comparison between four methods for rebonding orthodontic brackets

ABSTRACT

The purpose of this study was to compare in-vitro the shear bond strength of stainless steel brackets bonded to previously bonded teeth via 4 different procedures. Eighty-four human upper first bicuspids were used in this study. They were all etched and bonded using Po4 acid and Transbond Light Cure composite. The brackets were debonded one week later with debonding pliers and the buccal surfaces cleaned with a finishing bur. Then, they were divided into four equal groups, 21 bicuspids each. They were rebonded with new brackets using 4 different protocols. In Group I, the teeth were re-etched with phosphoric acid and rebonded with Reliance Two-paste system. In Group II the teeth were also re-etched with Po4 acid and rebonded with Transbond Light Cure composite. In Group III. First-step etching primer was applied and Reliance phase II two-paste system was used to rebond the teeth, In Group IV. First-step etching primer was applied and Transbond Light Cure composite was used to rebond the teeth. The 4 groups were stored individually in water at 37°C for 1 week. Brackets were then subjected to a shear bond strength test using a computerized testing Lloyds machine. Descriptive statistics were calculated for each group and One-Way ANOVA was used to compare between the two groups, followed by multiple comparison of group means [LSD]. It was found that rebonding teeth by re-etching with phosphoric acid yielded higher bond strength than when using etching primer. Also, it was bound that rebonding using two-paste composite yielded higher bond strength than when using light-cure composite