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Citation: Inchingolo, A.M.; Patano,
A.; De Santis, M.; Del Vecchio, G.;
Ferrante, L.; Morolla, R.; Pezzolla, C.;
Sardano, R.; Dongiovanni, L.;
Inchingolo, F.; et al. Comparison of
Different Types of Palatal Expanders:
Scoping Review. Children 2023,10,
1258. https://doi.org/10.3390/
children10071258
Academic Editor: Maria
Grazia Cagetti
Received: 4 July 2023
Revised: 14 July 2023
Accepted: 20 July 2023
Published: 21 July 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
children
Review
Comparison of Different Types of Palatal Expanders: Scoping
Review
Angelo Michele Inchingolo 1, Assunta Patano 1, Matteo De Santis 1, Gaetano Del Vecchio 1, Laura Ferrante 1,
Roberta Morolla 1, Carmela Pezzolla 1, Roberta Sardano 1, Leonardo Dongiovanni 1, Francesco Inchingolo 1, * ,
Ioana Roxana Bordea 2, * , Andrea Palermo 3, Alessio Danilo Inchingolo 1and Gianna Dipalma 1
1Department of Interdisciplinary Medicine, University of Bari “Aldo Moro”, 70121 Bari, Italy;
angeloinchingolo@gmail.com (A.M.I.); assuntapatano@gmail.com (A.P.); matteo_des@hotmail.it (M.D.S.);
dr.gdelvecchio@gmail.com (G.D.V.); lauraferrante79@virgilio.it (L.F.); robertamorolla@gmail.com (R.M.);
c.pezzolla3@studenti.uniba.it (C.P.); robertasardano@gmail.com (R.S.); leonardodng1994@gmail.com (L.D.);
ad.inchingolo@libero.it (A.D.I.); giannadipalma@tiscali.it (G.D.)
2Department of Oral Rehabilitation, Faculty of Dentistry, Iuliu Hatieganu University of Medicine and
Pharmacy, 400012 Cluj-Napoca, Romania
3College of Medicine and Dentistry, Birmingham B4 6BN, UK; andrea.palermo2004@libero.it
*Correspondence: francesco.inchingolo@uniba.it (F.I.); roxana.bordea@ymail.com (I.R.B.);
Tel.: +39-331-2111-104 (F.I.); +40-(744)-919-391 (I.R.B.)
Abstract:
Maxillary bone contraction is caused by genetics or ambiental factors and is often ac-
companied by dental crowding, with the possibility of canine inclusion, crossbite, class II and III
malocclusion, temporomandibular joint disorder, and obstructive sleep apnea (OSAS). Transverse
maxillary deficits, in which the maxillary growth is unusually modest, are frequently treated with
maxillary expansion. The purpose of this study is to compare the dental and skeletal effects of
different types of expanders, particularly the Leaf Expander, rapid and slow dental-anchored or
skeletal-anchored maxillary expanders. Methods: We chose studies that compared effects determined
by palatal expansion using a rapid palatal expander, expander on palatal screws, and leaf expander.
Results: Reports assessed for eligibility are 26 and the reports excluded were 11. A final number of
15 studies were included in the review for qualitative analysis. Conclusions: Clinically and radio-
graphically, the outcomes are similar to those obtained with RME and SME appliances; Therefore, it
might be a useful treatment choice as an alternative to RME/SME equipment in cases of poor patient
compliance or specific situations. Finally, all of the devices studied produce meaningful skeletal
growth of the palate. The use of skeletally anchored devices does, without a doubt, promote larger
and more successful growth in adolescent patients.
Keywords:
rapid palatal expander; hyrax; leaf expander; rep on screw; slow maxillary expansion;
palatine suture; dental anchorage; leaf spring activated expander; transverse maxillary deficit
1. Introduction
Transverse maxillary deficits, which are characterized by abnormally low maxillary
growth, are frequently treated with a rapid maxillary expansion (RME) [
1
–
3
]. A total
of 8–22% of orthodontic patients have this transverse maxillary discrepancy [
4
,
5
]. This
condition’s etiological reasons may be inherited or ambiental, and it is often accompanied
by dental crowding, with a possible risk of canine inclusion, crossbite, class II and III
malocclusion, dysfunction of the TMJ, and obstructive sleep apneas (OSAS) [
6
–
8
]. Regard-
less of surgical expansion, RME in orthodontics is typically carried out utilizing the RME
hyrax appliance, leaf expander appliance, and MARPE appliance. The palatine suture
opens up and the palate widens as a result of the various activation regimens of these
appliances. From the anterior palatine fissure to the posterior nasal spine, the median
palatine suture runs [
9
,
10
]. As the patient grows, more spicules form along the suture,
Children 2023,10, 1258. https://doi.org/10.3390/children10071258 https://www.mdpi.com/journal/children
Children 2023,10, 1258 2 of 17
resulting in stringent interdigitations. The ossification process of the suture is directly
associated with skeletal age and gender [
11
–
13
]. It gets harder to open the suture as the
patient ages. Research examines six cervical vertebral maturation stages, examining their
association with peak stature growth [
14
–
16
]. Between cervical vertebral stages 3 and 4,
mandibular and craniofacial growth increases, with rectangular bodies and concavity on
lower edges [
16
,
17
]. Angelieri et al. uses CBCT examination to examine palatine suture
morphology in five stages, showing partially interdigitated lines with high-density lines
and low bone density areas [14].
