Skeletal, Dentoalveolar, Dental, and Soft-Tissue Effects Following MARPE Treatment: A Review

Maxillary constriction, whether accompanied by unilateral or bilateral crossbite or without crossbite, is one of the main reasons for orthodontic treatment, with studies showing that approximately 10% of the general population and 30% of adult orthodontic patients present with this deficiency.^1-3 Other alterations associated with maxillary constriction can also affect the bony, dentoalveolar, and soft-tissue anatomical structures, as well as functional aspects. These alterations may include class II and class III malocclusions, premature contacts, crowding, and molar inclination and angulation, which can mask the pathology.⁴

Maxillary constriction does not exhibit spontaneous correction and typically should be treated as soon as possible by means of maxillary expansion. The optimal timing for treatment has been established to be 12 to 13 years of age by means of rapid palatal expansion (RPE).⁵ This treatment comprises the application of lateral forces that increase maxillary width and fracture the midpalatal suture (MPS), using expanders that may be either metal, such as the Hyrax type, or acrylic. Subsequently, reorganization of the suture occurs through repair of the connective tissue and formation of bone.^6,7

Sponsored

S Series Implant Portfolio

The S Series implant portfolio reimagines Nobel Biocare’s iconic implant designs around a single, harmonized prosthetic platform, simplifying clinical workflows.

RPE is achieved effectively in pediatric patients; however, in late adolescents and adults, the MPS and circummaxillary sutures begin to fuse and become more rigid. If expansion treatment using RPE is performed in adult patients, it can result in greater dentoalveolar and dental tipping, pain, tissue inflammation, root resorption, loss of marginal bone, gingival recession, and limited skeletal expansion.⁸

Using the miniscrew-assisted rapid palatal expansion (MARPE) technique, this expansion may be applied to female patients aged 14 to 15 years and male patients aged 16 to 17 years. The design of the skeletal expander in MARPE consists of two to four miniscrews, with the planning of the screw placement varying in direction depending on the amount of bone available, which may be monocortical, bicortical, or even tricortical, for the anchorage of the miniscrews.^4,9-11

Clinical studies have demonstrated successful outcomes using MARPE in adults.^12,13 However, maxillary expansion may not occur in some adult patients undergoing MARPE. The reasons for MARPE failure remain unclear, but variations in the maturation patterns of the MPS and craniofacial architecture (greater resistance) may be contributing factors.¹⁴ Hence, the use of these devices could be combined with minimally invasive surgical assistance, such as surgically assisted RPE (SARPE). Age appears to be a key factor for treatment success.¹⁵

Recent clinical studies using MARPE have demonstrated a high success rate of MPS separation—ranging between 71% and 92%—in young adults.^16,17 Another study observed that there was a lower probability of success in patients over 30 years old, with outcomes being more predictable in patients under 30 years old.¹⁸

The separation pattern of the MPS with MARPE differs from that of conventional RPE. While RPE results in a greater degree of fan-shaped opening, that is, greater anterior opening, most MARPE studies report the creation of a parallel separation pattern of the MPS.^17,19 Furthermore, MARPE can create an opening between the medial and lateral pterygoid sutures without surgery.^19,20

As far as the authors know, no randomized controlled clinical trials (RCTs) have been published on MARPE treatment in young adult patients. Serving, therefore, as a starting point, this systematic review aims to evaluate the effects at the skeletal, dentoalveolar, dental, and soft-tissue levels following MARPE treatment in adult and young adult patients using cone-beam computed tomography (CBCT).

Materials and Methods

Protocol and Registration

This review follows the PRISMA (preferred reporting items for systematic reviews and meta-analyses) checklist, recommended in the American Journal of Orthodontics and Dentofacial Orthopedics.^21,22

Inclusion and Exclusion Criteria

For the correct selection from the total number of articles obtained from the various searches, and the proper development of the systematic review, inclusion and exclusion criteria were established. The clinical question was formulated using the PICO format²³:

• Population: young adult and adult orthodontic patients with maxillary constriction in permanent dentition, with all teeth erupted except for third molars.

• Intervention: MARPE.

• Comparison: RPE or control.

• Outcomes: long-term skeletal, dentoalveolar, dental, and soft-tissue effects.

• Study design: prospective and retrospective studies, including RCTs, observational, and case–control studies.

Exclusion criteria included the following: meta-analyses and systematic reviews; publication bias, which was addressed by removing duplicate articles; studies in languages other than English and Spanish; patients who had undergone previous treatments; patients with facial asymmetry, cleft lip, and/or craniofacial syndromes.

