Date of Award

Spring 2001

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)



First Advisor

Bradley, Thomas

Second Advisor

Kittleson, Russell

Third Advisor

Stier, Erwin


The purpose of this study is to investigate whether extraction of four premolars as a requirement for orthodontic therapy in the African-American patjent population is a factor in the creation of tooth-size discrepancies, and to determine whether any tooth extraction combinations create more severe discrepancies. The study is carried out on the pre-treatment dental casts of 30 African-American orthodontic Patients with malocclusions. The dental casts were selected according to several criteria. No tooth-size discrepancy between the mandibular and maxillary dental arches existed before treatment. Pretreatment mesiodistal dimensions of mandibular and maxillary teeth were measured, recorded in a computer program, and subjected to Bolton' s analysis. Hypothetical tooth extractions were then performed on each patient by the following combinations: All first premolars, all second premolars, upper first and lower second premolars, and upper second and lower first premolars. The resultant measurements were again subjected to Bolton analysis to see whether a tooth-size discrepancy had been created. The results were evaluated statistically by the use of paired-sample t-tests. The difference between pre-treatment and post-extraction Bolton values were found statistically significant for the extraction of all first premolars, all second premolars and the removal of upper first and lower second premolars. The removal four first premolars created the most severe discrepancies in the overall sample, whereas the extraction of all four second premolars created the smallest range in the size of discrepancies. However, the extraction of upper first and lower second premolars were responsible for the most frequent discrepancies created.



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