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Article

Skeletal, Dental, and Nasal Changes After Slow Maxillary Expansion Using Quad-Helix

1
Department of Dentistry, Faculty of Dentistry, Alsmarya University, Zliten 02101, Libya
2
Division of Orthodontics, Mike Petryk School of Dentistry, University of Alberta, Edmonton, AB T6G 2R3, Canada
3
Department of Oral Medicine and Diagnostic Sciences, College of Dentistry, King Saud University, Riyadh 12372, Saudi Arabia
*
Author to whom correspondence should be addressed.
Appl. Sci. 2025, 15(20), 11042; https://doi.org/10.3390/app152011042
Submission received: 29 August 2025 / Revised: 1 October 2025 / Accepted: 10 October 2025 / Published: 15 October 2025
(This article belongs to the Special Issue Application of Advanced Therapies in Oral Health)

Abstract

The objective of this study was to assess the transverse maxillary skeletal, dental, and nasal effects of quad-helix treatment (slow maxillary expansion) in comparison to an untreated group. This study was performed on 24 patients. Before and after treatment, CBCT images for children who were treated with Wilson quad-helix were retrieved. The treatment group included 12 children with a mean age of 11.4 ± 1.2 years. The untreated control group had 12 matching patients aged 11.7 ± 0.7 years. AVIZO software (version 9.1) was utilized to place specific 3D anatomical landmarks. The segmentation of the nasal airway was performed using Mimics. The maxillary inter-molar width and inter-premolar widths increased significantly in the treatment group but not in the comparison group. These increases were statistically greater between groups. This study showed statistically significant increases in maxillary inter-molar and inter-premolar widths in patients who were treated with Wilson quad-helix to expand their upper arch. Buccal translation in the upper molars resulted after treatment. Quad-helix treatment caused more dental than skeletal effects. The nasal volume and surface area in the quad-helix group significantly increased.

1. Introduction

A narrow upper jaw is a common problem in orthodontic practice. A large percentage of children with transverse maxillary deficiency suffer from teeth crowding and posterior crossbite [1,2,3,4]. Crossbite cannot be self-corrected and early treatment is desirable to achieve stable and normal occlusion, balanced condyle growth, and overall growth in the lower jaw [4,5,6,7,8,9]. Untreated unilateral posterior crossbite can lead to lasting consequences for the growth of jaws and teeth [10,11]. Constriction in the maxilla locks the mandible which leads to the functional retrusion or retrognathism of the lower jaw [12].
One approach to correct transverse maxillary deficiency is slow maxillary expansion (SME). SME uses light force and creates less tissue resistance throughout circum-maxillary structures. As a result, it enhances bone formation in intermaxillary structures which is considered more physiological and shows less relapse [13,14,15,16]. Quad-helix treatment is one of the most popular SME appliances that is applied to treat a narrow upper arch as well as posterior crossbite [14]. Quad-helix treatment has advantages such as a low cost, less pain, less relapse, and needing less patient compliance [14]. In addition, it has been shown that quad-helix treatment has more control over lower facial height and skeletal vertical measurements [17].
Wilson quad-helix is a type of quad-helix expansion application (first introduced in 1983 by Wilson) that has an inserting/removing system which makes the insertion and removal of the quad-helix considerably easier to adjust than the soldered one [15]. Skeletal versus dental changes after SME using a quad-helix are still controversial. One study [18] reported that the skeletal expansion resulting from quad-helix treatment was relatively less than dental expansion; however, another study [19] found equal skeletal and dental effects after quad-helix treatment.
Most studies that have tried to address this topic were performed on dental casts or used two-dimensional (2D) radiographs. Dental models are susceptible to distortion resulting from impression material or procedures, and can be connected to measurement errors, while 2D imaging is subject to projection and landmark identification errors [7,20]. Cone Beam Computed Tomography (CBCT), on the other hand, provides 3D sectional images with no magnification or structural superimposition compared with traditional 2D radiographers. CBCT provides wider options of landmark identification in three dimensions, for example, dental pulp cavity, which may not be possible with 2D imaging and has made the assessment of nasomaxillary regions and nasal airway segmentation feasible [21].
One study utilized CBCT to assess dentoalveolar changes after quad-helix treatment; however, that study did not have a comparison group [22]. Although the effects of rapid maxillary expansion (RME) on the nasal cavity have been reported in previous studies [23,24], none have investigated the effects of SME using quad-helix treatment on nasal airways. A published study investigated the effects of SME using a nickel titanium leaf spring reported a significant increase in the nasal airway after using SME [25]. A recent study reported a significant increase in nasal cavity width at the premolar area (2.95 mm) and molar area (2.62 mm) after SME [26]. Another recently published study also reported an increase in the volume of the nasal airway which resulted from clear aligner treatment to expand the maxilla in patients with a narrow dental arch [27].
The primary objective of this study was to assess transverse skeletal and dental changes using CBCT associated with Wilson’s quad-helix expansion treatment compared to a matched comparison sample. The secondary objective was to evaluate the nasal airway change associated with quad-helix expansion treatment compared to a matched comparison sample.

