Objective: This study measured CBCT images to determine if a consistent ratio exists between the quantifiable number of millimeters a cemented rapid palatal expansion appliance is opened and the subsequent increase in the arch perimeter obtained due to lateral expansion of the arch.

Methods: The following measurements: arch perimeter, arch width at first molars, first bicuspids, appliance length, as well as arch depth; were taken from CBCT images of patients who had completed RME therapy. These were obtained both before and after maxillary palatal expansion therapy using a fixed rapid palatal expander. Correlations were calculated for each of the dental measurements with the appliance expansion and change in arch perimeter; and expressed as Pearson’s Correlation Coefficients at = 0.05. Repeat measurements were performed on 15 random patients and an Intraclass Correlation Coefficients of > .99 were observed.

Results: Forty-two (20 males with a mean age = 14.8 years old and 22 females with a mean age of 13.3 years old) patients were included in the study. Good correlations were observed between appliance expansion, change in arch perimeter and all other perimeters (r ≥ 0.648; p < .05) except change in arch depth (r ≤ 0.216; p > .05). Strongest correlations to the change in arch perimeter were noted with appliance expansion (r = 0.778; r2 = 0.606; p < .001) and change in arch width at first molars (r = 0.751; r2 = 0.564; p < .001) with the ratios of 0.83:1 and 1.02:1 respectively.

Conclusion: This study shows a statistically significant positive correlation between the change in appliance length and the gain in arch perimeter. The significance is moderate and strong enough to build a model off of, paving the way for an additional prospective study.

LLU Discipline

Orthodontics and Dentofacial Orthopedics


Orthodontics and Dentofacial Orthopedics


School of Dentistry

First Advisor

Kitichai Rungcharassaeng

Second Advisor

Joseph Caruso

Third Advisor

Gina Roque-Torres

Fourth Advisor

Guy Taylor

Degree Name

Master of Science in Orthodontics and Dentofacial Orthopedics (MSODO)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Palatal Expansion Technique; Spiral Cone-Beam Computed Tomography



Page Count

x; 45 p.

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