Etched glass ionomer liners: surface properties and interfacial profile with composite resins

The purpose of this study was to assess the surface alterations induced by acid etching on two glass ionomer lining cements (Ketac Bond, G-C lining cement) and to evaluate their interface with a composite resin (Herculite XR) following various surface treatments. The changes in the surface composition and topography of the etched liners were studied by electron microprobe and ESCA analyses. The interfacial treatments performed on the ionomer surfaces were: (i) application of a bonding resin; (ii) 20-s acid etching and application of a bonding resin; (iii) application of a dental adhesive based on a chlorophosphate ester of BisGMA (Scotch-bond LC), without acid etching. The interfacial sealing efficiency of these treatments was studied by the silver nitrate microleakage technique combined with optical and electron microscopy. According to the results the etched surfaces of both the liners present excessive porosity with glass and matrix dissolution. Significant changes in the surface chemistry of the liners were detected indicating severe degradation. The microleakage study revealed interfacial gaps and fractures in the etched samples. The best results were obtained from the non-etched ionomer liners which were subjected to the adhesive treatment. The efficiency of acid etching as a necessary step in the 'layered' technique is seriously questioned.