EVALUATION OF DEBONDING CHARACTERISTICS OF A NEW COLLAPSIBLE CERAMIC BRACKET

A new collapsible ceramic bracket designed with a metal-lined arch wir e slot has been recently introduced. The bracket also incorporates a v ertical slot designed to help create a consistent bracket failure mode during debonding. The new bracket is thought to combine the esthetic advantages of ceramics and the functional advantages of debonding meta l brackets. The purpose of this study was to compare (1) the shear bon d strength of the new collapsible bracket with a traditional ceramic b racket, (2) the compressive force required to debond the new bracket f rom the enamel surface with that needed to debond a traditional metal bracket, and (3) the bond failure location when debonding the new brac ket and a traditional ceramic bracket when pliers are used. Sixty-one Clarity collapsible ceramic brackets, 41 Transcend 6000 brackets, and 21 Victory Series metal brackets were bonded to the teeth with the sam e bonding system. The Zwick Universal Test Machine was used to determi ne the shear bond strength of 21 teeth bonded with the new bracket and 20 teeth bonded with the Transcend brackets. The same testing device was used to determine the compression force levels needed to debond 20 collapsible brackets and 21 metal brackets. Pliers were used to debon d both the new ceramic brackets and Transcend brackets to determine th e mode of bond failure. After debonding, all teeth and brackets were e xamined under 10x magnification. Any adhesive remaining after bracket removal was assessed according to the Adhesive Remnant Index (ARI). Th e findings indicated that the shear bond strength of the new Clarity c eramic bracket was comparable to that of a conventional ceramic bracke t. Similarly, there were no significant differences in the results of the compression tests comparing the magnitude of forces needed to defo rm and debond both the new ceramic and metal brackets. The ARI scores for both the shear and compression tests indicated a similar bond fail ure pattern when the new collapsible brackets were compared with eithe r the conventional ceramic or metal brackets. On the other hand, the c hi(2) test results indicated that, when debonding pliers were used, th ere was a significantly greater incidence of an ARI score of 1 with th e collapsible brackets. This indicated that, when debonding the new br ackets with the Weingart pliers, there was a greater tendency for most of the adhesive to remain on the enamel surface. In conclusion, the m ain advantage of the Clarity ceramic brackets is that they can be debo nded in the same manner as metal brackets. When the new ceramic bracke ts are debonded with the Weingart pliers, most of the residual adhesiv e remained on the enamel surface, a pattern that is similar to the one observed with metal brackets. The failure at the bracket-adhesive int erface decreases the probability of enamel damage but necessitates the removal of more residual adhesive after debonding.