Objectives: The aim of this study was to evaluate the effect of bioactive glass-ceramic particles (Biosilicate (R)) addition on surface nanoroughness and topography of Resin-modified glass ionomer cements (RMGICs). Methods: Experimental materials were made by incorporating 2 wt% of Biosilicate (R) into Fuji II LC (R) (FL) and Vitremer (R) (VT) powders. Disks of RMGICs (with and without Biosilicate (R)) measuring 0.5cm (diameter) x 0.5mm (thickness) were fabricated and polished. Samples were stored at 37 degrees C in dry or immersed in distilled water for 30days. Digital images (20 x 20m) from the surfaces were obtained by means of an atomic force microscopy. Three images were acquired for each sample, and four nanoroughness measurements were performed in each image. Nanoroughness (Ra, nm) was assessed by Nanoscope Software V7. Data were analyzed with ANOVA and Student-Newman-Keuls multiple comparisons (p<0.05). SEM images were obtained for surface topography analysis.Results: FL was significantly rougher than VT (p<0.05) in wet and dry conditions. The addition of Biosilicate (R) increased the surface roughness in VT and decreased in FL, regardless of the storage media (p0.05). No differences existed between materials and storage conditions after Biosilicate (R) addition. Significance: The Biosilicate (R) particles addition produced changes on the surface nanoroughness of the RMGICs. These changes depended on the particles size of the original cements in dry conditions. In water storage, dissolution of the Biosilicate (R) particles, a silica-rich gel formation, and a hydroxyl carbonate apatite precipitation on the surface of the materials changed the nanoroughness surface. FL was the roughest in both conditions.Significance: The Biosilicate (R) particles addition produced changes on the surface nanoroughness of the RMGICs. These changes depended on the particles size of the original cements in dry conditions. In water storage, dissolution of the Biosilicate (R) particles, a silica-rich gel formation, and a hydroxyl carbonate apatite precipitation on the surface of the materials changed the nanoroughness surface. FL was the roughest in both conditions.