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Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study Mohammed Almuzian a,b,*, Xiangyang Ju b, Anas Almukhtar c, Ashraf Ayoub d, Lubna Al-Muzian e, Jim P McDonald c a
Orthodontic Department, Sydney Dental Hospital, University of Sydney, Sydney, NSW, Australia Medical Devices Unit, NHS Greater Glasgow and Clyde, Glasgow, UK c Orthodontic Department, Glasgow Dental Hospital and School, MVLS College, University of Glasgow, Glasgow, UK d Oral & Maxillofacial Surgery, Glasgow Dental Hospital & School, MVLS College, University of Glasgow, Glasgow, UK e Deportment of Dental Public Health, School of Dentistry, Faculty of Medical and Human Science, University of Manchester, Manchester, UK b
article info
abstract
Article history:
Background and purpose: There is limited literature discussing the three dimnesional (3D)
Received 10 February 2015
impact of rapid maxillary expansion (RME) on upper airway. The purpose of this pro-
Received in revised form
spective Cone Beam Computerised Tomography (CBCT) based study is to assess the
19 November 2015
immediate 3D effects and to correlate the volumteric changes in the upper naspharyngeal
Accepted 22 December 2015
airway spaces secondary to RME.
Available online xxx
Materials and methods: Seventeen participants (8 male, 9 female, with a mean age of 12.6 ± 1.8 years), who required RME for the management of narrow maxillary arch, were
Keywords:
recruited for this study. The prescribed expansion regimen was quarter turn (0.25 mm),
CBCT
twice a day until over-expansion was achieved. The mean period for the active phase was
ITK snap software
14 days with a range of 12e21 days. Pretreatment (T1) and immediate post-expansion (T2)
OnDemand3D software
CBCT images were obtained and then processed using ITK snap and OnDemand3D softwar
Rapid maxillary expansion
packages. Paired t-test and Interclass Correlation Coefficient (ICC) were used to assess the
Airway space
reproducibility of the measurements, student t-test (P < 0.05) and Pearson Correlation Coefficient (PCC) were applied to evaluate the volumetric changes in the nasopharyngeal airway spaces, linear dentolaveolar changes and correlate these changes. Main findings: Though, the data of one patient was excluded from the study, owing to major differences (>5 degrees) in the head and neck posture between T1 and T2 CBCT scans, the study' findings shows that bonded RME is an effective dentoalveolar expander in growing patients (P¼ 0.01) with an average expansion of 3.7 mm and 2.8 mm in males and females respectively. Likewise, the upper nasopharynx (UNP) expanded significantly (15.2% in males and 12% in females). In comparison, the upper retropalatal space (URP) was significantly reduced, by almost one sixth of its original volume, more in males than females, 11.2% and 2.8% respectively. A strong direct correlation between the maxillary sinus volumetric changes, and between appliance expansion and dentoalveolar expansion were
* Corresponding author. Deportment of Orthodontics, University of Sydney, Sydney, NSW, 2006, Australia. Tel.: þ61 293518329x8314. E-mail address: [email protected] (M. Almuzian). http://dx.doi.org/10.1016/j.surge.2015.12.006 1479-666X/© 2015 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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evident (PCC ¼ 0.86, 0.75, respectively). There was also a moderate correlation between changes in the UNP and URP spaces. Conclusions: RME was found to be an effective dentoalveolar expander and significantly augment the UNP and minimize the URP space. A similar comparative clinical study with long-term follow-up would be beneficial in accurately deteremining the clinical impact of RME on the airway and breathing as well as the stability of these effects. © 2015 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.
Introduction Rapid maxillary (palatal) expanders (RME) act by applying heavy intermittent force, up to 10 kg, to split the midpalatal suture.1 The potential effects of RME are orthopaedic, dental, soft tissue, airway and miscelleneous such as effect on hearing, facial growth and nocturia.2e5 Changes in the nasal and pharyngeal airway spaces secondary to RME have been investigated extensively using two dimensional (2D) cephalometric radiographs 2,3; Rhinomanometry2,6 (R) and Acoustic Rhinomanometry (AR).7,8 However, due to the complex three dimensional (3D) anatomical architecture of the upper airway spaces, the effects of RME is difficult to be accurately assessed using 2D imaging modalities. This is mainly due the superimposition of bilateral structures and the presence of numerous bony structures, which are generally difficult to identify. Furthermore, 2D imaging modalities lack information regarding volumetric changes, and R and AR have their own restrictions like dearth of visual signs of changes and require a specialised operator and apparatus. All of these drawbacks encouraged the adoption of 3D technique such as Cone Beam Computerised Tomography (CBCT) for more accurate volumteric measurmeent and visualisation of airway spaces.9e11 However, most studies have produced results using slice data obtained after 3D CBCT scanning and there has been no consideration for the effect of tongue head and neck position on airway measurement.12,13 The aims of the study was to assess the 3D effect of RME on the volumes of the maxillary sinuses, the lower part of the nasal cavity, the upper oropharyngeal region, taking in consideration the limitations of previous trials. The study also aimed to correlate the volumetric changes with the magnitude of dentoalveolar expansion.
Caucasian patients, between 10 and 16 years of age with normal body mass index (BMI), who had constricted maxillary arch with unilateral or bilateral posterior crossbite No previous tonsillar, nasal, adenoid, head or neck surgery, and no craniofacial deformity No previous orthodontic treatment No major variation in the head and craniocervical orientation (>5 degrees) between the pre-treatment (T1) and post-expansion or post-treatment (T2) CBCT scans. A cast-cap appliance with a Hyrax screw (Forestadent, Germany), as an active component, was used for maxillary expansion. The capping component was constructed from a silver-copper alloy (SP70, Skillbond, UK) and had fully covered the buccal teeth, from first molar to the canines, and contained occlusal holes to aid removal (Fig. 1). The appliances were activated immediately after capturing the T1 scans, and the patients were monitored on a regular basis during the active expansion phase. The prescribed expansion regime was a quarter turn (approximately 0.25 mm), twice a day until over-expansion (OE) achieved. OE means the palatal cusps of upper molars, represented by the occluso-palatal angle of the metal capping of the RME, occluded with the buccal cusp tips of lower molars. At this point, T2 scans were taken. Both CBCT scans (T1 and T2) were taken by a trained radiographer using an iCAT scanner (Imaging Sciences
Participants and materials The sample size was computed using the Researcher's Toolkit calculator which indicated that a data from 14 participants would yield a confidence level of 95% and a Beta error level of 20%. Accordingly, 17 subjects were recruited to overcome the potential exclusion and an ethical approval was granted by (NHS/Greater Glasgow/09-S0709/40 and Victoria Hospital/Fife/09-062). The study had the following inclusion criteria:
Figure 1 e The cast cap splint RME.
Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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International, Hatfield, Pa, USA), the subjects were positioned with Frankfort plane parallel to the floor.14 The head was stabilised by a headband to prevent movement during the 20-s scan. The data files for the CBCT images have been saved and stored as DICOM format (Digital Imaging and Communication in Medicine) and analysed using two different types of software, namely OnDemand3D (Cybermed, Seoul, Republic of Korea) and ITK-SNAP version 2.2.0 (www.itksnap.org). ITK stands for Insight Tool Kit which is an open-access popular library image analysis algorithm funded by the US National Library of Medicine under the Visible Human Project.15 The points, planes and angles used in this study are described in Tables 1e3. Initially, OnDemand3D software package was used to measure IMD and AE (Fig. 2) and, based on the reported validity of 3D cephalometric assessments,16,17 head posture (P, R and Y angle) and cranio-cervical inclination (L angle) were measured. The angular measurements were recorded to the nearest degree (Figs. 3e6). Subjects were excluded if the change in head posture and/or lordosis between T1 and T2 scans was greater than 5 , as these changes have been proven to have a significant impact on nasopharyngeal airway measurements.18e20 Each of the T1 images were digitally oriented, thus Ptg LF and Z plane were all parallel to TH Plane. Then, the orientated images were saved and stored as New T1 (NT1) scans (Fig. 7). Next, T2 images were digitally orientated and superimposed on their corresponding NT1 scans (auto-registration) using the anterior and posterior
cranial bases as stable structures, and subsequently saved as New T2 (NT2) scan (Fig. 8). These strategies in orientation permitted standardised segmentation and eliminated effect of positional error's during segmentation. Using NT1 and NT2 scans; the airway boundaries were defined, segmented and measured in terms of volume using the ITK-SNAP software package (Table 4 and Figs. 9e10). The manufacturer's instructions for the use of ITK software package were followed.15 In an effort to minimise inclusion of the para-nasal sinuses and their related hiatus, the measurement of the volume of the lower nasal cavity was limited to the respiratory part of the nasal cavity. Cv2sp/H plane subdivides the retropalatal space into two distinct spaces, the upper (URP) and lower (LRP) retropalatal spaces taking in consideration that if the Cv2od was located superior to Spip/TH plane, then the whole segment would be considered as LRP space.10,11,21 All linear, angular and volumetric measurements were carried out by one examiner (MA) and repeated after one week, the two sets of measurements were compared to validate the reproducibility of the measurement technique. 3D virtual replicas of the airway spaces were generated using automatic and manual segmentation, which allowed for detailed localisation of changes (Fig. 11). Moreover, the segmentation permited exclusion of any potentially masking changes that adjacent or remote airway spaces might produce. This was a crucial step because each airway segment is associated anatomically and physiologically to a different function and/or disorder. The volume of these
Table 1 e Points and landmarks. Point ANS
Cv2sp Cg Cv2ig Cv2ip Cv2od LOr Lpo LtLtPtg Lzyg Molar Alveolar Crest (MAC) Nasion (N) PNS ROr RtLtPtg Rzyg Sella (S) Spip
Definition The tip of the bony anterior nasal spine at the inferior margin of the piriform aperture, in the midsagittal plane and often is used to define the anterior end of the palatal plane. It is the most superioreposterior extremity of the odontoid process of the second cervical vertebrae (Cv2) The most superior point of Crista galli bony structure The most superior-posterior extremity of the odontoid process of Cv2 The most inferio-posterior point on the body of Cv2 The most superior point of the odontoid process of Cv2 The lowest point of the left inferior orbital floor The most superior point of the outline of the left external auditory meatus (anatomic porion) The most posterior point of the left lateral pterygoid plate as viewed from the axial section The most lateral point of the left fronto-zygomatic suture as viewed from the coronal section The intersecting point of the buccal alveolar crest and the buccal surface of the maxillary first molar The most posterior point on the curvature of the nasal bridge at the junction of the nasal and frontal bones The most posterior point of the bony hard palate The lowest point of the right inferior orbital floor The most posterior point of the right lateral pterygoid plate as viewed from the axial section The most lateral point of the right fronto-zygomatic suture as viewed from the coronal section The center of the hypophyseal fossa (sella tursica) The most inferior-posterior point of the soft palate shadow as viewed from the axial section
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Table 2 e Lines and planes. Line and plane Appliance Expansion (AE) ANSV plane
Cv2sp/V plane CgeCv2od plane Cv2sp/H plane Left Frankfort (LF) Plane LOrH plane Intermolar Alveolar Crest width (IMD) Orbital (O) plane PAL PNSH plane PNSV plane Pterygoid (Ptg) Plane SN plane Spip/TH Plane SPPTV plane True horizontal (TH) plane True vertical line (TV) plane Zygomatic (Z) Plane
Definition The maximum separation of the right and left acrylic plate measured on coronal section (Fig. 2) A true vertical plane (TV) plane passing through point ANS, as shown from the sagittal view. If the mid-palatine split extends to involve the ANS, then the most anterior ANS is considered. TV plane passing through Cv2sp. A plane connecting Cg and Cv2od points TH plane passing through Cv2sp A plane connecting left Or and left Po points TH plane tangent to LOr point The distance between right and left MAC points measured on coronal section (Fig. 2) A plane connecting right and left Or points A plane connecting through the Cv2ig and Cv2ip points TH plane passing through PNS and extended to the posterior wall of the pharynx TV plane passing through PNS. If the mid-palatine split extends to involve the PNS, then the most posterior end of the palate is considered A plane connecting LtLtPtg and RtLtPtg points A plane connecting S and N points A plane parallel to the TH plane passing through the Spip A sagittal plane parallel to TV passing through the most lateral point of the maxillary sinus A reference plane constructed horizontal to the floor at any point A reference plane constructed perpendicular to the floor at any point A plane connecting Lzyg and Rzyg points
Table 3 e Cephalometric angles. Angle Pitch angle (P angle)
Roll angle (R Angle) Yaw angle (Y Angle)
Lordosis
Figure 2 e Diagram showing a post RME coronal slice: the red line represents IMD the blue line represents AE width.
Definition It is the inner angle of the intersecting SN and TH planes representing the change in head orientation in the sagittal plane (cranial base inclination angle) (Fig. 3). It is the inner angle of the intersecting Z and TH planes representing the change in head orientation in the frontal plane (Fig. 4) The change in head orientation in the medioelateral plane, measured by means of right (RY) and left (LY) angles. The first is the angle formed by (CgCv2od-RtLtPtg) while the second is the angle formed by (Cg-Cv2od-LtLtPtg) (Fig. 5). SN- PAL angle (Fig. 6)
Figure 3 e Pitch (P) angle.
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Statistical analysis
Figure 4 e Roll (R) angle.
SPSS (Version 13; SPSS, Chicago, IL, USA) was used to conduct the statistical analysis. The sample was found to be normally distributed for most parameters using the KolmogoroveSmirnov test, hence, the student t-test (P < 0.05) was applied to compare linear changes related to maxillary width and the expansion appliance, and volumetric changes in the nasopharyngeal spaces. Correlations between the changes were assessed using Pearson Correlation Coefficients (PCC). Friedman test was used to compare the findings of the two genders. Reproducibility and reliability of all measurements were undertaken using Dahlberg Error Test (DET) and Interclass Correlation Coefficient (ICC).22
Results
Figure 5 e Yaw (Y) angle.
