| Abstract|| |
Objective: This study aims to evaluate the pharyngeal airway dimensions among Chinese adults in relation to Class I and Class II facial skeletal patterns using three-dimensional cone-beam computed tomography (CBCT) images. Materials and Methods: A total of 156 initial CBCT images were evaluated, which were classified into skeletal Class I and Class II according to ANB angle with mean (SD) age being 22.56 ± 4.0 years and 22.32 ± 3.6 years. The pharyngeal airway volume, airway area, minimum cross-sectional area (MCA) and the distance from uvula (tip of the soft palate) to mental spine (U-MS distance) were assessed with Dolphin imaging software. Results: Compared with Class I group, Class II group displayed significantly smaller pharyngeal airway volume, airway area and MCA (P <.01, P =0.03, and P =0.008, respectively), and shorter U-MS distance (P <.001). Comparing gender subgroups, the female subgroup showed the smallest airway measurement. Spearman correlation test results showed that the airway volume and area had a significant positive correlation with U-MS distance (r = 0.22, P = 0.005, and r = 0.28, P < 0.005, respectively) and negative correlation with ANB angle (r = −0.23, P = 0.002, and r = −0.21, P = 0.007, respectively). Conclusions: Pharyngeal airway volume, airway area, MCA, and the U-MS distance were smaller in skeletal Class II than Class I Chinese adult subjects and lower in female Class II subgroup. Additionally, there was a correlation observed between the mandibular distance (U-MS), ANB angle and airway size.
Keywords: Adults, cone-beam computed tomography, mandible, pharyngeal airway
|How to cite this article:|
Firwana A, Wang H, Sun L, Wang J, Zhang WB. Relationship of the airway size to the mandible distance in Chinese skeletal Class I and Class II adults with normal vertical facial pattern. Indian J Dent Res 2019;30:368-74
|How to cite this URL:|
Firwana A, Wang H, Sun L, Wang J, Zhang WB. Relationship of the airway size to the mandible distance in Chinese skeletal Class I and Class II adults with normal vertical facial pattern. Indian J Dent Res [serial online] 2019 [cited 2019 Aug 24];30:368-74. Available from: http://www.ijdr.in/text.asp?2019/30/3/368/264121
| Introduction|| |
The upper airway complex is a dynamic, multifunctional neuromechanical system., Its configuration and dimensions are determined by its surrounding anatomical structures such as soft tissue, muscles and craniofacial skeleton., In the past few decades, there has been an increased interest in the relationship between upper airway and craniofacial morphology., Still, no certain relationship has been identified.
Studying upper airway and its relationship with craniofacial morphology is extremely important in orthodontic diagnosis and treatment planning because of their association with obstructive respiratory disorders. Some authors reported that abnormal respiratory function can lead to longer facial height, incompetent lips, constricted maxilla and open bite., According to Borzabadi-Farahani et al. those with severe skeletal Class II with small mandible can develop sleep apnea, which is not amenable to orthodontic treatment and would require orthognathic surgical intervention. Nevertheless, it is incorrect to relate different skeletal patterns and dental malocclusions only to upper airway pathologies. Several studies have tried to correlate the upper airway dimensions of patients with normal nasorespiratory functions and no upper airway disease with different malocclusions. Grauer et al. and El and Palomo  had confirmed that airway dimensions and shape vary among patients with different anteroposterior jaw relationships and different skeletal patterns.
However, most studies conducted were based on western population; further data for different ethnic groups and gender are required.,,, Chinese adults may have morphological features different from other ethnic groups., Samman et al. and Gu et al. provided reference values for pharyngeal airway among the Chinese population; however, both studies were based on lateral cephalograms. Compared with three-dimensional CBCT, the disadvantage of lateral cephalograms is the degradation of three-dimensional entity into two dimensions., CBCT also provided many advantages over the conventional (CT) such as lower radiation dose, lower cost and faster image acquisition.,, With the help of computer software, it is possible to assess the upper airway with good accuracy using CBCT in three dimensions., Still, there is limited data based on CBCT images of upper airway measurements for Chinese population. Thus, this study is designed to provide data concerning the airway measurements in three dimensions among Chinese adults with different skeletal patterns.
