DEPTH MICROHARDNESS OF GLASS-IONOMER CEMENTS

The purpose of this study was to observe the effect of different condi tions of storage on the surface and in the depth of luting glass ionom er cement by measuring microhardness. The hardness of a glass ionomer cement was measured after storage in wet and dry conditions and in an atmosphere of 80% relative humidity, for times up to 1000 h. Storage i n distilled water produced a softening effect, but the depth hardness increased progressively. The penetration of the water is a surface phe nomenon and does not affect the depth of the cement. However, the ceme nt is vulnerable to moisture to a depth of 600 mu m and marginal gaps evolve in the range of 40 to 80 mu m when the luting cement at the too th crown margin is always destroyed.