Clinical and cone-beam computed tomography outcomes of miniscrew-assisted rapid palatal expansion in the treatment of maxillary transverse deficiency: A prospective study

Abstract

This study evaluates skeletal and dental effects of miniscrew-assisted rapid palatal expansion (MARPE) in late adolescents and young adults with maxillary transverse deficiency. This prospective study enrolled 36 patients (12 males, 24 females; mean age 20.14 years) diagnosed with maxillary transverse deficiency and treated with a custom-made Hyrax-type MARPE anchored by 4 palatal miniscrews. The expansion protocol consisted of 2 daily activations (0.26 mm/day) until the desired expansion was achieved, followed by a 6-month retention period. Measurements were obtained at baseline (T0), post-expansion (T1), and post-retention (T2). The mean total expansion at the first molar level was 5.94 ± 3.57 mm, with 67.34% attributable to skeletal widening; and effective midpalatal suture separation was achieved. Nasal base width increased by 3.29 mm and nasal cavity width by 1.81 mm from T0 to T1, with minimal relapse at T2. Posterior maxillary segments showed both lateral and anterior displacement. Cephalometric parameters remained largely stable, indicating no adverse sagittal or vertical changes. Mild buccal tipping of alveolar segments was observed (first molar inclination change: right + 4.83°, left + 5.17° from T0 to T2). Upper first molars tipped buccally after expansion but showed partial relapse during retention. Buccal alveolar bone thickness decreased at molar and premolar levels, while palatal bone thickness increased, reflecting bone remodeling. MARPE in skeletally mature patients can achieve substantial skeletal expansion with controlled dental side effects, preserved vertical and sagittal relationships, and favorable nasal airway dimensional changes, supporting MARPE as a predictable, minimally invasive alternative in late adolescent patients.

1. Introduction

Maxillary transverse deficiency (MTD) is a prevalent orthodontic condition characterized by a constricted maxillary arch, posterior crossbite, deep palatal vault, dental crowding, and a narrow buccal corridor. It has been reported to affect approximately 10% of orthodontic patients. Clinically, failure to correct this deficiency can lead to compromised occlusal function, poor facial aesthetics, and long-term skeletal imbalances.^[1,2]

Traditionally, rapid palatal expansion (RPE) has been the treatment of choice in growing patients, ideally under 15 years of age, due to the relative patency of the midpalatal suture. However, in late adolescence and adulthood, increasing interdigitation and ossification of the suture often render conventional RPE ineffective for skeletal expansion, resulting instead in undesirable dental tipping and periodontal side effects. To overcome these limitations, surgically assisted rapid palatal expansion (SARPE) has been introduced, which enables skeletal expansion by surgical release of the suture. Nevertheless, SARPE carries surgical risks, high costs, and patient reluctance due to its invasive nature.^[3]

In recent years, miniscrews have revolutionized orthodontics by providing stable anchorage, expanding treatment possibilities, and overcoming previous biomechanical limits.^[4] Besides that, miniscrew-assisted rapid palatal expansion (MARPE) has emerged as a promising nonsurgical alternative. MARPE utilizes skeletal anchorage via palatal miniscrews, allowing for greater orthopedic effects with fewer dental side effects. Histological data further support that the midpalatal suture may retain some degree of patency even in adults, allowing for separation with sufficient force and better control, and more accuracy with digital application.^[5–7] Lee et al^[8] have also demonstrated its efficacy in young adults.

Despite growing international interest, the application of MARPE in Southeast Asian populations, including Vietnam, remains limited. While this study was conducted in Vietnam, our intent is not to suggest any ethnic predisposition to MTD. Instead, this research aimed to provide valuable clinical data on MARPE outcomes in a population that has not been well-represented in previous literature. We hypothesize that MARPE can achieve significant skeletal expansion in patients with mature skeletal structures, reducing the need for surgical intervention and minimizing undesired dental effects.

