Upper and lower pharyngeal airway space in West-Tamil Nadu population.

AIM: To compare the upper and lower pharyngeal airway (LPA) width in Class II malocclusion patients with low, average, and high vertical growth patterns. STUDY
DESIGN: Cross-sectional analytical study.
MATERIALS AND METHODS: Pretreatment lateral cephalometric films of 90 Class II subjects were used to measure the upper and LPAs. The inclusion criteria were subjects of West-Tamil Nadu, aged between 14 and 25 years, only skeletal Class II subjects of either gender and no pharyngeal pathology at initial visit. The sample comprised a total of 90 Class II subjects divided into three groups according to the vertical facial pattern: Normodivergent (n = 30), hypodivergent (n = 30), and hyperdivergent (n = 30). The assessment of upper and LPAs was done according to McNamara's airway analysis. STATISTICAL ANALYSIS: The intergroup comparison of the upper and LPAs was performed with one-way analysis of variance and the Tukey test was used to compare among the various vertical patterns.
RESULTS: Skeletal Class II subjects with hyperdivergent facial pattern showed statistically significant narrow upper pharyngeal width when compared to normodivergent and hypodivergent facial patterns. No statistically significant difference was found in the lower pharyngeal width in all three vertical facial growth patterns.
CONCLUSION: Subjects with Class II malocclusions and hyperdivergent growth pattern have significantly narrow upper pharyngeal airway space when compared to other two vertical patterns. Narrow pharyngeal airway space is one of the predisposing factors for mouth breathing and obstructive sleep apnea.

The function of respiration is highly relevant to orthodontic diagnosis and treatment planning. For the normal growth of the craniofacial structures, the normal airway is one of the important factors. By understanding the normal growth of the skull, the significance of the growth and function of the nasal cavities, the nasopharynx, and the oropharynx have been interpreted. In addition, the nasopharynx and the oropharynx both form part of the unit from which respiration and deglutition are carried out.[12]

Significant relationships between the pharyngeal structures and both dentofacial and craniofacial structures have been reported in several studies.[3456789] The interaction between pharyngeal dimensions and various vertical and sagittal facial growth patterns at varying degrees have been reported by numerous researchers.[1011] In determining the size and shape of the human face and thus of the airway, the heredity plays an important role; however, the environment appears to play a major part in the etiology of nasal obstruction. Normal upper pharyngeal airway space is 15–20 mm while lower pharyngeal airway (LPA) space is 11–14 mm. Skeletal features such as retrusion of the maxilla and mandible and vertical maxillary excess in hyperdivergent patients may lead to narrower anteroposterior dimensions of the airway.[12] On the other hand, the growth of craniofacial structures has been affected by the oropharyngeal airway.

Hereditary, developmental, and environmental factors play a large role in the dentofacial development and in the initiation of a malocclusion disorder. Other predisposing factors which causing the pharyngeal airway obstruction includes allergies, environmental irritants, and infections.[713] Gois et al. and Cuccia et al. reported that the association of vertical growth patterns with pharyngeal airway obstruction concomitantly with mouth breathing.[1415] However, some authors found that there is natural predisposition of narrower airway passages.[891011]

To breathe through the mouth, one must maintain an oral airway, and, to accomplish this, the mandible and the tongue are displaced downward and backward and the head is tipped back. The relationship of teeth, as well as the direction of jaw growth, have been suggested by the possible effect of these postural changes, which may become more downward and backward.[16] Mouth breathing has been associated with many unfavorable sequelae, which includes excessively long and tapered (dolicofacial) face form, increased lower face height, and narrow maxillary arch form. Yamada et al. found that posterior rotation of the mandible due to nasal obstruction, posterior-superior condylar growth, anterior open bite, obtuse gonial angle or constricted dental arches.[17] Receding jaw position, increased lower height, deep palatal vault, and posterior crossbite can also suggest respiratory problems.[181920]

Variations in pharyngeal airway have also been described with some sleep disorders like obstructive sleep apnea (OSA).[21] Turnbull and Battagel[22] concluded that the retrolingual airway dimension seems to be significantly decreased after mandibular setback surgery and a significant increase noted in this dimension after mandibular advancement. Battagel et al. demonstrated that an increase in oropharyngeal dimension was associated with mandibular advancement.[23] Thus, the knowledge of the upper and lower pharyngeal dimensions is very important and can help an orthodontist in various ways, especially during orthodontic diagnosis and treatment planning.

The aim of this study was to compare the widths of the upper and LPAs in Class II malocclusion with low, average, and high vertical growth patterns in patients reporting to Orthodontic Department, KSR Institute of Dental Science and Research, Tamil Nadu.

Methodology

This cross-sectional analytical study was conducted using data from 90 pretreatment lateral cephalographs of patients who visited the Department of Orthodontics, KSR Institute of Dental Science and Research, Tamil Nadu. The primary inclusion criteria were subjects of Tamil Nadu origin, only skeletal Class II patients of either gender, aged between 14 and 25 years, no previous history of orthodontic treatment, and having no pharyngeal pathology or complaints of nasal obstruction at the initial visit. Subjects with craniofacial syndromes and skeletal Class I or III malocclusions were not included in the study.

Lateral cephalograms were obtained for each subject. Same imaging device was used for each subject. All subjects were positioned in an upright position with Frankfort horizontal plane parallel to the floor and the patients were asked not to swallow and not to move their head and tongue, the teeth were in centric occlusion, and also to contact their lips lightly. The cephalometric tracings, landmark identifications, and measurements[24] for all radiographs were performed manually on acetate paper by one investigator and 15 randomly selected patients were repeated by other investigators for accurate landmark identification.

