Abstract
Objectives
To compare differential changes in nasal patency and dentoskeletal morphology after rapid palatal expansion (RPE) vs hybrid miniscrew-assisted rapid maxillary expansion (MARPE).
Materials and Methods
Thirty patients presenting with bilateral crossbite were randomized into RPE or hybrid MARPE treatment groups. MARPE patients were treated using the two-point hyrax appliance and RPE patients were treated using the conventional hyrax appliance. Nasal patency was evaluated using rhinomanometry and dentoskeletal changes were evaluated using cone beam computed tomography images.
Results
The success of suture opening was 53% and 60% in the RPE (mean age: 17.36 ± 1.80) and MARPE groups (mean age: 18.52 ± 1.80), respectively. The MARPE group showed significantly increased nasal airflow and decreased nasal resistance during inspiration and expiration compared to the RPE group after 4 months of treatment. The RPE group demonstrated nonsignificant changes in the same parameters after 4 months. Although significant differences between groups were observed in nasal flow during inspiration and expiration for both nostrils, intergroup differences in nasal resistance were not significant (P > .05). The MARPE group exhibited greater expansion in nasal, maxillary basal, and alveolar widths compared to the RPE group. A more pronounced decrease in buccal bone thickness was observed in the RPE group. The buccal inclination of the first premolars and molars significantly increased in both groups.
Conclusions
Although similar success rates for sutural opening were observed between MARPE and RPE, MARPE facilitated more pronounced changes in nasal patency and skeletal maxillary expansion compared to conventional RPE.
Keywords: MARPE, RPE, Rhinomanometry, CBCT
INTRODUCTION
Rapid palatal expansion (RPE) is a common treatment for correcting maxillary transverse deficiency in children and early adolescents. The feasibility of successful RPE in older age groups is controversial due to increasing rigidity of midpalatal and circummaxillary sutures. For late adolescents and adults, surgical-assisted rapid palatal expansion (SARPE) has been recommended to facilitate skeletal expansion of the maxilla and minimize dental and periodontal side effects.1 However, SARPE is an invasive procedure associated with risks and can incur significant costs for patients.
As a nonsurgical alternative for correcting transverse skeletal deficiency, temporary anchorage devices have allowed for the introduction of miniscrew-assisted rapid palatal expansion (MARPE), which uses two or four miniscrews inserted into the maxillary palate.2 In comparative studies of MARPE and SARPE, Jesus et al.3 reported similar efficacy between the two techniques, but noted fewer complications with MARPE. Meanwhile, de Oliveira et al.4 found that MARPE achieved significantly greater skeletal expansion at the palate and basal bone compared to SARPE.
Although MARPE has garnered significant attention in recent years, most publications on the topic are retrospective in nature. According to a relatively recent systematic review and meta-analysis, there is a notable absence of high-quality prospective studies, with a considerable risk of bias present in most of the studies examined.5 Only a limited number of prospective studies have explored the skeletal, dento-alveolar, and periodontal effects of MARPE in patients over the age of 16.6–8 Additionally, within this age group, only a single study assessed the impact of MARPE on nasal breathing function using objective and quantitative methods.9
The objective of this prospective randomized clinical trial was to compare differential changes in nasal patency and dentoskeletal morphology after maxillary expansion using either a conventional tooth-borne (TB) RPE Hyrax appliance or a tooth-bone-borne (TBB) hybrid MARPE appliance in late adolescents and young adults. Although the effects of MARPE on dental, skeletal, and airway structures have been well investigated in young adolescents using cone beam computed tomography, the impact of these changes on airway functionality remains largely unexplored. Accordingly, this study is one of the first to assess the impact of MARPE treatment on airway functionality in late adolescents and young adults.
