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 booster s, Enhance LC (Reliance, Itasca, III) and All-Bond 2 (Bisco, Schaumburg, II I), on the shear bond strength of new and rebonded (previously debonded) br ackets. Sixty new and 60 sandblasted rebonded brackets were bonded to 120 e xtracted human premolars with composite resin and divided equally into 6 gr oups based on the 2 adhesion boosters used: (1) new brackets/no booster (2) rebonded brackets/no booster (3) new brackets/Enhance (4) rebonded bracket s/Enhance (5) new brackets/All-Bond (6) rebonded brackets/All-Bond. Shear b ond strength of each sample was tested with an Instron machine (Instron Cor p, 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/Enha nce 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/n o booster group (14.2 +/- 7.2 MPa), and rebonded brackets/Enhance group (13 .6 +/- 6.7 MPa). No statistically significant difference was found among th e 3 groups utilizing new brackets. For groups of rebonded brackets/no boost er and rebonded brackets/Enhance, bond strength was significantly lower tha n groups of 3 new brackets and rebonded brackets/All-Bond. Rebonded bracket s/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) wh en new brackets are used, neither All-Bond 2 or Enhance LC improves bond st rength significantly, (2) without the use of any adhesion booster, sandblas ted rebonded brackets yield significantly less bond strength than new brack ets, (3) Enhance LC fails to increase bond strength of sandblasted rebonded brackets, (4) All-Bond 2 significantly increases bond strength of sandblas ted rebonded brackets, (5) sandblasted rebonded brackets with All-Bond 2 yi eld comparable bond strength to new brackets.