Date of Award
Summer 2023
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Dentistry
First Advisor
Liu, Dawei
Second Advisor
Okunseri, Christopher
Third Advisor
Han, Shengtong
Abstract
Objective: This study aimed to use the available database (2017-2023) of the patients treated in the orthodontic graduate clinic at Marquette University School of Dentistry to survey epidemiologic characteristics and to determine the contributing diagnostic factors and their weights in decision-making for extraction vs. non-extraction treatment plans. Methods: Data were deidentified and extracted from the orthodontic module of the internal clinical records database in axiUm. We evaluated patients who presented between 2017-2023 for comprehensive treatment and collected the following parameters: age, race, gender, anteroposterior occlusal classification (Class I, II, III), skeletal vertical classification (high, normal, or low mandibular plane angle), amount of crowding of upper and lower arches (measured as tooth size-arch length discrepancy), amount of lip protrusion (measured as upper/lower lip distance to E-plane), and extraction versus non-extraction treatment plans. Student t-test and logistic regression analysis were performed to determine contributing factors and their weights in orthodontic extraction or non-extraction decision-making. A p-value less than 0.05 was considered statistically significant. Results: 1,715 patients were identified in the database search. The average age was 15.89 ± 8.97 years. The patient population was primarily Hispanic (53%) followed by Caucasian (28%), African American (14%), and Asian (5%). There were more female (58%) than male (42%) patients. Of the patients who had crowding, defined as an arch length discrepancy between 0 and -9 millimeters, 201 subjects had complete data available for valid logistic regression analysis, including 119 (59%) recommended for a non-extraction treatment plan and 82 (41%) for premolar extractions. In a logistic regression analysis, we found statistically significant odds ratios for upper crowding, lower crowding, and age, but the other variables were not significant. Conclusion: At Marquette, the decision to extract or not extract premolars to resolve crowding is largely a function of the amount of crowding in the arch and the patient’s age. Specifically, each millimeter of crowding is associated with a 20% increase in the likelihood of extraction being recommended, and each additional year of age is associated with a 10% increase in the likelihood of extraction.