Sources of Information and Research

The studies were identified through various electronic databases: PubMed, Cochrane, and Scopus. The following search strategy was carried out using appropriate descriptors relevant to this topic, combined with Boolean operators (the number of results was recorded according to the database and search strategy applied): “microscrews” AND “orthodontics” (results: PubMed, 631; Cochrane, 2; Scopus, 131); “microscrews” AND “orthodontics” AND “CBCT” (results: PubMed, 39; Cochrane, 0; Scopus, 15); “microscrews” AND “orthodontics” AND “CBCT” AND “MARPE” (results: PubMed, 25; Cochrane, 0; Scopus, 8); “MARPE” AND “orthodontics” (results: PubMed, 153; Cochrane, 1; Scopus, 49).

Study Selection and Data Extraction Process

A primary reviewer examined the abstracts and full texts and determined the articles selected for evaluation. A second reviewer verified their accuracy.

Data List and Level of Evidence

The data collected from each study selected for the systematic review included: author, journal and year of publication, and type of study in order to determine the level of evidence of these articles using the classification of the Oxford Centre for Evidence-Based Medicine (OCEBM).²⁴ The articles selected are listed in
Table 1.^19,25-34

Risk of Bias in Individual Studies

For the assessment of the quality of the articles, the present authors used the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) scale,³⁵ with a moderate-to-low risk of bias (Table 2).

Results

Study Selection

The study selection process is summarized in a PRISMA flow diagram presented in Figure 1. After conducting the initial electronic search in the various databases, the authors obtained 1,054 articles, of which 628 were duplicates. Subsequently, the authors excluded 352 articles, because they were either irrelevant to the topic, written in a language other than English or Spanish, or systematic reviews or meta-analyses. Then, 22 articles were excluded that either contained irrelevant information, did not have an available abstract, or concerned patients with facial asymmetry, cleft lip, craniofacial syndromes, or previous orthognathic surgery.

Upon reviewing the remaining 52 articles, 41 were excluded due to lack of scientific evidence, as they either were case reports or lacked conclusive findings. Therefore, the articles included in the present review amounted to 11 total, with a moderate-to-high level of evidence and a moderate-to-low risk of bias, as reflected in Table 1 and Table 2, respectively.

Study Characteristics

A summary of the key characteristics and results of the selected articles are presented in Table 3.^19,25-34 (To view Table 3, “Conclusions of the Articles in the Review,” visit compendiumlive.com/go/cced2110.) All articles were in English, published between 2017 and 2023, and the sample sizes of the studies ranged from 14 to 40. Eight studies evaluated dental data at the molar level, and 10 studies also took into account skeletal or dentoalveolar data, while only one addressed the airways.

Risk of Bias in the Articles

The various domains for assessing the risk of bias in each study are presented in Table 2. The QUADAS-2 scale was used. The studies were heterogeneous, with moderate-to-high methodological quality, and all were considered to have a moderate-to-low risk of bias. Four studies were of high quality. Six studies were of moderate quality, meeting 50% to 64% of the QUADAS-2 criteria, and one study was of low quality. The weaknesses were reflected in the lack of comparison with the gold standard and the absence of blinding.

Level of Evidence

The OCEBM classification assesses the level of evidence according to each clinical setting.²⁴ The present systematic review has a “moderate level of evidence and strength of recommendation” (Table 1).

Discussion

Maxillary constriction is one of the main reasons for orthodontic treatment because it entails bone and dental alterations, and it is also associated with soft tissue and function.^1,4 To assess transverse problems, traditional diagnosis has relied primarily on study models and frontal radiographs, but thanks to 3-dimensional (3D) developments, CBCT now provides sufficient data to allow much greater diagnostic precision.^6,14,36-39 Therefore, only studies that incorporated CBCT into their methodology were selected for this review.

In pediatric patients, RPE is achieved effectively; however, in late adolescents and adults, the MPS and circummaxillary sutures begin to fuse and become more rigid.⁸ Therefore, the MARPE technique may be a better option for patients in late adolescence and young adulthood, with surgically assisted expansion being the preferred treatment for more mature adults.^4,10
Sample Size

The sample sizes in the studies included in this review ranged from 14 to 40 patients. Because these were retrospective studies, the sample sizes are considered acceptable; however, increasing the sample size would enhance the reliability of the results. Only one study compared MARPE with SARPE, while two studies compared MARPE with RPE, one of which included a control group.^19,25-34

The predominant age range across the studies was 17 to 36 years, which corresponds to the primary target population for this type of treatment. Only two studies included participants under 14 years of age.