Therefore, the most precise method for assessing the palatine suture and detecting
dentoskeletal alterations following RME is CBCT. Cone-beam computed tomography
(CBCT) can be used to evaluate the palatine suture bone bridges’ interdigitation quality
and density, which is a crucial factor in the device selection process [6,7,18].
The most contentious choice in treating transverse disparities in adolescent patients is
how to expand the upper jaw. Depending on the situation, the orthodontist should select a
“patient-oriented” appliance that can reduce the variety of potential side effects, including
appliance breakage, functional issues, periodontal tissue problems, and discomfort [
19
].
The hyrax expander (HEX), a permanent appliance with no externally visible elements
that are fastened to the upper first molars (to deciduous teeth when possible), is the most
widely used palatal expander [
8
,
20
–
22
]. It has a central screw that, when turned as directed
by the orthodontist (about 0.25 mm twice daily for 15 days), applies a force of around 10 kg
to split the palatine suture, causing the transverse diameter of the palate to enlarge. Thus,
the suture can be divided in a short period of time—in most situations, it takes around
15 days to do this [7,23,24]. After this, the expander must be left in place for an additional
six to nine months to allow the suture to ossify and consolidate in the new spaces [25].
Next to the conventional HEX, the Leaf expander (LEX) has been proposed as an
alternative without parental cooperation [
26
]. The patient should experience substantially
less discomfort as a result. Similar to HEX, it comprises a metal skeleton with two bands
that are bonded to the molars (deciduous wherever possible), as well as an expansion
screw that makes use of mild continuous forces produced by Ni-Ti springs. Comparing
LEX to HEX, the expansion takes place over a longer period of time. Along with the
vascular growth that promotes rapid neo-ossification, the intermaxillary suture mineralizes
concurrently with this gradual expansion, making it more consistent with histophysiology.
The Leaf expander (LEX) has been suggested as an alternative to the traditional HEX
without parental consent. The patient should experience substantially less discomfort as a
result [
27
]. Similar to HEX, it comprises a metal skeleton with two bands that are bonded
to the molars (deciduous wherever possible), as well as an expansion screw that makes
use of mild continuous forces produced by Ni-Ti springs. Compared to HEX, LEX has
a different action kinetics and the growth continued for several months [
28
]. It is more
consistent with histophysiology during this sluggish growth because the intermaxillary
suture is mineralized concurrently with the expansion and because vascular development
encourages rapid neo-ossification [29].
While HEX and LEX expanders are intended to act orthopedically, they invariably
result in unintended tooth movements. These tooth motions have the potential to change
how well the teeth and their roots are supported by the periodontal ligaments, but they can
also create space. From a biological perspective, the prognosis is really uncertain when such
extension is sought in adult patients or those who have otherwise reached their maximal
growth because of the increased interdigitation of the maxillary sutures and the rigidity of
the surrounding structures.
Rapid palatal expansion by skeletal anchoring (MARPE) can be employed on patients
who are in advanced phases of skeletal development to avoid unfavorable dentoalveolar
consequences and maximize skeletal expansion potential [
3
,
26
]. Lee et al. proposed the
first report of RME with skeletal anchoring in 2010 [
30
]. Two tiny implants in the palate
were used in the trial on a 14-year-old girl. The maxillary molars showed a modest buccal
inclination and successfully separated the mid-palatal suture. A second research using
Children 2023,10, 1258 3 of 17
MARPE on 69 adult patients with an average age of 20.9 years revealed an opening of the
mid-palatal suture success rate of 86.96% and an average increase in maxillary breadth of
2.11 mm. Additionally, there was a noticeable rise in the inter-molar distance and nasal
cavity width, measuring 1.07 mm and 8.32 mm, respectively [
31
]. The MARPE, therefore,
appears to be a viable alternative in cases of young adults, subject of course to a good
diagnostic assessment [32,33].
The purpose of this study is to compare the dental and skeletal effects of different
types of expanders, particularly the Leaf Expander, rapid and slow maxillary expanders
with dental or skeletal anchorage to determine whether there is one method that is more
effective and efficient than the others and to evaluate the pain they cause patients.
2. Materials and Methods
2.1. Protocol and Registration
This study was carried out in accordance with the Preferred Reporting Items for
Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR)
guidelines and submitted to PROSPERO (International Prospective Register of Systematic
Reviews) with ID 430622 [34–37].
2.2. Search Processing
With a restriction on English-language studies published between 1 January 2013
and 13 April 2023, we searched PubMed, Scopus, and Web of Science. To undertake an
evaluation that is current with the recent 10 years, this time frame was selected. The search
approach included the following Boolean keywords: (“hyrax” OR “rep on screws” OR “leaf
expander”) AND “treatment”. These phrases were chosen because they most accurately
reflected the aim of our investigation, which was to find out more about the expansion
brought about by employing various palatal expanders.
