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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 11  |  Issue : 4  |  Page : 166-171

Prevalence of airway obstruction: A cross-racial comparison


1 Resident, Division of Orthodontics and Dentofacial Orthopedics, Eastman Institute for Oral Health, University of Rochester, New York, USA
2 Chair, Division of Orthodontics and Dentofacial Orthopedics, Eastman Institute for Oral Health, University of Rochester, New York, USA
3 Statistician, Department of Biostatistics and Computational Biology, University of Rochester, New York, USA
4 Clinical Director, Division of Orthodontics and Dentofacial Orthopedics, Eastman Institute for Oral Health, University of Rochester, New York, USA

Date of Submission26-Aug-2020
Date of Acceptance28-Nov-2020
Date of Web Publication05-Feb-2021

Correspondence Address:
Dr. Shaima Malik
Division of Orthodontics and Dentofacial Orthopedics, Eastman Institute for Oral Health, University of Rochester, Rochester, New York
USA
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DOI: 10.4103/srmjrds.srmjrds_86_20

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  Abstract 

Purpose: The purpose of this study was to assess the prevalence of airway obstruction visible on lateral cephalometric radiographs among patients of different racial groups who presented to the Eastman Institute for Oral Health (EIOH) for orthodontic records. While many previous studies have confirmed the usefulness of the lateral cephalograms as a screening tool for airway obstruction, none have compared the prevalence and clinical presentation between two different patient groups, and our assumption is that the prevalence would be the same. Methods: Two groups of 56 patients with no history of adenoid/tonsil removal were identified. All patients were from two racial groups, African-American (A) and Caucasian (C), between the ages 9 and 15 years, and an equal number of male and female patients were selected. Lateral cephalometric radiographs were traced using Dolphin Imaging Software and the ImageJ program by NIH Image. Five airway measurements were used: three linear (McNamara's upper pharynx “UP,” and Linder-Aronson and Henrikson's A1 and A2), one ratio (Fujioka's adenoid-nasopharyngeal “A/N” ratio), and one area (Handelman and Osborne's Airway Percentage “Ad area”). Results: The prevalence of any clinical obstruction (enlarged adenoids and tonsils) warranting a referral to an ENT in the A Group was 0.25, and the C Group was 0.27. Two-sample t-test was used to compare the mean value of the two groups with a significance level of 0.05. The only mean airway measurement found to be significantly different between the two groups was Fujioka's A/N ratio. Conclusion: Based on our results, the prevalence of airway obstruction on lateral cephalometric radiographs between Caucasian and African-American patients presenting to EIOH for orthodontic records was not significantly different. Our sample size was small, and we believe that our study would benefit from an increased sample size. Future research could also benefit from looking at prevalence differences of airway obstruction on cone-beam computed tomography.

Keywords: Adenoids, airway obstruction, lateral cephalogram


How to cite this article:
Micaroni C, Rossouw P E, Feng C, Malik S. Prevalence of airway obstruction: A cross-racial comparison. SRM J Res Dent Sci 2020;11:166-71

How to cite this URL:
Micaroni C, Rossouw P E, Feng C, Malik S. Prevalence of airway obstruction: A cross-racial comparison. SRM J Res Dent Sci [serial online] 2020 [cited 2021 Mar 5];11:166-71. Available from: https://www.srmjrds.in/text.asp?2020/11/4/166/308791


  Introduction Top


Obstruction of the nasopharyngeal airway due to hypertrophic adenoid tissue during a child's development is thought to impact their craniofacial and dental growth and development due to the patient's obligate mouth breathing. Previous studies have shown that mouth breathing due to airway obstruction tends to produce certain craniofacial and dentoalveolar characteristics, sometimes termed “adenoid face,” including an increased anterior facial height, retroclined upper and lower incisors, posterior crossbite, and open bite tendency.[1],[2] It has also been shown that when completed at an appropriate time in growth and development, removal of the adenoids and the subsequent change to nose breathing is able to completely or partially correct many of the characteristics otherwise requiring orthodontic intervention, including incisor retroclination and crossbite.[1],[3],[4],[5] If radiographic airway obstruction is potentially identified during orthodontic records, a referral can be made to the patient's physician for further evaluation. Referral should also be seriously considered if there is any indication that the patient may have other conditions such as obstructive sleep apnea or a history of snoring. While it has been documented that there appears to be a genetic basis for airway obstruction and the subsequent facial morphology,[6],[7],[8] limited research has been conducted on the prevalence of obstruction among patients of different racial backgrounds. The evidence thus far has indicated that there are differences in craniofacial characteristics between children with altered nasorespiratory function from different racial groups[9] and adult patients of different racial groups with obstructive sleep apnea.[10],[11],[12] A comparison of the airway linearly, in ratio, or the area between patients of different racial backgrounds has not been conducted, to our knowledge.

