Date of Award

Summer 2022

Document Type


Degree Name

Master of Science (MS)



First Advisor

Liu, Dawei

Second Advisor

Nimeri, Ghada

Third Advisor

Mehta, Shivam


Objective: Ormco has proposed that the low-friction design of their self-ligation brackets allows for more efficient alignment of crowded teeth with less incisor proclination and faster treatment times compared to conventional MBT bracket systems. The purpose of this study is to examine the hypothesis that there is no difference between Damon PSL and conventional MBT brackets in factors related to leveling and alignment in-vitro. Methods:Damon Q2 .022” slot brackets and 3M Unitek .022” slot MBT brackets were bonded to 2 sets of typodont teeth. Typodont teeth were placed into 8 upper and lower Class I crowding wax forms (Kilgore, USA) with 4 sets per group (n=4). Each group reused its respective set of typodont teeth in each test run. .014” CuNiTi wires (Ormco) were inserted and the wax forms were placed in a 48C water bath for 10 minutes. Digital scans, photos, and lateral cephalograms of the wax models were taken before and after the water bath to evaluate incisor proclination, arch length, interincisal spacing, extraction space closure, intermolar and inter-canine width. After evaluation of leveling and alignment, frictional resistance was tested in the upper right and lower left quadrants in each group with the Autograph AGS-X series Universal Tensile testing machine (Shimadzu). As was done during the evaluation of alignment, each test run was repeated 4 times per group, per arch, with a .014” CuNiTi wire. Statistical analysis was completed with ANOVA, post-hoc, and t-test analysis. P values less than 0.05 were considered statistically significant. Results: The MBT bracket group showed a significantly greater increase in arch length, incisor proclination, interincisal spacing, and static friction for both upper and lower arches (p < 0.05). The MBT group also exhibited greater static friction in the upper arch than the lower arch (p < 0.05). The Damon bracket group exhibited a significantly greater decrease in upper arch extraction space and inter-canine width in both arches (p < 0.05). No difference was found in either arch between the groups’ pre and post-treatment intermolar width (p > 0.05). Conclusion: Based on the statistical analysis, the null hypothesis is rejected. We accept our working hypothesis that there is a difference between Damon and traditional MBT brackets during in-vitro leveling and alignment, which serves to support Ormco’s claims. Additional studies are required to determine the extent of clinical relevance.

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