Effect of Mini-screw Assisted Rapid Palatal Expansion on Midpalatal Suture in Post-pubertal Patients: a CBCT Study
Phase: NA
Conditions: Constricted Maxillary Arch
Sponsor: Mansoura University

 
 
 
 
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Mansoura University 
Faculty of Dentistry 
Department of Orthodontics
Effect of mini-screw assisted rapid palatal 
expansion on midpalatal suture in post-pubertal 
patients: a CBCT study
A Protocol of Thesis 
Submitted to Faculty of Dentistry, Mansoura University 
Partially fulfills the requirements of obtaining 
Master Degree in Orthodontics
Submitted by 
Asil Abdallah Rashid Al Naeimi 
  
BDS, 2020 
Oman Dental College 
2024

Supervisors 
Dr. Ahmed Maher Fouda 
Assistant Professor of Orthodontics 
Department of orthodontics 
Faculty of  Dentistry, Mansoura University 
Dr. Reham Ibrahim El-Gazzar 
Lecturer of orthodontics 
Department of orthodontics 
Faculty of Dentistry,  Mansoura University 
 
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INTROUDCTION 
Transverse maxillary deficiency, which affects many patients seeking orthodontic care, may 
be present in up to 23.3% of children.1 This issue typically arises during facial development 
and growth and if it is not treated, it can impact the permanent teeth since it is unlikely to 
correct itself, myofunctional disorders and habits like thumb sucking are common causes of 
this condition.2 When the tongue is positioned too low it can lead to the buccinator muscles 
applying excessive pressure on the maxillary arch which will cause constriction of the arch.3 
Simultaneously, genetic and hereditary influences can play a role in the development of 
maxillary transverse deficiencies, particularly in cases of patients with Class III 
malocclusion and mandibular prognathism.3 If left untreated in an appropriate time, these 
deficiencies, with or without posterior crossbite, can lead to various issues including 
occlusal disharmony, changes in tongue posture, damage to periodontal structures, 
functional shifts in the mandible, asymmetrical mandibular positioning, joint disorders, 
muscle function disturbances, and inadequate space for proper dental alignment.4-6  One of 
the most severe consequences of maxillary transverse deficiency is the narrowing of 
the nasal cavity, which can increase nasal air resistance and potentially contribute to 
obstructive sleep apnea syndrome (OSAS).7 
For managing the transverse maxillary deficiency, Early intervention yields better prognosis 
and outcomes, enhancing the likelihood of achieving morphological and functional 
correction, thereby promoting proper facial development. RPE is particularly effective 
during primary and mixed dentition, as well as the initial years of permanent dentition, with 
consistently high success rates.8 Certain authors argue that expanding the maxilla with 
conventional rapid palatal expansion in post-pubertal individuals is impractical 9  , and 
becomes more challenging as facial growth and craniofacial sutures nears completion 
including the midpalatal suture, these sutures become increasingly interdigitated and 
calcified.10 Studies have identified the post pubertal phase through the cervical vertebral 
maturation method ( C5 and C6), while other studies have linked the CVM with 
chronological age; in which the post-pubertal phase is after age of 15.11,12 
According to a previous systemic review, that correlated the chronological age 
with mid palatal suture maturation , it stated that the level of maturation in mid palatal 
suture varies significantly across age groups. Females tend to show more advanced 
maturation compared to males within the same age range. Before the age of 14, the 
significant occurrence of stages associated with sutural opening doesn't warrant the use of 
CBCT for evaluating the midpalatal suture (MPS). Instead, it endorses the adoption of a 
traditional approach for expanding the maxilla. However, in patients aged after 14 there's a 
higher prevalence of stages indicating sutural consolidation, an MPS assessment 
could be valuable for decision-making. In adults, MPS appraisal, along with other factors, 
may play a crucial role in determining the appropriate clinical protocol.13 
 
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To treat transverse maxillary deficiency in post- pubertal patients; surgically-assisted rapid 
palatal expansion (SARPE), involving a LeFort I osteotomy and surgical rupture of the 
midpalatal suture, is often recommended.14 However, despite its benefits, SARPE increases 
the biological and financial costs of treatment, requiring hospitalization and general 
anesthesia, which might deter patients from choosing surgical-orthodontic treatment.14 
The introduction of temporary anchorage devices (TADs) has given rise to a novel type of 
tooth-bone-borne (TBB) expansion appliance, employing either two or four screws to apply 
mechanical forces to the bone, this new expansion appliance is refered as mini-screw 
assessted rapid palatal expansion (MARPE). This design aims to minimize stress on 
anchored teeth, decrease adverse dentoalveolar effects, and achieve greater skeletal 
expansion compared to traditional tooth-borne RPE (TB-RPE).15  skeletal expansion 
involves opening of midpalatal suture, and according to a previous study which used cone-
beam computed tomography (CBCT) images have revealed a marked increase in the 
skeletal dimension in adolescent and young adult patients treated with MARPE .16  
However, Studies demonstrate conflicting results regarding the orthopedic effect  of 
MARPE and RME in young adult patients with different types of appliances.17 
The aim of this study is to assess the effect of  MARPE on MPS in post-pubertal patients 
using two mini-screw evaluated by CBCT. 
 