Use of CBCT and Software

There was substantial variability in the use of CBCT equipment and software. The most frequently used scanner systems were the iCat™ (DEXIS, dexis.com) and Alphard VEGA 3D (Asahi Roentgen Ind. Co., Ltd., asahi-xray.co.jp), and the most common software was Invivo5 (Anatomage, Inc., anatomage.com). Only one study³⁴ (Naveda, 2023) did not report the 3D scanner used. This variability does not affect the diagnostic approach per se, but rather it affects the image quality available for calibration and transverse diagnosis.

Appliances Used in Treatment

The predominant expander design was a Hyrax-type model, dentally supported on the molars and skeletally anchored by means of four miniscrews.^25-28,33 Four studies used the maxillary skeletal expander (MSE) model,^19,31,32,34 and one study employed a different model—the Dutch Maxillary Expansion Device (D-MED).³⁰

Regarding the number of miniscrews used for anchorage, all studies except one used four miniscrews with a diameter of 1.8 mm and a length that varied according to each patient, while in one study, two miniscrews of 12 mm length and 1.5 mm diameter were used.²⁹

Measurements Taken

At the soft-tissue level, only two studies examined nasal changes from a facial perspective,^28,33 and just one study assessed the airway in terms of contour, volume, and area.²⁹

At the skeletal level, several studies examined traditional transverse measurements assessed via frontal cephalometry (Z-Z, N-N, J-J, MA-MA, AG-AG),^19,25,33 with a focus on nasal cavity and basal bone width changes.^{25,26,28,29,32-34} Only one study measured the angles formed by the bony structures.¹⁹ Although similar measurements were taken, there was considerable variability in the methodology regarding the level of linear measurements.

Measurements at the dentoalveolar level were more consistent. Most studies used the jugal points of the maxillae as reference points at both the molar and premolar levels.^{25,26,28-30,32-34} Only one study measured the maxilla’s dental inclination.²⁶ Additionally, six studies took into account changes in the thickness of the bone plate at both the buccal and palatal levels as well as at the level of the alveolar bone crest.^{25,26,30,32-34} Five studies also assessed MPS opening, both anteriorly and posteriorly, and measured the total amount of separation.^26,27,30-32

There was considerable variability in dental-level measurements. The main measurement was the intermolar and interpremolar width, assessed at the intercuspal level.^25,26,28-34 On the other hand, only two studies referred to intercanine width at the cuspid level,^26,30 while others examined interapical width at the molar level.^26,28

Seven studies measured molar inclination relative to the maxillary plane, either at the level of the axial axis^25,26,30-33 or the palatal root axis.³⁴ Only Shin et al reported on palatal length and depth as well as on other craniofacial factors such as sagittal pattern and skeletal classification.²⁷

This review revealed considerable heterogeneity in the approach to treating the transverse plane and in quantifying the effects of these treatments. High-quality CBCT imaging and precise software are essential for obtaining accurate diagnostic data and standardizing measurement methods. With these tools, clinicians have the means to develop a correct diagnostic method for the transversal problem.

Despite variability in appliance design, all studies reported favorable outcomes with skeletal expanders for addressing transverse deficiencies in young adults. A case presentation illustrating treatment in a 16-year-old patient is shown in Figure 2 through Figure 39. (An additional case presentation may be viewed at compendiumlive.com/go/cced2110.) The studies also agree on the importance of individualizing miniscrew length and diameter in each case.^{25,26,30-32,34}

Most studies concur that MARPE treatment is more predictable than RPE in younger adults, with success rates decreasing after age 30.¹⁸

Conclusions

As a result of this literature review, several conclusions may be made. First, MARPE in young patients is an effective treatment for addressing transverse discrepancies, resulting in an increase in both dentoalveolar and skeletal widths; however, the success of the procedure appears to be age-dependent. Second, there is considerable heterogeneity when it comes to quantifying the transverse problem, and it would, therefore, be appropriate for the dental profession to seek a gold standard at the orthodontic level to achieve standardization to help ensure patients are provided with an accurate diagnosis and, consequently, an individualized treatment plan. Finally, effective transverse treatment depends not only on the design of the expander but also on the individualized selection of miniscrew specifications.