Airway obstruction due to hypertrophic adenoid tissue can be visible on the lateral cephalometric radiograph, which is taken routinely during orthodontic diagnostic records. While recent advances in imaging have allowed providers to view the airway in three dimensional, including cone-beam computed tomography (CBCT), the lateral cephalogram remains prevalent in both orthodontic records and airway analysis due to its relative cost-effectiveness and low, single dose of radiation.[13],[14] While data were unable to be found for private practitioners, a 2011 survey of postgraduate orthodontic programs in the United States found that only 18% of programs with a CBCT machine were using them for all patient records, with the remaining 82% taking a CBCT scan only in specific instances, such as craniofacial anomalies and impacted teeth.[15] In addition, in 2013, the American Academy of Oral and Maxillofacial Radiology published clinical recommendations for CBCT use in orthodontics, and airway assessment was not included in their recommendations for use.[16] Taking a lateral cephalometric radiograph is also an easier screening tool for nasopharynx obstruction in children compared to more invasive procedures, such as nasal endoscopy or videofluoroscopy,[14] and has even been shown to be as reliable as endoscopy.[17] Measurement of the adenoid-nasopharyngeal ratio (“A/N”), as described by Fujioka et al. in 1979,[18] and McNamara's line (Upper Pharynx, or “UP”), as described by McNamara in 1984,[19] have both been shown to be adequate tools for screening adenoid hypertrophy on lateral cephalometric radiographs[20],[21],[22],[23] even when compared to CBCT evaluation[24],[25] and magnetic resonance imaging.[26] Additional methods that have been recommended as reliable screening measures include two linear measurements (A1 and A2) described by Linder-Aronson and Henrikson in 1973[27] and an area measurement (“Ad area”) from Handelman and Osborne in 1974.[28],[29] Our hypothesis is that the prevalence of airway obstruction on lateral cephalometric radiographs is the same in both Caucasian and African-American patient populations.


  Methods Top


A retrospective search of patient records within the axiUm data system from 01/01/2009 to 12/31/2013 was completed. The patient records were saved in axiUm electronic record and Dolphin Imaging software associated with and housed in the Division of Orthodontics and Dentofacial Orthopedics, University of Rochester (UR), Eastman Institute for Oral Health. The search criteria included subjects aged 9–15 years who had self-reported as Caucasian (non-Hispanic) and African-American (non-Hispanic) who had orthodontic records taken between January 1, 2009 and December 31, 2013. If age, gender, or race could not be determined, the patient was excluded. If their records were incomplete (no usable radiographs) or had a history of tonsil and/or adenoid removal, they were also excluded. Patients for orthodontic treatment had already signed consent to release/use of records, as this is an educational institution; thus, subjects were not contacted regarding their participation in the study as only their records were needed. Two groups of 56 patients were identified within the criteria outlined. All patients were from two racial groups, African-American non-Hispanic (A) and Caucasian non-Hispanic (C), between the ages 9–15 years, and an equal number of male and female patients were selected. Sample size estimation was based on power analysis to achieve 80% power, with a significance level set at 0.05.

A random number was assigned to each subject's radiograph and all data were collected in a de-identified manner in an Excel spreadsheet by one investigator (CM) and stored on a password protected/encrypted computer located at Eastman's Division of Orthodontics and Dentofacial Orthopedics. All radiographs were traced using Dolphin Imaging Software for the dental and skeletal measurements and the ImageJ program, a public domain image-processing program by NIH Image for the airway measurements.[30] Dental and skeletal measurements were from the Eastman analysis on Dolphin Imaging and are shown in [Table 1] and [Figure 1]. Five airway measurements were used: three linear (McNamara's upper pharynx “UP,”4 Linder-Aronson and Henrikson's A1 and A23), one ratio, (Fujioka's adenoid-nasopharyngeal “A/N” ratio18), and one area (Handelman and Osborne's airway percentage[28] “Ad area”). A visual description of each airway measurement including landmark identification is visible in [Figure 2], and a description of each is present in [Table 2]. A two-sample t-test was used to compare the mean values between the two groups. The prevalence of obstruction was determined based on each separate airway measurement's threshold for referral to an ENT, per the original author's specifications. These thresholds are described in [Table 2].
Figure 1: Example of cephalometric tracing

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Figure 2: (a) Fujioka's A/N Ratio (b) Handelman and Osborn'e Ad area (c) McNamara linear UP measurement (d) Linder-Aronson and Henrikson linear A1 and A2 measurements

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Table 1: Definition of cephalometric landmarks

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Table 2: Summary of cephalometric airway analysis