The subjects were divided into three groups: Group 1 consisted of 30 subjects with Class II malocclusions, high vertical growth pattern, Group 2 consisted of 30 subjects with Class II malocclusions, average vertical growth pattern and Group 3 consisted of 30 subjects with Class II low vertical growth pattern. A point, nasion, B point (ANB) angle was used to select the skeletal Class II subjects (ANB > 4°). SN-GoGn was used to divide the sample into hypodivergent, normodivergent, hyperdivergent facial patterns with values of <28°, 28–36° and >36°, respectively.

McNamara airway analysis was used to measure the upper pharyngeal airway and LPA [Figures 1 and 2]. Upper pharyngeal width was measured from a point on the posterior outline of the soft palate to the closest point on the posterior pharyngeal wall. Lower pharyngeal width was measured from the intersection of the posterior border of the tongue and inferior border of mandible to closest point on the posterior pharyngeal wall.

Figure 1

Upper and lower pharyngeal airway space using McNamara's airway

Figure 2

Cephalometric tracings

Statistical analysis

The data were statistically analyzed on a computer with Statistical Package for Social Science (SPSS Inc., Chicago, Illinois, USA) for windows (version 13.0). Means and standard deviations for ages and upper and lower airways were calculated. The One-way analysis of variance (ANOVA) was used for intergroup comparison of upper and lower airways. To compare among various vertical patterns for skeletal Class II subjects the Tukey test were used at P < 0.05. The measurement error for the SN-GoGn, ANB angle, and pharyngeal airway space using McNamara's airway analysis were determined by the Paired t-test and no significant difference found between them.

Results

In each group, means and standard deviations of upper and LPA s for the sample were determined. According to ANOVA, statistically significant differences were found among three vertical growth patterns in upper airways and no significant intergroup differences were found in the LPAs [Tables 1 and 2].

Table 1

Means and standard deviations of upper pharyngeal airways in different vertical facial patterns of skeletal Class II subjects

Table 2

Means and standard deviations of lower pharyngeal airways in different vertical facial patterns of skeletal Class II subjects

The comparison was done among various vertical facial patterns for skeletal Class II subjects [Tables 3 and 4]. There was statistically significant narrow upper pharyngeal airway width were found in the hyperdivergent facial pattern subjects when compared to normodivergent and hypodivergent facial pattern. The upper pharyngeal airway width between normodivergent and hypodivergent facial showed no statistically significant difference in skeletal Class II patients. In LPA widths, no statistically significant difference was found in all three vertical facial growth patterns.

Table 3

Comparison amongst various vertical patterns for skeletal Class II subjects in upper airway

Table 4

Comparison amongst various vertical patterns for skeletal Class II subjects in lower airway

Discussion

Sufficient anatomical dimensions of the airway were very dependent for normal respiration. In recent years, many authors in their studies have found that skeletal pattern variations could predispose upper airway obstruction. In this cross-sectional study, we included only skeletal Class II subjects with no pharyngeal pathologies to omit the confounding effects of sagittal discrepancies.

Many researchers have used radiographs to compare the obstruction of upper and LPA width in mouth breathing.[101112141524] In this study, we used two-dimensional cephalometric films to evaluate only pharyngeal airway width-not airway flow capacity, which would have required a more complex three-dimensional cone-beam computed tomography (CBCT). Malkoc et al. noted that cephalometric films were significantly reliable and reproducible in determining the pharyngeal airway dimensions.[25] Cameron et al. compared computed tomography and cephalometric films in skeletal malocclusion subjects and found a significantly positive correlation between nasopharyngeal airway size on cephalometric films and CBCT scan determined its true volumetric size in adolescents.[26]

Dunn et al.[3] and Proffit et al.[27] showed that Class I and Class II malocclusions with vertical growth pattern had significantly narrower upper pharyngeal width than subjects with normal growth pattern. This shows upper airway width can be increased or decreased based on the growth pattern of craniofacial structures. de Freitas et al. reported that significant narrow upper pharyngeal airway found in Class I and Class II subjects and vertical growth patterns than those with Class I and Class II and normal growth patterns.[28] Yang-Ho Park et al. in their studies.

Kerr found narrow nasopharyngeal airway space in Class II malocclusions when compared to Class I and normal occlusion subjects.[7] Our study includes only sagittal Class II patients with vertically high, average, and low angle subjects. In addition, Mergen and Jacobs showed that the upper nasopharyngeal airway was significantly narrower in Class II malocclusions.[13]

Paul and Nanda found greater occurrences of mouth breathing and nasopharyngeal airway obstruction in Class II malocclusion subjects.[29] Sosa et al.[5] studied the relationship of adenoids and type of malocclusion in subjects of 80 Class I and 64 Class II, division 1 malocclusions. His conclusion shows that the airway space did not appear to vary with the type of malocclusion. In our study, we excluded any pathology and only sagittal Class II subjects with vertically high, average, and low angles were selected.

There was no association of LPA space seen with a different vertical growth pattern in our study. This is in accordance with the study conducted by de Freitas et al.[28] and Ucar and Uysal.[30]

To provide stability of the treatment results the orthodontists should recognize the pharyngeal airway morphologies during the time of diagnosing and treating the preadolescent children with malocclusion because that might be a predisposing factors of undesirable craniofacial development.

A longitudinal study of craniofacial morphology is recommended with a larger sample size and subjects of various sagittal (Class I, Class II, and Class III) and vertical facial growth patterns should be conducted in future studies.

Conclusion

Subjects with Class II malocclusions and hyperdivergent growth patterns have significantly narrow upper pharyngeal airway space when compared to other two vertical patterns

In LPA space, there was no significant difference seen in all the three vertical patterns

Narrow pharyngeal airway space is one of the predisposing factors for mouth breathing and OSA.