Figure 6 e Lordosis (L) angle.
segmented models were measured using the ‘Volume and Statistics' command within ITK-SNAP software package and the data was exported to a separate datasheet for statistical analysis.
The records of 17 subjects (9 females and 8 males) were obtained; mean age was 12.4 and 12.8 years for males and females respectively (Table 5; Fig. 12). The mean interval between T1 and T2 was 23 days (range: 12e56 days) and the mean duration of active expansion was 14 days (range: 12e21 days). One of the subjects was excluded due to significant change (greater than 5 degrees) in head orientation and lordosis between T1 and T2 scans (Fig. 12). The results of the reproducibility are presented in Tables 6 and 7, and indicate that there is no statistically significant difference between measurements taken at first week (W1) and the subsequent week (W2) (P > 0.05). The ICC ranged from 0.93 to 1.00 for orientation measurements and from 0.97 to 1.00 for volumetric measurements. Therefore, the reproducibility of the measurements were deemed satisfactory. Friedman test revealed no statistically significant difference in head orientation (P ¼ 0.65) or in volumetric measurements of the airway spaces (P ¼ 0.23) between males and females. On average, more dentoalveolar expansion was seen in males than females and the average change in IMD was 3.7 mm in males and 2.8 mm in females; though the differences between the two groups were not statistically significant (Table 8). Tables 9e11 compare and contrast the changes in volume of the airway spaces secondary to RME, the percentage of volumetric changes (PVC) is used to simplify the changes and represented with the [(T2/T1)-1*100] equation. There were limited PVC for both LMS and RMS, measured at 1.2% and 3.8% respectively. Although, the LNC space gained additional volume of 29.2% in males and 6.0% in females, the changes did not reach a statistical-significant level. On the other hand, PVC of the UNP space in both genders followed a similar trend, 15.2% in males and 12% in female, and conjointly was statistically significant. Generally, URP spaces lost 6.6% of its original volume while LRP space lost 9.6% (14.6% and 0.6% in males and females respectively). While a clear and direct correlation between the increase in the volume of the two maxillary sinuses and between AE and IMD was evident (PCC ¼ 0.86, 0.75, respectively), there was weak correlations among other variables (Table 12).
Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Figure 7 e The standardised orientation technique of T1 image to produce NT1 image.
Figure 8 e Superimposition of NT1 and T2 images, on the cranial base structure, to produce NT2 image.
Table 4 e Volumes of interest and their boundaries. Boundaries Volume of interest
Anteriorly
Posteriorly
Superiorly
Inferiorly
Medially
Laterally
Lower nasal cavity Upper nasopharynex Retropalatal (Velo-pharyngeal) Right and left maxillary sinus (RMS and LMS)
ANSV plane PNSV plane LOrH plane Inferior nasal wall Nasal septum Lateral nasal wall PNSV plane C2sp/V plane LOrH plane PNSH plane N/A SPPTV PNSV plane C2sp/V plane PNSH plane Spip/TH plane N/A SPPTV The whole sinus was included to the level of LOrH plane superiorly and the minimum constricted opening with the adjacent paranasal cavities.
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Figure 9 e Volumes of interest and their boundaries.
Figure 10 e Segmentation procedure using ITK-SNAP software. Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Figure 11 e Three-dimensional visualisation of nasal, paranasal and oropharyngeal cavities and spaces.
Table 5 e Gender distribution. Gender
Number (n)
Mean age (years)
Range (years)
Male Female
8 9
12.4 12.8
10.5 to 14.08 10 to 16.25
Discussion In all cases of this study, RME successfully splitted the midpalatal suture resulting in a transverse dentoalveolar expansion which reflects the effectiveness of bondable RME appliances in increasing the maxillary width.5,23 The detected magnitude of transverse dentoalveolar expansion was approximately one-third of that reported in a previous study,24 this may be related to variation in the activation regime and/or the type of RME appliance used. Although, the degree of dentoalveolar expansion was greater in males than in females, the difference was not
statistically significant. These differences may be a result of confounding factor, as the male patients in this study were younger than the female. The literature shows a variable effect of RME on the maxillary sinus, Garrett et al. demonstrated a limited volumetric reduction while Pangrazio-Kulbersh et al. reported one tenth of expansion.25,26 The current study showed limited reduction in maxillary sinus volume in line with previous studies,26,27 which might be due to upward displacement of the lateral structures of the nasoemaxillary complex relative to the superior boundary of the maxillary sinuses,28 reshaping of the maxillary sinuses,29 lateral bending and torque of the alveolar bone secondary to maxillary expansion,30 or simply difference in method used to define the boundaries of the maxillary sinus. The volume of the LNC increased secondary to RME, but this was not statistically significant, and may have occurred as a result of lateral displacement of the outer wall of the nasal cavity, the inferior turbinate bones, and the nasal wall conchae, or due to lateral alveolar bone bending and inferior movement of the nasal floor.31,32 Additionally, the volumetric changes of the LNC were five times greater in males compared to females (29.2% in females and 6.0% in males), these findings are parallel to those of da Silva Filho et al.31 The observed difference may be due to variation in the anatomical, physiological, maturational and chronological differences between genders, the male group in this study was on average younger than the female group. Although, the LNC volume expansion was not statistically significant, almost one fifth of the immediate expansion might be clinically significant and relevant. It is well documented that these changes are crucial in influencing the patterns of facial growth,33,34 reducing nasal resistance and an improving nasal breathing, these effects make RME a reasonable option for treatment of Paediatric Obstructive Sleep Apnea Syndrome (POSAS). In line with previous studies, this research has proven that the UNP space expands following RME and both genders display a similar response pattern.11,35,36 A possible explanation for this, is that the RME anteriorly displaced the two
Figure 12 e T1-T2 head orientation and lordosis.
Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Table 6 e Reproducibility of the angular measurements. T1W1:T1W2
T2W1:T2W2
Variables
DET
t-test
ICC
DET
t-test
ICC
P angle Lordosis Y angle RR angle LR angle
0.28 0.15 0.13 0.12 0.17
0.45 0.94 0.69 0.62 0.23
0.93 1.00 0.95 0.99 0.98
0.16 1.14 0.12 0.16 0.17
0.24 0.48 0.43 0.08 0.17
0.97 1.00 0.95 0.99 0.98
T1W1: Pre-treatment measurements on the 1st occasion, T1W2: pre-treatment measurements on the 2nd occasion, T2W1: posttreatment measurements on the 1st occasion, T2W2: posttreatment measurements on the 2nd occasion, SD: Standard deviation, DET: Dahlberg error test, ICC: interclass correlation.
Table 7 e Reproducibility of the volumetric and linear measurements. T1W1:T1W2
T2W1:T2W2
Variables
DET
t-test
ICC
DET
t-test
ICC
LMS RMS LNC UNP URP LRP IMD AE
7.53 17.98 41.73 13.72 5.88 6.41 0.04 0.01
0.59 0.16 0.14 0.22 0.48 0.37 0.28 0.32
1.00 1.00 0.99 1.00 1.00 1.00 1.00 0.97
11.40 7.61 3.98 10.19 1.40 62.25 0.07 0.02
0.72 0.12 0.62 0.84 0.38 0.38 0.37 0.60
1.00 1.00 1.00 1.00 1.00 0.99 1.00 1.00
palatal shelves which, in turn pivots around the pterygoidmaxillary junction, lead to forward displacement of the PNS which represents the anterior boundary of the UNP, consequently increasing the UNP volume.
