The purpose of the study was to evaluate the abrasive effect of different toothbrushes-soft-cross bristles (CB), extra-soft-parallel bristles (ES), and soft-parallel bristles (S)-on the surface roughness of conventional (C) and resin-modified (V) glass ionomer cements in vitro. Eight specimens of each material were prepared for each group: (1) V and CB; (2) V and ES; (3) V and S; (4) C and CB; (5) C and ES; and (6) C and S. Specimens were stored at 37 degrees C/24 hours and 100% humidity, polished, and initially analyzed with a surface roughness-measuring device. Next, they were fixed to the tooth-brushing device and abraded via toothbrushes, using a dentifrice slurry, performed at 250 cycles/minute with a 200 g load. The specimens were washed, dried, and analyzed identically with the same device. There was no significant interaction between material and toothbrush types. After tooth-brushing, V showed significantly higher surface roughness than C and CB and created higher surface roughness than S. No difference was observed between these toothbrushes and ES. Regardless of the toothbrush type used, resin-modified glass ionomer cement showed the highest roughness values.