Dentomaxillofacial Radiology (2023) 0, 20220346 © 2023 The Authors. Published by the British Institute of Radiology under the terms of the Creative Commons Attribution-NonCommercial 4.0 Unported License http://creativecommons.org/licenses/ by-nc/4.0/, which permits unrestricted non-commercial reuse, provided the original author and source are credited. birpublications.org/dmfr RESEARCH ARTICLE Correlation between the three-dimensional maxillomandibular complex parameters and pharyngeal airway dimensions in different sagittal and vertical malocclusions 1,2,3 Majedh Abdo Ali Al-Somairi, 2Yi Liu, 4Abeer A. Almashraq, 3,5Bushra S. Almaqrami, 1 Lina H. Alshoaibi, 1,2,3Enas S. Alyafrusee, 1Barakat Al-Tayar, 1Xiaoli An and 6,7Maged S. Alhammadi 1 Department of Orthodontics, School of Stomatology, Lanzhou University, Lanzhou, China; 2Department of Orthodontics, School of Stomatology, China Medical University, Shenyang, China; 3Department of Orthodontics and Dentofacial Orthopedics, Faculty of Dentistry, Ibb University,, Ibb, Republic of Yemen; 4Department of Pre-Clinical Oral Health Sciences, College of Dental Medicine, QU Health, Qatar University, Doha, Qatar; 5Department of Orthodontics, Ningbo Dental Hospital, Ningbo, Zhejiang, China; 6Orthodontics and Dentofacial Orthopedics, Department of Preventive Dental Sciences, College of Dentistry, Jazan University, Jazan, Saudi Arabia; 7Postgraduate Orthodontic Program, Department of Orthodontics, Pedodontics and Preventive Dentistry, Faculty of Dentistry, Sana’a University, Sana'a, Republic of Yemen Objectives: This study aimed to determine the three-dimensional (3D) correlation between maxillomandibular complex parameters and pharyngeal airway dimensions in different sagittal and vertical malocclusions. Methods: This retrospective cross-sectional study included the CBCT scans of 368 patients with a mean age of 23.81 ± 3.01 years. The patients were classified into three groups (skeletal Class I, II, and III). Each class group was divided into three subgroups based on vertical growth patterns (hypo-, normo-, and hyperdivergent). The maxillomandibular complex was evaluated in the three planes using 16 skeletal measurements. Naso-, oro-, hypo-, and total pharyngeal airway spaces were assessed in terms of width, volume, surface area, and minimum constricted area (MCA). Two-way ANOVA followed by the Bonferroni post-hoc test were used. Results: The nasopharyngeal airway space was significantly lowest regarding sagittal and lateral widths in the skeletal Class III patients, the lowest volume and surface area were in hyperdivergent patients, and MCA was the highest in Class II and hypodivergent patients. The oro- and hypopharyngeal sagittal width, volume, surface area, and MCA were the lowest in the hyperdivergent patients, and oropharyngeal lateral width and hypopharyngeal sagittal width were the highest in skeletal Class III. The total pharyngeal volume, surface area, and MCA were the lowest in the hyperdivergent patients, and skeletal Class II patients had the lowest MCA. Conclusions: The pharyngeal airway dimensions differ with various sagittal and vertical malocclusions. These differences could apply to diagnosis, treatment planning, and possible changes following orthodontic/orthopedic or surgical treatment. Dentomaxillofacial Radiology (2023) 0, 20220346. doi: 10.1259/dmfr.20220346 Cite this article as: Al-Somairi MAA, Liu Y, Almashraq AA, Almaqrami BS, Alshoaibi LH, Alyafrusee ES, et al. Correlation between the three-dimensional maxillomandibular complex parameters and pharyngeal airway dimensions in different sagittal and vertical malocclusions. Dentomaxillofac Radiol (2023) 10.1259/dmfr.20220346. Keywords: Cone-beam computed tomography; Growth; Malocclusion; Pharynx Correspondence to: Xiaoli An, E-mail: anxl@lzu.edu.cn Received 21 October 2022; revised 23 December 2022; accepted 26 December 2022; published online 24 January 2023 2 of 14 Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al Introduction The upper airway is a hollow space surrounded by hard and soft tissue structures. This complex and highly dynamic structure contributes to various actions like breathing, swallowing, and speaking; thus, it is critical to assess this dynamic space properly.1 Craniofacial growth and development involve complex mechanisms and multifactorial structures. Since the early 20th century, researchers have studied the relationship between craniofacial structures and respiratory functions.1 The most widely accepted theory for craniofacial growth and development is Moss’s functional matrix theory, which notes that most craniofacial growth and development is devoted to regulating the functional behavior of the surrounding soft tissues.2 Angle et al1 proposed that the function and anatomy of the pharyngeal airway strongly influence craniofacial growth and development. Consequently, any discrepancies in normal respiration through active craniofacial development can result in speech abnormalities, abnormal craniofacial development, and dental malocclusion. Previous studies have linked skeletal malocclusion to airway morphology changes and vice versa.3 Therefore, pharyngeal airway evaluation is important in diagnosing positional and structural dentofacial patterns. Through the extensive use of CBCT and advancement in medical care, pharyngeal airway evaluation has recently received much attention in the orthodontics.4 Several studies have evaluated airway measurements and their effects on craniofacial growth and development; some of these studies rely on lateral cephalogram (LC) analysis,3,5–9 while some are based on many CBCT radiographic images.10–23 CBCT allows the three-dimensional (3D) visualization and measurement of complex pharyngeal airway anatomy with less exposure to radiation and highly precise multiplanar and volumetric measurements of the pharyngeal airways.24 Figure 1 The 3D coordinate system. (a) The midsagittal plane constructed by the nasion and basion point and incisive foramen. (b) The horizontal plane: constructed by the right and left porions and the right orbitale. (c) The vertical plane constructed by the basion point and perpendicular to the horizontal and midsagittal plane. Dentomaxillofac Radiol, 0, 20220346 birpublications.org/dmfr CBCT studies in this context have yielded inconsistent and contradictory findings.10–16,18–22 The primary reasons for