The upper airway studies and its relationship with mandibular position, size and length are also extremely important. Many authors reported that mandibular retrognathism, short mandibular body and downward rotation cause a decrease in airway size., In their study based on lateral cephalograms, Ceylan and Oktay  noticed a negative correlation between the oropharynx (OP) size and ANB angle. Despite the negative correlation, the ANB angle is the most commonly used criteria in orthodontic practice; still, it is insufficient to evaluate the airway only from the skeletal point of view depending on the ANB angle and further detailed analysis could be required.,,, Based on their study using CBCT images, El and Palomo  confirmed the correlation observed by Ceylan and Oktay. Also, with a more detailed jaw-specific skeletal relationship, they reported that the Class II mandibular retrusion group had smaller airway volume. However, none of the mentioned studies used a measurement directly linking the mandible to the pharyngeal airway. Therefore, we have applied a new criteria to measure the distance between the mandible and the airway directly.
In this study, we evaluated the pharyngeal airway relationship in Class I and Class II skeletal patterns and gender subgroups using three-dimensional CBCT Images. We obtained data concerning airway measurements for each group specific to Chinese adults, and investigated the distance between the mandible and the pharyngeal airway.
| Materials and Methods|| |
A total of 164 CBCT images of Chinese adults who came to the Department of Orthodontics of Stomatology Hospital of Nanjing Medical University between 2014 and 2016 were evaluated. Inclusion criteria were adult subjects in the age group of 18–39 years without any previous orthognathic surgery, respiratory disorders, pharyngeal pathology, history of snoring, nasal obstruction, obstructive sleep apnea, adenoidectomy, and any syndrome or detectable pathology along the pharyngeal airway through CBCT images inspection. Exclusion criteria included images that did not show the fourth cervical vertebra (C4), severe hypodivergent (FMA < 23.5°) and severe hyperdivergent (FMA > 30.5°) growth patterns.,
Informed consent was obtained from all patients before participation in the study. The study was carried out in accordance with the Helsinki Declaration and approved by the Ethics Committee of the Stomatology School of the Nanjing Medical University in China (PJ2014-045-001).
All DICOMs were scanned by Newtom 5 g system (Verona, Italy) according to a standard protocol (16 × 18 cm FOV, 0.30 mm Voxel resolution, FSV: 110 kV: 8 mA. SSV: 110 kV: 10 mA, 4.8S scan time). All CBCT scans were taken while patients were in the supine position with head fitted into molded pillow and with teeth in maximum intercuspation.
The images were imported in DICOM format into Dolphin imaging software (version 11.8 Premium; Dolphin Imaging, Chatsworth, CA). ANB and FMA values of every subject were collected, sample was divided into two skeletal groups according to the ANB angle (Class I: 0.7°–4.7°, Class II: >4.7°) (Class I n = 88, Class II n = 68). These groups were further divided into four subgroups according to the subjects' gender. To define the pharyngeal airway margins, we used the limits proposed by Anandarajah et al. with the line between the anterior nasal spine ANS) and posterior nasal spine (PNS), extending to posterior pharynx wall as upper margin, and the line between anterior-superior edge of fourth cervical vertebra (C4) and menton (Me) as lower margin [Figure 1]. Using Dolphin 3D airway measurement tool, we evaluated the airway volume, airway area and the minimum cross-sectional area (MCA) according to the margins. The software calculated the airway volume, airway area and MCA automatically after manually checking CBCT images slice by slice horizontally to assure that all areas of the pharyngeal airway were included [Figure 2]a, [Figure 2]b, [Figure 2]c. To measure the distance between the pharyngeal airway and mandible, Dolphin imaging measurement tool was used to draw a line from the tip of the soft palate (U) to the middle of the mental spines (MS) [Figure 2]d. All variables and measurements used are shown in [Table 1].
