Usefulness of Hard Palate Measurements in Predicting Airway Dimensions in Patients Referred for Cone Beam CT

Mustafa Alkhader1, *, Mohammad S. Alrashdan1, 2, Nour Abdo3, Rashed Abbas4
1 Department of Oral Medicine and Surgery, Faculty of Dentistry, Jordan University of Science and Technology, Irbid, Jordan
2 Department of Oral and Craniofacial Health Sciences, College of Dental Medicine, University of Sharjah, Sharjah, United Arab Emirates
3 Department of Community Medicine, Faculty of Medicine, Public Health and Family Medicine, Jordan University of Science and Technology, Irbid, Jordan
4 Department of Preventive Dentistry, Faculty of Dentistry, Jordan University of Science and Technology, Irbid, Jordan

Article Metrics

CrossRef Citations:
Total Statistics:

Full-Text HTML Views: 244
Abstract HTML Views: 99
PDF Downloads: 113
Total Views/Downloads: 456
Unique Statistics:

Full-Text HTML Views: 159
Abstract HTML Views: 71
PDF Downloads: 95
Total Views/Downloads: 325

Creative Commons License
© 2021 Alkhader et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the JDepartment of Oral Medicine and Surgery, Faculty of Dentistry, Jordan University of Science and Technology, Irbid, Jordan; Tel: +0795175583; E-mail:



The aim of the study was to evaluate the usefulness of hard palate measurements in predicting airway dimensions in patients referred for cone-beam CT (CBCT).

Materials and Methods:

Six hundred forty-three patients (239 males and 404 females) were examined by CBCT. Using dedicated CBCT software (Kodak CS 3D imaging version 3.8.6, Carestream, Rochester, NY, USA); different hard palate (palatal interalveolar length, palatal arch depth, maxillo-palatal arch angle, and alveolar width) and airway measurements (airway volume, minimum cross-sectional area, minimum anteroposterior distance, minimum right to left distance and airway length) were obtained and correlated using Pearson’s correlation coefficients and regression analysis.


Although the correlation between hard palate and airway measurements was weak (Pearson coefficient (r) < 0.40), there were significant (P < 0.05) additive effects for hard palate measurements in predicting airway dimensions. Maxillo-palatal arch angle was the only hard palate measurement that had no effect in predicting airway dimensions.


Hard palate measurements are considered useful in predicting airway dimensions in patients referred for CBCT.

Keywords: Hard palate, Airway, Cone beam CT, Measurements, Patients, Sleep disorders.


Several studies have explored the possible correlation between oro-pharyngeal measurements and craniofacial structures in different populations and in particular in subjects with sleep disorders [1-3]. For this purpose, various modalities were utilized, including cephalometric radiographic measurements and magnetic resonance imaging [4-6]. More recently, the use of three-dimensional (3D) craniofacial reconstruction imaging approaches has led to the widespread use of 3D imaging techniques for calculating and correlating volumes of facial bones and air cavities [7, 8] and for the assessment, diagnosis and treatment of sleep disorders, particularly Obstructive Sleep Apnea (OSA) [9, 10]. The early detection and treatment of OSA have been shown to be of paramount importance in reducing the risk of cardiovascular diseases and death as well as the frequency of strokes [11].

Although OSA has been addressed in the literature, a complete understanding of the pathophysiology and Upper Airway (UAW) anatomic specifications is yet to be reached. The coexistence of specific anatomic features and neuromuscular disorders appears to contribute to the narrowing and closure of the pharynx during sleep [12]. Many authors have shown that certain physical alterations (craniofacial, dental-bite, pharyngeal soft tissue, UAW size and shape) can be recognized in patients with OSA [13-15]. For instance, patients with OSA have narrowing in the oropharynx, usually at the level of the uvula–soft palate complex or the base of the tongue [16, 17]. Interestingly, several oral features were proposed to be useful in predicting those patients at risk of having UAW abnormalities. These features include; maxillary constriction and shallow palate, mandibular retrognathia, tooth crowding, retroclination of the anterior teeth and posterior cross-bite [18].

