The effect of different reconditioning methods on bond strength of rebonded brackets: An in-vitro study

To evaluate the effect of three different reconditioning techniques on the shear bond strength (SBS) of rebonded brackets.

Forty-five orthodontic brackets were bonded to human premolar teeth using Transbond™ XT. After debonding, the samples were randomly assigned into equal groups to assess three techniques for the removal of residual adhesive from bracket bases: in Group A, each bracket base was sandblasted with aluminum oxide; in Group B₁, each base was cleaned superficially with a greenstone bur; and in Group B₂, the bases were thoroughly abraded with a greenstone bur. Subsequently, brackets were rebonded and the SBS and the adhesive remnant index (ARI) were determined. Data were analyzed using one-way analysis of variance (ANOVA), plus Tukey and Kruskal-Wallis post-hoc tests (P ≤ 0.05).

The average SBSs were: Group A, 11.75 (±4.83) MPa; Group B₁, 8.22 (±4.01) MPa; and Group B₂, 7.54 (±2.85) MPa. No statistically significant differences in SBS were found between Groups A and B₁(P = 0.051) and Groups B₁ and B₂(P = 0.885), but there was a significant difference between Groups A and B₂(P = 0.016). Regarding ARI scores, there were statistically significant differences between Groups A and B₂(P < 0.001) and between B₁ and B₂(P = 0.014), but not between Groups A and B₁(P = 0.068).

All reconditioning methods were found to have a positive effect, but the sandblasting technique performed best. Brackets reconditioned by sandblasting and superficial grinding mainly showed mixed-type failure, while in samples thoroughly reconditioned by greenstone bur, bonding failure occurred predominantly at the adhesive/bracket interface.