|Figure 1: Upper airway delineating margins and landmarks those were proposed according to the study by Anandarajah S.34: Superior: The line passing from the anterior nasal spine to posterior nasal spine (ANS to PNS) extended to the posterior wall of the pharynx, Inferior: The passing line from the anterior-superior edge of the fourth cervical vertebrae to the menton (CV4 to Me) Anterior: The anterior wall of the pharynx, Posterior: The posterior wall of the pharynx, Laterally: Lateral pharyngeal walls. Tip of soft palate (U) and mental spines (MS) forming the U-MS line|
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|Figure 2: (a) Two-dimensional view of the upper airway. (b) Three-dimensional view of the upper airway. (c) Minimum cross-sectional area (MCA). (d) Transverse view for the U-MS distance, the line from (U) uvula or tip of soft plate to (MS) mental spines|
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All measurements were repeated after a two-week interval by the same investigator. Investigator calibration was assessed with intraclass correlation coefficient (ICC), investigator's calibration was confirmed, as the results of the ICC were higher than 0.85 for all variables. A descriptive statistical analysis, including mean and standard deviation was performed for all pharyngeal airway measurements. The t-test was used to determine the difference between Class I and Class II measurements of the airway volume, area, MCA, and U-MS distance. Correlations among different variables and pharyngeal airway measurements were tested by Spearman correlation coefficient test.
| Results|| |
One hundred and fifty-six CBCT images of Chinese adult subjects were enrolled, 72 males (46 in Class I and 26 in Class II) and 84 females (42 in Class I and 42 in Class II), as shown in [Table 2]. Since this study targeted adult subjects, the mean age for Class I subjects was (22.56 ± 4.0 years) and for Class II subjects, it was (22.32 ± 3.6 years), and there was no statistical difference in age between the two groups (P = 0.7). The mean values of ANB and FMA for Class I subjects were (3.1° ± 0.9° and 24.66° ± 0.61°, respectively) and for Class II subjects, it was (6.1° ± 1.6° and 28.35° ± 0.72°, respectively). The FMA angle for all subjects was within normal (23.5° and 30.5°).
Pharyngeal airway dimensional measurements, including the mean values and standard deviations for the airway volume, airway area, MCA, and U-MS distance in Class I and Class II skeletal patterns and gender subgroups are shown in [Table 3]. Skeletal Class II subjects showed significantly smaller airway dimensions (volume, area, and MCA) (P <.01, P =0.03 and P =0.008) than Class I as following: airway volume (12770 ± 4345 vs. 14890 ± 5591 mm 3), airway area (614 ± 157 vs. 670 ± 160 mm 2), airway MCA (109 ± 54 vs. 138 ± 75 mm 2). While Class II female subgroup showed the smallest mean values for the airway dimensions (11760 ± 3732 mm 3, 576 ± 135 mm 2 and 106 ± 47 mm 2, respectively). Comparing gender subgroups, airway measurements (volume, area, and MCA) for female subgroup showed statistically significant difference between different skeletal patterns (P <.01, P =.04 and P <.01), but no significant difference in male subgroup. Those results are summarized in [Figure 3].
|Figure 3: Comparison of Airway measurements; (a) Volume (mm3), (b) Area (mm2), (c) minimum cross-sectional area (mm2) between Class I and Class II groups and gender subgroups. (*P < 0.05; **P < 0.01; ***P < 0.001 and NS: No significance)|
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Additionally, the U-MS distance was significantly shorter in skeletal Class II than skeletal Class I (51 ± 4 vs. 54 ± 4 mm) (P <.001). Meanwhile, when comparing U-MS in gender subgroups, the female subgroup displayed statistically significant difference (P =0.007), but not male subgroup [Figure 4].
|Figure 4: Comparison of U-MS distance (mm) between Class I and Class II groups and gender subgroups. (*P < 0.05; **P < 0.01; ***P < 0.001 and NS: No significance)|
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Correlations between pharyngeal airway dimensions, U-MS distance, and ANB angle were evaluated using Spearman coefficient correlations as shown in [Table 4]. U-MS distance showed significant positive correlations with both airway volume and airway area but not MCA. Furthermore, there were negative correlations between ANB angle and pharyngeal airway volume and area, but no significant correlation with MCA. Accordingly, there was a significant negative correlation between ANB angle and U-MS distance.