2.3. Eligibility Criteria and Study Selection
A quick palatal expander, an expander on palatal screws, and a leaf expander (Leaf
Expander
®
, Leone Ortodonzia e Implantologia, Via del Ponte di Quaracchi, 50, 50019
Sesto Fiorentino FI) were used in the research and we chose to compare the effects of
palatal expansion. The two steps of the selection process were the appraisal of the title and
abstract and the complete text. Any article that fit the following requirements was taken
into consideration: (a) clinical trials including human intervention; (b) comparison of the
therapy to other interventions; (c) English language complete text. Publications (such as
meta-analyses, research methods, conference papers,
in vitro
, or animal experiments) that
lacked original data were not included. Titles and abstracts from the preliminary search
were retrieved and evaluated for relevance. Full articles from pertinent research were
acquired for further analysis. The retrieved studies were assessed for inclusion using the
aforementioned criteria by two different reviewers (R.M. and A.P.).
2.4. Data Processing
R.M. and A.P., two reviewers, independently evaluated the studies’ quality based on
selection criteria after doing a database search to extrapolate the findings. To use with
Zotero, the chosen articles were downloaded in the 6.0.15 version. A senior reviewer (F.I.)
was consulted in order to address any disagreements between the two writers.
2.5. PICOS Requirements
The PICOS (Population, Intervention, Comparison, Outcome, and Study Design)
criteria, which are used in this evaluation, encompass population, intervention, comparison,
outcomes, and study design (Table 1).
Children 2023,10, 1258 4 of 17
Table 1. PICOS criteria.
Criteria Application in the Present Study
Population Children and adolescents (age range 6–16 years)
Intervention
Use of rapid palatal expander, rapid palatal expander on screws, leaf expander
Comparisons Comparing before and after palate expansion with different types of palatal
expanders.
Outcomes
Comparison of the palatal skeletal expansion techniques most used by ortho of
different types of expanders and the pain they cause.
Study design Clinical Trials.
3. Results
Selection and Characteristics of the Study
A total of 1008 publications were found in the online database (PubMed n= 675,
Scopus n= 1, and Web of Science n= 332); no papers were found using a manual search.
After 211 duplicate studies were removed, 797 studies were evaluated by looking at the
title and abstract. A total of 26 records were chosen out of 771 items that failed to fulfill the
requirements for inclusion. Reports requested for retrieval totaled 30, while reports not
found totaled 0. There were 26 reports evaluated for eligibility, and 11 reports were removed.
In the end, 15 studies were reviewed for the qualitative analysis. The selection process
and the summary of selected records are shown in Figure 1. The studies characteristics are
summarized in Table 2.
Figure 1. PRISMA ScR flowchart diagram of the inclusion process.
Children 2023,10, 1258 5 of 17
Table 2. Characteristics of the studies included in the qualitative analysis.
Authors Type of Study Object Study Design and Timeline Results
Lanteri et al. (2021) [38] Retrospective study
A comparison of cephalometric
dental and skeletal alterations
following the use of a RME and a
Ni-Ti (Leaf) expander with a group
of untreated controls.
Radiograms taken prior to and following maxillary
growth were noted. There were 11 women and 9 men
in the Leaf Expander group. There were 12 women
and 11 men in the RME group.
Leaf expander and RME have
overlapping effects in terms of
dental and skeletal changes.
Nieri et al. (2021) [39]Multicenter
randomized controlled
trial
Compare during the first 12 weeks
the expansion determined by a
screw with moderate and
continuous forces against a screw
for quick jaw expansion.
30 subjects in mixed dentition with a transverse
discrepancy of at least 3 mm, with a posterior crossbite
were divided into 3 groups: RME group; SME group; a
leaf expander (LE) group. Comparison of these
different techniques.
Major differences were found only
in reference to algic sensitivity felt
significantly less with leaf,
particularly during the first 7 days.
There were no differences detected
for the other factors.
Lanteri et al. (2018) [40] Retrospective study Dental and skeletal comparison
between the Leaf Expander and and
slow and rapid maxillary expansion.
Nasal, maxillary, mandibular, and upper permanent
molar width was measured in 30 patients with a
posterior crossbite. They were divided into 3 treatment
groups: (a) rapid maxillary expander (RME); (b) slow
maxillary expander (SME); (c) leaf expander (LE).
No differences were found among
the 3 groups, all measures increased
significantly
De Paula Machado Pasqua
et al. (2022) [41]Randomized clinical
trial
Comparison, through cone-beam
computed tomography, the
dento-skeletal changes obtained
from the use of the Hyrax palatal
expander and the Hybrid Hyrax.
42 patients divided into 2 groups: (1) group treated
with Hyrax Hybrid (HHG); (2) group treated with
Hyrax (HG). Before and 12 weeks after the activation
phase, CBCT was performed, in order to evaluate the
modifications.
The hybrid Hyrax had less dental
effects than skeletal ones
particularly in the first premolar
area. In the HHG, the level of
activation affected the greater nasal
skeletal alterations.
Celenk-koca et al. (2018) [42]Prospective
randomized clinical
trial
To assess the dental and skeletal
changes in adolescents using
conventional and
miniscrew-supported maxillary
expansion appliances.
40 patients divided into two groups: (1) rep with
dental anchorage; (2) rep on miniscrews. Changes in
transverse skeletal widths, buccal bone thickness,
dental tip and root length were evaluated with cone
beam radiography.