The clinical relevance of this study lies in its potential to validate MARPE as a less invasive yet effective alternative to SARPE for managing MTD in skeletally mature individuals. To our knowledge, this is the first prospective study conducted in Vietnam using both CBCT and cephalometric analyses to evaluate MARPE outcomes. By addressing this regional research gap, the study aims to provide data that could inform clinical practice in similar settings globally. This research may assist orthodontists in treatment planning and enhance outcomes for patients who previously would have been considered for surgical expansion.

2. Materials and methods

2.1. Study design

This was a prospective study, by approved by Institute of Clinical Medicine and Pharmacy 108 (IRB No. 425/QD-VNC). The study was conducted at the Department of Odonto-Stomatology, Hai Phong Medical University Hospital, from December 2018 to May 2022. Informed consent was obtained from all participants. The patients were treated with MARPE, and their clinical and radiographic data were collected at 3 time points: before treatment (T0), immediately after expansion (T1), and after a 6-month retention period (T2).

2.2. Inclusion criteria

• Patients diagnosed with MTD based on Penn CBCT criteria.

• Patients aged 16 years or older.

• Patients with a cervical vertebral maturation stage of 4 or higher.

• Patients with intact first molars.

2.3. Exclusion criteria

• Patients with craniofacial syndromes or abnormalities.

• Patients with previous orthodontic treatment.

• Patients unwilling to comply with the study protocol.

2.4. Sample size

$${\displaystyle \begin{array}{l}{\displaystyle n={\left(\frac{Z_{1-{}^{\alpha }/{}_2}+Z_{1-\beta }}{ES}\right)}^2}\end{array}}$$

$${\displaystyle \begin{array}{l}{\displaystyle \alpha =0.05}\end{array}}$$

$${\displaystyle \begin{array}{l}{\displaystyle \beta =0.2}\end{array}}$$

$${\displaystyle \begin{array}{l}{\displaystyle {\text{C}=(Z}_{\text{1}\text{-}\alpha /2}+{\text{Z}}_{\text{1}\text{-}\beta }{)}^{\text{2}}=7,85}\end{array}}$$

$${\displaystyle \begin{array}{l}{\displaystyle \text{E}S=(\mu 1-\mu 2)/\mathrm{\partial }}\end{array}}$$

$${\displaystyle \begin{array}{l}{\displaystyle =\mu 1-\mu 2}\end{array}}$$

∂: standard deviation

Where:

n is the minimum required sample size for the study.

μ1 and σ: the mean and standard deviation based on the study by Cantarella et al,^[9] with μ1 = 4.75 and σ=2.59.

μ2 = 3.5, the desired palatal suture expansion value in this study to achieve clinical significance.

α = 0.05, β = 80%

The calculated sample size was n >34. Therefore, a sample size of 36 patients was chosen.

2.5. Treatment protocol

All patients were treated with a custom-made MARPE appliance, featuring a Hyrax-type expander anchored by 4 miniscrews placed in the palatal bone. The expansion protocol required activating the appliance twice daily (0.26 mm per day) until the desired expansion was achieved. Following expansion, the appliance remained in place for a 6-month retention period to maintain stability.

2.6. Cephalometric evaluation

Cephalometric measurements were recorded at 3 time points: before treatment, immediately after maxillary expansion, and 6 months into the retention phase. The study utilized the following angular measurements on lateral cephalograms: facial axis angle, lower facial height (LFH) (ANS-Xi-PM), mandibular plane angle (MPA), palatal plane angle, Y-axis angle, angle between the palatal plane and the mandibular plane, maxillary depth (FH-NA), facial prominence (A-NPo), SNA angle (SN-NA), SNB angle (SN-NB), and ANB angle (NA-NB).

2.7. CBCT evaluation

The CBCT analysis assessed the maturation stage of the palatal suture, the degree of maxillary expansion, changes in the pterygopalatine suture, maxillary-zygomatic suture, and zygomatic-frontal suture, the curvature of the maxillary orbital rim, tooth inclination, and changes in the thickness of the buccal and lingual cortical bone of the anchor teeth after expansion.

