Student Theses, Dissertations and Capstones

Document Type


Degree Name

Master of Science (M.S.) in Dentistry


College of Dental Medicine

First Advisor

Lin, Chin-Yu

Publication Date / Copyright Date



Nova Southeastern University


Objective: The purpose of this ex vivo study was to assess the changes in tooth color and existing orthodontic bracket bonding when exposed to a bleaching agent. Methods: 120 freshly extracted human premolars were equally divided into 4 groups: a negative-control group, a positive-control bleaching group, a bracket-bonded group, and a bracket bonded-bleached group. The bleaching protocol was carried out as recommended by the manufacturer of Opalescence Go® – 30 minutes each day for 10 consecutive days. The color value of each tooth was measured daily by spectrophotometry for the negative-control group and the positive-control bleaching group in 6 different locations: central, occlusal, left, right, gingival, and lingual. The color values of the bracket-bonded group and bracket-bonded bleached group were measured initially at day 1 and after the debond test and removal of remaining composite at day 11. At the end of bleaching, the changes in existing bracket bonding were assessed by measuring shear bond strength (SBS), adhesive remnant index (ARI), and the number of tooth fractures during debond testing. Results: This orthodontic-specific bleaching system bleached teeth with no brackets bonded, comparing color values of the negative-control group and the positive-control bleaching group. However, it did not show an added whitening effect on teeth with existing brackets at the central, occlusal, and gingival sites, comparing the color values of the bracket-bonded group and the bracket-bonded bleached group. There were no statistically significant differences noted on SBS and ARI between the bracket-bonded group and the bracket bonded-bleached group. To our surprise, the bracket-bonded bleached group showed a statistically significant increase in the rate of tooth fracture during debond (33%), compared to the bracket-bonded group (10%). Conclusions: Using this bleaching protocol on teeth with existing bonded brackets did not have an added whitening effect at central, occlusal, and gingival sites. The added whitening effect was only noted at left, right, and lingual sites. Especially with no significant difference in the color values at the central sites, which were underneath the bonded brackets, there was no added bleaching effect with the use of this bleaching system on the teeth with existing bonded brackets. The bleaching did not show a significant effect on bracket bonding SBS or ARI. However, it may compromise the tooth structure and lead to an increase in enamel fractures during debond.




Health and environmental sciences, Bleaching, Orthodontics, Tooth



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