|Table 4: Correlations coefficient between: Mandibular distance between Uvula (tip of soft plate) to mental spines, ANB angle and airway (volume, area and airway minimum cross-sectional area)|
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| Discussion|| |
The objective of the study was to evaluate pharyngeal airway volume size, airway area and MCA within defined bony landmarks that adequately encompass the area of interest. All subjects were divided into two skeletal groups—Class I and Class II groups, according to the ANB angle (Class I: 0.7°–4.7°, Class II: >4.7°)., The ANB angle is reliable criteria to determine the anterior-posterior discrepancies, despite its limitations; it is widely used in orthodontic practice.,,,
All subjects in our study had a normal FMA angle (23.5° and 30.5°), as reported mandibular angle can influence the pharyngeal airway dimensions.,
Patient positioning from upright to supine or changing in head position during data acquisition could affect airway dimensions., For our study, the CBCT scanner used was (Newtom 5 g system Verona, Italy), patients were scanned in a supine position with patient head fitted into a molded pillow. Perhaps in future prospective studies, more measures should be considered to control head position during CBCT scanning.
Schendel et al. investigated normal pharyngeal airway changes during growth and development from the age of 6–60 years. They had mentioned that the length of PAS increases until the age of 20 years, followed by a variable period of stability. There is then a slow decrease in airway size up to the age of 50 years following which there is a rapid decrease in airway size. As for this study, the mean age for Class I group was 22.56 years, for Class II group, it was 22.32 years and the upper limit of age was 39 years. It is unlikely that age had significantly affected our study results.
Many studies have tested for CBCT accuracy and reliability in evaluating the airway dimensions. It was concluded that CBCT digital measurements are accurate and reliable for airway morphological assessment with low cost as well as low radiation dose.,,, Our study observed the simplicity of evaluating CBCT images in association with Dolphin imaging software to evaluate the pharyngeal airway. It has the capability to provide three-dimensional assessments, which cannot be obtained with conventional lateral radiographs.
Several studies were conducted to evaluate pharyngeal airway in relation to dento-maxillofacial morphology using lateral cephalometric or CBCT images.,,,,, Some studies were based on a two-dimensional airway evaluation using lateral cephalograms, which is not an accurate representation for such a three-dimensional complex.,, Some other 3D studies only assessed a segment of the pharyngeal airway, which is not necessarily a complete representation of the pharyngeal airway.,
Our results showed that pharyngeal airway volume, airway area, and MCA were significantly smaller in Class II than Class I subjects. Cabral et al. assessed the pharyngeal airway space in 42 CBCT images for adult patients, where they found that the volume and MCA in Class II subjects were smaller than the same measurements for Class I subjects. Grauer et al. compared airway volume and shape to facial morphology in 62 non-growing patient CBCT records. Their results showed that Class II group subjects had smaller measurements than the other groups. Castro-Silva et al. evaluated the pharyngeal airway for 60 patients and they found that Class II subjects have smaller airway volume than Class I and Class III, while Class III had the greatest airway volume. These are in line with our findings, but they have not mentioned the differences among gender subgroups in their studies. This study showed that in Chinese population the female subgroup showed a statistically significant difference for airway dimensions but not the male subgroup. Our study was much more comprehensive in terms of subjects' number.
Ceylan and Oktay  classified 90 subjects according to the ANB angle and investigated pharyngeal size on lateral cephalograms. They noticed a negative correlation between ANB angle and the oropharynx size. Based upon CBCT images with a bigger sample size and different limits used to delineate the pharyngeal airway in our study, we found out that among Chinese adults there were a significant correlation between ANB angle and airway dimensions (volume and area).
The relationship between pharyngeal airway and mandibular position, length and size have a great importance in orthodontic diagnosis,, many studies had addressed that mandibular retrognathism or back/downward rotation can induce a retro-displacement of the tongue position and hyoid bone, which may lead to a concomitant decrease in the upper airway volume.,,,,,,,, El and Palomo  investigated pharyngeal airway dimensions of 101 Caucasian patients aged between 14-18 and concluded that Class II mandibular retrusion group had the lowest values. Still, there is a need to evaluate mandible relationship with airway not just from the skeletal point of view; as ANB angle is a skeletal indicator to determine the anteroposterior relationship between maxilla and mandible, more detailed analysis could be required to link the mandible directly to the airway. Therefore, we had applied special measurement by linking the mandible directly to the airway to confirm the direct correlation between mandible and pharyngeal airway in conjunction with ANB angle. The U-MS distance showed a statistically significant difference between the different skeletal pattern groups and in female gender subgroups. Further, we noticed that there was a significant positive correlation between airway volume and airway area, and mandibular distance (U-MS distance) but not with airway MCA. Moreover, there was a significant negative correlation with ANB angle, which confirmed the reciprocal relationship between mandible position and airway size. These results might support what Trenouth and Timms  observed in their study, which was that the airway size was correlated with mandible length (menton to gonion) and that the mandibular length could influence the distance between the airway and mandible. However, our study targeted adult subjects with normal respiratory function in a different population.
