Shear bond strength of rebonded mechanically retentive ceramic brackets.

Abstract

The purpose of this study was to evaluate the bond strength of rebonded mechanically retentive ceramic brackets. Twenty new and 100 sandblasted rebonded ceramic brackets (Clarity, 3M Unitek, Monrovia, Calif) were bonded to 120 extracted human premolars with composite resin and divided into 6 equal groups according to how the bracket bases were treated: (1) new brackets, (2) rebonded/sandblasted, (3) rebonded/sandblasted/sealant, (4) rebonded/sandblasted/hydrofluoric acid (HF), (5) rebonded/sandblasted/HF/sealant on bracket base, and (6) rebonded/sandblasted/silane. Shear bond strength of each sample was tested with a testing machine. Results showed that the new brackets group had the highest mean strength (15.66 +/- 7.05 megapascals [MPa]), followed by the rebonded/sandblasted/sealant group (7.65 +/- 5.62 MPa), the rebonded/sandblasted/silane group (5.94 +/- 5.33 MPa), the rebonded/sandblasted group (2.97 +/- 2.29 MPa), the rebonded/sandblasted/HF group (1.22 +/- 1.66 MPa), and the rebonded/sandblasted/HF/sealant group (0.82 +/- 1.16 MPa). Statistical analysis showed that only the rebonded/sandblasted/sealant group was comparable with the new brackets group in bond strength (P >.05). It was concluded that in the process of rebonding mechanically retentive ceramic brackets, (1) new brackets have the highest mean bond strength when compared with rebonded brackets, (2) the bond strength of sandblasted rebonded brackets with sealant is not significantly different from new brackets, (3) silane does not increase bond strength of rebonded brackets significantly, and (4) HF treatment on sandblasted rebonded brackets significantly decreases bond strength.