these discrepancies include inconsistent methodologies, variations in airway measurement sites, and study sample diversity.25 Differences in such studies when assessing the airway during variable growth periods,12,19 taking malocclusion into account, disregarding the impact on airway measurements,14,22 or there are limited CBCT studies to evaluate sagittal and vertical craniofacial dimensions and ignoring the transverse dimension,12,19 two multiplanar image-based segmentation14 and airway saturation value was not being considered.26 The associations between the maxillary and mandibular sagittal and vertical positions significantly impact the pharyngeal airway, with few reports about the detailed offending dimension in the 3D complex region.21 The current study aimed to minimize these variations by making a comprehensive case selection, presentation, and pharyngeal airway assessment; this study aimed to determine the 3D correlation between the maxillomandibular complex parameters and the pharyngeal airway dimensions in different sagittal and vertical malocclusions. Methods Sample selection This retrospective cross-sectional study was approved by the ethics committee of the Hospital of Stomatology, Lanzhou University (No: LZUKQ-2019-056), and written informed consent was obtained from all participants upon registration in the institutional database. The inclusion criteria were as follows: (1) aged 18–28 years old, (2) normal nasal breathing, (3) normal body mass index (BMI）, (4) craniocervical inclinations were limited from 90° to 110° to minimize the head posture impact on pharyngeal airway measurements, and (5) good quality CBCT images. The exclusion criteria included: (1) history of temporomandibular joint disorders symptoms, (2) previous orthodontic treatment or orthognathic surgery, and (3) skeletal abnormalities in the craniofacial region. Sample size The sample size was determined using the G*power 3.0.10 software with an α level of 0.05 and a power level equal to 90%. The estimate is based on the study by Paul et al,27 where the mean oropharyngeal volume was 13240.1 ± 5112.1 and 7816.9 ± 2767.0 mm3 for skeletal Class I and II, respectively. A study by Wang et al28 revealed that the mean glossopharyngeal volume was 5997.06 ± 1674.9 and 4412.97 ± 972.9 mm3 for average and high growth patterns, respectively. The resulting sample size was 11 and 14 patients in each group. The minimum number of subjects included in this study in any subgroup was 40. Three-dimensional CBCT protocol CBCT images were acquired using the I-CAT Image System (Imaging Sciences International Inc. Hatfield) Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 3 of 14 Table 1 Definitions of anatomical landmarks, reference lines and planes, and pharyngeal airway borders Anatomical Landmarks Reference line and planes Name Abbreviation Definition Nasion Sella Basion N S Ba Subspinale Incisive foramen A IF Posterior nasal spine Right/Left Jugular PNS JR/JL Supramentale Menton Gnathion Right/Left Porion Right/Left Orbitale B Me Gn PoR/L OrR/ L Right/Left Gonion GoR/ L Right/Left Condylion CoR/L second cervical vertebra third cervical vertebra second cervical vertebra third cervical vertebra Nasopharyngeal anterior and posterior points Oropharyngeal anterior and posterior points Hypopharyngeal anterior and posterior points Nasopharyngeal left and right lateral points Oropharyngeal left and right lateral points Hypopharyngeal left and right lateral points Horizontal plane C2a C3a C2p C3p NP (A/P) Midsagittal plane Vertical plane Nasion perpendicular plane MSP VP N-FH Prep Sella-nasion line Cervical line Mandibular plane Posterior nasal spine plane second cervical vertebra plane third cervical vertebra plane SN Line C2p-C3p line MP PSN Plane C2 Plane C3 Plane That represents of nasofrontal structure in the midline The midpoint of the sella turcica The most inferoposterior of the foramen magnum is in the midline of the skull base The most concavity point in the upper labial alveolar process The center of incisive foramen centered mediolateral, exists posterior to the central incisors at maxillary mid palatine The distal midpoint of the posterior nasal spine of the palatine bone That represents a bilateral point on the jugular process at connecting the maxilla tuberosity outline and the zygomatic buttress The deepest point of the mandibular symphysis The most inferior point on mandibular symphysis The most anteroinferior aspect of the mandibular symphysis The right or left most superior point of the external auditory meatus The lowest point on each orbit's right and left is at the infraorbital margin. The midpoint at the gonial angle is traced by bisecting the mandible's posterior and inferior borders on each angle The most posterosuperior point on the outline of the right/left mandibular condyle The second cervical vertebra's most anteroinferior point The third cervical vertebra's most anteroinferior point The second cervical vertebra's most posteroinferior point The third cervical vertebra's most posteroinferior point The most anterior (NP-A) and posterior points (NP-P) in the PNS plane are in the axial view The most anterior (OP-A) and posterior points (OP-P) in the C2 plane are in the axial view The most anterior (HP-A) and posterior points (HP-P) in the C3 plane are in the axial view The most lateral left (NP-L) and lateral right (NP-R) points in the PNS plane in the axial view The most lateral left (OP-L) and lateral right (OP-R) points in the C2 plane in the axial view The most lateral left (HP-L) and lateral right (HP-R) points in the C3 plane in the axial view Passed through the right and left part (Po-R/L) and the right orbital portion (Or-R) Passed through points N, Ba, and IF Passed through the basion point and is perpendicular to the FH Passed through nasion (N), representing a true vertical reference plane perpendicular to FH The line passes between the S and N points The line passes between the C2p and C3p points Defined by three landmarks: gnathion, right, and left gonion Passed through PNS, describing and paralleling the plane of the FH Passed through C2, describing and paralleling the plane of the FH Passed through C3 represents and is parallel to the FH OP(A/P) HP(A/P) NP(L/R) OP(L/R) HP(L/R) FH (Continued) birpublications.org/dmfr Dentomaxillofac Radiol, 0, 20220346 Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 