Semester

Spring

Date of Graduation

2021

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Chris Martin

Committee Co-Chair

Peter Ngan

Committee Member

Susan Morgan

Abstract

Objective: The objective is to determine if there is a significant difference in shear bond strength and debonding characteristics between one-piece metal brackets made by metal injection molding (MIM) and multi-piece metal brackets made by machining then soldering/brazing with differing pad designs. Methods: A total of thirteen metal orthodontic brackets manufactured by 8 different companies were divided into two groups: one-piece MIM and multi-piece brackets. Each group consisted of 10 brackets for a total of 130 brackets. Brackets were bonded to stainless steel tubes with a universal bonding technique. Samples were tested on the universal Instron testing machine to measure the shear bond strength. Force required to debond each bracket was recorded. Brackets were observed after debond and an ARI score assigned. Data were analyzed using a two sample t-test. Results: The mean shear bond strength and ARI scores for the entire study sample were 3.7±1.7 and 4.2±0.7, respectively. The results of two sample t test showed that there was no significant difference between the one-piece MIM brackets (3.5±1.7) and the multi-piece brackets (4.0±1.8) in mean shear bond strength (t(128)=1.33, p=0.18). But the mean of ARI scores of the multi-piece brackets (4.4±0.7) was significantly higher than the one-piece MIM brackets (4.0±0.7) (t(128)=3.5, p=0.006). Conclusion: One-piece metal orthodontic brackets manufactured by MIM and multi-piece brackets manufactured by machining then soldering/brazing exhibit similar shear bond strengths. However, one-piece brackets showed a significantly lower ARI score than multi-piece brackets, indicating a higher percentage of adhesive left on the one-piece bracket surface after debond.

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