All MARPE procedures were performed by 2 orthodontists with over 10 years of clinical experience (P.T.H.T. and P.T.T). CBCT measurements were independently evaluated by 2 experienced investigators (H.V. and P.T.T.H.), both of whom had received calibration training prior to the study. Inter-examiner agreement was tested, and discrepancies were resolved through discussion and consensus.

2.8. Intervention

All patients underwent MARPE using a customized expander with 4 mini-implants inserted into the palatal bone. The activation protocol followed a rate of 0.2 mm per turn, with 2 turns per day until the required expansion was achieved. Post-expansion, patients were monitored weekly for retention stabilization, followed by a 6-month retention period.

2.9. Reference planes and displacement assessment

TMD Slice: The TMD slice passes through the pterygopalatine suture at the region where the posterior border of the perpendicular plate of the palatine bone articulates with the anterior surface of the lateral pterygoid plate of the sphenoid bone. In this region, the maxillary tuberosity is in close contact with the pterygoid process of the sphenoid bone. The lateral displacement of the posterior-most point of the maxilla along the anterior-most point of the lateral pterygoid fossa was analyzed to assess the looseness of the pterygopalatine suture under expansion forces.

Mid-Sagittal Plane (MSP): This plane passes through the anterior nasal spine (ANS), posterior nasal spine (PNS), and the most anterior point of the frontonasal suture (Nasion-Na). It runs through the center of the face and the maxilla. Maxillary displacement and its articulation with other bones were described by analyzing the movement of multiple reference points on the maxilla and its sutures relative to this plane under the influence of expansion forces. This plane was determined before and after expansion on CBCT images. The lateral displacement of the 2 halves of the maxilla was independently assessed by measuring the lateral shift of ANS and PNS from the MSP. Any asymmetry in displacement between the 2 sides was also recorded.

Posterior-Most Vomer Plane (PMVP): This is a plane perpendicular to the MSP in the vertical transverse direction, passing through the posterior-most point of the vomer bone.

2.10. Outcomes

The outcomes of this study were divided into primary and secondary outcomes, evaluated through both cone-beam computed tomography (CBCT) and lateral cephalometric radiographs at 3 time points: before treatment (T0), immediately after expansion (T1), and after a 6-month retention period (T2).

2.11. Primary outcomes

Primary outcomes focused on skeletal changes associated with MARPE treatment, including:

• Total maxillary transverse expansion at the first molar level, measured in millimeters.

• Midpalatal suture separation, assessed through CBCT imaging to determine skeletal contribution to total expansion.

• Maxillary displacement, evaluated by measuring lateral and anterior movement of anatomical landmarks (e.g., ANS, PNS) relative to the MSP and PMVP.

• Nasal base width and nasal cavity width, measured to assess the impact of MARPE on nasal structures.

2.12. Secondary outcomes

Secondary outcomes assessed dental and dentoalveolar changes, including:

• Alveolar bone inclination and inclination of upper first molars, measured on CBCT in both right and left quadrants.

• Alveolar bone thickness at the first premolar and first molar regions (buccal and palatal sides), before and after expansion.

• Cephalometric changes, including parameters such as ANB, SNA, SNB angles, LFH, MPA, and others to evaluate overall skeletal balance and vertical dimension changes.

These outcomes provided a comprehensive evaluation of both skeletal and dental effects of MARPE treatment in late adolescents and young adults.

2.13. Data statistics

All data were analyzed using SPSS 20.0 software (Chicago). Descriptive statistics were used to summarize demographic and baseline characteristics. The Shapiro–Wilk test was used to assess the normality of continuous variables. When normal distribution and equal variances were confirmed, paired t-tests were used to compare pre- and posttreatment measurements. A P-value <.05 was considered statistically significant.

3. Results

3.1. Participant characteristics

Among the 36 patients in the study, 12 were male (33.33%) and 24 were female (66.67%), with an average age of 20.14 years. A narrow smile was the most common clinical sign, observed in 91.67% of cases, followed by V-shaped narrow arches (47.22%) and dental crowding (45.71%). Tapered arches and impacted teeth were less frequent, occurring in 22.22% and 16.67% of cases, respectively. Regarding facial types, the majority of patients had an average face (72.22%), while long and short facial types were less common, at 16.67% and 11.11%, respectively. According to Angelieri classification, the most prevalent type was D (50.0%), followed by type E (36.1%) and type C (13.9%) (Table 1).

