FAILURE MODE ANALYSIS OF CERAMIC BRACKETS BONDED TO ENAMEL

The purpose of this study was to evaluate in vitro the failure pattern of ceramic brackets bonded to enamel with a light-cured orthodontic a dhesive. Five types of ceramic brackets and 125 incisors were used in the study. The brackets were bonded onto enamel with a light-cured ort hodontic adhesive. After 1 week storage and thermal cycling, the sampl es were debonded by one operator according to the individual technique for each bracket group proposed by each manufacturer. The fracture su rfaces were examined under a stereomicroscope to reveal the type of fa ilures. The effect of the debonding procedure on enamel structure was significantly affected by the various bonding mechanisms of the bracke t bases. Cohesive enamel fractures were detected from brackets that pr ovided a bonding mechanism of micromechanical retention and chemical a dhesion. The brackets that combined mechanical retention and chemical adhesion, presented both cohesive resin fractures and fractures locate d at the bracket resin or the resin enamel interface. The higher frequ ency of cohesive bracket fractures was obtained from a monocrystalline bracket.