 0.1 (0.1) mm for premolars and the first molar, respectively. However, none of
these small increases were clinically noticeable.
A total expansion of 4.5 (1.8) mm was obtained after MARPE, defined as the change
in the IMW for the first molar. Greater expansion amount (2.7 (1.0) mm) corresponds to
skeletal component and a lower proportion (1.8 (1.7) mm) to dentoalveolar expansion,
both changes being statistically significant. Significant changes were observed for IMW,
PMW and SEM. From the dentoalveolar expansion, the alveolar bone bending effect and
the dental inclination showed reduced mean values of 0.7 (1.6) mm and 1.1 (1.3) mm,
respectively. The amount of skeletal expansion achieved within the total expansion was 60
%, determined by mid-palatal suture expansion [2.7 (1.0) mm] in the center of the palate at
the first’s molar level, meaning 40% remaining corresponds to the dentoalveolar component
(1.8 mm). Flexion of the alveolar bone accounted for 15,5% of TE. The remaining fraction of
TE in the first molar resulted from dental inclination was 24.4%.
4. Discussion
It is generally accepted that chronological age is not a precise parameter to base
the skeletal maturation diagnosis [
32
] due to the high variability of midpalatal suture
development stages during a patients’ life [
52
]. Skeletal effects derived from maxillary
expansion have been observed to be greater in young patients, at the prepubertal stages,
while pubertal or post pubertal stages can have greater dentoalveolar effects [
49
]. However,
approximately 11% of adult population still present a pubertal stage 4 CVM. This percentage
is not high, but it should be considered relevant from a clinical standpoint [53].
Garrett found similar values to our study for alveolar bending after RME with the use
of tooth-borne expanders observing a 13% (0.84 mm) of alveolar bone bending, but higher
dental tipping effect of 39% at the premolar (2.34 mm) and 49% (3.27 mm) at the first molar
from the total expansion achieved in patients with a mean age of 13.8 years [
54
]. These
data show a trend of decreasing orthopedic skeletal effect, increasing alveolar bending
and orthodontic tipping from anterior to posterior in line with previous reports [
55
,
56
].
Compared to bone-borne maxillary expanders, tooth-born expanders showed as twice as
large alveolar bone bending effect [57].
4.1. Skeletal Changes
In our study, a total expansion of 4.5 (1.8) mm was achieved after MARPE, defined as
the change between the intermolar width at the level of the first molar (IMW). This change
was slightly lower compared to other report values [
34
], but in line with other study [
33
].
This may be due to the fact that no overcorrection was performed, but enough to correct
transversal discrepancy. Buccal and palatal maxillary width showed a significant increase
in all the teeth, confirming earlier studies’ results. Significant nasal and maxillary width
changes were seen, thus explaining a disjunction effect in the nasal cavity as some studies
show [13–15].
J. Clin. Med. 2022,11, 4652 14 of 20
The highest proportion of the enhanced total expansion, corresponds to skeletal
expansion (60%), determined by mean midpalatal suture expansion (SEM) measured in
the middle of the palate at first molar level (2.7 (1.0) mm), coincident with other studies
using the same measurements method and type of expander (2.55
±
0.71 mm) [
34
] over
skeletally mature patients (CVM 4) [
49
] similar to our sample. Ngan et al. [
34
] reports
a 41% of skeletal expansion (SE), with a 2.55
±
0.71 mm of midpalatal suture expansion
(SEM), and a total expansion (TE) of 6.26
±
1.31 mm, which means that proportionally
we have enhanced a higher percentage of skeletal expansion considering that most of our
patients where categorized as skeletally mature (stage IV, and V) [
49
] with a mean age
of 17.1
±
3.5 years. MARPE clinical efficacy and stability performed in young subjects
(between 19 and 26 years) report success rates of 86.96%, maintaining achieved skeletal and
dentoalveolar changes after disjunction, as well as periodontal structures solidity during
retention period [31].
Regarding suture opening, the available literature reports a marked suture opening
pattern [
44
] describing a tendency to result in a pyramidal pattern in the vertical aspect.
According to some studies, the triangular suture opening pattern presents the apex in the
nasal area and the base in the dental cusps, regardless of the mechanism used [
26
,
37
,
58
].
Lim et al. support MARPE is not only limited to the maxilla, involving also circummaxillary
structures [
25
]. Studies using tooth-borne expanders tend to describe a triangular pattern on
the sagittal view for suture opening, wider at the base of anterior maxillar portion [
54
,
57
,
59
]
whereas a more parallel pattern was found for bone-borne expanders [
57
]. These findings
could also could be influenced by the location of the appliance [
34
]. Expanders are tended
to be placed in the intermediate palatal position, described as “palatal T zone” [
36
] in order
to assure a higher bicortical anchoring and a more parallel suture opening pattern [
60
].
From our results, we could describe a uniform almost parallel opening along the mid
palatal suture in the axial view, not observing differences superior to 0.4 mm as we move
to the molar area, consistent with previous studies using bone-borne or tooth bone-borne
expanders [30,34,57,61].