Therefore, dentists can play an important role in early diagnosis and referral of patients at risk of sleep disorders, as they come in close contact with the oral cavity in daily practice, and if well trained, they may be able to identify those who are at risk of OSA [19, 20]. More specifically, practitioners who use Cone Beam Computed Tomography (CBCT) technology are in a unique position to evaluate their patients for OSA [21-26]. In the paediatric population, pedodontists and orthodontists have the unique advantage of working with populations whose breathing disorders have not yet been diagnosed, and who are at a stage of development at which growth patterns are still easily modifiable for treatment of OSA [18].

Accordingly, this approach of engaging dentists in early detection and referral of patients at risk of breathing disorders could be enhanced if a relationship could be established between certain oral measurements on one hand, and the airway dimensions on the other hand. In this context, this study was designed to evaluate the usefulness of specific hard palate measurements in predicting airway dimensions in patients referred for CBCT.


2.1. Patients

In our cross-sectional retrospective study, images for all patients aged over 40 years who underwent CBCT between January 2011 and January 2020 for dental implant treatment and other dental purposes at our dental radiology clinic were retrieved and evaluated. Only CBCT images showing the hard palate and oropharyngeal airway with correct patient positioning, normal jaw alignment, and free of pathologies and artefacts were included in the study. Cases with severe alveolar bone resorption or unilateral bone loss were excluded from the study. The patients included in the study were 643 patients. The present study is part of a protocol (20/2019) that was approved by our research review board.

2.2. Cone Beam Computed Tomography Examination

A KODAK 9500 Cone Beam 3D System (Carestream, Rochester, NY) CBCT apparatus with flat-panel detector was used. CBCT scanning parameters were: 0.2-mm as a voxel size, 90 kV as a tube voltage, 10 mA as a tube current and 10.8s as an exposure time. The patient was asked to stop swallowing and to keep teeth in maximum intercuspation. The occlusal plane was parallel with the floor and the field of view was 15x9 cm.

2.3. Images

Using dedicated CBCT software (Kodak CS 3D imaging version 3.8.6, Carestream, Rochester, NY, USA), one calibrated oral radiologist (MA) with 12 years of experience with CBCT was responsible for drawing the path of the oropharyngeal airway from the posterior nasal spine to the superior border of the epiglottis on a midsagittal section (Fig. 1). The software subsequently and automatically generated the following values: airway volume (AV: cm3), minimum cross-sectional area (MCA: mm2), minimum anteroposterior distance (MAD: mm), and minimum right to left distance (MRD: mm). In addition to this, airway length (AL: mm) was manually measured by drawing a vertical line connecting the superior and inferior border of the oropharyngeal airway (Fig. 2).

Fig. (1). Mid-sagittal CBCT image showing the airway measurements obtained automatically by the software after drawing the path of oropharyngeal airway.

Fig. (2). Mid-sagittal CBCT image showing the airway length.

Fig. (3). Coronal CBCT image showing the had palate measurements obtained on mid-palatal section.

For hard palate measurements (Fig. 3), the following measurements were obtained following the examples of Akbay and Lim et al. [27, 28]:

(1) Palatal Interalveolar Length (PIL): Top-view length of the line from one side' alveolar crest to the same point of the other side’s alveolar arch.

(2) Palatal Arch Depth (PAD): The length of the line from the intersection of hard palates to the inter-alveolar line.

(3) Maxillopalatal Arch Angle (MPAA): The angle which is formed by the lines from the interpalatal’s mergence point to both crests of alveolar arches.

(4) Palatal arch depth/palatal inter-alveolar length (PAD/PIL): The ratio of hard palate depth to the inter-alveolar length.

