Award Date
5-15-2026
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Dental Medicine
First Committee Member
Tanya Al-Talib
Second Committee Member
Charles Hill
Third Committee Member
Brian Chrzan
Fourth Committee Member
Amei Amei
Number of Pages
69
Abstract
Purpose: This retrospective study had two aims. The first aim was to evaluate the frequency of four premolar extractions across three bracket systems (Twin, Damon, and Pitts). The second aim was to compare post-treatment lateral cephalometric hard and soft-tissue differences between extraction versus non-extraction treatment, as well as the pre- to post-treatment changes.
Methods: Pre- and post-treatment records of 838 patients for extraction frequency and 757 patients for cephalometric outcomes at the University of Nevada, Las Vegas, School of Dental Medicine, Department of Orthodontics between 2018 and 2023 were analyzed. Participants were grouped by bracket system (Twin, n = 670; Damon, n = 119; Pitts, n = 49) and extraction status (four premolar extraction versus non-extraction). Cephalometric variables were collected using Dolphin Imaging software. Pearson chi-square analyses, multivariable logistic regression, and independent-samples t-tests (p < .05) were used to test significance.
Results: A significant association was found between bracket system and extraction frequency (χ² (2) = 12.32, p = .002). The Pitts group had a significantly lower extraction rate (2.0%) than both the Twin (23.7%; p = .001) and Damon groups (21.8%; p = .005). After adjusting for age, sex, and skeletal classification, logistic regression confirmed the significance. Cephalometric outcomes revealed that the extraction group completed treatment with significantly more upright and retrusive maxillary and mandibular incisors (p < .001) as well as a more retrusive lower lip to E-line (p = .002), more obtuse nasolabial angle (p = .003), and decreased mentolabial sulcus depth (p < .001). The global soft tissue convexity did not significantly differ between groups (p = .541), signifying that the overall soft tissue profile was not altered with either treatment modality.
Conclusions: Bracket system choice, particularly the Pitts system, is significantly associated with a lower extraction frequency. Extraction treatment affects both hard and soft tissue cephalometric variables, with a larger effect size in hard tissue, however it does not necessarily lead to a more flattened soft tissue profile compared to patients who do not undergo extraction therapy. The findings of the present study suggest that practitioner philosophy is as much a factor in extraction frequency as the mechanical systems of the bracket system itself.
Keywords
Cephalometric Analysis; Damon; Extraction; Orthodontics; Pitts; Twin
Disciplines
Computer Sciences | Dentistry | Medicine and Health Sciences
File Format
File Size
1230 KB
Degree Grantor
University of Nevada, Las Vegas
Language
English
Repository Citation
Esfandi, Julia, "Four Bicuspid Extraction Versus Non-Extraction Rates Across Bracket Systems and Associated Lateral Cephalometric Outcomes" (2026). UNLV Theses, Dissertations, Professional Papers, and Capstones. 5537.
https://oasis.library.unlv.edu/thesesdissertations/5537
Rights
IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/