The midpalatal suture expansion, on the coronal cross-sectional slice through the
midportion of first molar, evaluated at the Nasal and Palatal Floor levels, showed no
statistically significant differences between them, with a mean of 2.4 (1.0) mm, confirming
a parallel opening suture pattern also on the coronal view. These values are in congruence
with the dimension of suture expansion (SEM) at the first molar level on the axial view
with a mean of 2.7 (1.0) mm.
4.2. Dentoalveolar Changes
A smaller proportion (40%) corresponds to the dentoalveolar component (1.8 mm).
Alveolar bone bending (ABB) and dental inclination (DI) showed reduced mean values
of 0.7 (1.6) mm and 1.1 (1.3) mm, respectively. Flexion of the alveolar bone accounted for
15.5% of the total expansion and 24.4% of the dental inclination corresponding to the first
molar. Ngan [
34
] reported a higher dentoalveolar effect of 59%, observing 12% of alveolar
bone bending and 47% of first molar dental tipping (2.98
±
0.56 mm). These results are
in agreement with Choi [
31
] who reported an 87% success for orthopedic expansion in an
adolescent sample, where 43% of TE was derived from skeletal expansion [31].
Recent studies evaluating RME effect on periodontal structures found significant
reductions in buccal bone thickness (BBT) [
29
,
54
], while others reports did not find any or
only found minimal changes [
62
,
63
]. Garib [
20
] observed a buccal bone thickness (BBT)
reduction from 0.6 to 0.9 mm after RME with no statistical differences between tooth tissue
and tooth-borne expanders, regarding the buccal movement of the posterior teeth [
20
]. A
retrospective study treated with MARPE with tooth bone-borne expanders [
61
] described a
maxillary transverse deficiency correction reporting, 37.0% of skeletal expansion, 22.2% of
alveolar expansion and 40.7% of dental expansion, observing buccal bone thickness (BBT)
(0.6–1.1 mm) and buccal alveolar crest Level (BACL) (1.7–2.2 mm) reductions. Despite the
decrease in thickness and height of the buccal bone accompanied with buccal tipping of the
J. Clin. Med. 2022,11, 4652 15 of 20
maxillary first molar, a high percentage of skeletal expansion was achieved (37%). Some of
these changes are comparable to those observed after conventional RME [20,38,64].
Significant changes were found in our study regarding buccal bone thickness (BBT)
reductions which ranged from 0.1 (0.2) to 0.4 (0.4) mm for the premolar and molars, but no
significant changes were observed after treatment at any site with regards to buccal alveolar
crest Height BACL. Ngan [
34
] reported similar slight changes with a mean buccal bone
thickness reduction from 0.27 mm to 0.60 mm at the first molar where bands were placed.
As for palatal bone thickness (PBT), there were significant increases from
0.1 to 0.2 mm
on the left side for the three teeth, and a small buccal bone thickness (BBT) reduction
<0.5 mm was observed in same location after maxillary expansion. Therefore we can
deduce that these changes tended to show a more skeletal maxillar expansion pattern,
coincident with other studies reporting bilateral palatal bone thickness augmentation after
MARPE [
29
,
65
] or after RME [
20
,
38
]. Toklu et al. [
29
] found an equivalent reduction in
buccal bone thickness, but a palatal bone thickness increase in the anchored teeth with the
use of tooth borne and tooth bone-borne expanders after RME, observing a buccal bone
thickness reduction in the banded first molars (approximately 0.7–1.2 mm) with both types
of expanders in patients with a mean age of 13.8 years.
Dentoalveolar changes such as reduction in buccal bone thickness (BBT) and aug-
mentation of alveolar bone height or vertical buccal alveolar crest Level (BACL) have
been confirmed to be greater with the use of tooth-born expanders by one recent prospec-
tive comparative study on 60 adolescent patients treated with MARPE tooth bone-borne
maxillary expanders or tooth-born expanders [66].
4.3. Dental Changes
Buccal teeth inclination and dentoalveolar structures flexion are common findings
after RME. However, studies report small statistical relevance. When comparing dental
effects related to the use of tooth and tooth bone-borne expanders, one study observed
differences which are not statistically significant in terms of absolute dental tipping between
groups for the first premolar when this was banded, finding a dental inclination increase
of 2.33
◦
(3.03)
◦
with a tooth-borne expander, whereas it remained unchanged in the tooth
bone borne expander group (not banded) [
29
]. However, this finding should be cautiously
interpreted due the great individual variability that has been observed for tipping as shown
by previous studies [38,67].
In our study, dental inclination measured in degrees did not show any significant
variation after treatment, being minimal on all the evaluated teeth, showing a tendency to
positive tipping, slightly increasing from the first molar to the first premolar. Therefore,
it could be said that MARPE with tooth bone-borne expanders is an effective and safe
treatment to correct maxillary transversal discrepancy in adolescent patients when the
midpalatal suture is still not fully ossified and partially open.