4 of 14 Table 1 (Continued) Name Pharyngeal airway borders Abbreviation The anterior border of the NP The inferior border of the NP Definition Passed through the PNS point perpendicular to the FH Parallel to the FH through the PNS and perpendicular to the sagittal plane The inferior border of the NP Parallel to the palatal plane intersecting the most anteroinferior point of the second cervical vertebrae (C2a) The inferior border of the OP Parallel to the palatal plane intersecting the most anteroinferior point of the third cervical vertebrae (C3a) The posterior wall of the pharyngeal The superior border of the OP The inferior border of the OP The superior border of the HP The inferior border of the HP The posterior border with the following acquisition parameters: field of view (17.0 × 13.0 cm); 120 kV; 18.54 MAs, 8.9 exposure time, and the image voxel size was 0.3 mm. The scanning was done with maximum intercuspation, standardized head position, the Frankfort plane parallel to the floor, and no swallowing. The patients were instructed to swallow once before each exposure and hold their breath during the scan. The DICOMs (Digital Imaging and Communications in Medicine）of the CBCT images were collected and then imported into InVivo 6.0.3 (Anatomage, San Jose, CA) for skeletal measurements (maxilla and mandible). In contrast, the Dolphin 11.8 system (Dolphin Imaging and Management Solutions, Chatsworth, CA) was used for pharyngeal airway segmentation and measurements. The CBCT images were reoriented using coordinate system orientation, as shown in Figure 1, depending on the central landmarks chosen by Nasion, Incisive Foramen, and Basion; Orbital and Porion determined the horizontal landmarks, and the vertical landmark was according to the Basion point.29,30 are shown in Table 1, and pharyngeal airway space measurements are summarized in Table 2. The naso-, oro-, hypo-, and total pharyngeal airway space measurements are shown in Figures 2–5, respectively. A sinus/ airway module was used for the segmentation protocol, and the slice was chosen so that the optimum airway view coincided with the midsagittal plane.18 The pharyngeal airway area was then marked with seed points used to expand the airway. As recommended in previous studies, the sensitivity was set at 72 or 73.27,33 The chipping boundaries were added to restrict this extension. This method combines automated and manual segmentation and exploits the strengths of each segment. 54 CBCTs were chosen randomly and measured independently by two examiners over two 2-week periods to ensure the reading’s reliability. All measurements were performed under the supervision and guidance of oral and maxillofacial radiologists with more than 10 years of experience. Skeletal measurements The skeletal anatomical landmarks, reference lines, and planes are shown in Table 1 and the skeletal measurements are shown in Table 2. The subgroup distribution was evaluated using four measurements depending on Chinese norms; 31,32 the ANB° and AF-BF mm, to determine whether the patient classified as skeletal Class I, II, and III malocclusions where 0.7 ° ≤ ANB ≤ 4.7° and 0.8 mm ≤ AF B ≤ 6.4 mm were considered skeletal Class I, ANB > 4.7° and AF-BF > 6.34 mm were considered skeletal Class II, and ANB < 0.7° and AF-BF > 0.8 mm were considered as skeletal Class III. For determination of vertical pattern; GoGnSN° and SGo/NMe% were used to determine whether the patient belonged to hypo-, normo-, and hyperdivergent groups where 27.3° < GoGn SN < 37.7° and 62% < SGo/ NMe < 68% considered normodivergent, GoGn-SN ≥ 37.7° and SGo/NMe ≤ 62% considered hyperdivergent, and GoGn-SN ≤ 27.3° and SG/NMe ≥ 68% considered hypodivergent growth patterns. Statistical analysis The IBM SPSS Statistics, v. 24 for Windows (IBM Corp., Armonk, NY) was used to analyze the data. The intraclass correlation coefficient (ICC) and absolute and relative technical measurement errors (TEM and rTEM) were used to evaluate the reproducibility and reliability of skeletal and pharyngeal airway measurements. The skewness test was used to determine the normality of the data. Descriptive statistics were calculated and presented, including each variable’s standard and mean deviations. Two-way ANOVA was used, and the Bonferroni post-hoc test was used when significant. p ≤ 0.05 was chosen as the statistical significance level. Pharyngeal airway measurements The pharyngeal anatomical landmarks, reference lines and planes, pharyngeal airway borders are shown in Dentomaxillofac Radiol, 0, 20220346 birpublications.org/dmfr Results In total, 368 patients were involved in the study. Table 3 shows the chosen patients' age, sagittal and vertical skeletal relationship characteristics. Intra- and interexaminer reliability were high, where both intra- and interobserver R and ICC values were higher than 0.95, presented in Table 4. Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 5 of 14 Table 2 The skeletal and pharyngeal airway measurements used in this study Measurements Jaws relationship Sagittal Vertical Cranio-cervical inclination Sagittal position Maxilla Sagittal position Effective length Mandible Nasopharyngeal Oropharyngeal Hypopharyngeal Total pharyngeal Name Definition ANB ° AF-BFmm SGo /NMe % The angle between three points, A, N, and B points The line between the A-FH and B-FH The ratio between the posterior facial height (S-Go) and the anterior facial height (N-Me) An angle between the S-N line and the MP An angle between the S-N line and the C2p-C3p line The angle between three points S, N, and B. A line between point A and the NV Plane An average of the bilateral linear distance between Co and A points. The line between JR and JL points A line from point A to FH plane The angle between three points S, N, and B. GoGn-SN ° OP/SN ° SNA ° A-NV mm Co-A mm Width Vertical position Sagittal position JL-JR mm A-FH mm SNB° Sagittal position Body length B-NV mm Gn –Go mm Effective length Co-Gn mm Width Vertical position Sagittal width GoR-GoL mm B-FH mm NP(A-P) mm Lateral width NP(L-R) mm Volume NP-V mm3 Area NP-A mm2 Minimum constriction area Sagittal width Lateral width Volume NP-MCA mm2 OP (A-P) mm OP (L-R) mm OP-V mm3 Area OP-A mm2 Minimum constriction area Sagittal width Lateral width Volume OP-MCA mm2 HP (A-P) mm HP (L-R) mm HP-V mm3 Area Minimum constriction area Volume HP-A mm2 HP-MCA mm2 TP-V mm3 Area TP-A mm2 