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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 9  |  Issue : 1  |  Page : 66-72

Evaluation of relationship between pharyngeal airway space and varying dimensions of maxilla and mandible


Department of Orthodontics and Dentofacial Orthopaedics, Chettinad Dental College and Hospital, Kelambakkam, Tamil Nadu, India

Date of Submission17-Nov-2021
Date of Acceptance15-Feb-2022
Date of Web Publication06-Apr-2022

Correspondence Address:
Prema Anbarasu
Department of Orthodontics and dentofacial orthopaedics, Chettinad Dental College and Research Institute, Kelambakkam, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdrr.jdrr_177_21

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  Abstract 


Aim: Craniofacial abnormalities such as maxillary retrusion, mandibular retrognathism, short mandibular body, and downward and backward rotation of the mandible in hyperdivergent patients are considered to be the most important risk factor for upper airway obstruction. The aim of the study is to analyze the influence of maxillary and mandibular morphology on pharyngeal length. Materials and Methods: The study sample includes 146 pretreatment lateral cephalographs of both male and female patients aged between 18 and 30 years. The study sample was divided into three groups: Group I – Class I skeletal relationship, Group II – Class II, and Group III – Class III. Each group is further divided into three subgroups according to the growth pattern (A – horizontal, B – average, and C – vertical). The lateral cephalograms were traced both manually and digitally using FACAD imaging software. Results: Comparison of mean maxillary, mandibular, and airway dimensions done using one-way analysis of variance proclaims that the means of all the parameters of the study are statistically significant with P < 0.05 except the upper pharyngeal space. Pearson correlation test reveals a statistically significant positive correlation between the height of the ramus and the lower pharyngeal space. Conclusion: The upper pharyngeal space is reduced in Class III, and the lower pharyngeal space is reduced in Class II and Class III malocclusions. The airway dimension decreased in vertical growth pattern in all the skeletal malocclusion groups. Upper and lower pharyngeal space has a negative correlation with ANS-PNS (maxillary length) and length of the body of the mandible, respectively.

Keywords: Mandibular dimension, maxillary length, pharyngeal airway, vertical skeletal relation


How to cite this article:
Anbarasu P, Subramanian SK, Priya SM. Evaluation of relationship between pharyngeal airway space and varying dimensions of maxilla and mandible. J Dent Res Rev 2022;9:66-72

How to cite this URL:
Anbarasu P, Subramanian SK, Priya SM. Evaluation of relationship between pharyngeal airway space and varying dimensions of maxilla and mandible. J Dent Res Rev [serial online] 2022 [cited 2022 May 26];9:66-72. Available from: https://www.jdrr.org/text.asp?2022/9/1/66/342707




  Introduction Top


Respiration plays a very important role in the development of craniofacial structures. Any abnormalities in craniofacial skeleton and surrounding soft tissue can invariably affect the airway. The most common factors affecting pharyngeal dimensions are craniofacial anomalies such as Apert syndrome and cleidocranial dysplasia, nasal stenosis, adenoid hypertrophy, enlarged tongue, retropositioned mandible, enlarged soft palate, trauma to nasal structures, inferiorly positioned hyoid bone, posteriorly positioned tongue, and vertical growth pattern.[1] The relationship of maxilla and mandible to the cranial base significantly affects the airway, and the ultimate treatment goal is to correct maxillomandibular discrepancy, thereby increasing the pharyngeal dimensions. There are studies relating anteroposterior dimensions of mandible and pharyngeal airway space[2],[3],[4],[5],[6],[7],[8] which supports the finding that mandibular retrognathism and reduced mandibular length are associated with narrow pharyngeal airway space. In corroboration to these literature findings, there are studies to endorse that correction of retrognathic mandible by mandibular advancement using oral protraction appliance significantly improves the airway space in obstructive sleep apnea (OSA) subjects.[9],[10],[11],[12],[13]

It is to be unveiled that there are only limited studies to discern the relationship between pharyngeal airway space and maxilla. Studies comparing transverse dimensions of maxilla and pharyngeal airway space have also been reported.[14] Maxillary constriction with decreased transverse dimensions of maxilla is associated with narrow airway, and treatment of maxillary constriction by rapid maxillary expansion has a significant effect on improving the airway dimensions.[15],[16],[17],[18]

After an exhaustive literature review, it is noted that there are only a few or nil studies relating morphology of maxilla and airway, hence this study was done to evaluate the changes in pharyngeal airway space with varying dimensions of maxilla. Therefore, the aim of the study is to analyze the influence of morphology of maxilla (in particular) and mandibular morphology on pharyngeal airway space.


  Materials and Methods Top


The study was reviewed and approved by the Institutional Review Board (approval number 379/IHEC /10–17). The sample size was determined by using G power analysis, as n=150, with 80%power at 5% alpha error based on the study by Muto et al., 2015.[5] The study sample includes 156 pretreatment lateral cephalographs of both male and female patients aged between 18 and 30 years attending the orthodontic clinics at the Dental University. Patients with craniofacial syndromes, patients with history of having nasal obstruction, nasal stenosis, enlarged adenoids, history of adenoidectomy or tonsillectomy and any other pharyngeal pathology, and history of previous orthodontic or functional orthopedic treatment were excluded from the study.

