Effects of tooth bleaching on shear bond strength of brackets rebonded with a self-etching adhesive system

Abstract

The purpose of this study was to ascertain the effects of tooth bleaching on the shear bond strength of orthodontic brackets rebonded with a self-etching adhesive system. A total of 39 premolars were collected and divided into three equal groups: in group 1 bracket bonding was performed without bleaching treatment; specimens in group 2 were bonded immediately after bleaching; and group 3 teeth were bleached, then immersed in artificial saliva and left for 7 days before bonding. The shear bond strength was measured, with the bonding/debonding procedures repeated once after the first debonding, and the bracket/adhesive failure modes were evaluated by the adhesive remnant index after each debonding. Excepting the mean shear bond strength for group 2 after the first debonding, the overall mean values reached the minimum clinical requirement of 6 MPa. The mean values at the first and second debondings were significantly higher in groups 1 and 3 than in group 2. Between groups 1 and 3, significant differences were noted at the first debonding, but not at the second debonding. Group 2 showed significant differences in mean shear bond strength between the first and second debondings. Bond failure at the enamel-adhesive interface occurred more frequently in group 2 than in groups 1 or 3 after the first debonding. The bracket-rebonding procedure can recover the reduced shear bond strength caused by immediate bonding after bleaching to a clinically acceptable level, but not to the prebleaching level.

Orthodontic bonding to acid- or laser-etched prebleached enamel

“…However, in their study, the use of 2 acid etchings before and after the bleaching procedures could have masked the enamel changes created by the bleaching agent. The ARI scores in the study by Uysal et al,27 however, were very similar to those obtained in the present study and other studies,3,9,22-26 showing that the failure site moves to the enamel-adhesive interface when the bleached surfaces are bonded immediately.…”

“…This conclusion was supported by microscopic observation, which suggested that interaction between the resin and residual peroxide in the enamel influenced the bond-strength reduction 8. The results of a study by Abe et al26 were very similar to those of our study, but the authors chose a 1-week recovery period. After 1 week, SBSs were similar to, but slightly lower than, those in the nonbleached group.…”

“…Similar to the findings of the present study, others have reported recovery of bond strengths with different waiting periods after bleaching 9,24,26. One of these studies used 25% hydrogen peroxide for bleaching and reported recovery of bond strengths even after 1 day, and this result was consistent until 1 month, wherein a slight decrease was noted 9.…”

“…In the present study, the ARI scores for the group in which bonding was carried out 3 weeks later indicated a tendency to show breaks within the adhesive, similar to the findings in the unbleached control group. Similar patterns of decreased bond strength were noted in studies that used hydrogen peroxide in-office bleaching 3,9,22-26. Contradictory results are seen only in one study, in which the authors concluded there were no significant differences in bond strengths between a control group (nonbleached), an immediate-bonding group (bleaching with 35% hydrogen peroxide), and a 30-day delay group (bleaching with 35% hydrogen peroxide) 27.…”

Shear bond strength of rebonded brackets after removal of adhesives with Er,Cr:YSGG laser

“…[20]. Campoy et al [21] reported a bond failure rate of 6.08% in their study using new brackets, Transbond Plus self-etching primer and Transbond XT adhesive.…”