Minimum constriction area TP-MCA mm2 The line between point B and the NV plane The average of the bilateral linear distance from the Go and Gn points An average of the bilateral linear distance from the Co and Gn points A line from the GoR and GoL points A line from B point and horizontal plane The line between NPA and NPP points at the PNS plane in axial view The line between NPL and NPR points at the PNS plane in axial view Measured between R point and PNS plane at the midsagittal plane The area at the midsagittal plane between the R point and PNS plane Nasopharyngeal airway minimum constricted area The line between OPA and OPP at the C2plane in axial view The line between OPL and OPR at the C2plane in axial view Measured between PNS and C2 planes in sagittal, coronal and axial view Measured between PNS and C2 planes at the midsagittal plane Oropharyngeal airway minimum constricted area The line between HPA and HPP at the C3 plane in axial view The line between HPL and HPR at the C3 plane in axial view Measured between C2 and C3 planes in sagittal, coronal and axial view Measured between C2 and C3 planes at the midsagittal plane Hypopharyngeal airway minimum constricted area Measured between the roof of nasopharyngeal and C3 plane at the midsagittal plane Measured between the roof of nasopharyngeal and C3 plane at the midsagittal plane Total pharyngeal airway minimum constricted area * ° (degree), % (ratio measurements), mm (millimeters), mm2 (square millimeters), and mm3 (cubic millimeters) The descriptive analysis and statistical significance value for the skeletal, naso-, oro-, hypo-, and total pharyngeal airway space measurements are presented in Tables 5–9, respectively. Table 6 shows there were statistical differences for nasopharyngeal measurements; the sagittal NP (A-P) mm and lateral NP (L-R) mm widths were the lowest in the skeletal Class III of 25.64 ± 3.10 mm and 36.64 birpublications.org/dmfr Dentomaxillofac Radiol, 0, 20220346 6 of 14 Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al Figure 2 Nasopharyngeal airway. (a) Surface area (sagittal view). (b) Surface area (coronal view). (c) Surface area (axial view). (d) Airway area (multiplanar view) and minimal constricted area. (e) Airway volume (sagittal view). (f) Airway volume (coronal view). (g) Airway volume (axial view). (h) Sagittal width of nasopharyngeal NP (A-P). (i) Lateral width of nasopharyngeal NP (L-R). ± 5.49 mm respectively; the volumetric measurements NP-V mm3 and surface area NP-A mm2 were the lowest in the hyperdivergent group of 6398.83 ± 1327.42 mm3,and 246.40 ± 44.16 mm3 respectively, and minimum constriction area MCA mm2 was the highest in Class II and hypodivergent patients of 36.43 ± 17.57 mm2 and 24.85 ± 13.43 mm2 respectively. Concerning the oropharyngeal measurements in Table 7, oropharyngeal sagittal width OP (A-P) mm, lateral width OP (L-R) mm, volume OP-V mm,3 surface area OP-A mm,2 and minimum constriction area MCA mm2 were significantly lower in the hyperdivergent patients than the relative’s groups of, 12.12 ± 2.36 mm, 28.94 ± 4.95 mm, 14255.67 ± 3238.50 mm³, 517.87 ± 113.80 mm2, and 49.06 ± 18.31 mm2 respectively, and sagittal width OP (A-P) mm was significantly higher in patients with skeletal Class III malocclusion of 13.71 ± 2.93 mm. For the statistically different hypopharyngeal measurements presented in Table 8, sagittal width HP (A-P) mm, volume HP-V mm3, surface area HP-A mm2, and minimum constriction area MCA mm2 were the lowest in the hyperdivergent patients of 14.86 ± 2.24 mm, 4813.95 ± 1239.28 mm3, 180.43 ± 33.25 mm2 and 36.28 ± 16.32 mm2 respectively, and lateral width was highest in skeletal Class III malocclusion of 33.42 ± 3.62 mm. Figure 3 Oropharyngeal airway. (a) Surface area (sagittal view). (b) Surface area (coronal view). (c) Surface area (axial view). (d) Airway area and minimum constricted area (multiplanar view). (e) Airway volume (sagittal view). (f) Airway volume (coronal view). (g) Airway volume (axial view). (h) Sagittal width of oropharyngeal OP (A-P). (i) Lateral width of oropharyngeal OP (L-R). Dentomaxillofac Radiol, 0, 20220346 birpublications.org/dmfr Figure 4 Hypopharyngeal airway. (a) Surface area (sagittal view). (b) Surface area (coronal view). (c) Surface area (axial view). (d) Airway area and minimum constricted area (multiplanar view). (e) Airway volume (sagittal view). (f) Airway volume (coronal view). (g) Airway volume (axial view). (h) Sagittal width of hypopharyngeal OP (A-P). (i) Lateral width of hypopharyngeal OP (L-R). Table 9 showed there were statistically significant differences in total pharyngeal airway space volume TP-V mm3 and surface area TP-A mm2; both were lowest in the hyperdivergent group, 26003.60 ± 5343.68 mm3, and 944.36 ± 127.64 mm2 respectively, and minimum constriction area MCA mm2 was the lowest in the hyperdivergent and Class II patients of 42.60 ± 13.01 mm2 and 41.13 ± 11.50 mm2 repectively. Discussion Breathing is based on the airway’s anatomical dimensions. Several studies have shown that changes in skeletal patterns may predispose individuals to upper airway space obstruction.34 Therefore, evaluating patients’ airway dimensions among various sagittal/vertical craniofacial structures is critical to achieve orthodontic/ orthognathic treatment objectives, esthetics, and function during treatment. Previous studies are inconclusive regarding the effect of craniofacial patterns; thus, we aimed to improve field awareness by controlling for known variables. Many studies have reported that head posture influences airway size and morphology.35 To decrease the impact of head posture, all patients' craniocervical inclinations were between 90° and 110°.15,36 Figure 5 Total pharyngeal airway (a) Surface area (sagittal view). (b) Surface area (coronal view). (c) Surface area (axial view). (d) Airway area and minimal constricted area (multiplanar view). (e) Airway volume (sagittal view). (f) Airway volume (coronal view). (g) Airway volume (axial view). Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 7 of 14 Table 3 The study sample distribution among groups Facial growth Age Hypodivergent Normodivergent Hyperdivergent Total ANB° AF-BF mm GoGn-SN ° S-Go/N-Me % OPT/SN ° BMI Kg/m2 Hypodivergent Normodivergent Hyperdivergent Total Hypodivergent Normodivergent Hyperdivergent Total Hypodivergent Normodivergent Hyperdivergent Total Hypodivergent Normodivergent Hyperdivergent Total Hypodivergent Normodivergent Hyperdivergent Total Hypodivergent Normodivergent Hyperdivergent Total Group I Group II Group III Class I Mean ± SD 24.03 ± 2.73 N=(42) 23.35 ± 2.87 N=(42) 24.53 ± 2.67 N=(40) 23.96 ± 2.78 N=(124) 2.53 ± 1.08 3.02 ± 0.96 2.82 ± 0.85 2.79 ± 0.98 2.90 ± 1.52 3.37 ± 1.47 3.51 ± 1.47 3.26 ± 1.50 23.93 ± 2.43 32.81 ± 2.17 39.63 ± 1.64 32.00 ± 6.77 72.52 ± 2.71 65.64 ± 1.45 59.64 ± 1.64 66.04 ± 5.63 97.61 ± 4.64 101.49 ± 6.11 102.06 ± 4.79 100.36 ± 5.55 21.87 ± 2.52 24.70 ± 2.29 23.16 ± 1.87 23.24 ± 2.52 Class II Mean ± SD 24.15 ± 2.81 N=(40) 23.96 ± 3.17 N=(41) 24.06 ± 2.97 N=(42) 24.05 ± 2.96 N=(123) 6.11 ± 0.92 6.12 ± 1.20 6.10 ± 0.93 6.11 ± 1.02 7.62 ± 1.04 8.26 ± 1.53 8.40 ± 1.25 8.10 ± 1.33 26.45 ± 0.98 32.85 ± 2.05 40.07 ± 2.38 33.23 ± 5.90 71.19 ± 1.51 65.73 ± 1.34 60.36 ± 1.52 65.67 ± 4.67 99.85 ± 5.26 100.335.35 101.75 ± 4.49 100.66 ± 5.06 22.53 ± 3.93 25.20 ± 2.17 23.97 ± 1.94 23.91 ± 2.99 Class III Mean ± SD 22.86 ± 3.47 N=(40) 23.26 ± 3.21 N=(41) 25.23 ± 1.85 N=(40) 23.78 ± 3.09 N=(121) −1.07 ± 1.57 −1.15 ± 1.72 −0.76 ± 1.40 −1.00 ± 1.56 −3.27 ± 2.60 −2.96 ± 2.70 −2.88 ± 2.46 −3.03 ± 2.57 24.29 ± 0.98 31.62 ± 2.15 39.58 ± 2.18 31.83 ± 6.60 71.84 ± 2.53 65.58 ± 1.96 60.43 ± 1.33 65.95 ± 5.07 98.04 ± 5.55 97.50 ± 6.15 99.16 ± 4.38 98.23 ± 5.42 24.21 ± 2.68 24.20 ± 1.97 25.46 ± 2.29 24.62 ± 2.38 Total Mean ± SD 23.69 ± 3.05 N=(122) 23.52 ± 3.08 N=(124) 24.60 ± 2.57 N=(122) 23.93 ± 2.94 N=(368) 2.52 ± 3.16 2.67 ± 3.26 2.78 ± 3.02 2.65 ± 3.14 2.43 ± 4.99 2.89 ± 4.99 3.10 ± 4.98 2.81 ± 4.92 24.88 ± 0.98 32.43 ± 2.18 39.76 ± 2.09 32.36 ± 6.44 71.86 ± 2.36 65.65 ± 1.59 60.15 ± 1.54 65.88 ± 5.13 98.48 ± 5.20 99.79 ± 6.07 101.00 ± 4.70 99.76 ± 5.44 22.85 ± 3.23 24.70 ± 2.17 24.19 ± 2.24 23.92 ± 2.70 *SD: Standard deviation, N: Number of the subject, -°(degree), % (ratio measurements), mm (millimeters), mm2 (square millimeters), mm3 (cubic millimeters), and Kg/m2 (kilograms per square meter). In this study, skeletal Class III showed statistically smaller nasopharyngeal sagittal and lateral widths than skeletal Class III, which may manifest in skeletal Class III patients with a retruded and small maxilla, resulting in narrowing and decreasing of the nasopharyngeal airway dimensions. Also, we found that nasopharyngeal volume, surface area, and MCA were significantly smaller in the hyperdivergent group. This may be related to a patient with a hyperdivergent facial growth pattern having maxillary retrusion and decreased maxillary length and width. According to Ucar et al,7 the nasopharyngeal airway space in skeletal Class II subjects was larger in low-angle subjects than in high-angle subjects. A study by Joseph et al5 noted that hyperdivergent subjects had a smaller sagittal pharyngeal dimension, particularly at the nasopharynx’s hard palate level and the soft palate mandible tip level in the oropharynx, and this support the finding of this study. Another study by Memon et al8 reported that smaller airway dimensions might be correlated with some skeletal features in hyperdivergent patients, such as maxillary and mandibular retrusion or vertical maxillary excess. The nasopharyngeal volume finding in this study is supported by Alhmmadi et al,18 who showed no statistical significance in the volume between skeletal Class II and I; still, skeletal Class II was higher than skeletal Class I. Gungor and Turkkahraman37 evaluated the literature on the relationship between respiratory function and maxillary growth patterns and reported maxillary morphological differences between subjects with airway problems and control groups, indicating a possible etiological involvement of the airway in these subjects. Systematic review agree that maxillary expansion birpublications.org/dmfr Dentomaxillofac Radiol, 0, 20220346 8 of 14 Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al Table 4 Reliability analysis of all measurements used in this study. Intraobserver reliability Interobserver reliability Measurements ICC TEM rTEM R* ICC TEM rTEM R* ANB ° 0.9955 0.2901 7.4146 0.9864 0.9906 0.3495 9.0526 0.9801 AF-BF mm 0.9968 0.3011 6.3786 0.9936 0.9985 0.2030 4.3124 0.9971 GoGn- SN ° 0.9982 0.2826 0.8750 0.9963 0.9977 0.3148 0.9749 0.9954 SGo /NMe % 0.9917 0.4665 0.7080 0.9829 0.9911 0.4787 0.7266 0.9820 OP/SN° 0.9956 0.4644 0.4627 0.9911 0.9953 0.4839 0.4821 0.9904 SNA ° 1.000 0.2210 0.2676 0.9939 0.9959 0.2578 0.3125 0.9914 A-NV mm 0.9937 0.1963 6.6903 0.9948 0.9962 0.2558 8.5279 0.9907 Co-A mm 0.9963 0.3253 0.3408 0.9920 0.9958 0.3336 0.3499 0.9916 JL-JR mm 0.9941 0.3540 0.5374 0.9863 0.9940 0.3291 0.5004 0.9882 A-FH mm 0.9922 0.3669 1.2013 0.9840 0.9918 0.3758 1.2305 0.9832 SNB ° 0.9970 0.2354 0.2992 0.9939 0.9970 0.2331 0.2965 0.9940 B-NV mm 0.9968 0.0823 −4.642 0.9997 0.9982 0.1486 −8.456 0.9989 Gn-Go mm 0.9880 0.6470 0.7581 0.9755 0.9877 0.6546 0.7671 0.9748 Co-Gn mm 0.9969 0.4249 0.3525 0.9926 0.9969 0.4190 0.3476 0.9928 GoR-GoL mm 0.9988 0.3535 0.3811 0.9967 0.9987 0.3578 0.3858 0.9967 B-FH mm 0.9904 0.7712 1.1030 0.9811 0.9904 0.7692 1.1003 0.9812 NP (A-P) mm 0.9991 0.2118 0.7584 0.9952 0.9975 0.2939 1.0516 0.9907 NP (L-R) mm 0.9988 0.2527 0.6519 0.9971 0.9954 0.4672 1.2048 0.9903 NP-V mm 3 1.000 14.987 0.2178 0.9999 1.000 40.635 0.5914 0.9995 NP-A mm2 0.9970 5.3854 2.0787 0.9888 0.9923 6.8898 2.6518 0.9824 NP-MCA mm2 0.9795 3.4442 9.4880 0.9589 0.9797 3.9636 11.2225 0.9457 OP (A-P) mm 0.9949 0.3220 2.2246 0.9900 0.9942 0.3610 2.5106 0.9874 OP (L-R) mm 0.9977 0.4213 1.3291 0.9938 0.9968 0.4465 1.4111 0.9930 OP-V mm3 1.000 73.8340 0.4473 0.9998 0.9966 75.388 0.4569 0.9997 OP-A mm2 0.9984 6.1951 1.0837 0.9962 0.9984 6.7489 1.1787 0.9955 OP-MCA mm2 1.000 0.9865 1.6672 0.9984 1.000 0.7811 1.3247 0.9990 HP(A-P)mm 0.9965 0.2776 1.6498 0.9926 0.9966 0.2631 1.5594 0.9934 HP(L-R)mm 0.9973 0.3369 1.0349 0.9932 0.9979 0.2961 0.9100 0.9948 HP-V mm3 1.000 31.456 0.5152 0.9997 0.9998 38.839 0.6358 0.9996 HP-A mm2 0.9916 6.7736 3.1628 0.9817 0.9914 6.9822 3.2560 0.9806 HP-MCA mm2 1.000 1.0519 2.0442 0.9985 1.000 2.4561 4.6811 0.9918 TP-V mm3 1.000 79.360 0.2650 0.9998 0.9990 298.89 0.9996 0.9978 TP-A mm2 0.9967 12.9964 1.2606 0.9932 0.9956 14.5614 1.4094 0.9914 TP-MCA mm2 0.9865 2.6727 18.0851 0.9337 0.9728 0.3351 3.4967 0.9981 *ICC: Intraclass correlation coefficient TEM and rTEM indicate an absolute and relative technical error of measurement. °(degree), % (ratio