Microimplant assisted rapid palatal expansion vs surgically assisted rapid palatal expansion for maxillary transverse discrepancy treatment

Introduction

This study compared the skeletal and dental changes of microimplant assisted rapid palatal expansion (MARPE) with those produced by surgically assisted rapid maxillary expansion (SARPE) in postpeak adolescents and adults.

Methods

The sample comprised 17 patients (mean age, 26 ± 11 years) selected for the MARPE group and 15 (mean age, 28.5 ± 10.5 years) selected for the SARPE group. Cone-beam computed tomography scans taken just before and after the expansion were used to assess dental and skeletal changes and compare the changes between the groups.

Results

MARPE showed greater transversal skeletal changes in the midface and posterior and anterior maxillary base measurements. The transverse displacement of the alveolar process was greater but not significant for the SARPE group than the MARPE group. Regarding dental effects, the root distance measurements did not differ between the groups, but SARPE produced a significantly greater increase in intermolar and interpremolar distance and a greater buccal inclination of the alveolar process and supporting teeth than MARPE.

Conclusions

The MARPE technique showed an increase in skeletal transverse maxillary expansion at the midface and basal bone compared with SARPE, especially at the posterior palatal region; however, no difference was found in the expansion of the alveolar process between the 2 methods. MARPE presented a more parallel expansion in both a coronal and axial view, whereas SARPE led to a V-shaped opening. The greater buccal inclination of the alveolar process and supporting teeth was observed in the SARPE group.

Highlights

  • Microimplant assisted rapid palatal expansion produced better skeletal changes.

  • Microimplant assisted rapid palatal expansion produced a more parallel expansion.

  • Surgically assisted rapid palatal expansion produced a V-shaped opening.

  • Surgically assisted rapid palatal expansion produced greater dentoalveolar changes.

Treatment of transverse maxillary constriction using rapid palatal expansion (RPE) is most indicated in mixed dentition until adolescence during growth. RPE prognosis is related to the level of maxillary suture interdigitation, and its effect is inversely related to the success of the expansion; that is, the greater the interdigitation and more numerous the synostoses presented at the sutures, the lower the chances of splitting the maxilla without surgical intervention, known as surgically assisted rapid palatal expansion (SARPE). ,

In young adults and postpeak growth adolescents presenting skeletal maturity, the results of nonsurgical RPE may vary considerably. One study showed high success in young adults achieving a moderate expansion, whereas others found that age limited the RPE success rate in females aged up to 18 years and males aged up to 21 years. In patients aged more than 18 years, the skeletal effects are insignificant, exhibiting more dentoalveolar expansion of the maxillary arch.

Complications have been reported in the literature as a consequence of conventional tooth-borne RPE devices, including pain and swelling during expansion, buccal root resorption of the supporting teeth, buccal cortical and bone resorption, and bone dehiscence. Other authors reported patients with ischemia and necrosis in the palate mucosa when maxillary sutures do not respond to orthopedic forces applied through a tooth-supported expander.

The reason for the conventional RPE failures may be due to greater rigidity in craniofacial structures in skeletally mature patients. Therefore, SARPE is indicated to treat transverse maxillary deficiency in adult patients. Unfortunately, this treatment is often rejected because it is an invasive surgical procedure, with risks and high costs for the patient.

Miniscrews were recently developed for use as anchorage supporting orthopedic forces. , A microimplant assisted rapid palatal expansion (MARPE) technique has been advocated to optimize force distribution to the maxillary basal bone and circummaxillary structures, enhancing skeletal effects and minimizing dental inclination , , ; therefore, preserving periodontal health. , A recent clinical study showed that out of 69 patients treated using MARPE, 9 had failed to split midpalatal sutures (an 86.96% success rate) in young adults (mean age, 20.9 ± 2.9 years). Thus, because of this therapy’s high success rate, it may be recommended as an alternative to surgical expansion.

This study compared the skeletal and dental changes of MARPE with those produced by SARPE in patients with bone maturity. We believe that this information will help clarify the transversal changes achieved in both treatment modalities to better guide orthodontists to decide which method provides the most benefit to individual patients.

Material and methods

This clinical study was previously approved by the Research Ethics Committee of the Faculty of Dentistry of Araraquara of São Paulo State University (CCAAE Nos. 60393416.7.0000.5416 and 14484713.1.0000.5416).

The overall sample included 2 parallel controlled groups of patients treated for transverse maxillary deficiency using MARPE or SARPE. The MARPE sample consisted of 17 postpubertal adolescent and adults (4 men and 13 women) with a mean age of 22.9 years (minimum, 15; maximum, 37) treated between 2016 and 2019 at the Dental Center of Studies and Research (COESP), João Pessoa, Paraíba, Brazil and São Paulo State University (UNESP), Araraquara, São Paulo, Brazil. The SARPE group corresponded to a sample obtained from the archives of the Residency Program in Oral and Maxillofacial Surgery and Traumatology of Araraquara Dentistry College (UNESP) containing cone-beam computed tomography (CBCT) files (presurgery and postsurgery) of 15 patients (10 women and 6 men) with a mean age of 30.4 years (minimum, 18.7; maximum, 39.7) treated between 2010 and 2012. Patients who had undergone previous orthodontic treatment and who had severe facial deformities or syndromes were excluded. Selection criteria for both groups were transverse maxillary deficiency greater than 4 mm associated with unilateral or bilateral crossbite ( Table I ). The MARPE device used in this study had a 9-mm jackscrew expander and 4 miniscrews inserted paramedian to the midpalatal suture (Peclab, Belo Horizonte, Minas Gerais, Brazil) ( Fig 1 ). MARPE positioning was planned using initial CBCT images (T0) so that the miniscrews were inserted in a region of adequate bone thickness. After successful expansion, the patients underwent a second CBCT examination (T1).