Expansion through the use of
expander anchored on miniscrews
allowed an increase in maxillary
suture more than 2.5 times
compared to expansion with
conventional rep.
Halicioglu et al. (2016) [43]
Randomized controlled
trial
Examine and contrast the effects of a
memory screw versus a traditional
HE screw on the soft tissues and
skeletal features of the face.
32 patients divided into 2 groups: 17 treated with
memory screw palatal expander and 15 patients
treated with Hyrax screw expander.
Mid-palatal suture opening was
obtained in all patients. Anterior
and inferior rotation of the upper
jaw was observed in both groups;
instead, the jaw rotates downward
and backward especially in the
memory-screw group.
Children 2023,10, 1258 6 of 17
Table 2. Cont.
Authors Type of Study Object Study Design and Timeline Results
Manzella et al. (2021) [44]Retrospective
controlled clinical
study
In adolescent orthodontic patients
who have maxillary transverse
constriction to assess the dental
effects of the Ni-Ti Memoria®Leaf
Spring Activated Expander
(MLSAE)
The sample consisted of 22 patients who received Ni-Ti
MLSAE treatments in a row and 22 untreated controls.
Digital dental casts were obtained at baseline, 7 days,
4 weeks, and after jaw expansion. Misure of
inter-canine, inter-premolar, inter-first molar area,
depth and perimeter of arch, and angulation of molars
measurements of the maxillary dental arch were
assessed.
Ni-Ti MLSAE can achieve sufficient
expansion without significantly
tipping the patient’s teeth.
Ugolini et al. (2020) [20] Randomized trial
Analysis how two different type of
palatal expansion screws influenced
function throughout the first 7 days
of activation.
101 individuals were randomly allocated to one of two
groups: (1) those who received the Hyrax screw;
(2) those who received the LE. A comparison was made
between the two groups regarding reported pain.
Clinical activation protocol and
screw type have an impact on pain
experienced during maxillary arch
expansion. Patients who utilized a
LE reported much decreased
discomfort throughout the first
week of therapy.
Lanteri et al. (2020) [45] Clinical trial
After maxillary expansion using a
slow maxillary expansion protocol,
changes in vestibular bone thickness
(BT) and dento-alveolar buccal
tipping of first and second molars
were investigated.
The Leaf Expander protocol was used to treat
20 patients. Cone beam computed tomography (CBCT)
images were used to calculate the buccal alveolar BT,
buccal alveolar bone height (BH), dental TIP, and
inter-molar width (IW) regarding the first and second
primary molars.
After using LE appliance, it seems
that BT was not substantially
decreased. During mixed dentition,
the treatment of maxillary
hypoplasia through a slow
expansion with Ni-Ti springs looks
successful and secure.
Serafin et al. (2022) [46]Randomized clinical
trial
To compare skeletal and dental
changes following Leaf Expander
(LE)-performed rapid maxillary
expansion (RME) and slow
maxillary expansion (SME).
Patients treated with palatal expanders anchored on
deciduous second molars were divided into 2 groups:
(1) RME group (16 patients treated with Hyrax
expander); (2) SME group (16 patients treated with LE).
Then, they made a comparison of the effects of these
appliances.
Both RME and SME effectively
expanded the skeleton and the
dentoalveolar region; RME did so
more anteriorly than SME, but with
less control over the development of
permanent molar decompensation.
SME by LE could, therefore, be a
useful and effective alternative in
patients who are growing.
Davami et al. (2020) [47]Randomized clinical
trial
Evaluate and compare, with CBCT,
the skeletal and dental alterations
following maxillary expansion
through a tooth-supported
expander and with a
bone-supported expander.
29 young patients were separated into two groups:
(1) bone supported expander; (2) tooth supported
expander. Before and after the expansion CBCT was
taken.
Expansive results are
superimposable with both types of
expansion
Children 2023,10, 1258 7 of 17
Table 2. Cont.
Authors Type of Study Object Study Design and Timeline Results
Lanteri et al. (2018) [25] Pilot study
Study of the dentoalveolar effects of
SME using the LE in growing
patients with deficit of transverse
diameter of maxilla.
10 patients with mixed dentition were treated with LE.
5 factors were considered: (1) the distance between the
first upper permanent molars; (2) the distance between
the second upper deciduous molars; (3) the distance
between the cusps of the upper canines; (4) the
distance between the lower first permanent molars;
(5) the distance of the lower canine cusps.
The LE guarantees good results in
the correction of transverse
maxillary deficit in mixed dentition.
Silveira et al. (2021) [48]
Randomized controlled
clinical trial
Comparing the Hyrax and Mini
Hyrax’s impacts on growing
patients’ oral health, quality of life,
and pain perception.
34 boys with transverse maxillary deficiency were
divided into 2 groups, who had Mini Hyrax expander
(MHE) and who had Hyrax expander (HE). Dental
impacts were measured using digital overlays and
variations in quality of life were measured using a
questionnaire.
The dental outcomes, quality of life
impacts or pain perception of
teenagers wearing the Hyrax Mini
(MHE) and Hyrax Expanders (HE)
did not differ significantly.
Cossellu et al. (2020) [49] Clinical study
Evaluate the effects of SME on the
maxillary and mandibular arch,
using LE appliance inserted on the
second primary molar.
