To investigate the effect of five different polishing systems on the surface roughness of nanofilled composite resin and adhesion of Streptococcus mutans.

The nanofilled composite resin were selected for this study named Filtek Z350 XT, fifty four specimens were prepared and divided into 6 groups randomly. Five polishing groups specimens were subjected to five different polishing system (OptiDisc, HiLuster^Plus, Sof-Lex, Super-snap, Composite Polishing Kit CA0310) treatment, whereas one group received no further surface treatment. Average surface roughness (Ra) were assessed using confocal laser scanning microscope (CLSM) . Then Streptococcus mutans adhered to the 6 groups specimens were cultured in vitro, and the bacterial adhesion amount was measured. ANOVA was used to assess the surface roughness of specimens and the bacterial adhesion amount.

In the five polishing group, the lowest Ra value was obtained in the HiLuster^Plus group, except it had lower value than Composite Polishing Kit CA0310 (P= 0.016) , there was no significant difference between the other groups, showing the low surface roughness all. There was no significant difference in bacterial adhesion amount between the five polishing groups, which was lower than that of the non-polishing group (P<0.05) .

The smoothest surface was obtained by Filtek Z350 XT with the use of the polishing system of HiLuster^Plus. After polishing systems treatment the amount of the bacteria adhered to nanofilled composites resin decreased significantly.