The URP and LRP volumes reduced secondary to RME, particularly in males, but this was not statistically significant in contrast with the results of Chang et al.11 Edema and Trauma to the retropalatal tissue, resulting from midpalatal suture separation, might have caused reduction in the volume of the URP and LRP space, in particular as T2 images were taken immediately after the active phase of the RME. By contrast, the 4-month delay in taking T2 in Chang et al. study,11 could have allowed more settling of the soft tissue trauma and explain the different trend from our study. Furthermore, stretching of the palato-pharyngeal muscle due to forwards displacement of the palatal shelves and subsequent narrowing of the retropalatal space may be another hypothetical explanation. It is also reasonable to assume that lowering of the palatal plane secondary to RME or tongue movement and positional changes at the time of image acquisition may have also altered the URP and LRP volume.37 As previously reported, LRP volume reduced more in males than females similar to the finding of an other study27 and this might be related to the collapsibility of males' pharyngeal muscles38 or the large soft palate in males that makes them more susceptible to trauma secondary to palatal suture separation38,39 One further explanation is that females have increased pharyngeal dilator muscle activity when compared with males, resulting in better resistance to external effects.38,40 Unsurprisingly, PCC revealed a strong direct correlation between the changes in the right and left maxillary sinus (PCC 0.86), which is likely due to the analogous anatomical nature of the structures and the identical bony articulations. Likewise, there was a strong direct correlation between AE and IMD suggesting that RME is an effective modality for dentoalveolar expansion in growing patients.5 A long-term follow-up may provide a better understanding of the stability of the effects of RME on the nasopharyngeal region.
Table 8 e Dentoalveolar linear measurements, T1 and T2 for male, female and both genders. Variables
Both genders IMD AE Male group IMD AE Female group IMD AE
T1
T2
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
Mean (mm)
SD
Mean (mm)
SD
50.68 0.37
4.45 0.3
53.85 4.68
4.3 1.49
3.2 4.3
6.3 1165
0.01 0.01
52.61 0.57
5.32 0.37
56.3 5.32
4.27 1.77
3.7 4.7
7 833
0.01 0.01
49.33 0.23
3.38 0.13
52.13 4.23
3.58 1.14
2.8 4
5.7 1739
0.01 0.01
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
85.1 258 814.4 365.5 34.8 311
1.2 3.8 17 13.4 6.6 9.4
0.82 0.5 0.06 0.04 0.04 0.27
Table 9 e Nasopharyngeal volumetric measurements at T1 and T2 for both genders. Variables
LMS RMS LNC UNP URP LRP
T1
T2
3
3
Mean (mm )
SD
Mean (mm )
SD
6940 6855 4785 2736 527 3305
4207 3681 2195 1395 827 2265
6855 7113 5600 3101 492 2994
3728 3348 3374 1374 731 2226
Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Table 10 e Nasopharyngeal volumetric measurements at T1 and T2 for males. Variables
LMS RMS LNC UNP URP LRP
T1
T2
Mean
SD
Mean
SD
6696 6871 5512 2856 576 4325
5122 4584 3065 1439 1021 2099
6800 7371 7123 3290 511 3693
5067 4440 4596 1111 971 1701
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
104.3 500.0 1611 434.3 64.6 632
1.6 7.3 29.2 15.2 11.2 14.6
0.68 0.31 0.08 0.11 0.10 0.13
Table 11 e Nasopharyngeal volumetric measurements at T1 and T2 for females. Variables
LMS RMS LNC UNP URP LRP
T1
T2
Mean (mm3)
SD
Mean (mm3)
SD
7111 6844 4277 2652 492 2590
3727 3175 1266 1435 719 2191
6894 6933 4533 2969 478 2574
2753 2587 1755 1576 565 2476
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
218 88.6 256.5 317.4 14.0 16.1
3.1 1.3 6.0 12.0 2.8 0.6
0.72 0.92 0.51 0.25 0.12 0.67
Table 12 e Pearson correlation coefficients of the changes.
Gender LMS RMS LNC UNP URP LRP IMD AE
Gender
LMS
RMS
LNC
UNP
URP
LRP
IMD
AE
1.00 0.11 0.16 0.41 0.08 0.20 0.45 0.22 0.28
0.11 1.00 0.86 0.31 0.53 0.74 0.20 0.06 0.12
0.16 0.86 1.00 0.48 0.39 0.45 0.22 0.20 0.09
0.41 0.31 0.48 1.00 0.06 0.19 0.01 0.15 0.41
0.08 0.53 0.39 0.06 1.00 0.64 0.28 0.16 0.14
0.20 0.74 0.45 0.19 0.64 1.00 0.02 0.08 0.07
0.45 0.20 0.22 0.01 0.28 0.02 1.00 0.06 0.51
0.22 0.06 0.20 0.15 0.16 0.08 0.06 1.00 0.75
0.28 0.12 0.09 0.41 0.14 0.07 0.51 0.75 1.00
Conclusions ITK-SNAP software package is a reliable and cost effective method to assess airway changes following orthodontic treament. Furthermore, bonded RME is an efficient dentoalveolar expander in growing patients and associated with an expansion of both LNC and UNP spaces. The effects of RME on the upper nasopharyngeal region exhibited a mushroom-like pattern where the upper part expanded, the middle part significantly narrowed, and the lower part mildly but insignificantly narrowed. The immediate expansion of LNC and UNP secondary to RME might be associated with a reduction in nasal resistance, improvement in the nasal breathing and theoretically it can an option for treatment of Paediatric OSAH. However, regardless of these potential benefits, this orthopedic procedure should not be done to improve nasal breathing when it is the solitary indication. A further randomised controlled or comparative trial with larger sample size and long term follow up would be beneficial, and these studies could include a colour mapping for detailed visual localisation of the changes as the morphological changes of the airway space is as important as volumetric changes.