Table I
Sample characteristics, descriptive statistics, and comparative Student t test for the initial transversal discrepancy between the MARPE and SARPE groups
Group n Mean SD P ( t test)
MARPE 17 −6.00 2.34 0.185
SARPE 15 −7.26 2.93

Note. Transversal discrepancy is the distance between palatal cusps of maxillary first molars minus the distance between the central groove of maxillary first molars.
SD, Standard deviation.

Not significant ( P >0.05).

Fig 1
MARPE (A) and SARPE (B) expander devices.

The miniscrews were installed manually with a contra-angle driver (Peclab), and the torque was measured between 15 N and 20 N. Activation protocol was a 2/4 turn immediately after mini-implant placement, and 2/4 turns daily on the following days (from 14 to 18 days) until full correction was achieved.

The SARPE group underwent surgery, including LeFort I subtotal osteotomy in the lateral wall of the maxilla, pterygomaxillary suture, and midpalatal suture disruption performed under general anesthesia at the university medical hospital. A hyrax expander was used with an activation protocol of 1/4 turns (0.2 mm) 2 times daily until crossbite correction.

CBCTs at T0 and T1 with MARPE and SARPE were obtained using an i-CAT Next Generation (Imaging Sciences International, Hatfield, Pa) at these settings: 120 kVp; 36 mA; 0.25-mm voxel size; scan time, 7 seconds; and field view of 13 cm in height × 16 cm in depth. For both groups, the data were exported in the Digital Imaging and Communication in Medicine format and analyzed using NemoStudio software (Nemotec, Madrid, Spain). For sample blinding, examiner A (P.A.) coded the CBCT files, and examiner B was responsible for skeletal and dental measurements.

The images in 3-dimensional reformatting were positioned according to 3 spatial orientation planes (sagittal, coronal, and axial), as shown in Figure 2 .

Fig 2
Head position standardization. (A) The coronal view is in the axial plane line over the lower margin of the right and left orbits and the sagittal plane line coinciding with the nasal, (B) right sagittal view, and (C) left is a line of the axial plane coinciding with the Frankfurt plane and the coronal plane line passing through the posterior border of the pallium.

To measure the skeletal effects of expansion in both groups, linear measurements (in millimeters) of the maxillary bone structure were obtained in the upper and lower segments of the maxilla and the anterior and posterior segments to quantify the transverse changes in the nasal cavity and evaluate the maxillary split pattern. To evaluate the dental results, measurements were obtained to quantify the amount of expansion and inclination ( Fig 3 and Table II ).

Fig 3
Linear skeletal measurements of an axial slice: (A) MIF and (B) PP and PA; linear skeletal measurements on a coronal slice at the first molar plane: (C) MMW, MNM, and MAW; linear skeletal measurements at first premolar plane: (D) PMW, PNM, and PAW; angular and linear measurements used to measure the dental effect on the maxillary first molars: (E) IMR, IMC, RMA, and LMA; angular and linear measurements used to measure the dental effect on the premolars: (F) IPR, IPC, RPA, and LPA.

Table II
Skeletal and dental measures
Measurements Abbreviation Description
Skeletal measurements
Axial slice passing through the infraorbital foramina MIF Distance between the infraorbital foramina
Axial slice passing through the palatine processing center PP Distance between the greater palatine foramina
AP Distance between the lateral walls of the incisive foramen
Coronal slice passing through the maxillary right first molar root apex MMW Distance between the lateral maxilla walls at the plane that passes on the nasal floor
MNW Maximum width of the nasal cavity
MAW Greater distance between the maxillary buccal alveolar processes
Coronal slice passing through the maxillary right first premolar root apex PMW Distance between the lateral maxilla walls at the plane that passes on the nasal floor
PNW Maximum width of the nasal cavity
PAW Greater distance between the maxillary buccal alveolar processes
Dental measurements
Coronal slice (multiplanar reconstruction to locate each reference point used in dental measurements) IMR Distance between the apex of the palatal roots of the molars
IMC Distance between the buccal middle molar cusps
RMA Angle between the cusp-apex line of the right molar and the horizontal plane
LMA Angle between the cusp-apex line of the left molar and the horizontal plane
IPR Distance between the apex of the palatal roots of the premolars
IPC Distance between the buccal middle premolar cusps
RPA Angle between the cusp-apex line of the right premolar and the horizontal plane
LPA Angle between the cusp-apex line of the left premolar and the horizontal plane

Statistical analysis

To determine the intraexaminer error, 40% of the CBCT scans were reanalyzed randomly by the same examiner within a 2-week interval. The reproducibility of the method was evaluated using the intraclass correlation test and a paired t test for the linear and angular measurements. The intraclass correlation of the linear and angular measurements was greater than 0.92. The paired t test showed that the mean variation in the angular measurements was 0.20 and for the linear measurements was a maximum of 0.14 mm, indicating excellent intraexaminer reliability.

