[Radiographic assessment of upper airway size in skeletal sagittal and vertical jaw discrepancies]

ABSTRACT

An important factor in the process of diagnosis and orthodontic treatment planning is patient's respiratory function that has a direct correlation with the upper airway size. The aim of this study was to measure and compare nasopharyngeal, oropharyngeal and hypopharyngeal airway volumes in Iranian subjects with sagittal [Class I, II and III] and vertical [normodivergent, hyperdivergent and hypodivergent] jaw discrepancies using standard cephalometric radiographs. In this descriptive cross-sectional study, 100 pre-treatment lateral cephalograms of orthodontic patients were evaluated to assess the size of upper airway space including the nasopharynx, oropharynx and hypopharynx. In order to assess airway dimensions in patients with sagittal and vertical discrepancies, subjects were divided into two large groups of normal sagittal and normal vertical patterns. Airway size was measured in sagittal plane in 50 subjects with normal vertical patterns and in vertical plane in 50 subjects with normal sagittal patterns. Linear variables i.e. the size of nasopharyngeal space [PNS-UPW], oropharyngeal space [U-MPW] and hypopharyngeal space [V-LPW] were measured by cephalometric tracing. Data were analyzed using SPSS version 15 software and chi-square, ANOVA and Tukey's HSD tests. Understudy subjects had normal age and gender distribution pattern. In patients with normal sagittal pattern, by an increase in vertical dimension, size of nasopharynx [PNS-UPW], oropharynx [U-MPW] and hypopharynx [V-LPW] decreased and the mentioned volumes were significantly smaller in subjects with hyperdivergent facial patterns compared to hypodivergents. In subjects with normal vertical pattern, by an increase in ANB angle, size of oropharynx [U-MPW] and hypopharynx [V-LPW] decreased and the mentioned volumes in CL II patients were significantly smaller than in CL III subjects; whereas, the largest nasopharynx [PNS-UPW] was observed in CL I subjects. Sagittal and vertical discrepancies affect upper and lower airway dimensions and by an increase in facial height, the mentioned volumes decrease. Smaller ANB angle results in larger airway dimensions