references
1. Bishara SE, Staley RN. Maxillary expansion: clinical implications. Am J Orthod Dentofac Orthop 1987;91:3e14. 2. Chiari S, Romsdorfer P, Swoboda H, Bantleon H-P, Freudenthaler J. Effects of rapid maxillary expansion on the airways and earsda pilot study. Eur J Orthod 2009;3:135e41. 3. Cross DL, McDonald JP. Effect of rapid maxillary expansion on skeletal, dental, and nasal structures: a postero-anterior cephalometric study. Eur J Orthod 2000;22:519e28. 4. Schu¨tz-Fransson U, Kurol J. Rapid maxillary expansion effects on nocturnal enuresis in children: a follow-up study. Angle Orthod J 2008;78:201e8. 5. Ong S, Khambay B, McDonald J, Cross D, Brocklebank L, Ju X. The novel use of three-dimensional surface models to quantify and visualise the immediate changes of the midfacial skeleton following rapid maxillary expansion. Surg J 2015;13:132e8. 6. Zweiman B, Getsy J, Kalenian M, Lane A, Schwartz LB, Doty R, et al. Nasal airway changes assessed by acoustic rhinometry and mediator release during immediate and late reactions to allergen challenge. J Allergy Clin Immun 1997;100:624e31. € ku¨cu¨ O, Bic¸akc¸i AA, Yilmaz U, Tas‚ F. Comparison 7. Doruk C, So of nasal volume changes during rapid maxillary expansion
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Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study Mohammed Almuzian a,b,*, Xiangyang Ju b, Anas Almukhtar c, Ashraf Ayoub d, Lubna Al-Muzian e, Jim P McDonald c a
Orthodontic Department, Sydney Dental Hospital, University of Sydney, Sydney, NSW, Australia Medical Devices Unit, NHS Greater Glasgow and Clyde, Glasgow, UK c Orthodontic Department, Glasgow Dental Hospital and School, MVLS College, University of Glasgow, Glasgow, UK d Oral & Maxillofacial Surgery, Glasgow Dental Hospital & School, MVLS College, University of Glasgow, Glasgow, UK e Deportment of Dental Public Health, School of Dentistry, Faculty of Medical and Human Science, University of Manchester, Manchester, UK b
article info
abstract
Article history:
Background and purpose: There is limited literature discussing the three dimnesional (3D)
Received 10 February 2015
impact of rapid maxillary expansion (RME) on upper airway. The purpose of this pro-
Received in revised form
spective Cone Beam Computerised Tomography (CBCT) based study is to assess the
19 November 2015
immediate 3D effects and to correlate the volumteric changes in the upper naspharyngeal
Accepted 22 December 2015
airway spaces secondary to RME.
Available online xxx
Materials and methods: Seventeen participants (8 male, 9 female, with a mean age of 12.6 ± 1.8 years), who required RME for the management of narrow maxillary arch, were
Keywords:
recruited for this study. The prescribed expansion regimen was quarter turn (0.25 mm),
CBCT
twice a day until over-expansion was achieved. The mean period for the active phase was
ITK snap software
14 days with a range of 12e21 days. Pretreatment (T1) and immediate post-expansion (T2)
OnDemand3D software
CBCT images were obtained and then processed using ITK snap and OnDemand3D softwar
Rapid maxillary expansion
packages. Paired t-test and Interclass Correlation Coefficient (ICC) were used to assess the
Airway space
reproducibility of the measurements, student t-test (P < 0.05) and Pearson Correlation Coefficient (PCC) were applied to evaluate the volumetric changes in the nasopharyngeal airway spaces, linear dentolaveolar changes and correlate these changes. Main findings: Though, the data of one patient was excluded from the study, owing to major differences (>5 degrees) in the head and neck posture between T1 and T2 CBCT scans, the study' findings shows that bonded RME is an effective dentoalveolar expander in growing patients (P¼ 0.01) with an average expansion of 3.7 mm and 2.8 mm in males and females respectively. Likewise, the upper nasopharynx (UNP) expanded significantly (15.2% in males and 12% in females). In comparison, the upper retropalatal space (URP) was significantly reduced, by almost one sixth of its original volume, more in males than females, 11.2% and 2.8% respectively. A strong direct correlation between the maxillary sinus volumetric changes, and between appliance expansion and dentoalveolar expansion were
* Corresponding author. Deportment of Orthodontics, University of Sydney, Sydney, NSW, 2006, Australia. Tel.: þ61 293518329x8314. E-mail address: [email protected] (M. Almuzian). http://dx.doi.org/10.1016/j.surge.2015.12.006 1479-666X/© 2015 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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evident (PCC ¼ 0.86, 0.75, respectively). There was also a moderate correlation between changes in the UNP and URP spaces. Conclusions: RME was found to be an effective dentoalveolar expander and significantly augment the UNP and minimize the URP space. A similar comparative clinical study with long-term follow-up would be beneficial in accurately deteremining the clinical impact of RME on the airway and breathing as well as the stability of these effects. © 2015 Royal College of Surgeons of Edinburgh (Scottish charity number SC005317) and Royal College of Surgeons in Ireland. Published by Elsevier Ltd. All rights reserved.
Introduction Rapid maxillary (palatal) expanders (RME) act by applying heavy intermittent force, up to 10 kg, to split the midpalatal suture.1 The potential effects of RME are orthopaedic, dental, soft tissue, airway and miscelleneous such as effect on hearing, facial growth and nocturia.2e5 Changes in the nasal and pharyngeal airway spaces secondary to RME have been investigated extensively using two dimensional (2D) cephalometric radiographs 2,3; Rhinomanometry2,6 (R) and Acoustic Rhinomanometry (AR).7,8 However, due to the complex three dimensional (3D) anatomical architecture of the upper airway spaces, the effects of RME is difficult to be accurately assessed using 2D imaging modalities. This is mainly due the superimposition of bilateral structures and the presence of numerous bony structures, which are generally difficult to identify. Furthermore, 2D imaging modalities lack information regarding volumetric changes, and R and AR have their own restrictions like dearth of visual signs of changes and require a specialised operator and apparatus. All of these drawbacks encouraged the adoption of 3D technique such as Cone Beam Computerised Tomography (CBCT) for more accurate volumteric measurmeent and visualisation of airway spaces.9e11 However, most studies have produced results using slice data obtained after 3D CBCT scanning and there has been no consideration for the effect of tongue head and neck position on airway measurement.12,13 The aims of the study was to assess the 3D effect of RME on the volumes of the maxillary sinuses, the lower part of the nasal cavity, the upper oropharyngeal region, taking in consideration the limitations of previous trials. The study also aimed to correlate the volumetric changes with the magnitude of dentoalveolar expansion.
Caucasian patients, between 10 and 16 years of age with normal body mass index (BMI), who had constricted maxillary arch with unilateral or bilateral posterior crossbite No previous tonsillar, nasal, adenoid, head or neck surgery, and no craniofacial deformity No previous orthodontic treatment No major variation in the head and craniocervical orientation (>5 degrees) between the pre-treatment (T1) and post-expansion or post-treatment (T2) CBCT scans. A cast-cap appliance with a Hyrax screw (Forestadent, Germany), as an active component, was used for maxillary expansion. The capping component was constructed from a silver-copper alloy (SP70, Skillbond, UK) and had fully covered the buccal teeth, from first molar to the canines, and contained occlusal holes to aid removal (Fig. 1). The appliances were activated immediately after capturing the T1 scans, and the patients were monitored on a regular basis during the active expansion phase. The prescribed expansion regime was a quarter turn (approximately 0.25 mm), twice a day until over-expansion (OE) achieved. OE means the palatal cusps of upper molars, represented by the occluso-palatal angle of the metal capping of the RME, occluded with the buccal cusp tips of lower molars. At this point, T2 scans were taken. Both CBCT scans (T1 and T2) were taken by a trained radiographer using an iCAT scanner (Imaging Sciences
Participants and materials The sample size was computed using the Researcher's Toolkit calculator which indicated that a data from 14 participants would yield a confidence level of 95% and a Beta error level of 20%. Accordingly, 17 subjects were recruited to overcome the potential exclusion and an ethical approval was granted by (NHS/Greater Glasgow/09-S0709/40 and Victoria Hospital/Fife/09-062). The study had the following inclusion criteria:
Figure 1 e The cast cap splint RME.