Limitations of this study were the small sample size of male Class II subjects compared to female subjects. There were no attempts made to control respiratory movement or head position during CBCT acquisition. It would be interesting to consider the respiration phase, head position and body measurements in future studies. Furthermore, because of the nature of the airway structure, (U) point was used as a landmark to measure the distance between the airway and the mandible, which is not an immobile bony landmark.
| Conclusions|| |
Pharyngeal airway volume, airway area, MCA and U-MS distance are smaller in Class II subjects than Class I skeletal patterns, and smaller in female subgroup among the Chinese population. A positive correlation between the airway (volume and area) and mandibular distance, and a negative correlation with jaw anteroposterior discrepancies were observed.
This study was supported by the Jiangsu Provincial Key Medical Discipline (grant number ZDXKA2016026).
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Bilston LE, Gandevia SC. Biomechanical properties of the human upper airway and their effect on its behavior during breathing and in obstructive sleep apnea. J Appl Physiol (1985) 2014;116:314-24.
Wang T, Yang Z, Yang F, Zhang M, Zhao J, Chen J, et al.
A three dimensional study of upper airway in adult skeletal class II patients with different vertical growth patterns. PLoS One 2014;9:e95544.
Butterfield KJ, Marks PL, McLean L, Newton J. Linear and volumetric airway changes after maxillomandibular advancement for obstructive sleep apnea. J Oral Maxillofac Surg 2015;73:1133-42.
Schendel SA, Broujerdi JA, Jacobson RL. Three-dimensional upper-airway changes with maxillomandibular advancement for obstructive sleep apnea treatment. Am J Orthod Dentofacial Orthop 2014;146:385-93.
Guijarro-Martínez R, Swennen GR. Cone-beam computerized tomography imaging and analysis of the upper airway: A systematic review of the literature. Int J Oral Maxillofac Surg 2011;40:1227-37.
Flores-Mir C, Korayem M, Heo G, Witmans M, Major MP, Major PW, et al.
Craniofacial morphological characteristics in children with obstructive sleep apnea syndrome: A systematic review and meta-analysis. J Am Dent Assoc 2013;144:269-77.
Grauer D, Cevidanes LS, Styner MA, Ackerman JL, Proffit WR. Pharyngeal airway volume and shape from cone-beam computed tomography: Relationship to facial morphology. Am J Orthod Dentofacial Orthop 2009;136:805-14.
Silva NN, Lacerda RH, Silva AW, Ramos TB. Assessment of upper airways measurements in patients with mandibular skeletal class II malocclusion. Dental Press J Orthod 2015;20:86-93.
Linder-Aronson S. Adenoids. Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the denition. A biometric, rhino-manometric and cephalometro-radiographic study on children with and without adenoids. Acta Otolaryngol Suppl 1970;265:1-32.
Ricketts RM. Respiratory obstruction syndrome. Am J Orthod 1968;54:495-507.
Borzabadi-Farahani A, Eslamipour F, Shahmoradi M. Functional needs of subjects with dentofacial deformities: A study using the index of orthognathic functional treatment need (IOFTN). J Plast Reconstr Aesthet Surg 2016;69:796-801.
El H, Palomo JM. An airway study of different maxillary and mandibular sagittal positions. Eur J Orthod 2013;35:262-70.
Balakrishnan KP, Chockalingam PA. Ethnicity and upper airway measurements: A study in South Indian population. Indian J Anaesth 2017;61:622-8.
