All ETDs from UAB

Advisory Committee Chair

Terpsithea Christou

Advisory Committee Members

Ramakiran Venkata Chavali

Amjad Javed

Chung How Kau

Ejvis Lamani

Document Type


Date of Award


Degree Name by School

Master of Dentistry (MDent) School of Dentistry


Extraction of premolar teeth for orthodontic purposes is a common treatment approach. The effects of premolar extraction on the occlusion and the face have been studied extensively in the past. To date, however, the effects of premolar extractions on the smile have not been comprehensively quantified in the literature. The purpose of this study was to compare the smile outcome of patients treated with premolar extractions. Methods: This retrospective case-control study established 4 groups of 33 patients each for comparison. Three groups of patients with the same malocclusion were treated with different premolar extraction patterns. The remaining group of patients had the same malocclusion but was treated without extractions and comprised the control group. Patient photographs and radiographs were measured on 13 continuous variables at 1. Pretreatment, 2. Posttreatment, 3. Mean difference among the 4 groups and 4. Mean difference between each group. Results: After applying all inclusion and exclusion criteria, a total of 132 patients were included in the study for final statistical analyses, with 33 in each of the 4 groups. Most of the pretreatment values were found to be similar, suggesting a homogenous initial sample. Posttreatment, six variables demonstrated statistically significant change from treatment effects between the 4 groups: transverse width, upper and lower lip thickness, gingival display, upper incisor position and upper incisor inclination. Additionally, treatment duration was significantly different between the non-extraction and the extraction groups. Conversely, 7 variables showed to be nonsignificant: smile width, Lip symmetry, smile index, smile cant upper dental midline, buccal corridors (% and mm). Conclusion: Orthodontic treatment duration is likely to be longer in cases with extraction of premolar teeth versus non-extraction treatment. Orthodontic treatment improves the buccal corridors whether an extraction or non-extraction treatment protocol is used. Non-extraction showed the most dramatic change in in upper incisor position and U5L5 the least. None of the four different orthodontic treatment modalities affect the lips at rest or upon smiling.

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