90 patients with posterior crossbite and transverse
maxillary deficiency and were divided into 69
undergoing SME and 21 treated with RME.
The effectiveness of SME has been
confirmed on both the upper jaw
and mandibular arches.
Feldmann et al. (2017) [50]
Randomized controlled
trial
Assess the level of pain, degree of
discomfort, and jaw function
impairment during the first week
with RME
54 patients divided in different groups: (A)
Conventional Hyrax Group (HG), (B) Patients received
a HHA attached to anterior palate mini-implants. On
the 1st and 4th days following RME appliance
insertion, questionnaires were utilized to measure pain
severity, discomfort, analgesic intake, and impairment
of jaw function.
During the first week of treatment,
tooth and bone expansion was
generally well accepted by patients
and regardless of gender.
Children 2023,10, 1258 8 of 17
4. Discussion
Upper jaw transverse deficit associated with posterior crossbite is one of the most
prevalent malocclusions in developing patients, affecting an estimated 13.3% of adoles-
cents [41].
The transversal maxillary deficit does not resolve spontaneously with growth, there-
fore, it is advisable to intervene early to resolve it, thus preparing the bone bases for a
correct eruption of permanent teeth [49,51].
In 1860, Angell invented the first maxillary expander device (RPE) [47].
It was immediately considered safe and efficient and met with great success [49].
Since then, the interest in the RPE has gradually increased.
Maxillary expansion can be achieved with slow (SME) or rapid (RME) expanding
devices. RME is typically the first-choice treatment for transverse skeletal discrepancies [
38
]
(Figure 2).
Figure 2.
Three different types of palatal expander: (
a
) Hyrax expander; (
b
) Rep on mini screws; (
c
)
Leaf expander.
4.1. Effects of Leaf Expander
4.1.1. Dental Changes
Manzella et al., 2017 conducted a retrospective controlled clinical study to analyze
how the Ni-Ti Memoria
®
Leaf Spring Activated Expander (MLSAE) influences dental
health in young patients with orthodontics who have reduced transverse dimensions of the
upper jaw. The Ni-Ti MLSAE was used by 22 patients (mean age of 12 years) compared
to 22 untreated controls. Digital dental casts were taken at the pretreatment, one-week,
monthly, and post-expansion time periods. The maxillary dental arch’s inter-canine, inter-
premolar, inter-first molar, arch depth, arch perimeter, and molar angulation measures were
evaluated [
44
]. The overall mean expansion time was 4.21 months. Significant increases
were seen in the treatment group’s inter-canine, inter-first and second premolar, inter-first
molar, and arch perimeter measures between the first measurements and the final ones.
There were no observable differences between the controls. According to between-group
studies, there were statistically significant differences in all variables between the treatment
and control groups, with the exception of arch depth and molar angulation. Average
changes were 1.04, 5.65, 5.80, 4.70, and 2.15 mm for inter-canine, inter-first premolar, inter-
second premolar, inter-first molar, and arch perimeter, respectively. The Ni-Ti MLSAE can
achieve sufficient expansion in patients between the ages of 6 and 16 without significantly
tipping the teeth. When using the recommended protocol, it should be regarded as a device
for slow expansion that enables measured expansion at an average rate of 1.1–1.5 mm per
month [44].
Given its potential to bring about positive anatomical and functional changes, the Leaf
Expander (Figure 3) may be regarded as the first therapeutic option for treating mast cell
tumors. The primary benefits of using this device lie in its simplicity of activation, lack of
cooperation (no compliance), and the ability to control the movement of the teeth using
light, predictable, and cost-effective forces. The findings of a study conducted by Lanteri
et al. in 2018 demonstrate the effectiveness and usefulness of the LE even when applied
to solid teeth for the correction of transverse maxillary deficit in growing populations.
Complete correction of the posterior crossbite occurred in all patients in an average of
4 months, with a natural expansion of the first permanent molars. They were obtained [
25
].
Children 2023,10, 1258 9 of 17
Figure 3. Leaf expander with key activator.
In 2020, Cossellu and others said that Leaf Expander therapy is an effective therapeutic
option for treating transverse maxillary deficit [49].
4.1.2. Alterations of the Buccal Alveolar Bone of the Permanent First Molars and the
Deciduous Second Molars
Lanteri et al. 2020 conducted an interesting clinical study. After maxillary extension
employing a gradual expansion protocol of the maxilla, the alteration of the vestibular bone
thickness and vestibular tipping of primary second molars and permanent first molars
were investigated. With a mean age of 7 years, the Leaf Expander procedure was applied
to nine males and eleven women. Cone beam computed tomography (CBCT) images were
used to calculate the BT, BH, interdental angle (TIP), and IW of the first and second primary
molars. The bone width from the vestibule to the second primary molar and the intermolar
size of both teeth were the only variables that statistically altered. It would appear that
following treatment with LE, buccal bone depth from the vestibular to the first molars
did not decrease significantly. Using a SME with Ni-Ti springs suggests to be a safe and
effective approach for treating upper jaw hypoplasia during mixed dentition in clinical
settings [45].