] [Full text]
Kitahara T, Hoshino Y, Maruyama K, In E, Takahashi I. Changes in the pharyngeal airway space and hyoid bone position after mandibular setback surgery for skeletal class III jaw deformity in Japanese women. Am J Orthod Dentofacial Orthop 2010;138:708.e1-10.
Pinto S, Huang J, Tapia I, Karamessinis L, Pepe M, Gallagher PR, et al.
Effects of race on upper airway dynamic function during sleep in children. Sleep 2011;34:495-501.
Liu Y, Lowe AA, Zeng X, Fu M, Fleetham JA. Cephalometric comparisons between Chinese and Caucasian patients with obstructive sleep apnea. Am J Orthod Dentofacial Orthop 2000;117:479-85.
Samman N, Mohammadi H, Xia J. Cephalometric norms for the upper airway in a healthy Hong Kong Chinese population. Hong Kong Med J 2003;9:25-30.
Gu M, McGrath CP, Wong RW, Hägg U, Yang Y. Cephalometric norms for the upper airway of 12-year-old Chinese children. Head Face Med 2014;10:38.
Lenza MG, Lenza MM, Dalstra M, Melsen B, Cattaneo PM. An analysis of different approaches to the assessment of upper airway morphology: A CBCT study. Orthod Craniofac Res 2010;13:96-105.
Palomo JM, Rao PS, Hans MG. Influence of CBCT exposure conditions on radiation dose. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:773-82.
Scarfe WC, Farman AG. What is cone-beam CT and how does it work? Dent Clin North Am 2008;52:707-30, v.
Schendel SA, Jacobson R, Khalessi S. Airway growth and development: A computerized 3-dimensional analysis. J Oral Maxillofac Surg 2012;70:2174-83.
Ghoneima A, Kula K. Accuracy and reliability of cone-beam computed tomography for airway volume analysis. Eur J Orthod 2013;35:256-61.
Aboudara C, Nielsen I, Huang JC, Maki K, Miller AJ, Hatcher D, et al.
Comparison of airway space with conventional lateral headfilms and 3-dimensional reconstruction from cone-beam computed tomography. Am J Orthod Dentofacial Orthop 2009;135:468-79.
Muto T, Yamazaki A, Takeda S. A cephalometric evaluation of the pharyngeal airway space in patients with mandibular retrognathia and prognathia, and normal subjects. Int J Oral Maxillofac Surg 2008;37:228-31.
Trenouth MJ, Timms DJ. Relationship of the functional oropharynx to craniofacial morphology. Angle Orthod 1999;69:419-23.
Ceylan I, Oktay H. A study on the pharyngeal size in different skeletal patterns. Am J Orthod Dentofacial Orthop 1995;108:69-75.
Jacobson A. The “Wits” appraisal of jaw disharmony. Am J Orthod 1975;67:125-38.
Ferrario VF, Sforza C, Miani A Jr., Tartaglia GM. The use of linear and angular measurements of maxillo-mandibular anteroposterior discrepancies. Clin Orthod Res 1999;2:34-41.
van der Linden FP. Sheldon friel memorial lecture 2007: Myths and legends in orthodontics. Eur J Orthod 2008;30:449-68.
El H, Palomo JM. Airway volume for different dentofacial skeletal patterns. Am J Orthod Dentofacial Orthop 2011;139:e511-21.
Chiang CC, Jeffres MN, Miller A, Hatcher DC. Three-dimensional airway evaluation in 387 subjects from one university orthodontic clinic using cone beam computed tomography. Angle Orthod 2012;82:985-92.
Claudino LV, Mattos CT, Ruellas AC, Sant' Anna EF. Pharyngeal airway characterization in adolescents related to facial skeletal pattern: A preliminary study. Am J Orthod Dentofacial Orthop 2013;143:799-809.
Zhong Z, Tang Z, Gao X, Zeng XL. A comparison study of upper airway among different skeletal craniofacial patterns in nonsnoring chinese children. Angle Orthod 2010;80:267-74.
Anandarajah S, Abdalla Y, Dudhia R, Sonnesen L. Proposal of new upper airway margins in children assessed by CBCT. Dentomaxillofac Radiol 2015;44:20140438.