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Aim of the study 
The aim of this study is to assess the effect of  MARPE on MPS in post-pubertal 
patients using two mini-screws, evaluated by CBCT. 
 
5

Materials and Methods 
1-Sample size calculation: 
Hypothesis: 
Null hypothesis (H0): 
No statistically significant increase in MPS after mini screw assisted rapid maxillary 
expansion. 
Alternative hypothesis (H1): 
A statistically significant increase in MPS after mini screw assisted rapid maxillary 
expansion is hypothesized with a large effect size (Cohen’s d = 1.0). This 
hypothesis was based on two previous research by Mendoza et al. (2022)18 and 
Kolge et al. (2018)15 . In the research by Mendoza et al. (2022), the effect size 
(Cohen’s d) for MPS change before and after mini screw assisted rapid maxillary 
expansion was calculated based on their published data to be 2.54 at 1st premolar, 
2.07 at 2nd premolar, and 2.00 at 1st molar. In the research by Kolge et al. (2018), 
the effect size (Cohen’s d) for expansion change before and after mini screw 
assisted rapid maxillary expansion was calculated based on their published data to 
be 3.46 at inter premolar site, 9.24 at inter molar site, and 2.00 at 1M. 
Sample size 
A sample size of 10 data pairs achieves 89.8% power to reject the null hypothesis 
of zero effect size when the population effect size is 1.00 and the significance level 
(α) is 0.050 using a one-sided paired t-test. 
 
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2- participants, eligibility criteria, and setting 
The sample will consist of 10 patients. They will be selected from the Orthodontic 
Department, Faculty of  Dentistry, Mansuora University according to the following: 
Inclusion criteria: 
•
Transverse maxillary deficiency with or without crossbite; who requires maxillary 
expansion in their treatment plan as described by Tamburino et al.19  
•
Age after 16. 
•
presence of first and second upper premolars and first upper molars  
•
No previous orthodontic treatment. 
•
Good oral hygiene and healthy periodontal tissue. 
•
No significant dentofacial anomalies, any bone defects, or systemic disease. 
•
Not being pregnant. 
•
All patients are signed a written consent after accepting the treatment plan. 
 
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3- Treatment procedure: 
- First visit: Thorough explanation of procedures to the patient, clarifying 
all details and technical limitations and informing that failure may 
occur; placement of elastic separators on mesial and distal side of  
permanent maxillary first molars.  
- Second visit: The elastic separators will be removed and a proper size of 
orthodontic bands will be placed in permanent maxillary first molars. 
After LA infiltration in the palate a two OrthoEasy Pal mini-screw from 
Forestadent size 8* 1.7 mm will be placed paramedian 3mm away from 
the midpalatal suture between the first and second premolar area,20 using 
a manual drive attachment for contra-angle handpiece and attached to 
OrthoEasy blade 10 mm Octagonal.
 
8
3mm
Location of mini-screw
Mid palatal 
suture

After the placement of mini-screws in the desired location; two OrthoEasy 
Pal impression caps will be placed on the head of the mini-screws. After that, an 
impression will be taken using Alginate impression material, the molar bands 
will be removed from patient’s mouth using orthodontic band removal plier and 
placed in the impression tray. Also the impression cap will be removed from the 
patient’s mouth and placed in the impression tray. Elastic separators on mesial 
and distal side of  permanent maxillary first molars will be placed again. 
The impression tray will be sent to the lab for MARPE fabrication.
Laboratory steps:
1.
Before pouring the impression with regular white dental plaster, the 
impression caps will be removed from the impression tray and two 
OrthoEasy Pal lab analogs will be placed instead.
2.
The impression will be poured with regular white dental plaster.
3.
8, 10 or 12 mm of palatal expansion screw from Forestadent will be 
selected according to the palatal width. The posterior wires will be bent to 
reach the orthodontic bands and soldered to it, while the anterior wires will 
be soldered to the OrthoEasy Pal abutment (flat profile) which will be  
placed on the cast on top of the duplicated mini-screw heads. 
4.
followed by finishing and polishing of the device.
- Third visit: The elastic separators will be removed and the device will be 
placed to check its fitting. Once fitting is checked, cementation of the bands 
of the device to the first molar will be performed using glass ionomer 
cementation (GIC). After that, the OrthoEasy Pal abutments of the device 
will be retained to the mini-screws by OrthoEasy Pal Retaining screw using 
blade for OrthoEasy Pal retaining screw for contra-angle handpiece.
 
