Date of Graduation

2016

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Timothy Tremont

Committee Co-Chair

Richard Jurevic

Committee Member

Chris Martin

Committee Member

Peter Ngan

Abstract

Background and Objectives: Much previous attention has been paid in the orthodontic literature to craniofacial skeletal patterns and morphology of the upper airway and their association with obstructive sleep apnea (OSA). However, the majority of 3D airway investigations in recent years have analyzed the relationship of the airway with various anteroposterior (AP) skeletal patterns using traditional 2D cephalometric landmarks and measurements, such as SNA and SNB. The Six Elements of Orofacial Harmony is a diagnostic and treatment philosophy that has attempted to provide a more accurate and clinically relevant determination of the position of teeth and jaws. Element II specifically deals with AP position of the jaws relative to a reproducible referent, the goal anterior limit line (GALL). The specific aim of this study is to utilize cone-beam computed tomography (CBCT) to investigate pharyngeal airway morphology relative to various A-P jaw positions as described by Element II. E xperimental Design and Methods: A sample of 86 CBCT scans of pre-treatment orthodontic patients aged 18-30 from the private practice of Dr. Thomas Shipley was used for this study. IRB-approval was obtained, and an approval letter was obtained from Dr. Shipley for permission to use the records from his office. Exclusion criteria included history of orthodontic treatment, complex open bite with divergent occlusal planes, craniofacial/developmental deformity, adenoid hypertrophy, history of tonsillectomy/adenoidectomy, and poor image quality or artifacts. Pre-treatment CBCT scans were de-identified and DICOM files were analyzed using Dolphin Imaging 11.5 software. CBCT slices were used to extract a 2D lateral cephalogram for each subject, from which a GALL was determined and a Six Elements evaluation performed. Using this evaluation, subjects were divided into groups based on classification of individual AP positions of the maxilla and mandible relative to the GALL, as well as other craniofacial measurements. Subjects were also be divided in to skeletal groups based on traditional cephalometric SNA, SNB, and ANB angles to serve as control groups. Dolphin 3D was utilized to measure each subject's lower pharyngeal airway volume (AV), airway length (AL), and minimum cross-sectional area (mCA), as well as other dimensional characteristics of the oropharynx and hypopharynx, compared across skeletal groups. Data was analyzed using one-way ANOVA and unequal variances t-tests to determine statistical significance of the results. Results: In the optimal Mx-GALL group, the average AV (23296.1 +/- 1095.6 mm3) and MCA (332.3 +/- 16.4 mm2) were significantly higher (p = 0.011 and 0.023) than every other position group. No other craniofacial variables had a statistically significant correlation with airway dimensions. Conclusions: The anteroposterior position of the maxilla relative to GALL has a significant correlation with pharyngeal airway size and shape. This is a novel and clinically relevant finding that can have a significant influence on surgical and non-surgical treatment planning. Subjects grouped by SNA measurement did not display any correlation with airway dimensions, and this angular classification may be providing an incomplete picture of the position of the maxilla and its relationship with the pharyngeal airway.

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