MATERIALS AND METHODS
The protocol was approved by the Jacksonville University Institutional Review Board (no. 2018-038). The inclusion criteria for the study were: (1) skeletal maxillary deficiency accompanied by bilateral crossbite; (2) cervical maturation at stages 5–6;3 (3) good oral hygiene without any missing teeth; (4) healthy periodontal tissues (5) ages 16–21. The exclusion criteria were: (1) any craniofacial anomalies; (2) a history of previous orthodontic treatment; (3) systemic diseases and medications known to affect bone metabolism; (4) subjects with unilateral or bilateral total nasal obstruction; (5) rhinitis (6) body mass index greater than 24.9; (7) failure to open the midpalatal suture. The sample size was calculated with the G*Power 3.1.9.7 statistical program (Heinrich Heine Universitat Dusseldorf Institute fur Experimentelle Psychologie, Dusseldorf, Germany). To detect a 0.98 Pa s/cm3 difference in nasal airway resistance with a standard deviation of 0.4, according to the power analysis with 90% power and 0.05 level, the minimum sample size needed for each group was seven patients.10
Patients were equally distributed into either RPE or hybrid MARPE groups using simple randomization (version 2.0; Random Allocation Software, Isfahan, Iran). The patients in the RPE group were treated with a conventional TB Hyrax appliance (Figure 1). The patients in the hybrid MARPE group were treated with a TBB hybrid hyrax appliance with molar bands and two 1.7 × 8 mm miniscrews (Orthoeasy; Forestadent, Pforzheim, Germany) (Figure 2) placed distal of the third palatal rugae midsagitally. All patients in both groups were treated by the same orthodontist. The expander screw was activated at a rate of two-quarter turns per day (0.4 mm). Activation was discontinued when the lingual cusps of the maxillary first molars approximated the buccal cusps of the mandibular first molars. If the suture separation was not successful, a slow expansion protocol of two turns per week was implemented to address the skeletal transverse deficiency through dental means as effectively as the dentoalveolar housing allowed.
Figure 1.
TB Hyrax appliance. TB indicates tooth borne.
Figure 2.
MARPE appliance. MARPE indicates miniscrew-assisted rapid maxillary expansion.
Cone-beam computed tomography (CBCT) images were acquired for each patient pre- and post-treatment (Planmeca Pro Max 3D ProFace) with the acquisition parameters of 80 × 50 mm, 0.015 mm voxel size. DICOM files were imported into Dolphin Imaging software (version 12.0.09.58 Premium; Dolphin Imaging and Management Solutions, Chatsworth, CA, USA). Images were oriented in three planes using the midpalatal suture (axial slice), palatal plane (sagittal slice), and inferior level of the nasal floor (coronal slice) as guides. Figures 3–6 depict how the various measurements were assessed using axial and coronal slices.
Figure 3.
The widest intercortical distance of the incisive foramen.
Figure 6.
M Inclination: The angle formed by a line passing through the central pit and the apex of the palatal root of the maxillary first molar and the baseline drawn tangent to the hard palate at the level of the first molar furcation; Intermolar W: Distance between the central grooves of the maxillary first molars.
Figure 4.
Intermaxillary suture width measured between the right and left cortical border at the anteroposterior position of maxillary first premolars (SWP) and first molars (SWM).
Figure 5.
Nasal W M: Distance between right and left nasal lateral points parallel to the baseline drawn tangent to the hard palate at the level of the maxillary first molar furcation; Basal W M: Distance between maxillary right and left basal bone points constructed parallel to the baseline drawn tangent to the hard palate at the level of the maxillary first molar furcation; Alveolar W M: Distance between maxillary right and left alveolar points parallel to the baseline drawn tangent to the hard palate at the level of the maxillary first molar furcation; M Alveolar H: Distance from the most inferior alveolar point of the molar to the baseline drawn tangent to the hard palate at the level of the maxillary first molar furcation.
Nasal airflow refers to the movement of air through the nasal passages during respiration and nasal resistance refers to the opposition to this airflow. Nasal airflow and resistance are influenced by anatomical structures and mucosal conditions. Anterior rhinomanometry assesses resistance and airflow from the nasal opening to the choanal junction and posterior rhinomanometry evaluates resistance from the nasopharynx. Nasal airflow and nasal airway resistance were assessed before and after treatment with a research grade 4-phase clinical NR6 rhinomanometer (GM Instruments, Kilwinning, UK) and a facemask having an airtight seal against the face. For active anterior rhinomanometry (AR), disposable foam inserts were fitted into the nostril not being examined to allow pressure, flow, and resistance measurements to be obtained on the other nostril. For each subject, four respiratory cycles (inspiration and expiration) were recorded for each nostril and averaged. For AR, expiratory and inspiratory nasal airway resistances were calculated at reference pressures of 150 Pa. For active posterior rhinomanometry (PR), patients breathed into the facemask using both nostrils while sealing their lips around the pressure sensing tube in the oral cavity. For PR, expiratory and inspiratory nasal airway resistances were calculated at reference pressures of 75 Pa (Figure 7).
