Graduation Date

Fall 12-20-2019

Document Type


Degree Name

Master of Science (MS)


Medical Sciences Interdepartmental Area

First Advisor

Sundaralingam Premaraj

Second Advisor

Peter Giannini

Third Advisor

Gregory Oakley

Fourth Advisor

Sung Kim


Purpose of this study was to evaluate orthodontically induced external apical root resorption using cone beam computed tomography in patients receiving orthodontic treatment with or without extractions. Records of 188 consecutively treated patients who received orthodontic treatment with or without extractions were evaluated. Pre-and post-treatment root lengths of maxillary incisors, volumes of maxillary central incisors, and apex displacement of either right or left maxillary central incisors were measured using Invivo 5.4 or ITK-SNAP 3.8.0 software. After adjusting for initial length, treatment duration, tooth, sex, race, bracket type, and malocclusion, maxillary incisor reduction of root length in extraction group was 0.37 mm greater than patients without extraction (p = 0.003). The difference in volume change in maxillary central incisors between extraction and non-extraction treatment was not significant (p = 0.29). There was no statistically significant difference in the number of incisors exhibiting root length or volume loss of greater than 25% between the extraction and non-extraction groups. Significant change in the angle between the long axis of the incisor and palatal plane (PP) during orthodontic treatment demonstrated a large difference between the extraction and non-extraction groups. This study shows that there is a greater root resorption observed in the maxillary incisors during extraction treatment. However, from the clinical perspective this amount of loss may not be of clinical significance and noncontributory for periodontal health.