Brandon Malan


Introduction: Resorption of root apices is a ubiquitous occurrence in orthodontic treatment. Although most occurrence of resorption during orthodontic treatment is clinically inconsequential, a small percentage of patients have a severe amount of root structure that is lost. There are factors that are widely accepted as responsible for apical root resorption (RR), such as heavy compressive forces on the periodontal ligament (PDL). Unfortunately, it is still largely unpredictable if one patient will experience more root loss than what is considered normal. Thus, it is of clinical interest to further study what factors play a role in RR. Purpose: The purpose of this study was to utilize Cone Beam Computed Tomography (CBCT) to evaluate whether certain treatment-related and patient-related factors are associated with increased severity of orthodontically induced apical root resorption. Methods: Initial (T1) and final (T2) Digital Imaging and Communications in Medicine (DICOM) CBCT images of patients orthodontically treated at Loma Linda University were imported into OsiriX MD software (version 7.5.1, Pimeo, Bernex, Switzerland) for measuring RR of right and left maxillary central incisors. Using

fiduciary markers at the anterior nasal spine (ANS), posterior nasal spine (PNS), and nasion (Na), movement of the incisors were assessed at three dental landmarks, the incisal edge (I), the center of resistance (C), and the apex (A). Patient treatment records were reviewed for information regarding patient age, gender, ethnicity, medical history, expander appliances used, whether teeth were extracted, and time in treatment. Non-parametric Spearman-Rho correlation tests were performed to determine whether correlations existed between specific directions of tooth movement, time in treatment, or age of the patient and the severity of RR. Kruskal-Wallis and Mann-Whitney U tests were also used to determine differences in RR among groups of ethnicity, gender, expansion treatment, extraction treatment and asthmatics. Results: A total of 291 patients (582 teeth) were included in this study. Total movement at A, intrusion at A and retraction at I were directions of movement that had the highest correlations with RR at 0.344, 0.343, and 0.328 respectively. Time in treatment had a significant but weak correlation with RR of 0.213. There was no correlation with the patient age and amount of resorption. Males had statistically more RR than females. However, males also had statistically more total movement of the root apex. Incisors treated with extraction of two premolars also had more RR but also more total movement at the apex compared to non-extraction treatment. Patients treated with a rapid maxillary expansion appliance or a quad helix had more RR than those treated non-expansion. There were no differences in RR among ethnicities or between asthmatics and non-asthmatics. Conclusions: In our sample, total movement at the apex, intrusion at the apex, and retraction at the incisal edge had the highest correlation with root resorption. Treatment involving rapid palatal expansion and extractions had higher means of resorption. Additionally, there were no differences in severity of resorption among ethnicities or asthmatics and non-asthmatics.

LLU Discipline

Orthodontics and Dentofacial Orthopedics


Orthodontics and Dentofacial Orthopedics


School of Dentistry

First Advisor

Rungcharassaeng, Kitichai

Second Advisor

Caruso, Joseph M.

Third Advisor

Kan, Joseph

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Root Resorption; Cone-Beam Computed Tomography; Orthodontics; Corrective; Palatal Expansion Technique;

Subject - Local

Root structure loss; Apical Root Resorption; Non-parametric Spearman-Rho Correlation test; Rapid Palatal expansion



Page Count


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