(5) Alveolar Width (AW): The distance between right and left buccal alveolar bone

All of the hard palate measurements were obtained on a coronal section at mid-point of the hard palate length. The mid-point is the point located in the middle of the distance between anterior nasal supine and posterior nasal supine in the mid-sagittal plane (Fig. 4).

Fig. (4). Mid-sagittal CBCT image showing the hard palate length and mid-palatal section.

After 8 weeks, the same observer revaluated all of the airway and hard palate measurements. All images were evaluated on a high-definition liquid crystal display. The window settings were fixed for all cases.

2.4. Statistical Analysis

Data were described using means and were analysed using SAS 9.2 (SAS Institute, Cary, NC). Pearson’s correlation coefficient was used to determine the intra-rater correlation between first- and second-time measurements of the hard palate (PIL, PAD, PAD/PIL, MPAA, and AW) and airway (AV, MCA, MAD, MRD and AL) and the correlation between the hard palate and airway measurements. Independent samples t-test was used to compare the means of the variables between males and females. The interaction between different hard palate and airway measurements was tested using stepwise multivariate linear regression analysis. P < 0.05 was considered statistically significant.


This study included a total of 643 dental patients who were referred for CBCT (239 males and 404 females). Males had higher mean values for hard palate and airway measurements except for MPPA (Table 1). The differences in measurements were statistically significant except for MCA and MRD (t-test, P < 0.05).

The intra-rater correlations for hard palate and airway measurements were very strong (Pearson coefficient (r) ranged from .90-.98). Therefore, the two readings for each measurement were averaged to be used for further analysis. The correlation between average hard palate and average airway measurements was weak (Table 2).

Table 1. Summary Statistics for Each Parameter by Gender.
Parameter Female Male P-value*
Mean (Range) Standard Deviation Mean (Range) Standard Deviation
Age (years) 55 (40-83) 9.7 57.1 (40-96) 10.2 .009
AW (mm) 53.7 (36.9-65.3) 4.6 55.4 (42.6-70.3) 4.8 <.0001
PIL (mm) 37.1 (28.6-45.7) 3.3 38 (29-48.6) 3.8 0.0024
PAD (mm) 13.2 (7.5-19) 2.3 14.3 (8.1-22.3) 2.5 <.0001
MPAA (degree) 109.6 (80-135) 10.5 106.3 (75-136) 11 0.0002
PAD/PIL (ratio) 0.4 (0.2-0.6) 0.1 0.4 (0.2-0.7) 0.1 0.0002
AV (cm3) 10.4 (2.7-31.2) 4.4 13.7 (4.4-39.6) 5.3 <.0001
MCA (mm2) 126.7 (17.6-444.5) 80.8 132.9 (20.6-487.9) 78.1 0.3401
MAD (mm) 8.5 (3.2-20.8) 3.1 9.2 (4-18.4) 3 0.0042
MRD (mm) 20.9 (7.8-37.4) 6 21.4 (6.6-39) 6 0.2726
AL (mm) 47.8 (33.2-64.3) 5.8 57.8 (39-80.1) 6.4 <.0001
AW: Alveolar width. PIL: Palatal interalveolar length. PAD: Palatal arch depth. MPAA: Maxillo-palatal arch angle. AV: Airway volume. MCA: Minimum cross-sectional area. MAD: Minimum anteroposterior distance. MRD: Minimum right to left distance. AL: Airway length. *P-value was determined by running t-test.
Table 2. Correlation Matrix of variables.
AW Pearson r 0.06 -0.02 0.06 -0.1 0.12
P-value 0.13 0.58 0.11 0.2 0
PIL Pearson r 0.1 0.04 0.12 0 0.08
P-value 0.01 0.29 0 0.6 0.05
PAD Pearson r 0.22 0.07 0.12 0.1 0.26
P-value <0.0001 0.07 0 0 <0.0001
MPAA Pearson r -0.16 -0.05 -0.06 -0.1 -0.2
P-value <0.0001 0.21 0.14 0.1 <0.0001
PAD/PIL Pearson r 0.16 0.06 0.06 0.1 0.2
P-value <0.0001 0.16 0.14 0 <0.0001
Table 3. Results of the significant stepwise regression for each variable.
Parameter Parameter Estimate Standard Error P-value Overall Model
Intercept 8.92 1.8 <.0001 <0.0001
PAD 0.33 0.08 <.0001
Age 0.049 0.02 0.008
Gender -2.83 0.39 <.0001
Intercept 131.64 25.66 <.0001 0.0369
PAD 2.19 1.28 0.09
Age -0.58 0.32 0.07
Intercept -7.20 6.12 0.24 <0.0001
PIL 0.41 0.16 0.01
PAD -0.73 0.42 0.08
PAD/PIL 31.30 15.58 0.045
Gender -0.48 0.26 0.06
Intercept 23.58 2.74 <0.0001 0.0051
AW -0.12 0.05 0.02
PAD 0.30 0.10 0.003
Intercept 50.55 2.16 <0.0001 <0.0001
PAD/PIL 15.78 3.14 <0.0001
Age 0.18 0.02 <0.0001
Gender -9.23 0.47 <0.0001
AW: Alveolar width. PIL: Palatal interalveolar length. PAD: Palatal arch depth. AV: Airway volume. MCA: Minimum cross-sectional area. MAD: Minimum anteroposterior distance. MRD: Minimum center to center distance. AL: Airway length.