measurements), mm (millemeters), mm2 (square millemeters), mm3 (cubic millimeters) and Kg/m2 (kilograms per square meter). can improve the nasal airway volume and obstructive sleeping apnea in both growing and non-growing patients in the short term. Maxillary expansion is one of the treatment options for patients with obstructive sleeping apnea.38 As such, increasing maxillary width directly correlates to increased airway volume and functional improvement.39 This study showed that the oropharyngeal airway sagittal width, volume, surface area, and MCA were lower in the hyperdivergent group than in other groups. This result is related to most patients with hyperdivergent growth patterns having a component of mandibular deficiency and rotating downward and backward, thus decreasing the oropharyngeal airway dimensions.3 This is in contrast to the hypodivergent group having a larger mandible body length and anticlockwise rotation Dentomaxillofac Radiol, 0, 20220346 birpublications.org/dmfr than other groups. The oropharyngeal lateral widths were significantly higher in the skeletal Class III group. This is manifested in abnormal respiratory function being observed more frequently in skeletal Class II patients due to mandible deficiency.40 This finding is consistent with Yanagita et al,41 who reported oropharyngeal volume positively correlated with the mandibular body length and sagittal position of the mandible, and also supported by Hong et al,42 who noted higher oropharyngeal airway dimensions in skeletal Class III patients than in skeletal Class I and II patients; however, this difference was not statistically significant. Similarly, several studies found a smaller oropharyngeal volume in subjects with skeletal Class II than skeletal Class I or skeletal Class III malocclusion.11,19 Other studies had Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 9 of 14 Table 5 Descriptive statistics and results of two-way ANOVA test for comparison between the offending jaw/s measurements of patients with different skeletal classes and facial growth patterns Measurements SNA ° A-NV mm Co-A mm . JR -JL mm A-FH mm SNB ° B-NV mm GoL-GoR mm Gn-Go mm Gn-Co mm B-FH mm Facial growth Class I Mean ± SD Class II Mean ± SD Total Class III Mean ± SD Mean ± SD Hypodivergent 83.24 ± 2.07 84.21 ± 3.39 82.41 ± 2.57 83.28 ± 2.80a Normodivergent 81.80 ± 2.72 83.51 ± 2.79 81.51 ± 2.93 82.27 ± 2.93b Hyperdivergent 79.75 ± 2.37 81.39 ± 2.37 79.38 ± 2.86 80.19 ± 2.67c Total 81.63 ± 2.78B 83.01 ± 3.09A 81.10 ± 3.05C 81.92 ± 3.07 Hypodivergent 3.40 ± 2.62 3.99 ± 2.74 1.71 ± 2.44 3.04 ± 2.76 Normodivergent 3.20 ± 2.55 4.06 ± 2.96 1.47 ± 2.69 2.91 ± 2.92 Hyperdivergent 2.19 ± 2.41 3.48 ± 1.90 2.43 ± 3.67 2.71 ± 2.78 Total 2.94 ± 2.56B 3.84 ± 2.56A 1.87 ± 2.98C 2.89 ± 2.82 Hypodivergent 96.23 ± 3.96 97.16 ± 3.38 96.26 ± 3.95 96.54 ± 3.77a Normodivergent 94.68 ± 3.32 96.81 ± 3.60 93.40 ± 4.72 94.96 ± 4.13b Hyperdivergent 93.26 ± 3.05 94.06 ± 3.22 92.56 ± 2.69 93.30 ± 3.04c Total 94.75 ± 3.65B 95.98 ± 3.65A 94.07 ± 4.17B 94.94 ± 3.90 Hypodivergent 66.40 ± 3.33 66.88 ± 2.95 65.80 ± 3.72 66.36 ± 3.35a Normodivergent 65.79 ± 3.23 66.63 ± 3.00 64.61 ± 2.42 65.68 ± 3.00a Hyperdivergent 64.77 ± 3.56 64.30 ± 2.37 64.81 ± 2.09 64.62 ± 2.73b Total 65.67 ± 3.41 65.91 ± 3.00 65.07 ± 2.85 65.55 ± 3.11 Hypodivergent 29.61 ± 3.01 30.15 ± 3.46 29.87 ± 3.07 29.87 ± 3.17 Normodivergent 29.78 ± 2.85 31.33 ± 2.89 28.90 ± 2.44 30.00 ± 2.89 Hyperdivergent 29.75 ± 2.35 30.00 ± 2.64 29.33 ± 3.68 29.70 ± 2.93 Total 29.71 ± 2.74A 30.49 ± 3.04A 29.36 ± 3.10B 29.86 ± 2.99 Hypodivergent 80.71 ± 2.37 78.10 ± 2.84 83.48 ± 2.83 80.76 ± 3.44a Normodivergent 78.78 ± 2.80 77.38 ± 2.58 82.66 ± 3.18 79.60 ± 3.62b Hyperdivergent 76.93 ± 2.27 75.29 ± 2.13 80.14 ± 2.92 77.42 ± 3.17c Total 78.84 ± 2.91B 76.90 ± 2.78C 82.10 ± 3.28A 79.26 ± 3.68 Hypodivergent 0.69 ± 3.56 −3.93 ± 3.14 5.04 ± 3.70 0.60 ± 5.02 Normodivergent −0.13 ± 3.46 −4.28 ± 3.98 4.46 ± 3.82 0.02 ± 5.16 Hyperdivergent −1.32 ± 3.50 −4.97 ± 2.63 5.02 ± 4.22 −0.50 ± 5.41 Total −.23 ± 3.57B −4.40 ± 3.30C 4.84 ± 3.90A 0.04 ± 5.20 Hypodivergent 94.25 ± 5.98 91.59 ± 4.12 94.23 ± 5.86 93.37 ± 5.50 Normodivergent 92.40 ± 6.67 93.79 ± 5.16 93.06 ± 5.08 93.08 ± 5.67 Hyperdivergent 93.14 ± 5.15 92.22 ± 4.37 95.53 ± 4.15 93.60 ± 4.75 Total 93.26 ± 5.98B 92.54 ± 4.63B 94.26 ± 5.14A 93.35 ± 5.31 Hypodivergent 88.47 ± 3.76 82.92 ± 2.99 89.77 ± 4.14 87.08 ± 4.69a Normodivergent 85.71 ± 3.58 84.36 ± 4.63 87.3 ± 73.72 85.81 ± 4.15b Hyperdivergent 85.11 ± 3.45 82.55 ± 3.05 87.38 ± 3.41 84.97 ± 3.83b Total 86.45 ± 3.86B 83.28 ± 3.70C 88.17 ± 3.90A 85.95 ± 4.31 Hypodivergent 121.82 ± 5.58 119.17 ± 4.48 125.44 ± 4.51 122.14 ± 5.49a Normodivergent 121.11 ± 3.92 118.87 ± 5.79 123.13 ± 5.10 121.04 ± 5.25a Hyperdivergent 121.01 ± 3.75 117.86 ± 3.30 123.28 ± 4.63 120.67 ± 4.49b Total 121.32 ± 4.48B 118.62 ± 4.62C 123.94 ± 4.84A 121.28 ± 5.12 Hypodivergent 65.82 ± 4.92 66.10 ± 4.20 65.94 ± 5.39 65.95 ± 4.82c Normodivergent 69.41 ± 4.45 69.77 ± 4.28 68.46 ± 3.38 69.21 ± 4.07b Hyperdivergent 72.16 ± 4.73 71.63 ± 4.69 73.00 ± 4.13 72.25 ± 4.53a Total 69.08 ± 5.34 69.21 ± 4.93 69.13 ± 5.23 69.14 ± 5.16 Class Facial growth Class* Facial growth 0.000* 0.910 0.618 0.109 0.000* 0.226 0.000* 0.117 0.708 0.165 0.000* 0.540 0.083 0.417 0.717 0.038* 0.000* 0.002* 0.043* 0.650 0.000* 0.426 0.000* 0.000* 0.000* 0.076 0.010* 0.000* 0.000* 0.035* 0.000* 0.000* 0.997 *:Significant at p ≤ 0.05 - ° (degree) and mm (millimeters) A, B, C superscripts in the same row indicate statistically significant difference between classes, a, b, c superscripts in the same column indicate statistically significant difference between facial growth. reported low or negligible correlations between craniofacial and oropharyngeal airway parameters.12,19,21,42 The present findings agreed with Palomo et al,21 who measured the effective mandible length between the condylion and the mention, suggesting that mandible length contributes more to oropharynx size and volume than its position relative to the cranial base. This result was consistent with Trenouth and Timms,43 who found that the oropharyngeal airway correlated positively with mandibular length. Mandibular width was related to birpublications.org/dmfr Dentomaxillofac Radiol, 0, 20220346 Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 10 of 14 Table 6 Descriptive statistics and results of two-way ANOVA test for