2. Materials and Methods

2.1. Study Design

This study obtained ethical approval from the University of Alberta, Health Ethics Review Board (committee ethics approval number (Pro00047506)). Before and after the treatment, CBCT sets were retrieved from Orthodontic Graduate Clinic database at the University of Alberta.

2.2. Participants

Inclusion Criteria:
  • Male and female children between the ages of 10 and 13 years old (late mixed dentition, no race restriction) who had been diagnosed with a narrow maxilla and/or crossbite.
  • Patients with dental Class I and II were included.
  • Patients with skeletal Class I (ANB 1–3) and skeletal Class II (ANB > 3) were included.
  • Children who had Wilson quad-helix phase I expansion treatment without phase II to exclude possible confounding factors that phase II might introduce that would have affected the treatment outcome due to variabilities in patients’ cases/compliances.
  • Patients who had CBCTs before the installation of the quad-helix and following the removal of the quad-helix.
  • Undergoing the circumpubertal skeletal development stage. Patient selection was based on the cervical vertebrae maturation index (CVMI). CVMI is a tool to estimate a patient’s skeletal age, which is more accurate than chronological age or dental age. CVMI stages 2, 3, and 4, which indicate the circumpubertal development interval, were determined and selected [28].
  • Patients with no craniofacial abnormalities or previous orthodontic treatment, and no allergies or inflammation in the nasal airway during CBCT image collection.
Exclusion criteria:
Patients that did not meet the above inclusion criteria.

2.3. Intervention

Patients were treated with the Wilson quad-helix for an active period of half a year, and the appliance then was left in the mouth in a passive state for retention for one year on average. The Wilson quad-helix (RMO, Denver, CO, USA) fabricated of a 0.038 Blue Elgiloy wire was connected to the bands on the upper first molars through vertical spurs that can be inserted into vertical palatal tubes.
The appliance had been activated by 2 mm every 8 weeks until the required expansion was reached (i.e., when the palatal cusps of the upper first molars contacted the buccal cusps of the lower first molars). The appliance was then maintained in a passive state for approximately 12 months. T1 CBCTs were taken directly before the insertion of the Wilson quad-helix appliance. T2 CBCTs were taken following the removal of the appliance and before entering phase II of the treatment (full fixed bonding). The time between T1 and T2 CBCT images was around 1.6 years on average. To guarantee more precision and consistency when taking patients’ CBCTs, patients were given instructions to keep a certain head position, maintain natural breathing, and avoid swallowing or movements. CBCTs were taken by classic I-CAT (Imaging Sciences International, Hatfield, PA) with an 8.9 s scan time and a 16 × 13 cm field of view. Images were transferred into a DICOM file (0.3 mm voxel size).
To account for changes due to growth, a control group without treatment was needed. CBCT sets of age-matched patients who had their baseline CBCT for assessment and treatment purposes (the CBCT were taken because traditional 2D imaging methods did not provide sufficient information) and their treatment postponed 1.5 years for financial or personal reasons were retrieved. Then, new CBCTs were taken to provide a new treatment plan. A consent form was provided to all patients to sign to give permission to use their records in the research.
The matching process between the two groups was based on the age, gender, CVM skeletal maturity stages, and the period between 2 CBCTs. After obtaining a quad-helix sample, the researcher looked at each subject in the sample and searched for control subjects that had the same age, same gender, CVMI stage, and same or approximately same T1 and T2 CBCT interval. The researcher completed this for all quad-helix group subjects.