4.2. Comparison between RME and SME
4.2.1. Comparison between Memory Screw and Traditional Hyrax Screw (Figure 4)
The memory screw, which has both screw and nickel-titanium springs, is the first
banding device to apply a continuous force as opposed to intermittent force. The sagittal
and vertical effects of maxillary expansion brought on by a memory screw (MS) on the
dentofacial structures have not been investigated in any studies. The goal of Koray Halcolu
and Brahim Yavuz’s study from 2020 was to examine the differences between the sagittal
and vertical alterations in participants who had been treated with a memory screw with a
traditional Hyrax screw (HS). Two groups of 32 patients with maxillary transverse deficit
were created. A MSG included 17 patients (9f and 8m), while a HSG was composed of
15 people (8f and 7m). The individuals in the two groups were about 13 years old. In
the early stages of therapy (T1), the end of the expansion phase (T2) and the end of the
retention period (T3); lateral cephalograms of the patients were performed. In the MSG,
the average duration of expansion was 7 days, whereas in the HSG, it was about 35 days.
Children 2023,10, 1258 10 of 17
It may be said that all patients in both groups underwent sutural opening, which was
followed by significant dental and bone development. In both groups, the mandible turned
posteriorly and inferiorly as a result of the maxilla moving anteriorly and inferiorly. The
MSG had a larger rotation. The newly created MS opens the mid-palatal suture and extends
the maxilla with relatively lighter stresses over a shorter period of time, taking advantage
of protocols for both quick and slow maxillary expansion [43].
Figure 4. Hyrax expander on second primary molar.
4.2.2. Dento-Skeletal Changes
Serafin et al. in 2022 conducted a randomized clinical in which Leaf Expander (LE)
was used to compare RME and SME techniques [
46
]. Upper deciduous teeth serving
as anchorage were analyzed with 3D CBCT before and after therapy. According to the
current study’s findings, the following conclusions could be drawn: RME and SME can
both produce bone and dentoalveolar transverse expansion equally well; the anchoring of
deciduous teeth allows for clinically considerable transverse expansion while causing no
injury to permanent teeth; patients with respiratory problems and anterior dental crowding
may benefit more from RME, because it created a greater anterior expansion than SME;
SME is advised for patients with posterior dental crowding. Because SME releases forces
continuously, it also eliminates the need for home activation and allows a more controlled
dental movement [46].
4.2.3. Cephalometric Effects of Expansion
In 2018, Lanteri et al. also carried out a fascinating retrospective study. This study
contrasts the dental and orthopedic effects of the LE with the results of fast and SME.
Thirty patients with posterior crossbites were included in the sample and were split into
three groups: RME (3m, 7f), with an average age of 8.9 years; SME with an average age
of 12.2 years; LE, with an average age of 7.9 years. Postero-anterior cephalometric studies
were taken before treatment started (T1) and nine months later (T2). A calibrated examiner
has measured the width of the upper permanent molars, the mandible, the maxilla, and
the nasal canal. After the treatment, every measurement went up significantly. Average
maxillary length increased about by 4 mm, 2.8 mm, and 3.6 mm in the RME, SME, and LE
groups, respectively. In the RME, SME, and LE groups, the width of the upper permanent
molars increased by 5.4 mm, 5.4 mm, and 3.8 mm, respectively. There are no statistically
significant differences between the groups. It has been proven that the LE is effective at
correcting transversal deficiencies [25,52].
In 2021, Lanteri et al. performed retrospective research using bi-dimensional cephalom-
etry to compare and contrast the skeletal and dental alterations brought on by the use of a
RME and LE. Data were compared to a group that was not given any treatment. The LE
group had an average age of 8 years and consisted of 11 females and 9 boys. A total of
11 men (mean age: 7 years) and 12 women (mean age: 8 years) made up the RME group in
Children 2023,10, 1258 11 of 17
the current study. Dolphin Imaging software was used to trace digital cephalograms and
calculate all reported measurements. No statistically significant change was discovered,
with the exception of the angles between the upper incisor and the cranial base and bispinal
planes, which showed a reduction, and the angles between the lower incisors and the
mandibular plane, which showed an increase. It appears that both the RME and cause
similar changes to the bones and teeth [38].
4.3. Comparison between RME Conventional Jaw Expander and Mini-Screw Supported Expander
In addition to the opening of the medio palatal suture, which is its main objective,
RME causes various undesirable effects: buccal tipping, reduction of buccal bone and
marginal bone levels, thinning of anchoring teeth, root resorption, crossbite recurrence,
uncertain stability over time, and swelling and ulceration of soft tissues [
53
]. Many of these
changes can be prevented by using mini-screws in the palatal bone (Figure 5) as an anchor
in RME treatments [42].
Figure 5. Bond anchored maxillary expansion with mini-screw.
Researchers have performed various studies over the years to increase the desired ben-
eficial skeletal effects of palatal expansion and reduce its dental and tissue side effects [
47
].
For example, inserting four mini-screws into the Hyrax conventional expander design
for the treatment of palatal bone contraction, prior to orthognathic surgery, has been shown
to result in dental side effects and a high degree of stability over time. Other studies in this
regard also allow us to conclude that expanders anchored with mini-screws to the bone can
reduce the need for transverse orthognathic surgery [54].
Today, there are several types of bone-anchored jaw appliances. One of the first devices
was the Dresden expander. The Dresden B-RME was used for the first time in Germany as
a palatal distractor in adults undergoing orthognathic surgery, obtaining positive results in
the bilateral symmetrical correction of the inverse bite.
