A MICROSCOPIC EXAMINATION OF BOND SURFACES IN FAILED ELECTROLYTICALLYETCHED CAST METAL FIXED PROSTHESES

The aims of this investigation were to examine the patterns of resin c ement failure between debonded electrolytically etched (Maryland) brid ge retainers and their respective abutment teeth and to determine if t he clinical assessment of bond failure corresponded to the types of fa ilure observed in the scanning electron microscope. Twenty-eight (18 a nterior and 10 posterior), debonded bridges were examined. The results indicated that the classification of bond failures at the clinical le vel did not correspond to the SEM assessments of failure. It appeared from the specimens examined that loss of retention occurred as a resul t of resin failure within the cement layer close to the enamel-resin i nterface. Only one metal retainer specimen showed a small area of resi n-metal failure. There appeared to be no differences in the patterns o f resin failure between anterior and posterior bridges. The observatio ns also indicated that the resin cements used for bridge cementation a dhered well to electrolytically etched retainer surfaces.