A dental glass ionomer cement (GIC) was modified with cellulosic fibers. The microstructural analysis and physicochemical properties were evaluated in four groups: GIC (control) and GIC modified with different concentrations of fibers, GICMF1, GICMF2 and GICMF3. Within clinically acceptable limits, composites showed capacity of water absorption and solubility in water similar to GIC and no signs of disintegration were observed. GICMF2 provided greater resistance to compression, wear and adhesion, however it had no effect on the diametral tensile strength. Morphological and chemical element analyses of GICMF2 showed the formation of a new and stable composite with interaction between fiber/ionomer matrix/load particles. (C) 2012 Elsevier Ltd. All rights reserved.