Evaluation of debonding characteristics of a new collapsible ceramic bracket

Abstract

A new collapsible ceramic bracket designed with a metal-lined arch wire slot has been recently introduced. The bracket also incorporates a vertical 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 metal brackets. The purpose of this study was to compare (1) the shear bond strength of the new collapsible bracket with a traditional ceramic bracket, (2) the compressive force required to debond the new bracket from the enamel surface with that needed to debond a traditional metal bracket, and (3) the bond failure location when debonding the new bracket 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 same bonding system. The Zwick Universal Test Machine was used to determine 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 debond both the new ceramic brackets and Transcend brackets to determine the mode of bond failure. After debonding, all teeth and brackets were examined under 10× magnification. Any adhesive remaining after bracket removal was assessed according to the Adhesive Remnant Index (ARI). The findings indicated that the shear bond strength of the new Clarity ceramic bracket was comparable to that of a conventional ceramic bracket. Similarly, there were no significant differences in the results of the compression tests comparing the magnitude of forces needed to deform and debond both the new ceramic and metal brackets. The ARI scores for both the shear and compression tests indicated a similar bond failure pattern when the new collapsible brackets were compared with either the conventional ceramic or metal brackets. On the other hand, the χ2 test results indicated that, when debonding pliers were used, there was a significantly greater incidence of an ARI score of 1 with the collapsible brackets. This indicated that, when debonding the new brackets with the Weingart pliers, there was a greater tendency for most of the adhesive to remain on the enamel surface. In conclusion, the main advantage of the Clarity ceramic brackets is that they can be debonded in the same manner as metal brackets. When the new ceramic brackets are debonded with the Weingart pliers, most of the residual adhesive remained on the enamel surface, a pattern that is similar to the one observed with metal brackets. The failure at the bracket-adhesive interface decreases the probability of enamel damage but necessitates the removal of more residual adhesive after debonding. (Am J Orthod Dentofac Orthop 1997;112:552-9.)