Ion release by resin-modified glass-ionomer cements into water and lactic acid solutions

This study was undertaken to gain a fuller picture of the interaction of resin-modified glass-ionomers with aqueous solutions in terms of water sorption, solution buffering and ion-release.

Two commercial materials were employed (Fuji II LC, GC; Photac Fil Quick, 3M ESPE). Light-cured cylindrical specimens (6mm highx4mm diameter) were prepared and stored for up to 6 weeks in either water (pH 5.3) or aqueous lactic acid (2.7), six specimens of each materials per storage medium. Solutions were changed at weekly intervals. Specimens were weighed at weeks 1, 2, 4 and 6; solution pH values measured, and Na, Ca, Sr, Al, P and Si ion release determined using ICP-OES. Results were analysed by ANOVA.

Materials altered solution pH, and gained mass under all conditions. However, the net mass gain in lactic acid declined with time, suggesting that water sorption was partly offset by erosion under acid conditions. Na, Ca, Sr, Al, P and Si were detected in all solutions, with greater amounts in lactic acid than in water. Phosphorus release was much lower than found previously for conventional glass-ionomers.

Like their conventional counterparts, resin-modified glass-ionomers have been found to buffer their storage media and release ions. Hence the resin phase does not significantly alter these aspects of the interaction with aqueous solutions.