In order to evaluate the predictability of airway dimensions using hard palate measurements and demographics, we performed stepwise multivariate linear regression analysis (Table 3). There were significant additive effects for the PAD in predicting airway dimensions except for AL. While, a significant additive effect was shown for the: PIL in predicting MAD, AW in predicting MRD and the ratio of PAD/PIL in predicting MAD and AL. MPAA was the only hard palate measurement that had no effect in predicting airway dimensions.


OSA affecting different populations has been shown to be associated with age [29] and different anatomical abnormalities like hard palate depth and width [18-21, 26, 30]. Therefore, studying the anatomical characteristics of the hard palate by dentists in their clinic or by oral radiologists using CBCT images, will help in the identification of patients at risk of developing OSA.

In those previous studies [19, 20, 26, 30], the increase in PAD or the presence of deep palate was a common observation in OSA patients and increased the risk of developing OSA. Moreover, the increase in PAD was associated with posterior septal deviation [27]; this was also a significant finding in patients with OSA [30]. On the other hand, the presence of a narrow palate which can lead to low tongue position and narrowing of retroglossal airway space [26], is also a common and significant finding in patients with OSA [18-21, 26]. To overcome these abnormalities in hard palate dimensions, lowering and widening the palate by rapid maxillary expansion was shown to be successful in expanding the airway of adults with OSA [31].

Regarding CBCT airway measurements, most of them were formulated and investigated in relation to OSA by Tikku, Buchanan, Ogawa and Momany et al. [22-25]. In OSA patients, smaller measurements were obtained except for AL and MAD [23, 25]. To the best of our knowledge, there is no published research showing the usefulness of hard palate measurements in predicting airway dimensions. In contrast to airway measurements, palatal measurements can be easily obtained by using free CBCT software and even from a scan showing only the maxilla.

According to Ruangsri et al. [20], palatal depth and width can be classified into following: shallow palatal depth (<15 mm), normal depth (15–20 mm), deep palatal depth (>20 mm), narrow palatal width (<30 mm), normal width (30-42 mm), and large palatal width (>42 mm). However, we were unable to divide our patients following the same classification, since we used different methodologies for different populations.

The results of the current study imply that the dentist can early predict dimensions of the airway of the dental patients by calculating simple measurements of the hard palate in the clinic. This can be done directly inside the patient mouth or on CBCT images. Having only a CBCT image for the maxilla will be enough for getting the measurements. Patients with narrow dimensions of the airway can be referred to a sleep medicine specialist, this will help in identifying and treating patients with sleep apnea at an early stage.