ABOUT THE AUTHORS

Alberto-José López-Jiménez, DDS, MS, PhD
Associate Professor, Institution University of Mississippi, Complutense University of Madrid, Madrid, Spain; Private Practice limited to Orthodontics, Guadalajara, Spain

Miguel Hirschhaut, DDS, PhD
Private Practice limited to Orthodontics, Caracas, Venezuela

Daniel Diez-Rodrigalvarez, DDS, MS
Director, Masters in Orthodontics and Dentofacial Orthopedics, Institution University of Mississippi, Madrid, Spain

María Dolores Campoy, PhD
Private Practice limited to Orthodontics, Murcia, Spain

Figures and Images

Table 1

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 9

Figure 10

Figure 11

Figure 12

Table 2

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

Figure 37

Figure 38

Figure 39

Table 1

Figure 1

PRISMA flow diagram used in the methodology for identification and screening.

Figure 2

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 3

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 4

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 5

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 6

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 7

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 9

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 10

Case report. Pretreatment records: a 16-year-old female patient presented with a symmetrical class III malocclusion with maxillary compression and a 9 mm maxillomandibular discrepancy, which required orthognathic surgery. The patient, however, declined this option, and MARPE treatment was planned.

Figure 11

Pretreatment, panoramic radiograph.

Figure 12

Pretreatment, cephalometric radiograph.

Table 2

Figure 13

A MARPE procedure was planned to address the maxillary constriction problem, along with multibracket orthodontic treatment. These intratreatment photographs show treatment with a MSE and self-ligating brackets for maxillary expansion, dental alignment, and stable occlusal improvement.

Figure 14

A MARPE procedure was planned to address the maxillary constriction problem, along with multibracket orthodontic treatment. These intratreatment photographs show treatment with a MSE and self-ligating brackets for maxillary expansion, dental alignment, and stable occlusal improvement.

Figure 15

A MARPE procedure was planned to address the maxillary constriction problem, along with multibracket orthodontic treatment. These intratreatment photographs show treatment with a MSE and self-ligating brackets for maxillary expansion, dental alignment, and stable occlusal improvement.

Figure 16

A MARPE procedure was planned to address the maxillary constriction problem, along with multibracket orthodontic treatment. These intratreatment photographs show treatment with a MSE and self-ligating brackets for maxillary expansion, dental alignment, and stable occlusal improvement.

Figure 17

A MARPE procedure was planned to address the maxillary constriction problem, along with multibracket orthodontic treatment. These intratreatment photographs show treatment with a MSE and self-ligating brackets for maxillary expansion, dental alignment, and stable occlusal improvement.

Figure 18

In these intra-treatment photographs, maxillary expansion with MSE has been completed, having achieved increased transverse width and improved arch coordination.

Figure 19

In these intra-treatment photographs, maxillary expansion with MSE has been completed, having achieved increased transverse width and improved arch coordination.

Figure 20

In these intra-treatment photographs, maxillary expansion with MSE has been completed, having achieved increased transverse width and improved arch coordination.

Figure 21

In these intra-treatment photographs, maxillary expansion with MSE has been completed, having achieved increased transverse width and improved arch coordination.

Figure 22

In these intra-treatment photographs, maxillary expansion with MSE has been completed, having achieved increased transverse width and improved arch coordination.

Figure 23

This set of intratreatment photographs demonstrates placement of maxillary miniplates for skeletal traction and maxillary advancement with stable bone anchorage.

Figure 24

This set of intratreatment photographs demonstrates placement of maxillary miniplates for skeletal traction and maxillary advancement with stable bone anchorage.

Figure 25

This set of intratreatment photographs demonstrates placement of maxillary miniplates for skeletal traction and maxillary advancement with stable bone anchorage.

Figure 26

This set of intratreatment photographs demonstrates placement of maxillary miniplates for skeletal traction and maxillary advancement with stable bone anchorage.

Figure 27

This set of intratreatment photographs demonstrates placement of maxillary miniplates for skeletal traction and maxillary advancement with stable bone anchorage.

Figure 28

Post-treatment, facial photographs.

Figure 29

Post-treatment, facial photographs.

Figure 30

Post-treatment, facial photographs.

Figure 31

Post-treatment, facial photographs.

Figure 32

Post-treatment, intraoral photographs.

Figure 33

Post-treatment, intraoral photographs.

Figure 34

Post-treatment, intraoral photographs.

Figure 35

Post-treatment, intraoral photographs.

Figure 36

Post-treatment, intraoral photographs.

Figure 37

Post-treatment, panoramic radiograph.

Figure 38

Post-treatment, cephalometric radiograph.

Figure 39

Post-treatment, cephalometric superimpositions.