Title

CBCT Analysis of the Pharynx: Effects of Age and Sex

Date of Award

5-2011

Document Type

Thesis

Degree Name

Master of Dental Science (MDS)

Program

Orthodontics

Research Advisor

Edward F. Harris, Ph.D.

Committee

Daniel R. Merwin, D.D.S., M.S. William G. Parris, D.D.S., M.S.

Abstract

Morphology of the pharynx affects the volume of airflow, thereby affecting facial growth patterns, the risk of sleep apnea as well as breathing and swallowing patterns. Availability of cone beam computed tomography (CBCT) systems in dentistry make evaluation of the pharyngeal structures practical. The airway is easily imaged because of the large differences in X-ray attenuation between air and the soft tissues that are mostly water. Purpose: CBCT images were analyzed in a large (n = 263) cross-sectional sample of routine dental patients to develop normative standards of pharyngeal dimensions by sex and age. Methods: Dental CBCT images (taken in an upright seated position) were analyzed using Dolphin Imaging® to calculate pharyngeal volume, cross-sectional areas, and anteroposterior and mediolateral dimensions. Analysis of covariance was used to test for sex and age effects (range: 5 to 81 years). Age changes are interpreted with caution since the data are cross-sectional. Results: Sexual dimorphism (M > F) develops in childhood because of faster growth in boys, especially for craniocaudal heights, but the percent dimorphism typically becomes fully developed in adulthood (> 20 years). Pharyngeal volume, midsagittal area and craniocaudal height are significantly larger in men. Sexual dimorphism is greater for craniocaudal than anteroposterior or mediolateral dimensions. In no instance was adenoid hypertrophy the cause of maximum airway constriction. Some variables (upper airway volume, some cranial pharyngeal areas, Sella‑Hyoid distance) continued to increase during adulthood in men, but not women. No variable became significantly smaller with age, either in childhood or adulthood. Conclusions: Inter-individual variability is high for airway volume; linear dimensions are more uniform. Finding larger dimensions in men is consistent with their larger size and greater oxygen requirements. We suggest a methodology for characterizing the airway quantitatively and provide normative data for evaluating airway abnormalities.

DOI

10.21007/etd.cghs.2011.0300

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