Table 1.

Prevalence of clinical signs.

	No.	%
Clinical sign
Narrow smile	33	91.67
Dental crowding	16	45.71
V-shaped narrow arch	17	47.22
Tapered arch	8	22.22
Impacted teeth	6	16.67
Facial type
Average face	26	72.22
Long face	6	16.67
Short face	4	11.11
Angelieri classification No. %
C	5	13.9
D	18	50.0
E	13	36.1

3.2. Skeletal changes (primary outcomes)

3.2.1. Cephalometric skeletal changes

Cephalometric analysis showed a slight increase in ANB from 1.62° (T0) to 2.04° (T1), then a slight decrease to 1.88° (T2). LFH increased from 44.43° to 44.73° (P <.001). SNA and SNB angles exhibited minor fluctuations, while MPA, facial axis, and Y-axis remained stable. This stability suggests MARPE did not significantly alter sagittal or vertical skeletal relationships (Fig. 1 and Table 2).

Figure 1.

Cephalometric skeletal changes after 6 mo of treatment on the TMD slice.

Table 2.

Changes on lateral cephalometric radiographs.

Parameter (°)	T0	T1	T2	P
Facial axis	88.86 ± 2.75	88.88 ± 3.27	88.85 ± 3.27	<.001
LFH (mm)	44.43 ± 2.91	44.54 ± 3.65	44.73 ± 3.38	<.001
MPA (0)	23.05 ± 5.25	22.79 ± 5.99	23.27 ± 5.88	<.001
PPA (0)	0.15 ± 3.43	0.65 ± 2.11	0.68 ± 1.93	.051
Y-axis angle (0)	66.04 ± 2.97	65.93 ± 3.21	66.28 ± 2.99	<.001
PP-MP (0)	22.48 ± 5.87	22.24 ± 6.22	22.19 ± 5.88	<.001
FH-NA (0)	88.22 ± 3.27	88.2 ± 2.94	88.42 ± 2.89	<.001
A-Po (mm)	1.57 ± 3.14	1.83 ± 3.45	2.1 ± 3.12	<.001
SNA (0)	84.15 ± 3.88	84.61 ± 3.9	83.86 ± 3.28	<.001
SNB (mm)	82.44 ± 4.32	82.5 ± 3.83	82.56 ± 4.26	<.001
ANB (mm)	1.62 ± 2.73	2.04 ± 2.83	1.88 ± 2.68	<.001

ANB = a point-nasion-B point angle, A-Po = a point to pogonion distance, FH-NA = Frankfort horizontal to nasion-a point angle, LFH = lower facial height, MPA = mandibular plane angle, PPA = palatal plane angle, PP-MP = palatal plane to mandibular plane angle, SNA = sella-nasion-a point angle, SNB = sella-nasion-B point angle.

3.2.2. Midpalatal suture separation

CBCT analysis demonstrated effective separation of the midpalatal suture, with ANS displacement of 2.95 mm (right) and 2.62 mm (left), and PNS displacement of 2.57 mm (right) and 2.45 mm (left) (Table 3). The nearly symmetrical expansion suggests balanced orthopedic forces during activation.

Table 3.

Lateral and anterior displacement of maxilla through TMD.

		T0	T1	T2	P
Lateral displacement	The most anterior point of the right maxilla—MSP (mm)	10.39 ± 1.59	13.16 ± 1.94	13.97 ± 1.67	<.01
	The most anterior point of the left maxilla—MSP (mm)	11.78 ± 1.82	13.75 ± 1.32	13.91 ± 1.52	<.01
	The most posterior point of the right maxilla—MSP (mm)	22.16 ± 1.17	23.37 ± 1.66	24.42 ± 2.38	.08
	The most posterior point of the left maxilla—MSP (mm)	18.83 ± 1.43	19.63 ± 1.38	20.46 ± 1.31	<.01
Anterior displacement	The most posterior point of the right maxilla—PMVP (mm)	13.74 ± 1.92	14.60 ± 1.81	14.10 ± 1.69	<.001
	The most posterior point of the left maxilla—PMVP (mm)	14.53 ± 2.49	15.51 ± 2.64	15.23 ± 2.79	<.001

MSP = mid-sagittal plane, PMVP = posterior-most vomer plane.