The study sample was divided into three groups: Class I malocclusion (ANB 2°–4°, wits 0 to ±2mm), Class II malocclusion (ANB >4°, wits >2 mm), and Class III malocclusion (ANB <2°, wits < −2 mm). The number of subjects in each group was 52. Each group was divided into three subgroups as subgroup A – three horizontal growth patterns (n = 20), subgroup B as average growth pattern (n = 22), and subgroup C as vertical growth pattern (n = 10). The growth patterns were decided according to FMA, Y-Axis, and SN-Go-Gn: in Group A (FMA <17°, Y-Axis <53°, SN-Go-Gn <32°); in Group B (FMA 17°–28°, Y-Axis 53°66°, SN-Go-Gn 32°); and in Group C (FMA >28°, Y-Axis 66°, SN-Go-Gn >32°).

The lateral cephalographs used for the study were taken from the same cephalometric apparatus (Planmeca) operated at 90 kvp, with a maximum tube current of 100 mill amperes. The radiograph is taken at a distance of 168 cm between the focal point of the source and the patient. The cephalometric apparatus is a digitally compatible orthopanthomographic machine that has a static digital sensor plate which is a photostimulable phosphor plate. The sensor plates were processed using FUJI digital image processing scanner. Standardization of head posture was done before taking the X-ray.

The lateral cephalographs thus obtained were traced digitally. Digital tracing was done using FACAD imaging software, a digital software used for diagnosis as well as for treatment planning. The lateral cephalographs were imported to FACAD imaging software version 3.6. The images were calibrated to 45 mm using two points of the ruler present on the digital film.

The following parameters were measured using lateral cephalogram [Figure 1]:
Figure 1: Cephalometric parameters used for the study

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  1. Length of the maxilla – PNS-ANS
  2. Length of the body of mandible – Gonion-Gnathion
  3. Height of the ramus – Articulare-Gonion
  4. Effective length of the maxilla – Condylion–Point A
  5. Effective length of the mandible – Condylion–Gnathion


  6. Airway space measurement – done by McNamara's cephalometric analysis

  7. Upper pharyngeal airway space – Upper pharyngeal width is measured from a point on the posterior outline of the soft palate to the closest point on the pharyngeal wall. The measurement is taken on the anterior half of the soft palate outline
  8. Lower pharyngeal airway space – Lower pharyngeal width is measured from the point of intersection of the posterior border of the tongue and the inferior border of the mandible to the closest point on the posterior pharyngeal wall.


Statistical analysis

Descriptive statistical analysis has been carried out in the present study. In each group, means and standard deviations for all the airway parameters were determined. Analysis of variance (ANOVA) has been used to find the significance of study parameters between the groups. Post hoc Tukey test has been used to find the pair-wise significance. Pearson correlation coefficient was done to assess the correlation between pharyngeal length (PL) and maxillary as well as mandibular dimensions (variables).


  Results Top


The demographic details of the study participants are given in [Table 1]. [Table 2] shows the mean and standard deviation of the maxillary and the mandibular dimensions including the upper and lower PL under each group [Figure 2]. One-way ANOVA compares the means of three groups in order to determine whether there is statistical evidence that the means are significantly different. [Table 3] depicts the results of one-way ANOVA test which proclaims that the means of all the parameters of the study are statistically significant with P < 0.05 except the mean for the upper pharyngeal space. One-way ANOVA test is followed by post hoc Tukey test for pair-wise comparison between each group with significance level at subset alpha = 0.05 showing statistically significant mean value for all the parameters except the upper and the lower pharyngeal space.
Table 1: Demographic details

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Table 2: Mean and standard deviation for each airway parameter

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Table 3: Analysis of variance and Post hoc Tukey test

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Table 4: Pearson correlations between airway parameters

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Figure 2: Airway dimensions in different growth patterns

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Pearson correlation test was done to determine the correlation between the study parameters and the correlation between the maxillary and the mandibular dimensions with the upper and lower pharyngeal space. The upper pharyngeal space has a positive correlation with the entire maxillary and mandibular dimensions except the length of the body of the mandible having a negative correlation to the upper pharyngeal space. The lower pharyngeal space has a positive correlation with the entire maxillary and mandibular dimensions except the height of the ramus having a negative correlation to the lower pharyngeal space [Table 4].


  Discussion Top


According to Melvin Moss functional matrix hypothesis,[19] nasal breathing is important for proper growth and development of the craniofacial complex. Anomalies of maxilla such as narrow maxilla, small-sized nose, and maxillary hypotonic are the best examples for this theory where there is a lack of development of a structure due to lack of function (breathing).