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- Immediate 2 turns activation will be made in the hyrax after fitting the 
appliance.
- The activation protocol of MARPE will be 1 turn per day for 3 weeks. After 
3 weeks a cbct image will be taken to assess the MPS. Fixed appliance will 
be placed after 3-4 months period of retention.
- Activation will be discontinued when the lingual cusps of the upper first 
molars contacted the buccal cusps of the lower first molars. 
3. Records: 
For all patients the following records are made: 
1. Photographs: 
a) Extraoral 
b) Intraoral 
2. Upper and lower plaster casts. 
3. Radiographs: 
a)
Panoramic radiography. 
b)
Lateral cephalometric. 
c)
Cone-beam computed tomography systems (CBCT). 
Photographs will be taken 3 times; pre-operative, after MARPE placement and after 3 
weeks from the first activation 
Upper and lower diagnostic casts will be taken once, pre- operative. 
Lateral cephalometric and panoramic radiography will be taken once; pre-operative. 
CBCT will be taken twice; pre-expansion and after 3 weeks from the first activation 
 
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1.
Extra-oral and Intra-oral photographs: 
Extraoral photographs of the face in frontal and lateral views are taken. The frontal 
view is taken with the interpupillary line parallel to the floor and the midsagittal 
plane is perpendicular to the floor. The lateral view (left side) is taken after adjusting 
the Frankfort horizontal plane to be parallel to the the floor. on the other hand, the 
intraoral photographs are taken in frontal, lateral and occlusal views. 
2. Upper and lower casts: 
Upper and lower impressions of the dental arches will be taken using Alginate 
impression material.They will be poured immediately in a white dental plaster. A wax 
bite is obtained in centric occlusion to orient the upper and lower casts. The models 
are identified with the name of the patient, date of birth, and date of taking the 
impression. 
3. Radiographs: 
a.
Lateral cephalometric radiograph: 
Lateral cephalometric radiographs are done before treatment as a diagnostic aids and 
to record the cervical vertebrae maturation.11 
b. Panoramic radiographs: 
Panoramic radiographs are taken before treatment as a diagnostic aids and to 
determine any pathological abnormalities that can hinder the study. 
c. Cone-beam computed tomography systems (CBCT): 
CBCT image (Soredex Cranex 3Dx) will be  taken before expansion to record the 
stage of mid palatal suture21 and to assess the MPS. Another image will be taken after 
3 weeks from the first activation for evaluating the mid-palatal suture.  
At the following setting:  
- Exposure time: 9 s, 4.0mA, 89kV, field of view [FOV]: 8*15 cm voxel size: 0.32 
mm).
According to a  previous puplished reseach, CBCT scans were taken before expansion 
(T1) and 1 week after active expansion (T2).22Another puplished research took CBCT 
scans before expansion (T1) and 10 days after active expansion (T2). 23 The CBCT 
setting will be reduced as much as possible with small field of view following the low 
dose protocol with the help of a radiologist from Mansuura university to ensure that the  
total radiation of repeated CBCT imaging during the experiment doesn’t exceed the 
recommended annual dose limit (1 mSv).24 
 
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Digital Imaging and Communications in Medicine (DICOM) file image reconstruction 
and analysis will be  performed with OsiriX Lite software. 
CBCT analysis 24 
For CBCT analysis; the following will be determined: 
• dimensional reference planes for craniofacial structures orientation and to 
standardize linear measurements in the axial plane: 
-
In the axial plane, the mid-palatine suture will be used. 
-
 In the mid-sagittal plane. the horizontal palatal plane will be  
the selected reference 
-
 In the coronal plane, the image was oriented perpendicular to 
the patient’s midsagittal plane tangent to the most inferior level 
of nasal floor at the level of first molar where the crown and 
palatal root can be seen at their greatest length.  
 
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• After the image is oriented: 
1.
For the pre-expansion images, the axial view will be chosen to 
determine the maturation stage of MPS and will be recorded. 
2.
In both pre-expansion and after 3 weeks from the first 
activation images; points will be marked in the axial plane at 3 
different locations assisted from coronal plane: first premolar, 
second premolar and first molar. 
•  For the first premolar and the first molar: points will be 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. 
 
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• Measuring the distance between the external right and left maxilla edges in 
the axial view before expansion and after 3 weeks from the first activation 
3. Statistical analysis 
Software: 
Data will be entered and analyzed using IBM-SPSS software (IBM Corp. 
Released 2020. IBM SPSS Statistics for Windows, Version 27.0. Armonk, 
NY: IBM Corp.) 
Data expression: 
Qualitative data will be expressed as N and percentage (%). 
Quantitative data will be initially tested for normality using Shapiro-
Wilk’s test with data being normally distributed if p>0.050. The presence 
of significant outliers (extreme values) will be tested for by inspecting the 
boxplots. 
Quantitative data will be expressed as mean ± standard deviation (SD) if 
normally distributed or median and interquartile range (IQR) if not. IQR is 
the difference between 75th percentile minus 25th percentile. 
 
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Data comparison: 
Quantitative paired data: 
Paired-samples t-test or its nonparametric equivalent, Wilcoxon’s signed 
rank Test will be used. 
Significance level: 
For any of the used tests, results will be considered as statistically 
significant if p value ≤ 0.050. 
Charts: 
Appropriate charts will be used to graphically present the results whenever 
needed. 
4. Ethical standard 
The study will be approved from the research ethical committee of faculty 
of dentistry, Mansoura university. 
5. Esitmated cost : 
20,000 L.E 
6. Estimated time : 
One year 
 
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