CEPHALOMETRIC STUDY OF UPPER PHARYNGEAL AIRWAY SPACE IN GROWING THAI ORTHODONTIC PATIENTS WITH DIFFERENT SAGITTAL SKELETAL PATTERNS

Abstract

Objective: Part I aimed to estimate means of upper pharyngeal airway dimensions, evaluate the effects of sex, skeletal age, and sagittal skeletal patterns on the upper pharyngeal airway dimension, and position and dimension of surrounding structures, and to test the ability of new angular variables in measuring hyoid and tongue position. Part II aimed to correlate upper pharyngeal airway dimension measured by lateral cephalometric radiographs, reconstructed lateral cephalometric radiographs, and CBCT scans. Materials and Methods: Part I consisted of 418 pretreatment lateral cephalometric radiographs of growing orthodontic patients [6-20 years old; mean age, 13.95±3.62 years; divided into 3 skeletal ages, pre-pubertal (CS 1,2), pubertal (CS 3,4), and post-pubertal (CS 5,6)], Faculty of Dentistry, Chulalongkorn University were collected. 12 angular, 13 linear, and 3 area cephalometric measurements were analyzed. The three-way ANOVA, Factor analysis, Pearson’s and Spearman’s correlation analysis were applied to compare sex, skeletal age, and sagittal skeletal pattern differences and variable correlations, including the new angular measurements and the existing linear measurements of tongue and hyoid. Part II consisted of 40 presurgical radiographs; 20 lateral cephalometric radiographs and 20 CBCT scans taken in the same period of treatment time. 5 linear, 3 area, and 3 volume airway measurements were analyzed. Paired t-test was applied to compare upper pharyngeal airway measurements from lateral cephalometric radiographs and reconstructed lateral cephalometric radiographs. Pearson’s correlation coefficient was applied to correlate 2D linear and area measurements and 3D volumetric measurements. Results: Part I, Post-pubertal, Skeletal Class III, and male subjects had larger airway dimensions due to more anteriorly positioned surrounding structures than others. Skeletal ages, positions of mandible, tongue and hyoid, and tongue size significantly and positively correlated with pharyngeal airway dimensions. Linear airway measurements presented moderately high correlation with the area measurements. Angular measurements of tongue and hyoid position showed significantly moderate to high correlation with linear measurements. Part II, 2D airway measurements from lateral cephalometric radiographs were not different from reconstructed lateral cephalomeric radiographs, and correlated well with 3D volumetric measurements from CBCT. Conclusion: Although there was inter-individual variability in upper pharyngeal airway, relationships among sex, skeletal ages, sagittal skeletal patterns, surrounding structures and upper pharyngeal airway dimensions in growing subjects were found. Airway widths behind the palate and soft palate, and angular hyoid and tongue positions were good parameters to measure nasopharyngeal and oropharyngeal airway width, and tongue and hyoid position.