Date of Graduation

2005

Document Type

Thesis

Degree Type

MS

Committee Chair

Peter Ngan

Abstract

Objectives: To 1) determine if enamel bleaching affects the in vivo survival rate and in vitro bond strength of orthodontic bracket adhesive; 2) determine the mode of bracket failure in vivo and in vitro 3) determine if an in vitro anti-oxidant such as sodium ascorbate can reverse the compromised bonding. Methods: I. The in vitro study utilized one hundred and five (105) extracted human premolars from a jar. The teeth were randomly divided into seven groups: 1 control group; 4 groups that were exposed to varying amounts of 2 bleaching agents for varying time periods; 2 groups were also exposed to sodium ascorbate anti-oxidant; then brackets were bonded to the teeth and debonded within 24 hours. The debonding force were measured on an Instron machine, and compared. II. The in vivo study consisted of 38 patients that had one arch bleached, while the other unbleached arch served as the control. They were randomly divided into 2 groups: the first group had the brackets bonded within 24 hours of the bleaching procedure, while the second group had the bonding done after a three week interval. Results: There was a significant difference between the bond strengths of the control and the groups bleached within 24 hours of bonding, and an anti-oxidant will somewhat increase the bond strength of compromised bleached enamel in vitro. There was a significant difference in the bracket survival rate between controls and mandibular arches bleached with 38% H2O2 within 24 hours of the bonding in vivo.

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