Surface roughness and gloss of polished nanofilled and nanohybrid resin composites

There is limited literature on the polishability of new launched nanofilled and nanohybrid. The aim of this study is to evaluate the polishability of nanofilled and nanohybrid composites by measuring surface roughness and gloss values and explore the surface qualities of composite before and after polishing in vitro.

One nanofilled resin composite, two nanohybrid resin composites and one microhybrid resin composite were selected. All specimens were light cured against celluloid matrix strips. Then surface roughness(Ra) and gloss(GU) values were tested as negative control. Specimens were roughened with a 600-grit silicon carbide paper for 30 s to serve as positive control and then polished with Sof-Lex polishing disk system. Mean Ra and GU values of each step were measured with a profilometer and a small-area glossmeter. The surface qualities were observed by scanning electron microscope.

Ra values of polished surfaces were significantly higher than negative control and lower than positive control(P < 0.05). All materials showed no significant difference on Ra values after polishing(P > 0.05). GU values of polished surfaces were significantly lower than negative control and higher than positive control(P < 0.05). After polishing the microhybrid resin composite showed lower GU values than nanofilled and nanohybrid resin composite groups. The SEM images showed surface textures and irregularities were corresponded to the results of surface roughness and gloss.

No significant differences were noted on surface roughness among nanofilled, nanohybrid, and microhybrid composites after polishing with Sof-Lex disc system. Microhybrid composite presented lower gloss values than nanofilled and nanohybrid resin composites.