Effect of resin-removal methods on enamel and shear bond strength of rebonded brackets.

The objective of this study is to determine (1) the effect of different resin-removal methods on shear bond strength (SBS) of rebonded brackets, (2) condition of the enamel surface, (3) time spent to remove resin remnants, and (4) the location of the bond failure. A total of 80 premolars were included in the study. Fifty of them were divided into five groups and bonded using Light Bondtrade mark sealant and Quick Curetrade mark adhesive. Ten of the samples were debonded, and the SBS of the first debonding was calculated. Forty brackets were debonded using pliers and examined by an optical microscope (16x) to determine the location of the bond failure interface, using a modified Adhesive Remnant Index (ARI). The remnant adhesives were cleaned with four methods: (1) low-speed tungsten-carbide bur (TCB), (2) high-speed TCB, (3) Sof-Lex finishing disks, and (4) microetcher. The brackets were rebonded, and a second set of SBS and ARI values were calculated and statistically evaluated. Thirty of the premolars were divided into five groups receiving the same resin-removal methods and examined by scanning electron microscope. Rebonded teeth had a greater SBS than the initial bonding, except in group 4. The rebonded SBS values were similar in groups 1-3, and only group 4 showed a statistical difference. Sof-lex discs were the most time-consuming procedures and left much adhesive remnant. The high-speed TCB was found to be the most hazardous to the enamel. The scarring of enamel after the debonding is inevitable but can be reduced.