Abstract: Objective To compare the surface roughness of nanofilled dental composite resin and microhybrid composite
resins after curing and polishing. Methods A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum,
and AP-X) were fabricated from the lateral to the medial layers to prepare 8 mm×8 mm×5 mm cubical specimens. The 4 lateral
surfaces of each specimens were polished with abrasive disks (Super-Snap). Profilometer was used to test the mean surface
roughness (Ra) after polishing. Results P60 had the lowest Ra (0.125±0.030 μm) followed by Z250 and Spectrum. The Ra of
Z350 (0.205±0.052 μm) was greater than that of the other 3 resins, and AP-X had the roughest surfaces. Under scanning electron
microscope, the polished faces of P60 resin were characterized by minor, evenly distributed particles with fewer scratches; the
polished faces of Z350 presented with scratches where defects of the filling material could be seen. Conclusion The nanofilled
composite Z350 has smooth surface after polishing by abrasive disks, but its smoothness remains inferior to that of other
micro-hybrid composite resins.