Tensile bond strength of reused orthodontic metal brackets

Forty-five orthodontic brackets were used in this study on the bond strength of new and reused metal brackets using an Instron testing machine. First, new brackets were bonded to recently extracted human premolars and subjected to a bond strength test. After the test, the residual resin on 15 brackets each were removed by one of three methods, oven-treated, flame-treated and bur-treated. They were then rebonded to the cleansed tooth surface and again subjected to a bond strength test. The new brackets were found to have the greatest bond strength (13.71 +/- 2.95 kg) with the oven-treated brackets in second place (12.42 +/- 2.57 kg), followed by flame-treated (11.35 +/- 2.32 kg) and bur-treated (9.11 +/- 2.30 kg). The results were subjected to the Mann-Whitney U test. The differences in bond strength between the new and reused brackets were found to be statistically significant (p less than 0.05), except for the oven-treated group. The differences in bond strength between the reused brackets were also found to be statistically significant (p less than 0.05), with the exception of the comparison between the oven-treated and flame-treated groups.