Introduction: Functional appliances are intended to correct by incremental advancement of the mandible for correction of skeletal Class 11 relationships. Similar in design to functional appliances, mandibular advancing devices (MAD) are used for obstructive sleep apnea (OSA) patients as they increase the size of the airway by drawing the tongue and soft palate forwards, and thus maintain its patency during sleep. It has been shown that significant increases in airway dimensions and decreases in airway resistance were gained in OSA patients while evaluated with a MAD in place. This retrospective study evaluated volumetric, cross-sectional area and linear changes in the pharyngeal airway in skeletal Class 11 malocclusion patients treated with fixed functional appliances (functional appliance group) and compared measurements with skeletal Class 1 malocclusion patients treated with orthodontic mechanics that did not alter skeletal relationships (control group).

Materials and Methods: The functional appliance group consisted of 12 patients (10 male, 2 female; mean age =15.1 years) who were treated with fixed functional appliance therapy until Class 1 molar occlusion was achieved and who also had pre-treatment (Tl) and progress (T2) core beam computed tomography (CBCT) images available. The control group included twelve gender-and age-matched patients (10 male, 2 female; mean age =15.3 years) who completed treatment for Class I malocclusion with orthodontic mechanics without orthopedic effects and had pre-treatment (Tl) and post-treatment (T3) CBCT images available. Thirteen pharyngeal measurements were recorded at each time period for each subject using Dolphin Imaging Solutions v.11.0 (Chatsworth, CA, USA). The measurements included were pharyngeal volume, and the cross-sectional area, length, and width at each of the four planes (Area A, B, C, D). Area A was the upper limit of the velopharynx. Area B was the boundary between the velopharynx and the oropharynx. Area C was the boundary between the oropharynx and the hypopharynx, and Area D was the lower limit of they hypopharynx. The data at different time intervals and between groups were analyzed using paired- and independent-samples t-tests at the significance level of a=0.05 respectively.

Results: In the control group, the pharyngeal volume between TI and T3 (Mean treatment time = 33.6 months) increased with statistical significance (p = .003). All other measurements within the control group were not statistically different. Between TI and T2 (mean treatment time =11.1 months) in the functional appliance group, statistically significant increases in measurements were found in both the area A width (p = .047) and the area C length (p = .022). No statistically significant differences were found at any measurement level between control and experimental groups (p > .05).

Conclusions: The functional appliance group did not show a statistically significant increase in airway measurements compared to the skeletal Class I control group. Despite the difference in the mean treatment time between the control and experimental groups (22.5 months), both groups displayed similar increases in airway dimensions. This may or may not indicate accelerated airway growth with functional appliance therapy.

LLU Discipline

Orthodontics and Dentofacial Orthopedics


Orthodontics and Dentofacial Orthopedics


Graduate Studies

First Advisor

Joseph M. Caruso

Second Advisor

Jung-Wei Chen

Third Advisor

V. Leroy Leggitt

Fourth Advisor

Kitichai Rungcharassaeng

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Orthodontics, Corrective; Orthodontic Appliances, Functional; Airway Obstruction; Sleep Apnea Syndromes; Sleep Apnea, Obstructive -- therapy; Malocclusion, Angle Class II; Activator Appliances; Pharynx -- radiography; Oropharynx -- radiography; Diagnostic Imaging -- methods; Cone-Beam Computed Tomography; Cross-Sectional Studies; Predictive Value of Tests



Page Count

xii; 55

Digital Format


Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives