A microscopic examination of bond surfaces in failed electrolytically etched cast metal fixed prostheses

The aims of this investigation were to examine the patterns of resin cement failure between debonded electrolytically etched (Maryland) bridge retainers and their respective abutment teeth and to determine if the clinical assessment of bond failure corresponded to the types of failure observed in the scanning electron microscope. Twenty-eight (18 anterior and 10 posterior), debonded bridges were examined. The results indicated that the classification of bond failures at the clinical level did not correspond to the SEM assessments of failure. It appeared from the specimens examined that loss of retention occurred as a result of resin failure within the cement layer close to the enamel-resin interface. Only one metal retainer specimen showed a small area of resin-metal failure. There appeared to be no differences in the patterns of resin failure between anterior and posterior bridges. The observations also indicated that the resin cements used for bridge cementation adhered well to electrolytically etched retainer surfaces.