Effect of etching glass-ionomer cements on bond strength to composite resin

The use of glass-ionomer cement in restorative dentistry has seen a revival because of its capacity for being etched and bonded to composite resin. Past investigators compared an etched cement surface with an unetched surface that was set against a smooth surface. Clinically, however, a glassy smooth surface is not produced when the cement is used as a base. Using Scotchbond bonding resin, we developed this two-part study to evaluate the tensile bond strengths of P-30TM composite resin to several glass-ionomer cements that were (a) unetched but allowed to set in air and (b) etched for 30 s with orthophosphoric acid, and to compare them with the cohesive strength of the respective cement. Using a silver nitrate staining technique, we also evaluated the microleakage of class V cavities restored with SiluxTM composite resin under a base of etched or unetched Ketac Bond cement. Although there were significant differences among three cements between their cohesive strength and the resin bond strength after the two surface treatments (p less than 0.01), the bond to the unetched surface was generally similar to that of the etched surface of the cement. The remaining groups showed no statistical difference. The microleakage was similar in the two groups. SEM micrographs showed a rough topography of the unetched cement that resembled that of the etched surface. This in vitro study suggests that acid-etching a glass-ionomer base for resin-bonding may not be necessary for specific materials. Further clinical evaluation is recommended to validate this observation intra-orally.