Zhang J, Chen G, Li W, Xu T, Gao X. Upper airway changes after orthodontic extraction treatment in adults: A preliminary study using cone beam computed tomography. PLoS One 2015;10:e0143233.
Kim YJ, Hong JS, Hwang YI, Park YH. Three-dimensional analysis of pharyngeal airway in preadolescent children with different anteroposterior skeletal patterns. Am J Orthod Dentofacial Orthop 2010;137:306.e1-11.
Alves M Jr. Franzotti ES, Baratieri C, Nunes LK, Nojima LI, Ruellas AC, et al.
Evaluation of pharyngeal airway space amongst different skeletal patterns. Int J Oral Maxillofac Surg 2012;41:814-9.
Joseph AA, Elbaum J, Cisneros GJ, Eisig SB. A cephalometric comparative study of the soft tissue airway dimensions in persons with hyperdivergent and normodivergent facial patterns. J Oral Maxillofac Surg 1998;56:135-9.
Pae EK, Lowe AA, Sasaki K, Price C, Tsuchiya M, Fleetham JA, et al.
A cephalometric and electromyographic study of upper airway structures in the upright and supine positions. Am J Orthod Dentofacial Orthop 1994;106:52-9.
Souza FJ, Evangelista AR, Silva JV, Périco GV, Madeira K. Cervical computed tomography in patients with obstructive sleep apnea: Influence of head elevation on the assessment of upper airway volume. J Bras Pneumol 2016;42:55-60.
Hatcher DC. Cone beam computed tomography: Craniofacial and airway analysis. Dent Clin North Am 2012;56:343-57.
Pachêco-Pereira C, Alsufyani NA, Major M, Heo G, Flores-Mir C. Accuracy and reliability of orthodontists using cone-beam computerized tomography for assessment of adenoid hypertrophy. Am J Orthod Dentofacial Orthop 2016;150:782-8.
Cabral M, de Queiroz Ribeiro LR, Cardeal CM, Bittencourt MA, Crusoé-Rebello IM, Souza-Machado A, et al.
Evaluation of the oropharynx in class I and II skeletal patterns by CBCT. Oral Maxillofac Surg 2017;21:27-31.
Endo S, Mataki S, Kurosaki N. Cephalometric evaluation of craniofacial and upper airway structures in Japanese patients with obstructive sleep apnea. J Med Dent Sci 2003;50:109-20.
Conley RS, Haskell BS. Characterization of the upper airway morphology and its changes in the apneic patient using cone beam computed tomography. In: Kapila S, editor. Cone Beam Computed Tomography in Orthodontics: Indications, Insights, and Innovations. Hoboken: Wiley 2014. p. 273-87.
Abé-Nickler MD, Pörtner S, Sieg P, Hakim SG. No correlation between two-dimensional measurements and three-dimensional configuration of the pharyngeal upper airway space in cone-beam computed tomography. J Craniomaxillofac Surg 2017;45:371-6.
Castro-Silva L, Monnazzi MS, Spin-Neto R, Moraes M, Miranda S, Real Gabrielli MF, et al.
Cone-beam evaluation of pharyngeal airway space in class I, II, and III patients. Oral Surg Oral Med Oral Pathol Oral Radiol 2015;120:679-83.
Han S, Choi YJ, Chung CJ, Kim JY, Kim KH. Long-term pharyngeal airway changes after bionator treatment in adolescents with skeletal class II malocclusions. Korean J Orthod 2014;44:13-9.
Li L, Liu H, Cheng H, Han Y, Wang C, Chen Y, et al.
CBCT evaluation of the upper airway morphological changes in growing patients of class II division 1 malocclusion with mandibular retrusion using twin block appliance: A comparative research. PLoS One 2014;9:e94378.
Gobeille DM, Bowman DC. Hyoid and muscle changes following distal repositioning of the tongue. Am J Orthod 1976;70:282-9.
Cuozzo GS, Bowman DC. Hyoid positioning during deglutition following forced positioning of the tongue. Am J Orthod 1975;68:564-70.
Ferrazzini G. Critical evaluation of the ANB angle. Am J Orthod 1976;69:620-6.
Dr. Wei-Bing Zhang
Institute of Stomatology, Nanjing Medical University, Nanjing, Jiangsu 210029
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]