3.2.3. Maxillary displacement

The most anterior point of the right maxilla moved laterally from 10.39 ± 1.59 mm (T0) to 13.97 ± 1.67 mm (T2), and the left side from 11.78 ± 1.82 mm to 13.91 ± 1.52 mm. The posterior maxilla also shifted laterally on the left (18.83 mm to 20.46 mm, P <.01) and anteriorly on both sides (right: 13.74 mm to 14.10 mm, left: 14.53 mm to 15.23 mm, P <.001). These results confirm that expansion forces were transmitted posteriorly, enabling movement of maxillary segments beyond the anterior region (Table 3).

3.2.4. Nasal base and nasal cavity width

Nasal base width increased from 29.63 ± 3.10 mm (T0) to 33.62 ± 3.21 mm (T1), before slightly decreasing to 32.92 ± 3.43 mm (T2). Nasal cavity width increased from 26.88 ± 1.85 mm (T0) to 28.90 ± 1.80 mm (T1) and remained at 28.69 ± 1.91 mm (T2) (P <.001) (Table 4). These airway dimension changes could have positive implications for nasal breathing.

Table 4.

Changes in the palatal bone angle and nasal cavity dimensions.

	Mean ± SD	P
Changes in the palatal bone angle on the transverse section through TMT slides
Palatal angle – Right (0)
T0	79.53 ± 16.56	<.001
T1	74.50 ± 14.54
T2	74.65 ± 14.31
Palatal angle – left (0)
T0	82.64 ± 11.91	<.001
T1	77.72 ± 11.72
T2	77.34 ± 11.72
Changes in nasal cavity dimensions
Nasal base width (mm)
T0	29.63 ± 3.10	<.001
T1	33.62 ± 3.21
T2	32.92 ± 3.43
Nasal cavity width (mm)
T0	26.88 ± 1.85	<.001
T1	28.90 ± 1.80
T2	28.69 ± 1.91

SD = standard deviation.

3.2.5. Maxillary transverse expansion

MARPE produced significant skeletal expansion, with a mean total expansion of 5.94 ± 3.57 mm at the first molar level. Skeletal contribution accounted for 67.34% of total expansion, as confirmed by CBCT measurements. This high proportion of skeletal change highlights the effectiveness of MARPE in overcoming midpalatal suture resistance in late adolescents and adults (Table 5).

Table 5.

Inclination (⁰) of the alveolar bone at the first molar and upper first molar on the right and left sides

Inclination (0) of the alveolar bone at the first molar
	Mean ± SD	p
Right
T0	107.22 ± 8.22	<.001
T1	111.29 ± 7.40
T2	111.05 ± 7.33
Left
T0	108.36 ± 7.09	<.001
T1	112.78 ± 6.80
T2	113.53 ± 7.16
Inclination (°) of the upper first molar on the right and left sides
Right
T0	95.44 ± 4.34	<.001
T1	102.62 ± 6.41
T2	100.12 ± 6.68
Left
T0	95.31 ± 6.91	<.001
T1	103.82 ± 7.96
T2	98.69 ± 8.01

SD = standard deviation.

3.3. Dental and dentoalveolar changes (secondary outcomes)

3.3.1. Alveolar bone inclination

At the first molar level, alveolar bone inclination increased from 107.22° (T0) to 111.05° (T2) on the right, and from 108.36° (T0) to 113.53° (T2) on the left (P <.001, Table 5). These changes indicate mild buccal tipping of the alveolar segments accompanying skeletal expansion.

