Abstract
Aims: The objective of this study is to determine (1) the effect of different resin-removal methods on tensile bond strength (TBS) of rebonded new brackets (2) compare various methods of enamel resin-removal to define the best method that produces adequate bond strength (3) to compare the bond strength of newly bonded enamel (virgin enamel) with previously bonded enamel after resin removal from the enamel surface with different methods. Materials and Methods: Seventy human premolars were bonded with stainless steel new brackets, then the teeth were randomly assigned in to 7 groups, each group of 10 teeth. Group1 (control group) where TBS at the first debonding was evaluated (initial bond). Group2 brackets were debonded by bracket removal plier and the remnant adhesive removed by high-speed tungsten carbide bur (TCB) and rebonded with brackets as in initial bond, then the TBS were tested. Group3 as with group2 except that the remaining resin were removed by low-speed TCB . Group 4 as with group2 except that the remaining resin were removed by Diamond carbide Disk . Group 5 as with group2 except that the remaining resin were removed by a microetcher, Group 6 as with group 2 except that the remaining resin were removed manually by composite removing pliers, Group 7 as with group6 except that rebonding bracket without cleaning enamel with rubber cup and pumice. Results: All rotary instrument groups (G2, G3 and G4) showed significant increase in the TBS in comparing with the other groups (G1, G5, G6 and G7) also there were significant decrease in the TBS of the manually removal of adhesive remnant groups in comparing with control group, while there were no significant differences between microetcher group and control group with greater mean value for control group. Conclusions: The outcomes of this study showed that the use of the rotary instrument in the removal of adhesive remnant gives the highest tensile bond strength in compared with the other methods used in this study .
