Introduction: Orthodontically induced apical root resorption (OIARR) can be a risk to orthodontic treatment. Advancements in imaging warrant further investigation into potential causes and solutions are worthwhile. Purpose: This study compared incidence and severity of OIARR in incisors during orthodontic treatment with and without bicuspid extractions. Materials and Methods: This study included 63 patients (504 teeth). DICOM CBCT images were imported into OsiriX MD software (version 10.0.3) for tooth length measurements from coronal and sagittal views in all incisors and incisal angulation for central incisors. Difference in tooth length from incisal edge to root apex from pre-treatment and post-treatment measurements determined OIARR. Mann-Whitney U and Friedman’s analyses compared OIARR and incisal angulation changes. Spearman Rho coefficients expressed correlations between OIARR and age, treatment duration, incisal angulation change, and extraction timing. An ANOVA test determined changes in OIARR based on gender or ethnicity. All analyses were performed at α = 0.05. Results: Mean OIARR in extraction patients (0.16 ± 0.08 mm) was statistically significantly greater than in non-extraction patients (0.09 ± 0.06 mm) [p < .05] for coronal and sagittal views. There were no statistically significant differences in OIARR

between coronal and sagittal views (p > .05). There was a statistically significant difference (p < .05) for incisal angulation change for all central incisors between groups. Age, treatment time, and extraction timing exhibited no statistically significant correlation with OIARR (p > .05). There was no statistically significant change to OIARR with gender or ethnicity (p > .05). Incisal angulation change showed a statistically significant correlation to OIARR for the extraction group (p.05). Conclusions: The study demonstrated extraction of four premolars during orthodontics resulted in a statistically significant increase in root resorption compared to treatment without extractions. Positive incisal angulation change accompanies non-extraction treatment and negative incisal angulation change accompanies extraction treatment. Resorption and angulation change are correlated in the extraction group, but not in the non-extraction group. No correlation was observed between OIARR and age, treatment duration, or extraction timing. Gender and ethnicity demonstrated no significant effect on OIARR.

LLU Discipline

Orthodontics and Dentofacial Orthopedics


Orthodontics and Dentofacial Orthopedics


School of Dentistry

First Advisor

Kitichai Rungcharassaeng

Second Advisor

Gabriela Garcia

Third Advisor

V. Leroy Leggitt

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Root Resorption; Tooth Extraction



Page Count

x, 38 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