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International, Hatfield, Pa, USA), the subjects were positioned with Frankfort plane parallel to the floor.14 The head was stabilised by a headband to prevent movement during the 20-s scan. The data files for the CBCT images have been saved and stored as DICOM format (Digital Imaging and Communication in Medicine) and analysed using two different types of software, namely OnDemand3D (Cybermed, Seoul, Republic of Korea) and ITK-SNAP version 2.2.0 (www.itksnap.org). ITK stands for Insight Tool Kit which is an open-access popular library image analysis algorithm funded by the US National Library of Medicine under the Visible Human Project.15 The points, planes and angles used in this study are described in Tables 1e3. Initially, OnDemand3D software package was used to measure IMD and AE (Fig. 2) and, based on the reported validity of 3D cephalometric assessments,16,17 head posture (P, R and Y angle) and cranio-cervical inclination (L angle) were measured. The angular measurements were recorded to the nearest degree (Figs. 3e6). Subjects were excluded if the change in head posture and/or lordosis between T1 and T2 scans was greater than 5 , as these changes have been proven to have a significant impact on nasopharyngeal airway measurements.18e20 Each of the T1 images were digitally oriented, thus Ptg LF and Z plane were all parallel to TH Plane. Then, the orientated images were saved and stored as New T1 (NT1) scans (Fig. 7). Next, T2 images were digitally orientated and superimposed on their corresponding NT1 scans (auto-registration) using the anterior and posterior
cranial bases as stable structures, and subsequently saved as New T2 (NT2) scan (Fig. 8). These strategies in orientation permitted standardised segmentation and eliminated effect of positional error's during segmentation. Using NT1 and NT2 scans; the airway boundaries were defined, segmented and measured in terms of volume using the ITK-SNAP software package (Table 4 and Figs. 9e10). The manufacturer's instructions for the use of ITK software package were followed.15 In an effort to minimise inclusion of the para-nasal sinuses and their related hiatus, the measurement of the volume of the lower nasal cavity was limited to the respiratory part of the nasal cavity. Cv2sp/H plane subdivides the retropalatal space into two distinct spaces, the upper (URP) and lower (LRP) retropalatal spaces taking in consideration that if the Cv2od was located superior to Spip/TH plane, then the whole segment would be considered as LRP space.10,11,21 All linear, angular and volumetric measurements were carried out by one examiner (MA) and repeated after one week, the two sets of measurements were compared to validate the reproducibility of the measurement technique. 3D virtual replicas of the airway spaces were generated using automatic and manual segmentation, which allowed for detailed localisation of changes (Fig. 11). Moreover, the segmentation permited exclusion of any potentially masking changes that adjacent or remote airway spaces might produce. This was a crucial step because each airway segment is associated anatomically and physiologically to a different function and/or disorder. The volume of these
Table 1 e Points and landmarks. Point ANS
Cv2sp Cg Cv2ig Cv2ip Cv2od LOr Lpo LtLtPtg Lzyg Molar Alveolar Crest (MAC) Nasion (N) PNS ROr RtLtPtg Rzyg Sella (S) Spip
Definition The tip of the bony anterior nasal spine at the inferior margin of the piriform aperture, in the midsagittal plane and often is used to define the anterior end of the palatal plane. It is the most superioreposterior extremity of the odontoid process of the second cervical vertebrae (Cv2) The most superior point of Crista galli bony structure The most superior-posterior extremity of the odontoid process of Cv2 The most inferio-posterior point on the body of Cv2 The most superior point of the odontoid process of Cv2 The lowest point of the left inferior orbital floor The most superior point of the outline of the left external auditory meatus (anatomic porion) The most posterior point of the left lateral pterygoid plate as viewed from the axial section The most lateral point of the left fronto-zygomatic suture as viewed from the coronal section The intersecting point of the buccal alveolar crest and the buccal surface of the maxillary first molar The most posterior point on the curvature of the nasal bridge at the junction of the nasal and frontal bones The most posterior point of the bony hard palate The lowest point of the right inferior orbital floor The most posterior point of the right lateral pterygoid plate as viewed from the axial section The most lateral point of the right fronto-zygomatic suture as viewed from the coronal section The center of the hypophyseal fossa (sella tursica) The most inferior-posterior point of the soft palate shadow as viewed from the axial section
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Table 2 e Lines and planes. Line and plane Appliance Expansion (AE) ANSV plane
Cv2sp/V plane CgeCv2od plane Cv2sp/H plane Left Frankfort (LF) Plane LOrH plane Intermolar Alveolar Crest width (IMD) Orbital (O) plane PAL PNSH plane PNSV plane Pterygoid (Ptg) Plane SN plane Spip/TH Plane SPPTV plane True horizontal (TH) plane True vertical line (TV) plane Zygomatic (Z) Plane
Definition The maximum separation of the right and left acrylic plate measured on coronal section (Fig. 2) A true vertical plane (TV) plane passing through point ANS, as shown from the sagittal view. If the mid-palatine split extends to involve the ANS, then the most anterior ANS is considered. TV plane passing through Cv2sp. A plane connecting Cg and Cv2od points TH plane passing through Cv2sp A plane connecting left Or and left Po points TH plane tangent to LOr point The distance between right and left MAC points measured on coronal section (Fig. 2) A plane connecting right and left Or points A plane connecting through the Cv2ig and Cv2ip points TH plane passing through PNS and extended to the posterior wall of the pharynx TV plane passing through PNS. If the mid-palatine split extends to involve the PNS, then the most posterior end of the palate is considered A plane connecting LtLtPtg and RtLtPtg points A plane connecting S and N points A plane parallel to the TH plane passing through the Spip A sagittal plane parallel to TV passing through the most lateral point of the maxillary sinus A reference plane constructed horizontal to the floor at any point A reference plane constructed perpendicular to the floor at any point A plane connecting Lzyg and Rzyg points
Table 3 e Cephalometric angles. Angle Pitch angle (P angle)
Roll angle (R Angle) Yaw angle (Y Angle)
Lordosis
Figure 2 e Diagram showing a post RME coronal slice: the red line represents IMD the blue line represents AE width.
Definition It is the inner angle of the intersecting SN and TH planes representing the change in head orientation in the sagittal plane (cranial base inclination angle) (Fig. 3). It is the inner angle of the intersecting Z and TH planes representing the change in head orientation in the frontal plane (Fig. 4) The change in head orientation in the medioelateral plane, measured by means of right (RY) and left (LY) angles. The first is the angle formed by (CgCv2od-RtLtPtg) while the second is the angle formed by (Cg-Cv2od-LtLtPtg) (Fig. 5). SN- PAL angle (Fig. 6)
Figure 3 e Pitch (P) angle.
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Statistical analysis
Figure 4 e Roll (R) angle.
SPSS (Version 13; SPSS, Chicago, IL, USA) was used to conduct the statistical analysis. The sample was found to be normally distributed for most parameters using the KolmogoroveSmirnov test, hence, the student t-test (P < 0.05) was applied to compare linear changes related to maxillary width and the expansion appliance, and volumetric changes in the nasopharyngeal spaces. Correlations between the changes were assessed using Pearson Correlation Coefficients (PCC). Friedman test was used to compare the findings of the two genders. Reproducibility and reliability of all measurements were undertaken using Dahlberg Error Test (DET) and Interclass Correlation Coefficient (ICC).22
Results
Figure 5 e Yaw (Y) angle.
Figure 6 e Lordosis (L) angle.
segmented models were measured using the ‘Volume and Statistics' command within ITK-SNAP software package and the data was exported to a separate datasheet for statistical analysis.
The records of 17 subjects (9 females and 8 males) were obtained; mean age was 12.4 and 12.8 years for males and females respectively (Table 5; Fig. 12). The mean interval between T1 and T2 was 23 days (range: 12e56 days) and the mean duration of active expansion was 14 days (range: 12e21 days). One of the subjects was excluded due to significant change (greater than 5 degrees) in head orientation and lordosis between T1 and T2 scans (Fig. 12). The results of the reproducibility are presented in Tables 6 and 7, and indicate that there is no statistically significant difference between measurements taken at first week (W1) and the subsequent week (W2) (P > 0.05). The ICC ranged from 0.93 to 1.00 for orientation measurements and from 0.97 to 1.00 for volumetric measurements. Therefore, the reproducibility of the measurements were deemed satisfactory. Friedman test revealed no statistically significant difference in head orientation (P ¼ 0.65) or in volumetric measurements of the airway spaces (P ¼ 0.23) between males and females. On average, more dentoalveolar expansion was seen in males than females and the average change in IMD was 3.7 mm in males and 2.8 mm in females; though the differences between the two groups were not statistically significant (Table 8). Tables 9e11 compare and contrast the changes in volume of the airway spaces secondary to RME, the percentage of volumetric changes (PVC) is used to simplify the changes and represented with the [(T2/T1)-1*100] equation. There were limited PVC for both LMS and RMS, measured at 1.2% and 3.8% respectively. Although, the LNC space gained additional volume of 29.2% in males and 6.0% in females, the changes did not reach a statistical-significant level. On the other hand, PVC of the UNP space in both genders followed a similar trend, 15.2% in males and 12% in female, and conjointly was statistically significant. Generally, URP spaces lost 6.6% of its original volume while LRP space lost 9.6% (14.6% and 0.6% in males and females respectively). While a clear and direct correlation between the increase in the volume of the two maxillary sinuses and between AE and IMD was evident (PCC ¼ 0.86, 0.75, respectively), there was weak correlations among other variables (Table 12).
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Figure 7 e The standardised orientation technique of T1 image to produce NT1 image.
Figure 8 e Superimposition of NT1 and T2 images, on the cranial base structure, to produce NT2 image.
Table 4 e Volumes of interest and their boundaries. Boundaries Volume of interest
Anteriorly
Posteriorly
Superiorly
Inferiorly
Medially
Laterally
Lower nasal cavity Upper nasopharynex Retropalatal (Velo-pharyngeal) Right and left maxillary sinus (RMS and LMS)
ANSV plane PNSV plane LOrH plane Inferior nasal wall Nasal septum Lateral nasal wall PNSV plane C2sp/V plane LOrH plane PNSH plane N/A SPPTV PNSV plane C2sp/V plane PNSH plane Spip/TH plane N/A SPPTV The whole sinus was included to the level of LOrH plane superiorly and the minimum constricted opening with the adjacent paranasal cavities.
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Figure 9 e Volumes of interest and their boundaries.
Figure 10 e Segmentation procedure using ITK-SNAP software. Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Figure 11 e Three-dimensional visualisation of nasal, paranasal and oropharyngeal cavities and spaces.
Table 5 e Gender distribution. Gender
Number (n)
Mean age (years)
Range (years)
Male Female
8 9
12.4 12.8
10.5 to 14.08 10 to 16.25
Discussion In all cases of this study, RME successfully splitted the midpalatal suture resulting in a transverse dentoalveolar expansion which reflects the effectiveness of bondable RME appliances in increasing the maxillary width.5,23 The detected magnitude of transverse dentoalveolar expansion was approximately one-third of that reported in a previous study,24 this may be related to variation in the activation regime and/or the type of RME appliance used. Although, the degree of dentoalveolar expansion was greater in males than in females, the difference was not
statistically significant. These differences may be a result of confounding factor, as the male patients in this study were younger than the female. The literature shows a variable effect of RME on the maxillary sinus, Garrett et al. demonstrated a limited volumetric reduction while Pangrazio-Kulbersh et al. reported one tenth of expansion.25,26 The current study showed limited reduction in maxillary sinus volume in line with previous studies,26,27 which might be due to upward displacement of the lateral structures of the nasoemaxillary complex relative to the superior boundary of the maxillary sinuses,28 reshaping of the maxillary sinuses,29 lateral bending and torque of the alveolar bone secondary to maxillary expansion,30 or simply difference in method used to define the boundaries of the maxillary sinus. The volume of the LNC increased secondary to RME, but this was not statistically significant, and may have occurred as a result of lateral displacement of the outer wall of the nasal cavity, the inferior turbinate bones, and the nasal wall conchae, or due to lateral alveolar bone bending and inferior movement of the nasal floor.31,32 Additionally, the volumetric changes of the LNC were five times greater in males compared to females (29.2% in females and 6.0% in males), these findings are parallel to those of da Silva Filho et al.31 The observed difference may be due to variation in the anatomical, physiological, maturational and chronological differences between genders, the male group in this study was on average younger than the female group. Although, the LNC volume expansion was not statistically significant, almost one fifth of the immediate expansion might be clinically significant and relevant. It is well documented that these changes are crucial in influencing the patterns of facial growth,33,34 reducing nasal resistance and an improving nasal breathing, these effects make RME a reasonable option for treatment of Paediatric Obstructive Sleep Apnea Syndrome (POSAS). In line with previous studies, this research has proven that the UNP space expands following RME and both genders display a similar response pattern.11,35,36 A possible explanation for this, is that the RME anteriorly displaced the two
Figure 12 e T1-T2 head orientation and lordosis.
Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Table 6 e Reproducibility of the angular measurements. T1W1:T1W2
T2W1:T2W2
Variables
DET
t-test
ICC
DET
t-test
ICC
P angle Lordosis Y angle RR angle LR angle
0.28 0.15 0.13 0.12 0.17
0.45 0.94 0.69 0.62 0.23
0.93 1.00 0.95 0.99 0.98
0.16 1.14 0.12 0.16 0.17
0.24 0.48 0.43 0.08 0.17
0.97 1.00 0.95 0.99 0.98
T1W1: Pre-treatment measurements on the 1st occasion, T1W2: pre-treatment measurements on the 2nd occasion, T2W1: posttreatment measurements on the 1st occasion, T2W2: posttreatment measurements on the 2nd occasion, SD: Standard deviation, DET: Dahlberg error test, ICC: interclass correlation.
