Aim: The purpose of this study was to determine the prevalence of orthodontic extraction cases and the rationale for the decision-making. Materials & Methods: The records of consecutive patients who had completed orthodontic treatment at Graduate Orthodontic Clinic, Loma Linda University School of Dentistry, between January 2010 and December 2014 were reviewed for prevalence of orthodontic extractions. Cone beam computed tomograms (CBCTs) of patients, that had extraction(s) prescribed as part of orthodontic treatment, were analyzed dentally and skeletally. Patients were then categorized according to the degree of crowding in each dental arch. A one-way ANOVA (Kruskal-Wallis) test and Mann Whitney U with Bonferroni adjustments for post-hoc pair-wise comparisons were used for statistical analysis at α = 0.05. Results: There were 211 orthodontic extraction cases from 889 completed cases (23.7%). However, only 144 patients had sufficient records for further analysis in this study. Premolar extraction was prescribed in 134 patients (93.0%). Evaluation of each parameter based on degree of crowding revealed statistically significant differences in mandibular incisor to mandibular plane angle (L1-MP), interincisal angle, and maxillary incisor to Nasion-A point distance (U1-NA) [p < 0.05]. Furthermore, regardless of the degree of crowding, greater than 5 mm mandibular incisor to Nasion-B point distance (L1-NB) was observed in the majority of the cases (73.6%). Conclusions: Besides the degree of crowding, interincisal angle, L1-MP, U1-NA and L1-NB seem to be the determining factors in planning for orthodontic extraction cases.

LLU Discipline

Orthodontics and Dentofacial Orthopedics


Orthodontics and Dentofacial Orthopedics


School of Dentistry

First Advisor

Rungcharassaeng, Kitichai

Second Advisor

Caruso, Joseph M.

Third Advisor

Olson, Gregory W.

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Tooth Extraction -- Statistics & numerical data; Orthodontics - Corrective; Cone-beam Computed Tomography;

Subject - Local

Orthodontic extraction; Dentists - Decision Making; Mandibular incisor to mandibular plane angle; Interincisal angle; Dental crowding



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