Flexural properties of resin-modified "hybrid" glass-ionomers in comparison with conventional acid-base glass-ionomers.

The mechanical properties of resin-modified "hybrid" glass-ionomers, for both restorative and liner/base applications, were assessed by a flexural test and compared with those of conventional acid-base glass-ionomers. Flexural strength, flexural modulus, and the modulus of resilience were determined 30 minutes after mixing, and at 24 hours and 3 months after aging in distilled water at 37 degrees C. With a microscope and SEM observations, a comparison of marginal breakdown was made between a resin-modified and a conventional glass-ionomer restoration in bovine cavities, after cyclic loading with steel balls. It was found that resin-modified glass-ionomers were stronger, more flexible, and more resilient than conventional acid-base glass-ionomers. This was in accord with the finding that less marginal breakdown and surface deterioration occurred in a resin-modified glass-ionomer than in a conventional analogue. For some materials the flexural properties progressively improved between 24 hours and 3 months, while others showed no improvement or even deteriorated.