Table 7 e Reproducibility of the volumetric and linear measurements. T1W1:T1W2
T2W1:T2W2
Variables
DET
t-test
ICC
DET
t-test
ICC
LMS RMS LNC UNP URP LRP IMD AE
7.53 17.98 41.73 13.72 5.88 6.41 0.04 0.01
0.59 0.16 0.14 0.22 0.48 0.37 0.28 0.32
1.00 1.00 0.99 1.00 1.00 1.00 1.00 0.97
11.40 7.61 3.98 10.19 1.40 62.25 0.07 0.02
0.72 0.12 0.62 0.84 0.38 0.38 0.37 0.60
1.00 1.00 1.00 1.00 1.00 0.99 1.00 1.00
palatal shelves which, in turn pivots around the pterygoidmaxillary junction, lead to forward displacement of the PNS which represents the anterior boundary of the UNP, consequently increasing the UNP volume.
The URP and LRP volumes reduced secondary to RME, particularly in males, but this was not statistically significant in contrast with the results of Chang et al.11 Edema and Trauma to the retropalatal tissue, resulting from midpalatal suture separation, might have caused reduction in the volume of the URP and LRP space, in particular as T2 images were taken immediately after the active phase of the RME. By contrast, the 4-month delay in taking T2 in Chang et al. study,11 could have allowed more settling of the soft tissue trauma and explain the different trend from our study. Furthermore, stretching of the palato-pharyngeal muscle due to forwards displacement of the palatal shelves and subsequent narrowing of the retropalatal space may be another hypothetical explanation. It is also reasonable to assume that lowering of the palatal plane secondary to RME or tongue movement and positional changes at the time of image acquisition may have also altered the URP and LRP volume.37 As previously reported, LRP volume reduced more in males than females similar to the finding of an other study27 and this might be related to the collapsibility of males' pharyngeal muscles38 or the large soft palate in males that makes them more susceptible to trauma secondary to palatal suture separation38,39 One further explanation is that females have increased pharyngeal dilator muscle activity when compared with males, resulting in better resistance to external effects.38,40 Unsurprisingly, PCC revealed a strong direct correlation between the changes in the right and left maxillary sinus (PCC 0.86), which is likely due to the analogous anatomical nature of the structures and the identical bony articulations. Likewise, there was a strong direct correlation between AE and IMD suggesting that RME is an effective modality for dentoalveolar expansion in growing patients.5 A long-term follow-up may provide a better understanding of the stability of the effects of RME on the nasopharyngeal region.
Table 8 e Dentoalveolar linear measurements, T1 and T2 for male, female and both genders. Variables
Both genders IMD AE Male group IMD AE Female group IMD AE
T1
T2
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
Mean (mm)
SD
Mean (mm)
SD
50.68 0.37
4.45 0.3
53.85 4.68
4.3 1.49
3.2 4.3
6.3 1165
0.01 0.01
52.61 0.57
5.32 0.37
56.3 5.32
4.27 1.77
3.7 4.7
7 833
0.01 0.01
49.33 0.23
3.38 0.13
52.13 4.23
3.58 1.14
2.8 4
5.7 1739
0.01 0.01
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
85.1 258 814.4 365.5 34.8 311
1.2 3.8 17 13.4 6.6 9.4
0.82 0.5 0.06 0.04 0.04 0.27
Table 9 e Nasopharyngeal volumetric measurements at T1 and T2 for both genders. Variables
LMS RMS LNC UNP URP LRP
T1
T2
3
3
Mean (mm )
SD
Mean (mm )
SD
6940 6855 4785 2736 527 3305
4207 3681 2195 1395 827 2265
6855 7113 5600 3101 492 2994
3728 3348 3374 1374 731 2226
Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
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Table 10 e Nasopharyngeal volumetric measurements at T1 and T2 for males. Variables
LMS RMS LNC UNP URP LRP
T1
T2
Mean
SD
Mean
SD
6696 6871 5512 2856 576 4325
5122 4584 3065 1439 1021 2099
6800 7371 7123 3290 511 3693
5067 4440 4596 1111 971 1701
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
104.3 500.0 1611 434.3 64.6 632
1.6 7.3 29.2 15.2 11.2 14.6
0.68 0.31 0.08 0.11 0.10 0.13
Table 11 e Nasopharyngeal volumetric measurements at T1 and T2 for females. Variables
LMS RMS LNC UNP URP LRP
T1
T2
Mean (mm3)
SD
Mean (mm3)
SD
7111 6844 4277 2652 492 2590
3727 3175 1266 1435 719 2191
6894 6933 4533 2969 478 2574
2753 2587 1755 1576 565 2476
T2-T1
% Of changes (T2/T1)1*100
Paired t-test
218 88.6 256.5 317.4 14.0 16.1
3.1 1.3 6.0 12.0 2.8 0.6
0.72 0.92 0.51 0.25 0.12 0.67
Table 12 e Pearson correlation coefficients of the changes.
Gender LMS RMS LNC UNP URP LRP IMD AE
Gender
LMS
RMS
LNC
UNP
URP
LRP
IMD
AE
1.00 0.11 0.16 0.41 0.08 0.20 0.45 0.22 0.28
0.11 1.00 0.86 0.31 0.53 0.74 0.20 0.06 0.12
0.16 0.86 1.00 0.48 0.39 0.45 0.22 0.20 0.09
0.41 0.31 0.48 1.00 0.06 0.19 0.01 0.15 0.41
0.08 0.53 0.39 0.06 1.00 0.64 0.28 0.16 0.14
0.20 0.74 0.45 0.19 0.64 1.00 0.02 0.08 0.07
0.45 0.20 0.22 0.01 0.28 0.02 1.00 0.06 0.51
0.22 0.06 0.20 0.15 0.16 0.08 0.06 1.00 0.75
0.28 0.12 0.09 0.41 0.14 0.07 0.51 0.75 1.00
Conclusions ITK-SNAP software package is a reliable and cost effective method to assess airway changes following orthodontic treament. Furthermore, bonded RME is an efficient dentoalveolar expander in growing patients and associated with an expansion of both LNC and UNP spaces. The effects of RME on the upper nasopharyngeal region exhibited a mushroom-like pattern where the upper part expanded, the middle part significantly narrowed, and the lower part mildly but insignificantly narrowed. The immediate expansion of LNC and UNP secondary to RME might be associated with a reduction in nasal resistance, improvement in the nasal breathing and theoretically it can an option for treatment of Paediatric OSAH. However, regardless of these potential benefits, this orthopedic procedure should not be done to improve nasal breathing when it is the solitary indication. A further randomised controlled or comparative trial with larger sample size and long term follow up would be beneficial, and these studies could include a colour mapping for detailed visual localisation of the changes as the morphological changes of the airway space is as important as volumetric changes.
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Please cite this article in press as: Almuzian M, et al., Does rapid maxillary expansion affect nasopharyngeal airway? A prospective Cone Beam Computerised Tomography (CBCT) based study, The Surgeon (2016), http://dx.doi.org/10.1016/j.surge.2015.12.006
