Orthodontic-specific Bleaching Increased Tooth Fracture During Bracket Debonding

Objectives: The purpose of the study was to assess the changes in tooth color and orthodontic-bracket bonding when bracket-bonded teeth exposed to Opalescence Go^®, an orthodontic-specific bleaching system, ex vivo.
Methods: 120 freshly extracted human premolars were equally divided into 4 groups: a negative-control group (G1), a positive-control bleached group (G2), a bracket-bonded group (G3), and a bracket-bonded-bleached group (G4). Tooth bleaching was performed according to the manufacturer, 30 minutes per day for 10 days, in G2 and G4. Tooth colors in G1 and G2 were measured by spectrophotometry at day0 and day10. For G3 and G4, colors were measured before bracket bonding at day0 and after bracket debonding and composite removal at day10. The shear bond strength (SBS), adhesive remnant index (ARI), and numbers of tooth fracture were measured in G3 and G4 at day10 in the bracket-debonding test. Significant differences were determined by a Kruskal-Wallis test with post-hoc Steel-Dwass comparison and a non-parametric Behrens-Fisher pairwise test for tooth color, a t-test for SBS, a Fisher’s exact test for ARI, and a chi-squared test for tooth-fracture rate (a=0.05).
Results: At day0, there was no statistical difference in tooth color between groups. The orthodontic-specific bleaching system did bleach teeth (G1 Vs G2 at day10, p<0.001). However, it didn’t add whitening effects on teeth bonded with brackets (G3 Vs G4, p=0.257). There was no statistically significant difference noted on SBS (p=0.069) and ARI (p=0.165) between G3 and G4 in the bracket-debonding test. To our surprise, G4 showed a statistically significant increase in tooth fracture (33%), compared to that of G3 (10%), during bracket debonding (p=0.028).
Conclusions: Orthodontic-specific bleaching may not add tooth whitening or change bracket bonding on teeth bonded with orthodontic brackets. However, it may compromise the tooth structure and lead to an increase in tooth fracture during bracket debonding.