Although this pilot study was conducted with a specific protocol on a specific ethnic group, its validity can be tested in future studies by correlating the CBCT measurements with the gold standard used to diagnose sleep disorders (polysomnogram study).


In conclusion, hard palate measurements are considered useful in predicting airway dimensions in patients referred for CBCT.


The present study is part of a protocol (20/2019) which was approved by Research Review Board of Jordan University, Jordan.


No animals were used in this research. All human research procedures were followed in accordance with the ethical standards of the committee responsible for human experimentation (institutional and national), and with the Helsinki Declaration of 1975, as revised in 2013.


Informed consent was obtained from all patients before CBCT examination.


The data supporting the findings of the article is available from the corresponding author [M. K.] upon reasonable request.




The author declares no conflict of interest, financial or otherwise.


Declared none.


[1] Battagel JM, L’Estrange PR. The cephalometric morphology of patients with obstructive sleep apnoea (OSA). Eur J Orthod 1996; 18(6): 557-69.
[2] Tangugsorn V, Krogstad O, Espeland L, Lyberg T. Obstructive sleep apnea (OSA): A cephalometric analysis of severe and non-severe OSA patients. Part I: Multiple comparison of cephalometric variables. Int J Adult Orthodon Orthognath Surg 2000; 15(2): 139-52.
[3] Cillo JE Jr, Thayer S, Dasheiff RM, Finn R. Relations between obstructive sleep apnea syndrome and specific cephalometric measurements, body mass index, and apnea-hypopnea index. J Oral Maxillofac Surg 2012; 70(4): e278-83.
[4] Eslami E, Katz ES, Baghdady M, Abramovitch K, Masoud MI. Are three-dimensional airway evaluations obtained through computed and cone-beam computed tomography scans predictable from lateral cephalograms? A systematic review of evidence. Angle Orthod 2017; 87(1): 159-67.
[5] Okubo M, Suzuki M, Horiuchi A, et al. Morphologic analyses of mandible and upper airway soft tissue by MRI of patients with obstructive sleep apnea hypopnea syndrome. Sleep 2006; 29(7): 909-15.
[6] Chi L, Comyn F-L, Mitra N, et al. Identification of craniofacial risk factors for obstructive sleep apnoea using three-dimensional MRI. Eur Respir J 2011; 38(2): 348-58.
[7] Dah-Jouonzo H, Baron P, Faure J, Treil J, Borianne P. 3DVolumetric measurements of maxillary basal bones and facial air cavities using 3D imagery. Int Orthod 2005; 3: 269-89.
[8] Chen H, van Eijnatten M, Aarab G, et al. Accuracy of MDCT and CBCT in three-dimensional evaluation of the oropharynx morphology. Eur J Orthod 2018; 40(1): 58-64.
[9] Papadopoulos MA, Christou PK, Christou PK, et al. Three-dimensional craniofacial reconstruction imaging. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002; 93(4): 382-93.
[10] Zhao X, Liu Y, Gao Y. Three-dimensional upper-airway changes associated with various amounts of mandibular advancement in awake apnea patients. Am J Orthod Dentofacial Orthop 2008; 133(5): 661-8.
[11] Marin JM, Carrizo SJ, Vicente E, Agusti AG. Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: An observational study. Lancet 2005; 365(9464): 1046-53.
[12] Iwasaki T, Hayasaki H, Takemoto Y, Kanomi R, Yamasaki Y, Himeji Y. Oropharyngeal airway in children with Class III malocclusion evaluated by cone-beam computed tomography. Am J Orthod Dentofacial Orthop 2009; 136(3): 318.e1-9.
[13] Woodson BT. Examination of the upper airway. Oral Maxillofac Surg Clin North Am 1995; 7: 257-67.