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  Results Top


Airway obstruction measurements and prevalence

The prevalence of any airway obstruction (when the minimum threshold for recommending ENT referral was met in at least one of the five airway measurements) in the A Group was 0.25 and 0.27 in the C Group [Table 3]. When the patient met the threshold for referral in every measurement, the A Group prevalence was 0.054 and C Group was 0.036 [Table 3]. The overall prevalence of any obstruction was 0.26 and obstruction in all measurements was 0.045. The differences in both prevalence's between the two groups, A and C, were not significantly different. The only mean airway measurement significantly different between A and C Groups was A/N.
Table 3: Obstruction prevalence

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Skeletal and dental measurements

For the dental and skeletal measurements, the mean values between the A and C Groups were compared statistically. Every measurement was significantly different between the two groups (P < 0.05) except for U1-Na(°). All measurements are shown in [Table 4].[31],[32]
Table 4: Descriptive statistics for cephalometric measurements

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  Discussion Top


Since the overall prevalence of airway obstruction between A and C Groups was not significantly different whether we considered it to be any obstruction or obstructed in all measurements, we believe our hypothesis to be confirmed that there is no difference in airway obstruction prevalence between African-American and Caucasian non-Hispanic patients. We did find a difference in the prevalence of obstruction between the A and C Groups when one measurement in particular was considered, Fujioka's A/N ratio. The A Group prevalence of airway obstruction according to the A/N ratio was 0.089, whereas the C Group prevalence was only 0.036. According to this measurement, airway obstruction was more prevalent in the African-American patient sample, which is a finding that is contrary to our overall results and conclusion. In addition, there was a statistically significant difference between the A and C Group A/N overall averages, with the A Group having a higher sample-wide average A/N of 0.49, compared to the C Group average A/N of 0.44. Given that A/N was the only airway measurement to show a statistically significant difference in both prevalence and mean measurement between the two groups, this airway measurement perhaps requires further investigation.

For the dental and skeletal measurements, only the overall means of each measurement two groups have been compared at this time. Racial differences in craniofacial measurements on lateral cephalometric radiographs have been noted in prior studies[10] and our numbers confirm these differences, with every measurement between the two groups having a statistically significant difference except for U1-Na(°). The African-American non-Hispanic patients overall had a higher average ANB (4.64°), SNA (85.26°), and SNB (80.61°), which indicates a tendency overall toward a Class II profile with a prognathic maxilla and orthognathic mandible. By comparison, the Caucasian on-Hispanic patients had lower average values for ANB (2.69°), SNA (80.83°), and SNB (76.86°), showing an overall tendency toward a Class I profile with an orthognathic maxilla and mildly retrognathic mandible. The C Group numbers align more closely than the A Group with the standard published norms for these measurements, which is expected given that these norms are historically based on mostly Caucasian non-Hispanic patients.[33] One interesting finding was that the standard deviation for the C Group SNB was 10.72, while the A Group standard deviation was only 4.05, possibly due to the much larger range of SNB in the C Group than the A Group. The A Group FH-MP (28.17°) and SN-MP (35.61°) averages were higher compared to the C Group FH-MP (24.98°) and SN-MP (33.49°) averages, which indicates an A Group tendency toward vertical or hyperdivergent growth pattern. This again confirms the A Group in our sample favoring a Class II skeletal relationship and a more normodivergent or normal growth tendency for the C Group. Facial heights for the A Group were also overall higher (upper face height, lower face height , and total face height) than the C Group, again indicating that these patients were more likely to have a vertical skeletal growth tendency. For the dental measurements, the lower incisor to mandibular plane angle was much higher in the A Group (97.08°) than the C Group (93.92°), indicating a higher average lower incisor proclination in the African-American patients. In the future, a comparison of the skeletal and dental measurements of patients with airway obstruction to those with no obstruction within each of the racial groups would be beneficial. As there was no documented difference in the prevalence of airway obstruction between the A and C Groups, we do not have reason to believe that the skeletal and dental measurements are related to the airway obstruction prevalence at this time.


  Conclusion Top


The overall prevalence of airway obstruction between A and C Groups was not significantly different, so our hypothesis is accepted. According to one of the five airway measurements (A/N ratio), the African-American patient sample had both a significantly higher mean airway obstruction and an increased prevalence of obstruction. Future studies could benefit from increasing the sample size and looking into any differences in craniofacial measurements between the patients with and without airway obstruction. In addition, comparing between inter and intra-observer measurements would be beneficial in the future, as well as including and comparing Hispanic patients, which is an ethnic group not a racial group. Looking at airway obstruction on CBCT on patients of different racial backgrounds would also be a beneficial future study as the usage of CBCT in clinical practice increases.

Acknowledgments

The authors have no financial relationships to disclose and deny any conflicts of interest.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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