comparison between the nasopharyngeal airway measurements of patients with different classes and facial growth patterns. Measurements NP (A-P) mm NP (L-R) mm NP-V mm³ NP-A mm² NP-MCA mm² Facial growth Class I Mean ± SD Class II Mean ± SD Class III Mean ± SD Total Mean ± SD Hypodivergent 28.11 ± 3.56 27.60 ± 3.82 26.69 ± 2.73 27.48 ± 3.43a Normodivergent 28.16 ± 2.47 28.33 ± 3.26 25.64 ± 3.29 27.38 ± 3.24a Hyperdivergent 26.99 ± 2.85 27.96 ± 2.19 24.60 ± 2.98 26.54 ± 3.02b Total 27.77 ± 3.02A 27.97 ± 3.14A 25.64 ± 3.10B 27.14 ± 3.25 Hypodivergent 38.40 ± 6.29 36.42 ± 3.41 36.98 ± 5.05 37.28 ± 5.11 Normodivergent 38.73 ± 3.91 39.28 ± 4.27 37.41 ± 5.52 38.48 ± 4.65 Hyperdivergent 38.83 ± 4.95 38.89 ± 3.45 35.51 ± 5.83 37.76 ± 5.04 Total 38.65 ± 5.11A 38.22 ± 3.91A 36.64 ± 5.49B 37.84 ± 4.95 Hypodivergent 7617.50 ± 1589.27 7230.92 ± 1555.83 7514.32 ± 1597.14 7456.92 ± 1576.43a 7013.87 ± 1979.70 a Normodivergent 7029.29 ± 1855.22 7511.88 ± 1909.81 Class Facial growth Class* Facial growth 0.028* 0.238 0.145 0.092 0.000* 0.232 0.001* 0.006* 0.000* 0.011* 0.000* 0.003* 7183.76 ± 1913.54 Hyperdivergent 6204.74 ± 1369.09 6809.61 ± 1352.10 6161.62 ± 1180.04 6398.83 ± 1327.42b Total 6962.54 ± 1708.30 7180.71 ± 1633.75 6897.57 ± 1702.93 7014.10 ± 1681.74 Hypodivergent 290.33 ± 59.99 254.12 ± 51.98 275.28 ± 53.00 273.52 ± 56.74a Normodivergent 261.55 ± 62.39 281.07 ± 67.09 256.25 ± 67.86 266.25 ± 66.13a Hyperdivergent 239.62 ± 46.42 258.04 ± 45.98 240.97 ± 38.08 246.40 ± 44.16b Total 264.22 ± 60.10 264.44 ± 56.50 257.49 ± 55.83 262.08 ± 57.45 Hypodivergent 33.50 ± 15.89 48.69 ± 15.69 38.60 ± 18.00 40.15 ± 17.64a Normodivergent 30.99 ± 14.52 33.57 ± 14.21 39.81 ± 17.47 34.21 ± 15.72b Hyperdivergent 23.38 ± 12.91 27.53 ± 15.69 23.49 ± 11.05 24.85 ± 13.43c Total 29.39 ± 15.02B 36.43±17.57A 33.45±17.30A 33.08 ± 16.84 0.338 0.562 0.001* *Significant at p ≤ 0.05 -mm (millimeters), mm2 (square millimeters), and mm3 (cubic millimeters) A, B, C superscripts in the same row indicate statistically significant difference between classes, a, b, c superscripts in the same column indicate statistically significant difference between facial growth. the dimensions of the oropharyngeal. This finding is consistent with Nejaim et al,17 who reported a positive correlation between mandibular width and oropharyngeal volume. The current study considered more in skeletal Class II and III than in skeletal Class I malocclusion; this consideration is more important in patients undergoing mandibular surgery because more negative/positive changes in the pharyngeal airway space dimensions may occur. Because the mandible is associated with the hyoid bone, tongue, and soft palate by muscles, any movement in the mandible can affect the size of the airway space. Table 7 Descriptive statistics and results of two-way ANOVA test for comparison between the oropharyngeal airway measurements of patients with different skeletal classes and facial growth patterns Measurements OP (A-P) mm OP (L-R) mm OP-V mm³ OP-A mm2 OP-MCA mm² Facial growth Class I Mean ± SD Class II Mean ± SD Class III Mean ± SD Total Mean ± SD Hypodivergent 13.68 ± 2.95 13.23 ± 3.65 14.49 ± 2.84 13.80 ± 3.18a Normodivergent 14.10 ± 3.26 13.31 ± 2.73 14.24 ± 3.28 13.88 ± 3.10a Hyperdivergent 12.49 ± 2.72 11.49 ± 2.08 12.40 ± 2.17 12.12 ± 2.36b Total 13.44 ± 3.04A 12.66 ± 2.98B 13.71 ± 2.93A 13.27 ± 3.01 Hypodivergent 31.07 ± 5.42 30.98 ± 3.95 31.11 ± 5.68 31.05 ± 5.04a Normodivergent 31.33 ± 4.63 31.63 ± 3.78 30.63 ± 4.52 31.20 ± 4.31a Hyperdivergent 29.41 ± 5.05 28.03 ± 5.00 29.43 ± 4.77 28.94 ± 4.95b Total 30.62 ± 5.07 30.19 ± 4.54 30.40 ± 5.02 30.40 ± 4.87 Hypodivergent 15318.02 ± 3888.89 15415.82 ± 3357.97 15683.99 ± 4324.78 15470.08 ± 3848.57a Normodivergent 15548.48 ± 4232.78 15307.62 ± 3805.97 16097.33 ± 4235.44 15650.32 ± 4077.49a Hyperdivergent 14476.87 ± 3876.62 13846.26 ± 2845.39 14464.34 ± 2953.69 14255.67 ± 3238.50b Total 15124.74 ± 3998.61 14843.81 ± 3405.43 15420.86 ± 3921.50 15128.21 ± 3781.19 Hypodivergent 556.79 ± 104.68 558.82 ± 102.73 561.64 ± 102.56 559.05 ± 102.51a Normodivergent 555.42 ± 100.39 557.74 ± 97.20 550.59 ± 96.50 554.59 ± 97.31a Hyperdivergent 537.29 ± 97.15 489.90 ± 144.55 527.83 ± 86.27 517.87 ± 113.80b Total 550.03 ± 100.41 534.93 ± 120.64 546.72 ± 95.60 543.90 ± 106.06 Hypodivergent 61.86 ± 33.57 59.93 ± 21.69 62.41 ± 16.58 61.41 ± 24.96a Normodivergent 59.46 ± 26.46 61.10 ± 18.88 60.95 ± 27.43 60.50 ± 24.39a Hyperdivergent 48.89 ± 21.93 46.65 ± 18.66 51.74 ± 13.39 49.06 ± 18.31b Total 56.86 ± 28.16 55.79 ± 20.69 58.39 ± 20.51 57.01 ± 23.38 Class Facial growth 0.000* 0.898 0.000* 0.580 0.008* 0.969 0.004* 0.467 0.000* 0.955 0.016* 0.813 0.510 0.530 0.693 *Significant at p ≤ 0.05 -mm (millimeters), mm2 (square millimeters), and mm3 (cubic millimeters) A, B, C superscripts in the same row indicate statistically significant difference between classes, a, b, c superscripts in the same column indicate statistically significant difference between facial growth Dentomaxillofac Radiol, 0, 20220346 birpublications.org/dmfr Class*facial growth Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al 11 of 14 Table 8 Descriptive statistics and results of two-way ANOVA test for comparison between the hypopharyngeal airway measurements of patients with different skeletal classes and facial growth patterns Measurements HP (A-P) mm HP (L-R) mm Facial growth Class III Mean ± SD Total Mean ± SD 16.00 ± 2.95 15.85 ± 2.50 16.56 ± 3.43 16.14 ± 2.97a Normodivergent 15.83 ± 2.56 15.49 ± 2.96 16.36 ± 3.59 15.89 ± 3.06a Hyperdivergent 15.58 ± 2.09 14.48 ± 2.23 14.54 ± 2.26 14.86 ± 2.24b Total 15.81 ± 2.55 15.26 ± 2.63 15.82 ± 3.26 15.63 ± 2.83 Hypodivergent 32.91 ± 3.68 31.43 ± 2.53 33.08 ± 5.32 32.48 ± 4.04 Normodivergent 32.19 ± 3.40 34.02 ± 2.64 32.87 ± 2.69 33.02 ± 3.01 Hyperdivergent 30.78 ± 2.74 33.08 ± 3.03 34.31 ± 1.83 32.73 ± 2.95 Total HP-A mm² Class II Mean ± SD Hypodivergent Hypodivergent HP-V mm³ Class I Mean ± SD Class 31.98 ± 3.39B 32.86 ± 2.93A 33.42 ± 3.62A 6008.64 ± 1364.34 5499.98 ± 1520.04 6142.57 ± 1742.64 5885.77 ± 1559.00a a 5889.05 ± 1489.70 5929.79 ± 2091.19 5899.88 ± 1806.07 Hyperdivergent 4935.37 ± 1396.33 4586.18 ± 1099.62 4931.69 ± 1207.82 4813.95 ± 1239.28b Total 5619.27 ± 1607.36 5317.64 ± 1475.60 5670.18 ± 1788.29 5535.19 ± 1630.84 Hypodivergent 220.61 ± 45.97 194.29 ± 45.39 221.50 ± 42.39 212.27 ± 46.03a Normodivergent 209.65 ± 46.18 204.22 ± 