Figure 7.
Rhinomanometric curve of a patient. Initial measurements are shown in pink, final measurements are shown in blue. (A) Anterior left nasal side measurements depicting considerable improvement. (B) Anterior right nasal side measurements showing minimal improvement. (C) Posterior nasal measurements displaying improvement.
Statistical Analysis
Intraexaminer reliability was evaluated by remeasuring all the variables in 30% of the samples after a minimum 15-day interval. Intraclass correlation coefficient (ICC) was used for intraexaminer agreement assessment. The assumption of normality was checked with the Shapiro-Wilk test. For normally distributed variables, paired t-test was used to evaluate the changes from T0 to T1 in each group and 2 independent-samples t-test was used to compare the mean differences between the groups. For variables that were not normally distributed, Wilcoxon test was performed to evaluate the changes between T0 and T1 in each group, while Mann-Whitney U test was used to compare the means of two independent groups. To evaluate the correlation between rhinomanometry and CBCT findings, Pearson's correlation was used when the data followed a normal distribution, whereas Spearman's correlation was employed for non-normally distributed data. Only the measurements of the patients with successful sutural opening were included for analysis. All analyses were made using IBM SPSS 25 program.
RESULTS
The RPE group consisted of five males and 10 females (mean age: 17.36 ± 1.80 years), whereas the hybrid MARPE group comprised nine males and six females (mean age: 18.52 ± 1.60 years). There were no statistically significant differences between the groups in terms of age or sex distribution (P > .05). No patients presented with evident breathing issues at the onset of the study. No significant intergroup differences were observed in any of the rhinomanometry parameters prior to treatment. Significantly greater dimensions of buccal bone thickness, tooth inclination, alveolar heights of the premolar and molar teeth, and intermolar width, were present in the RPE group prior to treatment. The intraclass coefficient for all CBCT measurements ranged from 0.886 to 0.998, indicating good reproducibility.
Among the 30 patients evaluated, 13 experienced failure of palatal suture opening, including four females and three males in the RPE group, and one female and five males in the MARPE group. The success of suture opening was 53% and 60% in the RPE and MARPE groups, respectively (P = .712).
Descriptive data of rhinomanometry and CBCT measurements before and after expansion, and the significance of treatment changes in each group, are summarized in Tables 1 and 2, respectively. A comparison of changes in nasal airflow and nasal resistance between RPE and MARPE groups are presented in Table 3. A comparison of skeletal and dentoalveolar changes between RPE and MARPE groups are presented in Table 4.
Table 1.
Nasal Airflow and Nasal Resistance Changes for the Groupsa
| RPE Group |
