Effects of Tooth Bleaching and Desensitization on Shear Bond Strength of Orthodontic Brackets.

Abstract

Objective: To evaluate the effects of beyond cold light whitening and desensitization on shear bond strength of orthodontic metal brackets.

Materials and methods: Ninety-eight extracted human premolars were randomly divided into seven groups (n = 14). Group 1 was the control (no treatment). Group 2 underwent bleaching, followed by bonding after 24 h. Group 3 received desensitization, then bonding after 24 h. Group 4 combined bleaching and desensitization, with bonding after 24 h. Groups 5, 6, and 7 followed the same procedure as Group 4, but bonding occurred 1, 2, and 3 weeks later, respectively. All samples were stored in 37°C artificial saliva after treatment and bonded with 3 M light-cure composite resin using halogen light. Shear bond strength was tested with a universal testing machine (INSTRON 5848). Adhesive remnant index (ARI) scores were assessed post-debonding. Statistical analysis was conducted using Analysis of Variance (ANOVA), Tukey's test, and chi-square tests, with significance set at p < 0.05.

Result: The shear bond strength 24 h after bleaching (7.5 ± 1.77 MPa) was significantly lower than the control (12.24 ± 3.71 MPa, p < 0.05). Desensitization alone (11.68 ± 3.49 MPa) showed no significant difference compared with the control (p > 0.05). Shear bond strength significantly decreased 24 h after bleaching and desensitization (p < 0.05) but recovered to control levels after 1 week (p > 0.05). ARI scores showed no significant differences.

Conclusions: (1) Brackets bonded 24 h after bleaching or combined treatment showed reduced shear bond strength but were clinically acceptable; (2) The use of nano-biomaterial desensitizers slightly reduces the shear strength of brackets, but it will repair the damage of teeth caused by bleaching; (3) The impacts of bleaching and desensitization gradually reduce and return to normal levels after 1 week.