3.3.2. Dental tipping

The inclination of upper first molars increased significantly after expansion: right side from 95.44° (T0) to 102.62° (T1), then decreased to 100.12° (T2); left side from 95.31° (T0) to 103.82° (T1), then decreased to 98.69° (T2) (P <.001, Table 5). The partial relapse during retention suggests adaptive changes and occlusal settling.

3.3.3. Alveolar bone thickness

At the first premolar, buccal thickness decreased (right: 1.01 mm to 0.88 mm, left: 0.89 mm to 0.83 mm) while palatal thickness increased (right: 2.19 mm to 2.61 mm, left: 2.09 mm to 2.50 mm). At the first molar, buccal bone (mesial and distal) decreased significantly, while palatal bone increased (Table 6). These changes may reflect physiological bone remodeling under expansion forces.

Table 6.

Changes in alveolar bone thickness at the first premolar and molar of the maxilla.

	Thickness (mm)	Mean ± SD	P
Changes in alveolar bone thickness at the first premolar of the maxilla	Right
	Outer
	T0	1.01 ± 0.79	<.001
	T1	0.84 ± 0.58
	T2	0.88 ± 0.59
	Inner
	T0	2.19 ± 0.69	<.01
	T1	2.65 ± 0.73
	T2	2.61 ± 0.74
	Left
	Outer
	T0	0.89 ± 0.55	<.001
	T1	0.76 ± 0.50
	T2	0.83 ± 0.47
	Inner
	T0	2.09 ± 0.97	<.001
	T1	2.48 ± 1.18
	T2	2.50 ± 1.21
Changes in alveolar bone thickness at the first molar of the maxilla	Right
	Mesial outer
	T0	1.41 ± 0.81	<.01
	T1	1.00 ± 0.71
	T2	1.06 ± 0.75
	Distal outer
	T0	2.18 ± 0.94	<.01
	T1	1.68 ± 0.74
	T2	1.75 ± 0.70
	Inner
	T0	1.43 ± 0.56	<.01
	T1	1.76 ± 0.79
	T2	1.83 ± 0.77
	Left
	Mesial outer
	T0	1.21 ± 0.59	<.01
	T1	1.06 ± 0.75
	T2	1.07 ± 0.79
	Distal outer
	T0	2.20 ± 0.76	.00
	T1	1.95 ± 0.92
	T2	1.99 ± 0.82
	Inner
	T0	1.52 ± 0.56	<.01
	T1	1.76 ± 0.69
	T2	1.84 ± 0.68

4. Discussion

The study confirmed that MARPE could achieve significant skeletal expansion with minimal dental side effects in late adolescents and young adults with MTD. MARPE produced a mean total expansion of 5.94 mm at the first molar level, of which 67.34% was skeletal. Primary outcomes showed effective midpalatal suture separation, posterior maxillary displacement, and increased nasal base and nasal cavity width. Secondary outcomes demonstrated mild dental tipping, changes in alveolar bone inclination and thickness, and stable cephalometric parameters without undesirable vertical or sagittal alterations.

The skeletal expansion results in this study were consistent with previous findings by Paredes et al,^[10] Park et al,^[11] and Celenk-Koca et al.^[12] All patients in this study had a skeletal maturity of CS4 or higher, with an average age of 20.1 years. Furthermore, Oliveira et al^[13] found that MARPE achieved greater skeletal expansion compared to surgically assisted expansion, with parallel expansion occurring in both the vertical and horizontal planes. A key observation in this study was that maxillary expansion on the transverse plane was asymmetrical between the right and left sides. The ANS shifted 2.95 mm to the right and 2.62 mm to the left, while the PNS shifted 2.57 mm to the right and 2.45 mm to the left. The exact cause of this asymmetric expansion remains unclear, but one possible explanation is the initial structural asymmetry of the maxilla.^[3] Additionally, external forces, such as masticatory forces in cases of unilateral crossbite, may contribute to unilateral maxillary displacement. Another important factor is the surrounding craniofacial structures, for the maxilla to expand, the adjacent sutures connecting it to other bones must also separate and move. The maxilla tends to shift toward the side with less resistance.