Some authors state that a 1–24
◦
molar inclination increase is inevitable, probably due
to alveolar bending and posterior teeth tipping effect [
61
,
68
]. A previous study evaluating
this effect after RME observed a significant bilateral first molar buccal tipping with mean
values of 5.6
◦−
6.2
◦
[
51
]. Park et al. [
61
] reported similar values after MARPE, observing a
higher degree of buccal tipping in the first molar compared to the first premolar, related
to the buccal bone thickness (BBT) and the crest height (BACL) reduction observed in
their study. Perhaps these results can be influenced by a greater mean age of this sam-
ple (
20.1 ±2.4 years
, range: 16–26 years) compared to our sample. In line with these
results, other research reported similar inclination changes, but with lower tipping values
of 2.5
◦
[
20
], and 3.9
◦
, respectively [
69
]. On the other hand, one recent study found greater
first molar inclinations between 4.95
◦−
6.99
◦
after MARPE, but such differences were not
significant when compared to first premolar inclinations [
61
]. Lim et al. [
25
]. observed a
reduction of 0.23
◦
per year for buccal tooth inclination after MARPE completion, which
is associated to the previously explained remodeling of buccal bone apposition. In this
same line of research, Lagraverèet al. [
12
] in a comparative study between tooth-borne
J. Clin. Med. 2022,11, 4652 16 of 20
and tooth bone-borne expander with control group, showed similar changes in the trans-
verse dimension and a significant crown inclination in the posterior segments with both
type of appliances.
The high potential of CBCT for evaluating maxillary structures has been confirmed.
Good resolution, accuracy (only about 2% magnification), precision, non-invasiveness,
lower effective radiation dose compared to other diagnostic methods, with shorter acquisi-
tion times have been described as its main advantages (60 s) [70–73].
Despite all efforts to minimize patient radiation exposure as much as possible, an
optimal quality image is needed to perform accurate measurements. Voxel size influences
the final image, thus affecting the accuracy of the performed measurements [
74
,
75
]. Several
studies assessing linear measurements in skull and jaw bones in CBCT have been carried
out [
76
–
78
]. Unfavorable effects such as poor image sharpness and artifacts derived from
CBCT imaging are inevitable and can influence alveolar accuracy measurements [
74
,
79
].
Specifically related to alveolar bone dimensions, the study of Sun et al. concluded that
alveolar bone-height and thickness measurements can be achieved with CBCT images with
good to excellent repeatability, pointing out that decreasing voxel size from 0.4 to 0.25 mm
can improve alveolar bone linear measurement accuracy, observing that measures with a
voxel size of 0.25 mm were closer to the direct measurements than when using 0.4 mm [
74
].
However, another study evaluating bone height and width, showed that 0.4 mm voxel
images provided results as accurate as 0.125 mm voxel images [
80
]. Moreover, Torres
and coauthors did not find differences between voxel sizes of 0.2, 0.3 and 0.4 mm, when
evaluating linear bone measurements, in agreement with previous results [
81
]. Although a
higher radiation dose when using lower voxel size values is inevitable, this can be justified
by its higher resolution needed for this type of measures. A 0.2 voxel size was used in our
study in accordance with other similar research considered as reference [29,57].
Some limitations such as small sample size and the short-term follow up have been
considered and discussed, though the desired goals have been fulfilled. Moreover, a control
group could be used to compare different expander designs or treatments. However, no
sufficient homogeneous sample could be collected. On the other hand, the high precision
of quantitative analyses on CBCT images contributes to the reliability of the outcomes,
making the small sample size acceptable [
20
]. Therefore, it would be interesting to confirm
our results in future studies with longer retention periods and larger samples.
5. Conclusions
From the analysis of our results, we can conclude that:
1.
MARPE with tooth bone-borne expanders is an effective method for treating maxillary
deficiency in adolescent patients with incomplete ossification of the midpalatal suture,
observing a significant maxillary expansion.
2.
Although, some periodontal or dentoalveolar changes such as buccal bone thickness
reduction were observed radiographically after treatment, none of these effects were
clinically detectable.
3.
Maxillary deficiency correction with MARPE resulted in a larger skeletal expansion,
with reduced dentoalveolar and dental effects and the buccal alveolar crest remained
practically unchanged.
4.
Tendency of parallel midpalatal suture opening pattern was observed after treatment
in the coronal and axial view.
5.
Aside from the use of tooth bone support for maxillary expansion, no significant
dental inclination effect was observed after treatment.
Author Contributions:
Conceptualization, P.S.M. and B.S.M.; methodology, P.S.M.; software, P.S.M.;
validation, P.S.M., E.S.R. and B.S.M.; investigation, P.S.M. and P.A.P.; resources, P.S.M.; data curation,
P.A.P.; writing—original draft preparation, P.S.M.; writing—review and editing, P.S.M.; supervision,
E.S.R. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
J. Clin. Med. 2022,11, 4652 17 of 20
Institutional Review Board Statement:
The study was conducted in accordance with the Declaration
of Helsinki, and approved by the Ethics Committee of hospital universitario Vírgen Macarena-Virgen
del Rocío (238e1b02c492fe6c37e2e9cf37c737297f4cf746) 14 December 2020.
Informed Consent Statement:
Informed consent was obtained from all subjects involved in the study.
Conflicts of Interest: The authors declare no conflict of interest.
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