[14] Deegan PC, McNicholas WT. Predictive value of clinical features for the obstructive sleep apnoea syndrome. Eur Respir J 1996; 9(1): 117-24.
[15] Woodson BT. Predicting which patients will benefit from surgery for obstructive sleep apnea: The ENT exam. Ear Nose Throat J 1999; 78(10): 792-795, 798-800.
[16] Bradley TD, Brown IG, Grossman RF, et al. Pharyngeal size in snorers, nonsnorers, and patients with obstructive sleep apnea. N Engl J Med 1986; 315(21): 1327-31.
[17] Crumley RL, Stein M, Gamsu G, Golden J, Dermon S. Determination of obstructive site in obstructive sleep apnea. Laryngoscope 1987; 97(3 Pt 1): 301-8.
[18] Steffy DD, Tang CS. Radiographic Evaluation of Sleep-Disordered Breathing. Radiol Clin North Am 2018; 56(1): 177-85.
[19] Kale SS, Kakodkar P, Shetiya SH. Assessment of oral findings of dental patients who screen high and no risk for obstructive sleep apnea (OSA) reporting to a dental college - A cross sectional study. Sleep Sci 2018; 11(2): 112-7.
[20] Ruangsri S, Jorns TP, Puasiri S, Luecha T, Chaithap C, Sawanyawisuth K. Which oropharyngeal factors are significant risk factors for obstructive sleep apnea? An age-matched study and dentist perspectives. Nat Sci Sleep 2016; 8: 215-9.
[21] Bruwier A, Poirrier R, Albert A, et al. Three-dimensional analysis of craniofacial bones and soft tissues in obstructive sleep apnea using cone beam computed tomography. Int Orthod 2016; 14(4): 449-61.
[22] Tikku T, Khanna R, Sachan K, Agarwal A, Srivastava K, Lal A. Dimensional and volumetric analysis of the oropharyngeal region in obstructive sleep apnea patients: A cone beam computed tomography study. Dent Res J (Isfahan) 2016; 13(5): 396-404.
[23] Buchanan A, Cohen R, Looney S, Kalathingal S, De Rossi S. Cone-beam CT analysis of patients with obstructive sleep apnea compared to normal controls. Imaging Sci Dent 2016; 46(1): 9-16.
[24] Ogawa T, Enciso R, Shintaku WH, Clark GT. Evaluation of cross-section airway configuration of obstructive sleep apnea. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007; 103(1): 102-8.
[25] Momany SM, AlJamal G, Shugaa-Addin B, Khader YS. Cone beam computed tomography analysis of upper airway measurements in patients with obstructive sleep apnea. Am J Med Sci 2016; 352(4): 376-84.
[26] Yu C, Ahn HW, Kim SH. Three-dimensional morphological evaluation of the hard palate in Korean adults with mild-to-moderate obstructive sleep apnea. Korean J Orthod 2018; 48(3): 133-42.
[27] Akbay E, Cokkeser Y, Yilmaz O, Cevik C. The relationship between posterior septum deviation and depth of maxillopalatal arch. Auris Nasus Larynx 2013; 40(3): 286-90.
[28] Lim HM, Park YC, Lee KJ, Kim KH, Choi YJ. Stability of dental, alveolar, and skeletal changes after miniscrew-assisted rapid palatal expansion. Korean J Orthod 2017; 47(5): 313-22.
[29] Alkhader M, Geijer M. Comparative analysis of the oropharyngeal airway in patients aged over 40 years: A cone beam computed tomography study. Eur J Gen Dent 2019; 8: 76-9.
[30] Zonato AI, Martinho FL, Bittencourt LR, de Oliveira Camponês Brasil O, Gregório LC, Tufik S. Head and neck physical examination: Comparison between nonapneic and obstructive sleep apnea patients. Laryngoscope 2005; 115(6): 1030-4.
[31] Vinha PP, Thuler ER, de Mello-Filho FV. Effects of surgically assisted rapid maxillary expansion on the modification of the pharynx and hard palate and on obstructive sleep apnea, and their correlations. J Craniomaxillofac Surg 2020; 48(4): 339-48.