2.4. Study Sample

The sample size was calculated based on a significance level (α) of 5%, power of 80%, and maxillary inter-molar width difference of 2.5 mm, based on the Zhou et al. study [29]. Sample size calculation showed that a minimum of 11 cases in each group was required. The sample included 24 patients. Both the treatment group and the control group included 12 participants aged 11.4 ± 1.2 years and 11.7. ± 0.7 years, respectively. However, during nasal airway analysis, 11 cases in each group were included because 1 case was lost in each group due to a technical issue when images did not open in Mimics. Table 1 provides a description of the treatment and control samples used in the study at baseline (T1).
The groups were well matched. There was no statistically significant difference between the groups regarding T1 age (p = 0.46), T1 to T2 time interval (p = 0.95), T1 inter-molar width (p = 0.43), or T1 nasal cavity volume (p = 0.13).
To minimize bias, blinding was achieved by recruiting a person who was not involved in the study to code the cases. The operator was blinded about which group the patient belonged to during the placement of the landmarks and the segmentation. Also, data were labeled with numbers during statistical analysis.

2.5. Measurement Method

2.5.1. Dental and Skeletal Distances

Skeletal- and dental-specific anatomical landmarks were chosen to measure transverse dental and skeletal distances based on a previous study [30] (Table 2).
DICOM format files were imported into AVIZO version 9.1 (Visualization Sciences Group, Burlington, MA, USA). The determination of landmark locations was completed by the primary investigator using axial, coronal, and sagittal slices in addition to the 3D reconstruction of the CBCT images in AVIZO (Figure 1).
Next, 3D digit markers (0.5 mm) were placed in the center of each landmark. Each landmark had three coordinates (X, Y, Z). The distance between each landmark and its contra-lateral counterpart was measured using the following formula:
D   =   ( x 1 x 2 ) 2 + ( y 1 y 2 ) 2 + ( z 1 z 2 ) 2
where D is the distance between the landmarks.

2.5.2. Nasal Airway Segmentation

Mimics software [Mimics 19.0, Materialise NV, Leuven, Belgium] was used for the nasal airway manual segmentation and the reconstruction of nasal 3D models. Manual segmentation is the standard approach in the segmentation of the nasal airway and was used in previous studies to test the validity of their newly introduced software [21,31]. Manual segmentation is more valid than automatic because the examiner can adjust the threshold while segmenting each slice.
The region of interest extended from the anterior nasal nares anteriorly to the last coronal slice before the nasal septum transitions into the pharynx posteriorly and from the hard palate inferiorly to the superior nasal meatus superiorly. The segmentation terminated at an imaginary line extending from a point bisecting the line formed between the nasion and the tip of the nasal bone anteriorly and the sphenopalatine foramina posteriorly [21]. The maxillary sinus and the ethmoid cells were not included in the region of interest. One CBCT in each group was excluded because of their inability to be opened in the Mimics software due to a technical issue. The mask tool in Mimics was applied to manually select the gray level threshold for each axial slice in the region of the interest and the manual nasal airway segmentation (Figure 2) was performed as detailed in the study by Alsufyani et al. [21]. After editing the segmentation and creating 3D models of the nasal airway, the models were saved in ASCII STL format to prepare for the smoothing and wrapping stages. To minimize investigator bias, the smoothing process was standardized. A standard smoothing factor (factor 0.7) in Mimics was used. A smoothing factor is an automatic filter used to smoothen the rough edges of the 3D models for better superimposition and comparison without affecting their measurements. The volume and surface area of the 3D models formed of the segmentation of the right and left nasal cavities were calculated and combined.
In addition to using volume and surface area in analyzing and comparing 3D models, a point-based analysis and color mapping were applied. The point-based analysis was performed by the “Part comparison tool”, a tool in 3-matic (version 9.0; Materialise) used to measure the distance (in mm) between one airway model (T1) to the surface of the reference airway model (T2) [21].
To compare the (T1) and (T2) 3D models, T1 and T2 CBCTs for each patient were superimposed (image registration stage) using specific anatomical landmarks (the tip of the clivus, the tip of the nasal bone, the right oval foramen, the left oval foramen, the right spinosum foramen, and the left spinosum foramen), and their reliability was tested in an earlier study [21]. The superimposed models were then saved and exported to 3-matic (version 9.0; Materialise) to start the point-based analysis.
The threshold of the part comparison was set at 5 mm based on what is considered clinically significant based on the Alsufyani study [21]. The part comparison and deviation map show above zero and below zero deviation areas. This implies that the surface of the inspected nasal airway model (T2) model is above or below the T1 model. In the color maps, triangular nodes which traveled distances within threshold boundaries would be seen as green, distances less than −5 mm would appear as blue (minimum part comparison), and distances of more than 5 mm would be seen as red (maximum part comparison) (Figure 3).