The Dresden B-RME is supported by two bone anchors, a palatal implant on one
side and a mini-screw on the other. For patient comfort and rapid insertion, the expander
features two cylinders with three prongs for retention.
Tugce Celenk-Koca et al. in 2018 observed significant differences between two groups
of adolescent patients undergoing RME, for all skeletal variables, except for the measure-
ment of the width of the nasal cavity at the level of the maxillary first premolars [42,55].
-
The Hyrax with dental anchoring supported the often-described wedge-shaped open-
ing of the suture by showing the highest increase in width at the incisive foramen and
the lowest rise at the level of the maxillary first molar.
-
RME performed with anchorage on mini-screws showed a greater recovery of space
in the premolar region and very similar increases in width in the incisive foramen and
the molar suture. This led to a more parallel sutural opening with an almost three
times greater expansion in the suture medio palatal [
42
]. The expansion, however,
which took place with expanders on mini screws led to the straightening of the upper
molars with a significant advantage for the buccal alveolar bone support.
Children 2023,10, 1258 12 of 17
There was no difference in the length of the molar roots between the two expansion
groups, and most individuals in both groups had bigger anterior suture openings.
An RCT research conducted in 2021 by Silveira et al. focused on palatal expansion by
contrasting the dental outcomes and quality of life consequences of teenagers treated with
Mini Hyrax and Hyrax expanders (Figure 6). With the help of a pre- and post-treatment
and post-restraint questionnaire, the effect on quality of life was evaluated. Between the
Mini Hyrax users and the Hyrax wearers, there were no appreciable variations in the dental
impacts over time, as well as the influence on the quality of life: there was a worsening of
function 14 days after the application of the devices probably determined by the activation
of the screw and by the applied forces, while there was an improvement the overall quality
of life six months after the start of treatment given by the adolescent’s recognition that he
was on the way to resolving the malocclusion [48].
Figure 6.
Dental effect of (
a
) Hyrax anchored on molars and (
b
) Rapid palatal expander anchored on
mini screws.
4.4. Evaluation of Skeletal Changes Using Three-Dimensional Images
As we know, before the introduction of three-dimensional (3D) imaging, such as
conventional CBCT, to evaluate the results of orthodontic treatment with RPE on dentoalve-
olar structures, researchers have commonly used two-dimensional radiographic images
such as lateral and posteroanterior cephalograms. However, these methods have many
limitations and that is why today we prefer to use three-dimensional scans that allow us
to measure, with values corresponding to reality, the skeletal, dental, dentoalveolar, and
suture variations pre and post-expansive treatment [42,56].
The computerized cone-beam tomography was used in a study by Bruno de Paula
Machado Pasqua et al. in 2022 to compare dental electrophysiological changes to rapid
maxillary expansion with dental transmission equipment. The patient-accepted HH device
divides the risk of expansion between two mini-screws in the front palate and two posterior
teeth with orthodontic tubes. In addition, the risk of infection is low and the placement
of mini-screws is minimally invasive. A total of 42 patients between the ages of 11 and 14
with a lack of transverse maxilla were divided into two study groups: HHG (Hybrid Hyrax
group) and HG (Conventional Hyrax group) [41].
Before and three months following the activation period, the CBCT was conducted.
The following settings were used for the CBCT: 120 kVp, 18 mA, 8.9 s exposure time,
0.2 mm 25 voxel size, and a field of view (FOV) of 160
×
60 mm. Scans have been focused
on the breast area to reduce radiation exposure to a minimum. To standardize the position
of the test during CBCT acquisition, the patient was oriented with the Francoforte oblique
piano parallel to the pavement and the Francoforte medial piano perpendicular to the latter.
The scans were obtained prior to treatment (T0) and three months after the active phase
(T1).
The Dolphin software was used to extract the data for analysis.
The primary objectives included changes to the nominal dimensions. The spacing
between the teeth was used to measure dental changes in accordance with the points of the
wearer’s cuspids and the tips of the palatal radicles. The axial inclinations (degrees) of max-
illary first premolars and permanent first molars have been evaluated. All measurements
were evaluated in the first premolar and first molar regions.
Children 2023,10, 1258 13 of 17
Dolphin software was used to extract data for analysis. First premolars and first
permanent molars in the maxilla were measured for their axial inclinations (degrees). The
first premolar and first molar areas served as evaluation sites for all measures.
In conclusion, Hybrid Hyrax has demonstrated more skeletal changes and less dental
side effects, particularly in the area of the first premolar. The degree of activation has
influenced the more significant scheletric nasal changes in the hybrid hyrax group.
•
Compared to a dental expander (Hyrax), the osso expander (Hybrid Hyrax) has caused
a greater increase in skeletal changes in the newborn cells’ primary region of the brain.
Hybrid Hyrax has shown a noticeably greater rise in the size of the nasal cavitation in
the areas of the first premolars and the first molars; in the first premolars following RME
with Hybrid Hyrax, only minimal changes in the angle of the teeth have been observed.
•
There were no significant differences between the groups in terms of dental changes
made after RME in the area of the first molars.
