Microstructure characterization of silicate and glass ionomer cements has been carried out using, SEM, EDAX and ion microprobe techniques. The distribution of aluminum, calcium, fluorine, phosphorus or silicon was measured in the set cement surfaces.Cracks in the cement specimens produced by mechanical breaking, in contraction during setting, or as a result of SEM preparation were observed to occur mainly in the matrix and in the interface between matrix and particle. Powders of silicate and glass ionomer cements were separated into various fractions using sieves or cyclone separation technique. Compressive strength measurements ot specimens made ot powders with various size distributions have been assessed. The fractionation did not reveal any strong effect on the compressive strength properties either for the silicate or the glass ionomer cement.