MARPE Group |
|||||
|---|---|---|---|---|---|---|
| Pre (T0) |
Post (T1) |
Pre (T1) |
Post (T0) |
|||
| X ± SD (M) | X ± SD (M) | P Value | X ± SD (M) | X ± SD (M) | P Value | |
| Inspiration | ||||||
| Left nasal airflow (cm³/s) | 206.32 ± 93.56 (235.06) | 183.76 ± 105.21 (182.85) | .315 | 177.68 ± 78.37 (159.1) | 292.4 ± 88.54 (322.9) | .010* |
| Left nasal resistance (Pa·s/cm³) | 1.23 ± 0.79 (1.16) | 1.35 ± 0.79 (0.9) | .563 | 1.19 ± 0.71 (1) | 0.61 ± 0.29 (0.47) | .008* |
| Right nasal airflow (cm³/s) | 179.6 ± 113.07 (165.7) | 201.13 ± 111.25 (212.85) | .351 | 125.7 ± 71.84 (109.9) | 242.76 ± 63.18 (249.5) | .008* |
| Right nasal resistance (Pa·s/cm³) | 1.64 ± 0.76 (1.46) | 1.24 ± 0.55 (1.21) | .184 | 1.73 ± 1.11 (1.39) | 0.77 ± 0.4 (0.6) | .008* |
| Posterior nasal airflow (cm³/s) | 333.51 ± 108.57 (311.45) | 269.76 ± 86.31 (306.5) | .441 | 226.71 ± 103.68 (178.5) | 365.45 ± 145.86 (398.5) | .001* |
| Posterior nasal resistance (Pa·s/cm³) | 0.7 ± 0.81 (0.32) | 1.2 ± 1.19 (0.54) | .528 | 1.38 ± 1.55 (0.55) | 0.37 ± 0.36 (0.22) | .015* |
| Expiration | ||||||
| Left nasal airflow (cm³/s) | 204.71 ± 104.23 (254.23) | 192.8 ± 107.08 (217.58) | .866 | 146.53 ± 69.16 (126.4) | 255.16 ± 92.25 (267) | .008* |
| Left nasal resistance (Pa·s/cm³) | 1.6 ± 0.89 (1.66) | 1.35 ± 0.72 (1.12) | .218 | 1.51 ± 1.2 (1.23) | 0.67 ± 0.34 (0.5) | .008* |
| Right nasal airflow (cm³/s) | 193.09 ± 109.01 (207.3) | 199.18 ± 113.75 (203.8) | .836 | 121.62 ± 67.28 (106.2) | 225.03 ± 77.42 (250.3) | .001* |
| Right nasal resistance (Pa·s/cm³) | 1.38 ± 1.02 (1.02) | 1.14 ± 0.87 (1.01) | .258 | 1.67 ± 0.95 (1.52) | 0.64 ± 0.26 (0.6) | .008* |
| Posterior nasal airflow (cm³/s) | 273.31 ± 60.27 (266.7) | 236.98 ± 105.71 (250.4) | .118 | 244.57 ± 172.36 (213) | 251.18 ± 127.37 (216.8) | .044* |
| Posterior nasal resistance (Pa·s/cm³) | 0.72 ± 0.76 (0.33) | 0.56 ± 0.67 (0.33) | .528 | 1.33 ± 1.59 (0.63) | 0.39 ± 0.2 (0.39) | .051 |
RPE indicates rapid palatal expansion; MARPE, mini-screw assisted rapid palatal expansion; M, median.
P < .05.
Table 2.
Skeletal and Dentoalveolar Changes for the Groupsa
| RPE Group |
MARPE Group |
|||||
|---|---|---|---|---|---|---|
| Pre (T0) |
Post (T1) |
Pre (T0) |
Post (T1) |
|||
| X ± SD (M) | X ± SD (M) | P Value | X ± SD (M) | X ± SD (M) | P Value | |
| Nasal W Pm (mm) | 25.6 ± 2.03 (25.89) | 27.23 ± 2.29 (27.5) | .000* | 26.02 ± 2.93 (26.67) | 29.21 ± 2.96 (29.09) | <.001* |
| Nasal W M (mm) | 30.17 ± 2.16 (30.61) | 31.37 ± 2.48 (31.78) | .008* | 29.82 ± 2.84 (30.26) | 32.58 ± 2.56 (32.61) | <.001* |
| Basal W Pm (mm) | 36.29 ± 2.29 (36) | 38.89 ± 2.61 (38.53) | <.001* | 37.06 ± 3.23 (36.08) | 40.97 ± 3.32 (39.82) | <.001* |
| Basal W M (mm) | 59.54 ± 3.21 (59.93) | 61.28 ± 3.47 (61.79) | <.001* | 64.44 ± 4.81 (65.93) | 67.6 ± 4.66 (69.04) | <.001* |
| Alveolar W Pm (mm) | 45.74 ± 3.54 (46.83) | 48.44 ± 3.87 (49.55) | <.001* | 44.26 ± 2.66 (44.02) | 47.99 ± 2.7 (47.36) | <.001* |
| Alveolar W M (mm) | 60.06 ± 3.25 (60.43) | 61.09 ± 4.96 (61.08) | .453 | 62.92 ± 4.96 (63.06) | 66.67 ± 5.04 (67) | <.001* |
