Effects of two adhesion boosters on the shear bond strength of new and rebonded orthodontic brackets.

The purpose of this study was to evaluate the effects of 2 adhesion boosters, Enhance LC (Reliance, Itasca, Ill) and All-Bond 2 (Bisco, Schaumburg, Ill), on the shear bond strength of new and rebonded (previously debonded) brackets. Sixty new and 60 sandblasted rebonded brackets were bonded to 120 extracted human premolars with composite resin and divided equally into 6 groups based on the 2 adhesion boosters used: (1) new brackets/no booster (2) rebonded brackets/no booster (3) new brackets/Enhance (4) rebonded brackets/Enhance (5) new brackets/All-Bond (6) rebonded brackets/All-Bond. Shear bond strength of each sample was tested with an Instron machine (Instron Corp, Canton, Mass). Results show that the new brackets/All-Bond group yielded the highest strength (20.8 +/- 7.5 MPa), followed by the new brackets/Enhance group (18.6 +/- 6.5 MPa), rebond brackets/All-Bond group (17.3 +/- 7.2 MPa), new brackets/no booster group (16.8 +/- 6.3 MPa), rebonded brackets/no booster group (14.2 +/- 7.2 MPa), and rebonded brackets/Enhance group (13.6 +/- 6.7 MPa). No statistically significant difference was found among the 3 groups utilizing new brackets. For groups of rebonded brackets/no booster and rebonded brackets/Enhance, bond strength was significantly lower than groups of 3 new brackets and rebonded brackets/All-Bond. Rebonded brackets/All-Bond group had comparable bond strength to all 3 new brackets groups. It was concluded that in the process of replacing a failed bracket, (1) when new brackets are used, neither All-Bond 2 or Enhance LC improves bond strength significantly, (2) without the use of any adhesion booster, sandblasted rebonded brackets yield significantly less bond strength than new brackets, (3) Enhance LC fails to increase bond strength of sandblasted rebonded brackets, (4) All-Bond 2 significantly increases bond strength of sandblasted rebonded brackets, (5) sandblasted rebonded brackets with All-Bond 2 yield comparable bond strength to new brackets.