46.76 212.41 ± 53.19 208.77 ± 48.51a Hyperdivergent 182.91 ± 38.03 174.69 ± 31.23 183.99 ± 30.08 180.43 ± 33.25b Total 204.74 ± 46.08a 190.91 ± 43.09b 206.02 ± 45.57a 200.54 ± 45.33 HP-MCA mm² Normodivergent 50.27 ± 21.03 43.48 ± 21.29 50.33 ± 27.59 47.20 ± 17.67 0.349 0.405 0.000* 0.000* 0.763 0.000* 0.462 0.000* 0.599 0.002* 32.75 ± 3.37 5881.24 ± 1831.07 48.14 ± 24.45 0.001* 0.215 Normodivergent Hypodivergent Facial Class*facial growth growth 46.30 ± 21.29 0.184 0.012* a a 48.67 ± 20.23 49.76 ± 22.99 Hyperdivergent 34.52 ± 13.97 33.85 ± 17.86 40.60 ± 16.34 36.28 ± 16.32b Total 44.46 ± 21.37 42.47 ± 23.42 45.51 ± 18.36 44.14 ± 21.15 0.530 *Significant at p ≤ 0.05 -mm (millimeters), mm2 (square millimeters), and mm3 (cubic millimeters) A, B, C superscripts in the same row indicate statistically significant difference between classes, a, b, c superscripts in the same column indicate statistically significant difference between facial growth. This current study showed smaller statistical significance in the hypopharyngeal airway sagittal width, volume, surface area, and MCA in the hyperdivergent group and a statistically significant difference in lateral width with a higher value in the Class III group. The patients with skeletal Class II and hyperdivergent growth patterns exhibited a retruding mandible and verse versa in Class III, which means the sagittal position of the mandible affects the hypopharyngeal airway. Thus, we need to take into account control of the mandibular position during the manipulation of the jaws because any movement is accompanied by a change in position of the hyoid bone. This is clearly explained by Jiang et al,44 who concluded that hyoid bone moved superiorly Table 9 Descriptive statistics and results of two-way ANOVA test for comparison between the total pharyngeal airway measurements of patients with different skeletal classes and facial growth patterns Measurements Facial growth Hypodivergent TP-V mm³ TP-A mm² Class I Mean ± SD Class II Mean ± SD Class III Mean ± SD Facial Class*Facial Class growth growth Total Mean ± SD 29567.53 ± 6540.35 28188.31 ± 5268.73 29595.60 ± 7205.71 29124.53 ± 6372.45a 0.000* 0.684 0.000* 0.437 0.000* 0.238 a Normodivergent 29341.18 ± 6286.89 29669.52 ± 5289.99 28402.72 ± 7135.84 29139.45 ± 6254.87 Hyperdivergent 26370.76 ± 6701.32 25406.26 ± 3445.08 26263.66 ± 5533.25 26003.60 ± 5343.68b Total 28459.65 ± 6616.36 27732.08 ± 5022.91 28089.93 ± 6760.14 28094.90 ± 6171.73 Hypodivergent 1058.52 ± 161.24 1001.39 ± 136.95 1066.73 ± 179.96 1042.48 ± 161.66a Normodivergent 1031.99 ± 146.78 1036.76 ± 166.36 1012.92 ± 173.10 1027.26 ± 161.34a Hyperdivergent 948.48 ± 159.96 930.98 ± 98.41 954.28 ± 120.29 944.36 ± 127.64b 1014.04 ± 161.69 989.14 ± 142.48 1011.33 ± 165.30 Total Hypodivergent TP-MCA mm² Normodivergent 47.72 ± 16.19 44.41 ± 12.08 50.57 ± 13.39 41.38 ± 11.88 1004.82 ± 156.75 53.31 ± 21.90 50.49 ± 17.50a 52.25 ± 14.04 a 0.682 0.405 46.00 ± 13.40 Hyperdivergent 41.48 ± 12.31 36.20 ± 9.49 45.94 ± 10.66 41.13 ± 11.50b Total 44.59 ± 13.80B 42.60 ± 13.01B 50.52 ± 16.40A 45.87 ± 14.81 0.000* *Significant at p ≤ 0.05 -mm (millimeters), mm2 (square millimeters), and mm3 (cubic millimeters) A, B, C superscripts in the same row indicate statistically significant difference between classes, a, b, c superscripts in the same column indicate statistically significant difference between facial growth. birpublications.org/dmfr Dentomaxillofac Radiol, 0, 20220346 12 of 14 Pharyngeal airway in different sagittal and vertical malocclusions Al-Somairi et al and forward in the mandibular advancement group, causing the widening of the hypopharyngeal airway. The total pharyngeal volume, surface area, and MCA were the smallest statistically significant in hyperdivergent patients; MCA was the smallest statistically significant in skeletal Class II patients. This is supported by Abbas Shokri et al,45 who found the anteroposterior jaws relation influences airway measurements. In general, this effect should be considered during orthognathic surgery; specifically, in the mandibular setback or advancement surgery in skeletal Class III or II malocclusion patients. These procedures can cause negative or positive alterations in the pharyngeal airway. In summary, according to the present study’s findings, comparing the pharyngeal airway space in patients with normal nasal breathing revealed a significant difference between different craniofacial growth patterns. Generally, the knowledge of pharyngeal airway differences caused by sagittal and vertical could help diagnose pharyngeal airway pathologies and be considered during clinical diagnosis and planning for craniofacial orthopedics and orthognathic surgical treatment. Acknowledgments We thank the Stomatological Hospital of Lanzhou University staff for their support and cooperation. Competing interests The authors declare any conflicts of interest. Funding Conclusion Based on this study’s findings, the following could be concluded: (1) Skeletal Class II malocclusion was significantly associated with greater nasopharyngeal sagittal width and MCA, and hypodivergent patients had a significantly greater nasopharyngeal volume, surface area, and MCA. (2) The hyperdivergent patients had a significantly smaller oropharyngeal sagittal width, volume, surface area, and MCA, and skeletal Class III had the greatest sagittal width. (3) The hyperdivergent patients had a significantly smaller hypopharyngeal sagittal width, volume, surface area, and MCA, and skeletal Class III had the greatest lateral width. (4) The hyperdivergent group had the smallest total pharyngeal airway volume, surface area, and MCA significantly; skeletal Class II patients had the lowest MCA. This work was supported by the project of the National Natural Science Foundation of Gansu Province, China (No. 20JR5RA264) and the study funds of Stomatology, School of Stomatology, Lanzhou University, Gansu Province, Lanzhou 730000, PR China (lzukqky-2020-t04) Consent for publication Not applicable. Ethics approval and consent to participate The ethical committee of clinical scientific research of the school of stomatology of Lanzhou University approved this study (No: LZUKQ-2019-056). Moreover, every participant provided their informed consent. REFERENCES 1. Angle EH. Treatment of Malocclusion of the Teeth: Angle’s System. 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