| Pm Buccal W (mm) | 2.19 ± 0.85 (2.05) | 1.5 ± 0.65 (1.28) | .015* | 1.07 ± 0.25 (1.02) | 1.12 ± 0.29 (1.07) | .325 |
| Molar Buccal W (mm) | 2.16 ± 0.46 (2.1) | 1.42 ± 0.34 (1.34) | .005* | 1.23 ± 0.27 (1.24) | 0.84 ± 0.32 (0.79) | <.001* |
| Pm Alveolar H (mm) | 16.85 ± 1.74 (16.69) | 16.43 ± 1.69 (16.28) | .071 | 15.33 ± 1.03 (15.32) | 15.26 ± 1.01 (15.3) | .154 |
| M Alveolar H (mm) | 15.88 ± 2.22 (15.15) | 15.73 ± 2.19 (15.25) | .548 | 13.57 ± 0.81 (13.58) | 12.51 ± 0.74 (12.75) | <.001* |
| Pm Inclination (o) | 100.56 ± 4.42 (100.36) | 104.74 ± 6.91 (102.96) | .025* | 96.71 ± 3.73 (95.38) | 99.07 ± 3.76 (98.02) | <.001* |
| M Inclination (o) | 110.35 ± 5.42 (110.63) | 114.36 ± 7.17 (117.1) | .038* | 108.71 ± 5.04 (108.32) | 111.93 ± 4.44 (111.06) | <.001* |
| Interpremolar W (mm) | 35.36 ± 1.45 (35.65) | 39.44 ± 1.65 (39.01) | <.001* | 35.74 ± 2.04 (35.38) | 40.15 ± 1.7 (39.93) | <.001* |
| Intermolar W (mm) | 44.04 ± 1.71 (44.14) | 48.42 ± 1.65 (48.44) | <.001* | 46.29 ± 1.64 (45.81) | 51.03 ± 4.64 (51.92) | .011* |
| Suture W Inc For (mm) | 3.77 ± 0.44 (0.72) | 4.94 ± 0.53 (1.95) | <.001* | 3.57 ± 0.72 (0.43) | 6.31 ± 1.38 (3.68) | .008* |
| Suture W Pm (mm) | 0.36 ± 0.33 (0.42) | 1.7 ± 0.48 (1.7) | <.001* | 0.49 ± 0.12 (0.47) | 3.27 ± 0.85 (3.63) | <.001* |
| Suture W M (mm) | 0.23 ± 0.25 (0.21) | 1.29 ± 0.54 (1.08) | .001* | 0 ± 0 (0) | 2.96 ± 0.41 (3.05) | <.001* |
RPE indicates rapid palatal expansion; MARPE, mini-screw assisted rapid palatal expansion; W, width; Pm, premolar; M, molar; H, height; Inc For, incisive foramen; M, median.
P < .05.
Table 3.
Comparison of Nasal Airflow and Nasal Resistance Changes Between Groupsa
| RPE Group |
MARPE Group |
Intergroup Comparison |
|
|---|---|---|---|
| T0-T1 X ± SD (M) | T0-T1 X ± SD (M) | P Value | |
| Inspiration | |||
| Left nasal airflow (cm³/s) | −22.56 ± 58.95 (−7.38) | 114.72 ± 103.13 (71.4) | <.001* |
| Left nasal resistance (Pa·s/cm³) | 0.12 ± 0.55 (0.08) | −0.59 ± 0.75 (−0.37) | .046* |
| Right nasal airflow (cm³/s) | 21.53 ± 60.92 (14.64) | 117.06 ± 67.21 (155.6) | .004* |
| Right nasal resistance (Pa·s/cm³) | −0.4 ± 0.78 (−0.46) | −0.97 ± 1 (−0.75) | .200 |
| Posterior nasal airflow (cm³/s) | −63.75 ± 128.81 (−2.15) | 138.74 ± 78.38 (130.1) | <.001* |
| Posterior nasal resistance (Pa·s/cm³) | 0.49 ± 1.65 (0.04) | −1.01 ± 1.49 (−0.27) | .093 |
| Expiration | |||
| Left nasal airflow (cm³/s) | −11.91 ± 57.33 (5.64) | 108.63 ± 93.85 (74.8) | <.001* |
| Left nasal resistance (Pa·s/cm³) | −0.25 ± 0.51 (−0.27) | −0.84 ± 1.04 (−0.42) | .481 |
| Right nasal airflow (cm³/s) | 6.09 ± 79.98 (7.47) | 103.4 ± 63.61 (96.94) | .006* |
| Right nasal resistance (Pa·s/cm³) | −0.24 ± 0.56 (−0.28) | −1.03 ± 0.88 (−0.92) | .093 |
| Posterior nasal airflow (cm³/s) | 6.61 ± 207.87 (49.68) | 36.34 ± 81.64 (−11.7) | .059 |
| Posterior nasal resistance (Pa·s/cm³) | −0.16 ± 1.09 (−0.09) | −0.94 ± 1.61 (−0.26) | .321 |
RPE indicates rapid palatal expansion; MARPE, mini-screw assisted rapid palatal expansion.