Retrognathic mandible and reduced mandibular length are associated with narrow airway space. The fact that the position of the jaws has an influence on airway can be substantiated by surgical advancement of mandible or bimaxillary advancement surgeries showing significant improvement in airway dimensions and can be used to treat OSA in accordance with the research by Pavoni et al.,[20] showing an improvement in sagittal airway dimension following treatment of Class II subjects with functional appliance therapy.

Hence, this study was undertaken to understand the relationship of various dimensions of maxillary and mandibular morphology on the pharyngeal airway space in different malocclusion groups with varied growth patterns. The airway measurement is an important part of orthodontic diagnosis and treatment planning. Various methods to measure the airway include nasal pharyngoscopy, fluoroscopy, cephalometric radiographs, computed tomography (CT), magnetic resonance imaging, cone-beam CT (CBCT), and acoustic reflection. Studies by Savoldi et al.[21] show that the values of pharyngeal airway dimensions obtained from lateral cephalograms are reliable and equal to that obtained from CBCT. Since this study is focused to analyze the correlation between the length of the maxilla and mandible (anteroposterior dimension of maxilla and mandible) and the airway space, lateral ceph was used for studying the airway parameters as well as maxillary and mandibular dimensions in our study.

The normal upper pharyngeal airway size was 15–20 mm and lower pharyngeal airway size was 11–20 mm for both males and females. According to the present study, the upper pharyngeal space is normal in Class I and Class II malocclusions and reduced in Class III malocclusion. In agreement with our findings, Sosa et al.[22] could find no clear-cut relationship between the nasopharyngeal area and Class I or Class II, division 1, malocclusions. Most recently, de Freitas et al.[23] measured the dimensions of the upper and lower oropharynx and found no significant difference between Class I and Class II malocclusions. The lower pharyngeal space is reduced in Class II and Class III malocclusions when compared to Class I malocclusion. This finding is similar to Kerr,[24] who reported that Class II malocclusion subjects showed smaller nasopharyngeal dimensions compared with Class I and normal occlusion subjects. The result of our study is in accordance with a study by Yin et al.,[25] who reported that children with Class III malocclusion have larger tongue volume, upward displacement of hyoid, and smaller nasopharyngeal volume. Children with Class II malocclusion have small tongue volume, downward displacement of hyoid, and small oropharyngeal volume.

The result of our study reported that the upper airway dimension decreased in vertical growth pattern in all the skeletal malocclusion groups, which is similar to the result of Zhong et al.,[26] who reported that vertical facial pattern was responsible for the deficiency in depth of the superior part of the upper airway because of the craniomaxillary complex. Assessment of correlation between the maxillary and mandibular dimensions and the pharyngeal space although not statistically significant reveals that upper pharyngeal space has a positive correlation with all the maxillary and the mandibular dimensions except ANS-PNS (maxillary length) showing a negative correlation with the upper pharyngeal space. Hence, a decrease in the length of the maxilla may be correlated to the increase in the airway space. The lower pharyngeal space has a positive correlation with all the maxillary and the mandibular dimensions except length of the body of the mandible showing a negative correlation with the lower pharyngeal space. Hence, a decrease in the length of body of mandible may be correlated to the increase in the airway space. However, ramus height shows a statistically significant positive correlation with the lower pharyngeal space. Hence, an increase in the ramus height results in increased airway space. The findings of our study are similar to the result of Lam et al.,[27] who found that retroposition of the mandible was associated with severe OSA in Chinese subjects. Similarly, the research of Hou et al.[28] showed that mandibular body length was a significant predictor for OSA. Ang et al.[29] suggested that the mandible tended to be more retrognathic in their moderate-to-severe sample of OSA patients. However, Wenzel et al.[30] reported no correlations between airway size and mandibular morphology, although a significant relationship was observed between changes in nasopharyngeal airway size and maxillary prognathism. Hence, it may be recommended to increase the sample size to obtain statistically significant result in order to assess the correlation between the maxillary and mandibular dimensions and pharyngeal space.

Clinical significance of the study

Hence, this study was undertaken to find out the correlation between the length of the maxilla in particular and the pharyngeal airway space, which may influence treatment planning, especially during surgical correction method of surgical treatment with regard to the length of the maxilla.

Limitation of the study

Decreased sample size and the study can be done using advanced technology like CBCT.


  Conclusion Top


  1. The upper pharyngeal space is reduced in Class III malocclusion. The lower pharyngeal space is reduced in Class II and Class III malocclusions
  2. The airway dimension decreased in vertical growth pattern in all the skeletal malocclusion groups.


Upper pharyngeal space has a positive correlation with all the maxillary and the mandibular dimensions except ANS-PNS (maxillary length) showing a negative correlation with the upper pharyngeal space. The lower pharyngeal space has a positive correlation with all the maxillary and the mandibular dimensions except length of the body of the mandible showing a negative correlation with the lower pharyngeal space.

Ethical clearance

The study was reviewed and approved by institutional review board (approval number 379/IHEC/10-17).

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

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



 

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