2.6. Statistical Analysis

The intra-examiner reliability of landmark identification was assessed for 10 randomly selected cases. Each landmark was measured three times with one week between trials. The mean error for each landmark was assessed and mean differences in intra-examiner reliability greater than 1 mm were considered clinically significant based on the Lagravere study [30].
To assess the intra-examiner reliability of the segmentation, five random cases were selected. The nasal airways were segmented three times for every CBCT image by one investigator in one-week intervals between the three trials. Next, a volume, surface area, and part comparison with color mapping was used to identify the differences between the three trials.
Independent t-tests were conducted to evaluate the differences between the groups at baseline for the age at T1 and the time interval between T1 and T2. The intra-class correlation coefficient (ICC) and the descriptive statistics were applied to test the intra-examiner reliability of the landmarks and nasal airway segmentation. One-way ANOVA was used to assess between-group dental and skeletal linear transverse distance change. A paired t-test was conducted to evaluate differences within groups. Independent t-tests were conducted to differentiate the nasal measurements between the groups.

3. Results

3.1. Dental and Skeletal Outcomes

The intra-examiner reliability was excellent for all landmarks (in all X, Y, and Z planes). The ICC values were more than 0.99. The largest difference value was for the right infraorbital foramen in the Z axis (1.2 mm ± 1.1). Overall, 97% of the landmarks in the reliability test had a mean difference of less than 1 mm which means that this study is reliable.
There was a statistically significant increase in the inter-molar width from T1 to T2 in the Wilson group (p < 0.01) compared with the comparison group (Table 3). The distance between the upper first molars increased by 3.6 mm on average at the pulp chamber and by 3.5 mm on average at the root apex in the Wilson group. The increase in the comparison group was less than 1 mm on average at the pulp chamber and the root apex. The Wilson treatment group had a statistically significant increase in the inter-premolar width at the pulp chamber (3.0 mm on average) from T1 to T2, but not at the root apex (0.6 mm on average). The control group did not demonstrate a statistically significant increase in inter-premolar width at the pulp chamber or root apex (Figure 4). The width change at the alveolar bone at the molar and premolar areas was not statistically significant either within groups or between groups. There was a statistically significant increase in the distance between the left and right palatine foramina (1.5 mm on average) as well as the left and right infraorbital foramina (1.0 mm on average) from T1 to T2 in the Wilson group. There was no statistically significant difference in the distance between the palatine foramina or the infraorbital foramina from T1 to T2 in the comparison group. The change in distance between the infraorbital foramina from T1 to T2 was significantly different between groups.

3.2. Nasal Airway Outcomes

The intra-examiner reliability of the nasal airway segmentation was excellent. The ICC values among the three trials were 0.99 for the nasal volume and 0.97 for the nasal surface area. The mean intra-examiner differences obtained from the three trials for the volume and surface area were 0.04 ± 0.08 cm3 and 0.1 ± 0.1 cm2, respectively. In the median part analysis, the mean difference was 0.03 ± 0.06 mm.
There was a statistically significant difference in the nasal parameters between the Wilson group and the control group (Table 4) (Figure 5). The nasal airway volume and surface area for the quad-helix group significantly increased (2.5 cm3) (13%) and (1.9 cm2) (12%), respectively. However, there was no significant difference in the average mean part analysis.