P < .05.
Table 4.
Comparison of Skeletal and Dentoalveolar Changes Between Groups
| RPE Group |
MARPE Group |
Intergroup Comparison |
|
|---|---|---|---|
| T0-T1 X ± SD (M) | T0-T1 X ± SD (M) | P Value | |
| Nasal W Pm (mm) | 1.63 ± 0.51 (1.67) | 3.19 ± 0.66 (3.33) | <.001* |
| Nasal W M (mm) | 1.20 ± 0.51 (1.17) | 2.77 ± 0.58 (2.89) | <.001* |
| Basal W Pm (mm) | 2.59 ± 1.04 (2.94) | 3.91 ± 0.28 (4.04) | <.001* |
| Basal W M (mm) | 1.74 ± 0.8 (1.53) | 3.16 ± 0.37 (3.22) | <.001* |
| Alveolar W Pm (mm) | 2.7 ± 0.83 (2.74) | 3.73 ± 0.51 (3.75) | .006* |
| Alveolar W M (mm) | 1.03 ± 3.66 (2.45) | 3.75 ± 0.22 (3.75) | <.001* |
| Pm Buccal W (mm) | −0.69 ± 0.61 (−0.62) | 0.05 ± 0.14 (0.05) | .010* |
| M Buccal W (mm) | −0.74 ± 0.53 (−0.57) | −0.39 ± 0.15 (−0.38) | .046* |
| Pm Alveolar H (mm) | −0.42 ± 0.55 (−0.18) | −0.07 ± 0.13 (−0.02) | .236 |
| M Alveolar H (mm) | −0.15 ± 0.67 (−0.01) | −1.06 ± 0.22 (−1.11) | .122 |
| Pm Inclination (o) | 4.18 ± 4.15 (3.64) | 2.36 ± 0.92 (2.05) | .370 |
| M Inclination (o) | 4.01 ± 4.45 (5.28) | 3.22 ± 0.93 (3.09) | .093 |
| Interpremolar W (mm) | 4.07 ± 0.69 (4.27) | 4.41 ± 0.7 (4.24) | .332 |
| Intermolar W (mm) | 4.38 ± 0.78 (4.07) | 4.75 ± 3.85 (6.04) | .006* |
| Suture W Inc For (mm) | 1.17 ± 0.25 (1.24) | 2.74 ± 1.14 (3.24) | .006* |
| Suture W Pm (mm) | 1.34 ± 0.43 (1.32) | 2.78 ± 0.83 (3.16) | <.001* |
| Suture W M (mm) | 1.06 ± 0.55 (0.89) | 2.96 ± 0.41 (3.05) | <.001* |
RPE indicates rapid palatal expansion; MARPE; mini-screw assisted rapid palatal expansion; W, width; Pm, premolar; M, molar; H, height; Inc For, incisive foramen.
P < .05.
DISCUSSION
Prior reports concluded RPE and MARPE may positively affect nasal function through increased nasal cavity width and/or volume.11 However, such studies were mainly anatomical and did not examine dynamic changes in airway function after treatment. Given the limited direct functional assessments available, it remains unclear whether MARPE effectively improves nasal function, particularly in late adolescents and young adults.
In the current study, increases in nasal airflow in the MARPE group ranged from 15% to 61%, whereas decreases in nasal resistance varied from 49% to 61%. Using posterior rhinomanometry, Timms12 reported an average reduction of 36.2% in nasal resistance among RPE patients aged 10.10 to 19.6 years, a finding that contrasted with the results of the current study, in which no significant improvement in nasal breathing was observed in the RPE group. This may be attributed to the slightly younger age group in that study, that likely experienced greater skeletal changes leading to a more noticeable improvement in nasal breathing. In the study conducted by Bazargani et al.,10 the TBB appliance was compared to the TB expander in growing patients aged 8 to 13 years. Rhinomanometry results indicated that the TBB MARPE significantly enhanced nasal airway flow and reduced nasal resistance compared to TB RPE. The current study demonstrated that, in late adolescence, although sutural opening can still be achieved with RPE, skeletal effects on the airway were substantially reduced compared to MARPE treatment. These findings highlight that sutural opening does not necessarily translate to improved nasal function. In the current study, the MARPE group exhibited significantly greater sutural expansion and increases in nasal cavity width compared to the RPE group. Such observations may have accounted for the improvements in nasal airflow and resistance with MARPE treatment.