•
The degree of activation has an impact on the more pronounceable scheletric nasal
changes on Hybrid Hyrax.
These studies have several limitations that should be considered. For example, the
generalizability of the results may be restricted to children between the ages of 11 and 14 as
well as the types of technology used. These findings need to be carefully considered by
patients outside of this age group.
4.5. Influence of Palatal Expansion on the Lower Arch
As argued by Cossellu et al. in 2020, based on some research carried out, the tongue
plays a fundamental role during expansive orthodontic treatment, regardless of the type
of device, because, due to the palatal presence of the expander, it lowers its position and
together with the new intercuspidation, during chewing promotes expansive forces in the
lower arch. The jaw expansion, therefore, acts on the balance of the tongue and cheek and
consequently stimulates an expansive action in the lower arch [49].
4.6. Device’s Pain
The following table taken from Ugolini et al. study of 2020 shows the difference
between the level and index of pain during the first four days after the use of two different
devices: a leaf expander and standard Hyrax (Table 3) [20].
Table 3. Pain level and pain index for Hyrax and Leaf expander, respectively.
Device Pain Level Pain Index
Hyrax 88.6% 51.4%
Leaf expander 25% 9.7%
Pain caused by expansion is closely related to the activation protocol and lifestyle of
the patient. The analysis was performed through patients’ completion of a questionnaire
on the analysis of pain and discomfort caused by the apparatuses. For the analysis of pain
intensity, the Wong–Baker scale was used, during the first week of apparatus placement.
As shown in the table, it can be seen that subjects treated with leaf expander experienced
less pain both from the point of view of intensity and duration than subjects treated with
standard Hyrax [20].
In the following study of Nieri et al., 2021 the difference in pain generated in the
first S12 weeks of treatment in leaf expander patients and conventional RME patients was
analyzed. Patients and parents were asked to fill out a questionnaire, as a result of which
the following results were obtained. Pain was analyzed according to the VAS scale, and
it was reported that the subjects with conventional RME showed a higher mean of pain
(
0.6 ±0.5
), compared with the mean of the leaf expander-treated group (0.3
±
0.4), and that
Children 2023,10, 1258 14 of 17
the maximum difference in pain was noted mainly in the first week of treatment. Based on
these data, we conclude that leaf expander causes fewer complications than conventional
RME. The pain originated from the inflammation of the mediopalatine suture during its
expansion and the pressure generated on the periodontal ligament, and it was shown that
the pain fee decreased significantly with the use of ketoprofen or with the reduction of the
number of daily apparatus activations [39,57].
In the following study, conducted by Feldmann et al., 2017, conventional hyrax and
hybrid hyrax are compared, evaluating their pain at day 1 and day 4 after activation. There
was not a statistically significant variation between the two groups, although hybrid hyrax
showed slightly lower levels of pain, the only difference reported in the hyrax hibrid treated
group compared to conventional hyrax was pain at the molars and incisors [50].
It was noted that patients treated with RME apparatology reported pain mainly
during the first 10 activations, reaching a maximum level at day 3–4 and decreasing on
subsequent days. Pain was analyzed with the VAS scale, and patients were asked to answer
questions associated to jaw function impairment during free time, use of analgesics, overall
discomfort, and pain severity [50].
5. Conclusions
After analyzing these studies, we can state that both rapid and slow expansion method-
ologies achieve similar expansion effects and, therefore, the choice of therapeutic means is
individualized based on the patient’s degree of collaboration. The differences in expansion
obtained between RME and Leaf expander are not clinically relevant. Therefore, the choice
of the therapeutic means is the responsibility of the clinician.
In conclusion, all devices analyzed promote relevant skeletal expansion of the palate.
Certainly, the use of skeletally anchored devices promotes greater and more effective
expansion in the adult patient.
Author Contributions:
Conceptualization, A.M.I., A.P. (Assunta Patano), M.D.S. and G.D.V.; method-
ology, L.F., R.M., C.P. and R.S.; software, L.D., I.R.B. and A.D.I.; validation, F.I., A.P. (Andrea Palermo)
and G.D.; formal analysis, A.M.I., A.P. (Assunta Patano) and G.D.; investigation, M.D.S. and G.D.V.;
data curation, L.F., R.M., C.P. and R.S.; writing—original draft preparation, M.D.S., G.D.V., L.F., R.M.
and C.P.; writing—review and editing, A.M.I., A.P. (Assunta Patano) and R.S.; visualization, L.D.,
I.R.B. and A.D.I.; supervision, A.D.I., F.I. and G.D.; project administration, F.I., A.P. (Andrea Palermo)
and G.D. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
Abbreviations
BT Buccal alveolar bone thickness
BH Buccal alveolar bone height
CBCT Cone beam computed tomography
RPE Rapid palatal expander
MLSAE Leaf spring activated expander
MARPE Miniscrew assisted rapid palatal expansion
RME Rapid maxillary expansion
SME Slow maxillary expansion
LE Leaf expander
HHA Hybrid Hyrax Appliance
HHG Hybrid Hyrax group
HG Conventional Hyrax group
Children 2023,10, 1258 15 of 17
IW Inter-molar width
MSG Memory screw group
MS Memory screw
HSG Hyrax screw group
TAD’s temporary anchorage device
TMJ temporary mandibular joint
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