4. Discussion

4.1. Skeletal and Dental Outcomes

The greatest transverse dental expansion observed in the Wilson quad-helix group was mostly seen in the posterior region of the maxilla at the level of the upper first molars’ pulp chambers and roots.
Corbridge et al. [22] used CBCT in their study and documented an increase in the maxillary inter-molar width of up to 6 mm, while in the present study expansion was 3.5 mm. Corbridge et al. used records of patients that were 2.5 years younger than the cases in the present study. Also, in this study, most cases had late mixed dentition where it was hard to use a fixed appliance on the remaining deciduous teeth. Their study measured linear distances on the CBCT slices while in our study the three Cartesian coordinate landmarks system was used.
The crown expansion from the Wilson quad-helix was approximately the same as the root expansion of the maxillary first molars which could be interpreted as bodily movement of the teeth. This finding is inconsistent with the outcomes of Erdinc et al. [31] who reported buccal tipping after quad-helix treatment. Boysen et al. [18], on the other hand, reported the buccal translation movement of the upper first molars resulting from the quad-helix which was similar to the findings in the present study. The buccal tipping reported in Erdinc et al. [32] study might be due to the rate of appliance activation, which was every month, whereas in the present study the appliance was activated every two months and the vertical slots of Wilson appliance and vertical spurs inserted into them allowed for a buccal root torque effect/expression on the upper first molars.
A recent study reported a significant increase in inter-molar width (5 mm) after using a quad-helix in growing children with a transverse maxillary discrepancy [33]. The results of that study are larger than our study results; however, this study used study models and occlusal radiographs rather than using CBCT. In addition, Nair’s study measured the inter-molar width from the tips of the right and left first molar, while in the present study inter-molar width was measured from the center of the pulp champers on the CBCTs. In Nair’s study the distance between the maxillary molars at the level of the roots was not measured because of the limitation of dental models and occlusal radigraphs in comparison with CBCT imaging. Therefore, the type of maxillary molar movement is not confirmed to be buccal translocation or buccal tipping.
The present study (SME) did not identify significant alveolar bone changes. Based on this finding, since the alveolus did not expand, the bone could be thinner and may in fact have dehiscence or root apex perforation. However, we did not investigate the buccal bone thickness to confirm this and the SD for these measurements was large. It is recommended in future study to measure the buccal bone thickness.
Our study showed a statistically significant increase in the distance between the right and left greater palatine foramina (1.48 mm) and infraorbital foramina (1.01 mm) within the Wilson group. Based on Manuel’s study a change greater than 1 mm would be considered clinically relevant [33]. The change in the infra-orbital foramen distance (1 mm) is similar to the intra-examiner error (1 mm). Although statistically significant, the reader is cautioned that the change is similar to the intra-examiner error in landmarking the infra-orbital foramen.
The skeletal expansion at the greater palatine foramen area was smaller than the dental expansion between the upper first molars (ratio about 1:3). However, the skeletal expansion at the greater palatine foramen area was not statistically significant between groups.
The inter-molar changes at the pulp chamber and root apex levels were statistically significant and clinically significant. In addition, the increase in the inter-premolar width at the pulp chamber was statistically significant and clinically significant based on the Lagravere study [30]. The increases between skeletal landmarks (the left and right palatine foramina and the left and right infraorbital foramina) were statistically significant and clinically significant (1.48 mm and 1.01 mm, respectively).

4.2. Nasal Airway Outcomes

The nasal airway can be affected by many factors that can change the nasal airway volume such as allergies and inflammation. This was demonstrated in our study where the standard deviation was large. Two cases in each group had negative nasal cavity volume differences which in fact mean that the nasal airway volume decreased.
However, volume and surface area are non-specific parameters and do not show the location and distribution of the change. As such, a part comparison analysis was used in this study, similar to a previous study that tested the reliability of the semi-automatic segmentation of upper airways [21]. Cevidanes et al. used a similar analysis method to evaluate 3D surface growth in the craniofacial area [34,35].
The color mapping showed more red areas (differences of 5 mm or more marked by red) in the Wilson group than in the control group. The purpose of using the color mapping feature of part analysis was to show and determine the areas that have changes more than 5 mm. The increase in the treatment group in nasal airway volume was 13% and 12% in nasal surface area. The change in the control group nasal airway volume and surface area was only 2%.
This study showed a significant increase in the nasal cavity volume for patients treated for maxillary expansion with the quad-helix. This new finding revealed that the slow expansion of the maxilla using a quad-helix might present an effective impact on the nasal cavity similar to other expansion appliances such as the nickel titanium leaf spring (SME) and Hyrax used in previous studies [10,22]. Despite the statistical significance in the nasal variables, clinical significance depends on the nasal resistance and improving nasal airway function. Increases in nasal volume and surface area decrease the nasal resistance and in turn may improve breathing function. However, more investigation is needed to see how much nasal resistance would decrease with these increased percentages to estimate clinical significance.