Large differences in the extent of skeletal changes observed after MARPE treatment have been reported in the literature. Such variation was likely due to differences in the number and position of miniscrews, as well as the placement of the expander, and variations in ages of the patients. In late adolescents and adults, a systematic review and meta-analysis,5 along with a recent prospective study,7 reported success rates of midpalatal suture separation using MARPE to be 92.5% and 100%, respectively. These reported success rates5,7,8,13,14 were higher than the 60% observed in the current study. Factors such as age, midpalatal suture density, maturation stage of the midpalatal suture, midpalatal bone thickness, and widths of the zygomaticomaxillary and pterygomaxillary sutures can influence separation of the midpalatal suture and the skeletal effects of maxillary expansion.14–16 The relatively low success rates of suture opening observed in this study were likely due in part to the single screw design and monocortical engagement of the appliance. In a study evaluating the effects of monocortical vs bicortical mini-implant anchorage on maxillary skeletal expansion, Li et al.17 found that bicortical engagement was crucial for achieving satisfactory maxillary expansion. However, in the current study, miniscrews were placed in the anterior palate, resulting in monocortical engagement. Additionally, Cho et al.18 indicated that placing miniscrews in the posterior palate, near the resistance area, allowed the separation force to distribute along the entire length of the midpalatal suture, leading to greater skeletal effects. In contrast, the miniscrews in the present study were positioned in the anterior palate, where cortical bone thickness is greatest.
A meta-analysis by Copello et al.19 indicated that MARPE could result in less loss of buccal bone thickness and alveolar height in the premolar region compared to conventional RME, based on low quality evidence, with a recommendation for needing more research. In the current study, reduction in buccal bone thickness at the levels of the first premolar and first molar in the RME group were greater than those in the MARPE group. Considering the buccal bone loss observed in the RPE group, the greater pretreatment cortical bone thickness in this group appeared to be a clinical advantage. In cases in which cortical bone is thinner and alveolar height is lower before treatment, the extent of bone loss in the RPE group would likely be even more critical, making MARPE a more favorable option in such cases.
It was noted in the current study that using a monocortically retained two-screw hybrid appliance improved treatment outcomes compared to conventional RPE in individuals aged 16–21 who experienced successful midpalatal sutural opening (success rate: 60%). However, this finding should be interpreted cautiously, as individual variability may limit generalizability, particularly regarding multifactorial outcomes such as nasal airflow. Additionally, it is important to note that there was no significant difference in the number of cases with successful suture opening between the two groups, thus warranting long-term assessment of the reported outcomes.
Limitations of this study included the absence of evaluation of the nasal cavity by ear, nose, and throat specialists and the relatively small sample of patients who experienced suture opening. Nevertheless, the study met the required sample size based on a priori power calculations, achieving a statistical power of 95%, which exceeded the commonly accepted threshold of 80%. In addition, statistical significance was achieved for the primary outcome: breathing, due to the observed effect size between the intervention groups. Lastly, this study did not report long-term follow-up data. Even with these limitations, this study provided useful new insights regarding changes in airway function and dentoskeletal morphology following MARPE and RPE treatment among late adolescents.
CONCLUSIONS
In late adolescents and young adults who experienced successful sutural separation, MARPE using a hybrid hyrax appliance significantly enhanced nasal breathing, as indicated by nasal airflow and resistance measurements. Conversely, RPE did not affect respiratory function, even in individuals with successful sutural opening.
Although RPE using conventional Hyrax appliances can achieve a limited amount of skeletal transverse expansion, MARPE exhibited major changes, resulting in greater skeletal expansion.
The results reported suggest that greater skeletal changes promote major changes in nasal patency.
RPE and MARPE treatment modalities resulted in successful dentoalveolar treatment of posterior crossbite.
ACKNOWLEDGMENTS
Dr. Aras received the Orthodontic Faculty Development Fellowship Award from the American Association of Orthodontists Foundation for the current research.
REFERENCES
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