The findings demonstrate that MARPE effectively achieves skeletal expansion comparable to traditional methods used in younger patients. Several studies^[5,14,15] have also concluded that bone-anchored expansion minimizes dental and alveolar inclination compared to conventional expansion methods. The expansion of the teeth and alveolar bone is a secondary effect of maxillary expansion. In this study, the expansion of maxillary orbital rim at the first premolar position was 0.6 mm (10.1% of total expansion), while dental expansion was 1.34 mm (22.56% of total expansion). Dental inclination was also observed, likely due to the rotational movement of the maxillary halves during expansion, with the rotation center at the fronto-maxillary suture. The inclination of the first premolar was 7.18° on the right and 8.49° on the left. After 6 months of retention, these values decreased to 4.68° on the right and 3.38° on the left. Although mini-implants were used for skeletal anchorage, dental inclination still occurred due to the angulation of mini-implants within the bone. This angulation may have resulted from a small gap between the mini-implant and the predesigned hole in the expansion screw. The expansion screw was activated to an average of 8.67 mm over 32.52 days, and the measured palatal suture expansion (in the vertical transverse plane) was 4.43 mm anteriorly and 4.26 mm posteriorly, confirming that skeletal expansion does not occur in a strict 1:1 ratio with screw activation. High expansion forces can compress the periodontal ligament of anchor teeth, leading to alveolar bone resorption and reduced bone thickness.

The findings of this study highlight the potential of MARPE as a first-line treatment for MTD in late adolescents and young adults. However, clinicians should carefully evaluate individual patient factors, including palatal suture maturation and bone density, before selecting MARPE as the treatment modality, the study had some limitations. The small sample size may limit the generalizability of the results to a broader population. The follow-up period of 6 months may not be sufficient to assess long-term stability and relapse rates. Future studies with larger sample sizes and extended follow-up periods are needed to validate these findings. Additionally, factors such as individual variations in bone density, suture maturation, and miniscrew placement were not extensively analyzed, which could influence treatment outcomes. Lastly, this study focused primarily on skeletal and dental changes, and further research is required to explore functional improvements, particularly in airway dimensions and breathing efficiency.

5. Conclusion

MARPE can produce a mean total expansion of 5.94 mm at the first molar level, with 67.34% of the change attributable to skeletal expansion. Effective midpalatal suture separation increased nasal base and cavity widths, and controlled posterior maxillary displacement were observed, while dental tipping and buccal bone reduction remained within clinically acceptable limits. The underlying mechanism is likely related to direct skeletal anchorage via miniscrews, enabling force transmission to midpalatal and circummaxillary sutures even in skeletally mature patients. These results are clinically significant as they support MARPE as a minimally invasive, predictable alternative to SARPE, reducing surgical risks and treatment costs while preserving periodontal health. Future studies with larger sample sizes, longer follow-up periods, and the inclusion of functional outcomes.

Author contributions

Conceptualization: Pham Thi Hong Thuy, Hoang Viet.

Data curation: Pham Thi Hong Thuy, Pham Thu Trang, Pham Thi Thu Hang, Hoang Viet.

Formal analysis: Pham Thi Hong Thuy, Hoang Viet.

Funding acquisition: Pham Thi Thu Hang.

Investigation: Pham Thi Thu Hang.

Methodology: Pham Thi Hong Thuy, Pham Thu Trang, Pham Thi Thu Hang, Hoang Viet.

Project administration: Pham Thu Trang, Hoang Viet.

Resources: Pham Thi Hong Thuy, Pham Thu Trang, Pham Thi Thu Hang, Hoang Viet.

Software: Pham Thu Trang.

Supervision: Pham Thi Hong Thuy.

Validation: Pham Thi Hong Thuy, Pham Thu Trang, Hoang Viet.

Writing – original draft: Pham Thi Hong Thuy, Pham Thu Trang, Pham Thi Thu Hang, Hoang Viet.

Writing – review & editing: Pham Thi Hong Thuy, Pham Thu Trang, Pham Thi Thu Hang, Hoang Viet.