Limitations

Caution should be used in the interpretation of the results, in view of the small sample size and high variability (standard deviation) in the measured changes. In addition, some confounding factors that might affect changes were difficult to control, for example, changes for natural growth and not standardizing the time of day or season of the year. In addition, the treatment protocol was standardized for all cases; however, the treatment was not performed by a single operator. Even though the intra-examiner reliability test was excellent, the inter-examiner reliability was not assessed in this study due to the lack of trained investigators on nasal segmentation. Future studies with a much larger number of patients and with a second treatment group (RPE patients) would be recommended to overcome the limitations of this study as well as a prospective randomized clinical trial to confirm this study’s results.

5. Conclusions

Despite the limitations in this research, the following conclusions can be drawn:
  • The Wilson quad-helix caused a significant increase in maxillary inter-molar and inter-premolar widths with the buccal bodily movement of the upper molars and the buccal crown tipping of the upper premolars.
  • There was no significant transverse alveolar maxillary expansion with Wilson quad-helix treatment.
  • There was a significant difference in nasal airway dimensions between the quad-helix group and their controls.

Author Contributions

Conceptualization, R.N. and T.E.-B.; methodology, R.N., M.L., N.A. and T.E.-B.; software, R.N., M.L. and N.A.; validation, R.N., M.L., N.A., P.W.M., H.L. and T.E.-B.; formal analysis, R.N.; investigation, R.N., M.L. and T.E.-B.; resources, R.N., M.L. and T.E.-B.; data curation, R.N.; writing—original draft preparation, R.N.; writing—review and editing, R.N., T.E.-B., M.L., P.W.M. and N.A.; visualization, R.N. and T.E.-B.; supervision, T.E.-B.; project administration, R.N. and T.E.-B.; funding acquisition, T.E.-B. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was approved by the University of Alberta Health Ethics Review Board (protocol number: Pro 00047506, approved date is 9 April 2014).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. The arrows show 3D digit markers (0.5 mm with gold color) were placed in the center of the pulp chamber of the maxillary first molar in the 3D reconstruction, axial, coronal, and sagittal views of the CBCT images. Upper first molar pulp chamber was used as the landmark.
Figure 1. The arrows show 3D digit markers (0.5 mm with gold color) were placed in the center of the pulp chamber of the maxillary first molar in the 3D reconstruction, axial, coronal, and sagittal views of the CBCT images. Upper first molar pulp chamber was used as the landmark.
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Figure 2. (a) Importing CBCTs into Mimics. (b) Nasal airway segmentation limits and creating nasal airway models.
Figure 2. (a) Importing CBCTs into Mimics. (b) Nasal airway segmentation limits and creating nasal airway models.
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Figure 3. Color maps of participant 5 (treatment group) and control 5 (control group) with a lateral view and the color map scale in millimeters.
Figure 3. Color maps of participant 5 (treatment group) and control 5 (control group) with a lateral view and the color map scale in millimeters.
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Figure 4. The mean difference of the intermolar distance (upper image) and the mean difference of the inter premolar distance (lower image). * Indicates the difference is statistically significant.
Figure 4. The mean difference of the intermolar distance (upper image) and the mean difference of the inter premolar distance (lower image). * Indicates the difference is statistically significant.
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Figure 5. The mean difference of the nasal volume between the groups.
Figure 5. The mean difference of the nasal volume between the groups.
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Table 1. Group information at baseline.
Table 1. Group information at baseline.
GroupT1, T2 CBCT
Interval Mean ± SD
T1 Inter-Molar Width (mm)
Mean ± SD
T1 Nasal Cavity
Volume (cm3)
Mean ± SD
Wilson
12 participants
(9 males, 3 females)
11.4 ± 1.21.6 ± 0.447.7± 2.4
Control
12 participants
(8 males, 4 females)
11.5 ± 0.61.6 ± 0.448.7 ± 1.6
Table 2. Measured dental and skeletal distances and their definitions.
Table 2. Measured dental and skeletal distances and their definitions.
Distance MeasuredDefinition
Dental
Inter-molars (pulp chamber)The distance measured between the pulp chambers of the right and left upper first molars
Inter-molars (root apex)The distance measured between the mesiobuccal root apices of the right and left upper first molars
Inter-premolars (pulp chamber)The distance measured between the pulp chambers of the right and left upper first premolars
Inter-premolars (root apex)The distance measured between the buccal root apices of the right and left upper first premolars
Alveolar
Inter-molars (alveolar bone)The distance measured between the buccal cortices of the alveolar bone of the upper right and left first molars at the level of the mesiobuccal root apices
Inter-premolars (alveolar bone)The distance measured between the buccal cortices of the alveolar bone of the upper right and left first premolars at the vertical level of the buccal root apices
Skeletal
Inter-infraorbitalThe distance measured between the right and left infraorbital foramina
Inter-greater palatineThe distance measured between the right and left greater-palatine foramina
Table 3. The mean expansion in the transverse dimension for the Wilson group and the comparison group (dental and skeletal distances) *.
Table 3. The mean expansion in the transverse dimension for the Wilson group and the comparison group (dental and skeletal distances) *.
Distance Measured
Dental
Wilson Group Control Group p Value
(Between Groups)
Mean ± SDpMean ± SDp
Inter-molars
(pulp chamber)
3.61 ± 2.41<0.010.7 ± 1.80.2510.006
Inter-molars
(root apex)
3.51 ± 2.29<0.010.86 ± 2.40.2430.012
Inter-premolar
(pulp chamber)
3.01 ± 2.210.001−0.1 ± 2.50.9070.010
Inter-premolars
(root apex)
0.64 ± 3.190.5850.5 ± 1.50.2720.270
Alveolar
Inter-molars
(alveolar bone)
0.75 ± 2.640.346−0.5 ± 2.500.6610.367
Inter-premolars
(alveolar bone)
0.41 ± 2.170.9670.6 ± 1.70.2920.785
Skeletal
Inter-infraorbital1.01 ± 1.010.004−1.14 ± 1.160.0850.008
Inter-greater palatine1.48 ± 1.940.0230.89 ± 0.90.0640.554
* p value > 0.05 (nonsignificant). Bolded p values are significant.
Table 4. The mean differences in the nasal airway volume, nasal airway surface area, and part analysis of the Wilson group and the comparison group *.
Table 4. The mean differences in the nasal airway volume, nasal airway surface area, and part analysis of the Wilson group and the comparison group *.
Parameter MeasuredWilson GroupControl Groupp Value
Mean ± SDMin.Max.Mean ± SDMin.Max.
Average Volume Difference (cm3)
%
2.4 ± 4.1
13 ± 22
−5.88.7−0.4 ± 1.4
2 ± 7
−6.51.30.02
Average Surface Area Difference (cm2)
%
1.9 ± 1.8
12 ± 12
−2.140.3 ± 1.8
2 ± 12
−2.63.50.04
Average Mean Part Analysis (mm)0.8 ± 0.40.31.30.7 ± 0.30.041.30.46
* p value > 0.05 (nonsignificant). Bolded p values are significant.
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MDPI and ACS Style