Shapiro-Wilk and Levene tests verified the normality of the data distribution and homogeneity of variances, respectively. The data are shown as the mean and standard deviation of the variables with a normal distribution.

RPE using MARPE and SARPE were compared before and after treatment using a Student t test for dependent samples. The Student t test for independent samples was used to evaluate differences between the MARPE and SARPE groups.

Statistical analysis was performed using SPSS for Windows (version 16.0; SPSS, Chicago, Ill) with a significance level of 5% (α = 0.05).

Results

A significant difference in all skeletal measurements was found after maxillary expansion with MARPE ( P <0.05). The SARPE results showed a significant change after expansion in the majority of the skeletal measurements ( P <0.05), with the exception of the midfacial width and posterior maxillary base ( Table III ). MARPE showed significantly greater expansion in the midfacial area, nasal cavity, anterior and posterior palate, and posterior maxillary base than SARPE. No statistically significant difference was found for expansion between MARPE and SARPE at the level of the alveolar process and anterior maxillary base ( Table III ).

Table III
Comparison of the skeletal and dental changes between the MARPE and the SARPE groups after maxillary expansion
Area of interest Measurement MARPE (n = 17) SARPE (n = 15) MARPE − SARPE Comparisons
Mean SD P Mean SD P Mean SEM P ( t test)
Skeletal
Midfacial area (mm) MIF 2.90 1.20 <0.001∗ 0.21 0.37 0.051∗∗ 2.70 0.31 <0.001∗ MARPE > SARPE
Posterior palate (mm) PP 2.75 0.85 <0.001∗ 0.89 0.63 <0.001∗ 1.86 0.27 <0.001∗ MARPE > SARPE
Anterior palate (mm) AP 3.69 1.42 <0.001∗ 2.53 1.48 <0.001∗ 1.16 0.51 0.031∗ MARPE > SARPE
Posterior maxillary base (mm) MMW 2.27 1.10 <0.001∗ 0.11 0.63 0.513∗∗ 2.16 0.31 <0.001∗ MARPE > SARPE
Posterior nasal cavity (mm) MNW 2.92 1.13 <0.001∗ 1.10 0.80 <0.001∗ 1.82 0.35 <0.001∗ MARPE > SARPE
Posterior alveolar process (mm) MAW 3.86 1.20 <0.001∗ 4.05 1.46 <0.001∗ −0.19 0.47 0.694∗∗ MARPE = SARPE
Anterior maxillary base (mm) PMW 3.26 2.58 <0.001∗ 2.74 1.80 <0.001∗ 0.52 0.80 0.518∗∗ MARPE = SARPE
Anterior nasal cavity (mm) PNW 2.89 2.04 <0.001∗ 0.95 1.56 0.033∗ 1.94 0.65 0.005∗ MARPE > SARPE
Anterior alveolar process (mm) PAW 4.30 1.87 <0.001∗ 5.05 1.96 <0.001∗ −0.75 0.68 0.277∗∗ MARPE = SARPE
Dental
U6 root distance (mm) IMR 3.81 1.55 <0.001∗ 3.31 1.21 <0.001∗ 0.49 0.50 0.326∗∗ MARPE = SARPE
U6 cusp distance (mm) IMC 5.25 2.34 <0.001∗ 7.91 2.00 <0.001∗ −2.66 0.78 0.002∗ MARPE < SARPE
U6 right angulation (°) RMA 2.87 1.94 <0.001∗ 7.78 4.05 <0.001∗ −4.91 1.15 <0.001∗ MARPE < SARPE
U6 left angulation (°) LMA 3.39 2.41 <0.001∗ 6.82 3.76 <0.001∗ −3.43 1.10 0.004∗ MARPE < SARPE
U4 root distance (mm) IPR 4.03 1.76 <0.001∗ 4.34 1.99 <0.001∗ −0.30 0.66 0.649∗∗ MARPE = SARPE
U4 cusp distance (mm) IPC 5.21 2.25 <0.001∗ 7.19 2.47 <0.001∗ −1.98 0.84 0.025∗ MARPE < SARPE
U4 right angulation (°) RPA 1.40 1.74 0.004∗ 4.71 3.98 <0.001∗ −3.31 1.11 0.008∗ MARPE < SARPE
U4 left angulation (°) LPA 1.88 2.33 0.004∗ 4.60 3.61 <0.001∗ −2.72 1.06 0.016∗ MARPE < SARPE
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Jun 12, 2021 | Posted by in Orthodontics | Comments Off on Microimplant assisted rapid palatal expansion vs surgically assisted rapid palatal expansion for maxillary transverse discrepancy treatment
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