OBJECTIVETo compare the surface roughness of nanofilled dental composite resin and microhybrid composite resins after curing and polishing.

METHODSA 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.

RESULTSP60 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.

CONCLUSIONThe nanofilled composite Z350 has smooth surface after polishing by abrasive disks, but its smoothness remains inferior to that of other micro-hybrid composite resins.

Acrylic Resins ; Composite Resins ; Dental Materials ; Dental Polishing ; Materials Testing ; Polyurethanes ; Surface Properties

Objective To evaluate the effect of thermal cycling on surface microstructure of different light-curing composite resins. Methods A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage and 40 000 thermal cycles (5/55℃). The mean surface roughness (Ra) were measured and compared before and after thermal cycling, and the changes of microstructure were observed under scanning electron microscope (SEM). Results Significant decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024μm to 0.140±0.017μm, P<0.001) and Z250 (from 0.169 ± 0.035μm to 0.144 ± 0.033μm, P<0.001), whose Ra approximated that of P60 (0.121 ± 0.028μm) with smoothly polished surface. SEM revealed scratches and shallower pits on the surface of all the 5 resins, and fissures occurred on Z350 following the thermal cycling. Conclusions Water storage and thermal cycling may produce polishing effect on composite resins and cause fissures on nanofilled composite resins.

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±0.052μm) 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.

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±0.052μm) 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.

Objective To evaluate the effect of thermal cycling on surface microstructure of different light-curing composite resins. Methods A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage and 40 000 thermal cycles (5/55℃). The mean surface roughness (Ra) were measured and compared before and after thermal cycling, and the changes of microstructure were observed under scanning electron microscope (SEM). Results Significant decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024μm to 0.140±0.017μm, P<0.001) and Z250 (from 0.169 ± 0.035μm to 0.144 ± 0.033μm, P<0.001), whose Ra approximated that of P60 (0.121 ± 0.028μm) with smoothly polished surface. SEM revealed scratches and shallower pits on the surface of all the 5 resins, and fissures occurred on Z350 following the thermal cycling. Conclusions Water storage and thermal cycling may produce polishing effect on composite resins and cause fissures on nanofilled composite resins.