Njie, R.; Major, P.W.; Lagravere, M.; Alsufyani, N.; Lai, H.; El-Bialy, T. Skeletal, Dental, and Nasal Changes After Slow Maxillary Expansion Using Quad-Helix. Appl. Sci. 2025, 15, 11042. https://doi.org/10.3390/app152011042

AMA Style

Njie R, Major PW, Lagravere M, Alsufyani N, Lai H, El-Bialy T. Skeletal, Dental, and Nasal Changes After Slow Maxillary Expansion Using Quad-Helix. Applied Sciences. 2025; 15(20):11042. https://doi.org/10.3390/app152011042

Chicago/Turabian Style

Njie, Rabia, Paul W. Major, Manuel Lagravere, Noura Alsufyani, Hollis Lai, and Tarek El-Bialy. 2025. "Skeletal, Dental, and Nasal Changes After Slow Maxillary Expansion Using Quad-Helix" Applied Sciences 15, no. 20: 11042. https://doi.org/10.3390/app152011042

APA Style

Njie, R., Major, P. W., Lagravere, M., Alsufyani, N., Lai, H., & El-Bialy, T. (2025). Skeletal, Dental, and Nasal Changes After Slow Maxillary Expansion Using Quad-Helix. Applied Sciences, 15(20), 11042. https://doi.org/10.3390/app152011042

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