Effect of different polishing systems on discoloration, surface roughness, and bacterial adhesion of contemporary composite resins

Abstract The purpose of this study was to evaluate the impact of different polishing systems on discoloration, surface roughness, and bacterial adhesion of universal composites with high chromatic adaptability. The study groups included four different composite resins (CR): Brilliant EverGlow (BEG), Clearfil Majesty Esthetic (CME), Neo Spectra ST HV (NST), and Omnichroma (OMN), with 48 specimens fabricated from each CR. Each group was further subdivided into four subgroups ( n = 12) based on the polishing systems: Mylar Strip (control) (C), OneGloss (OG), OptiDisc (OD), and Clearfil Twist Dia (CT). Following the application of the polishing systems, surface roughness was measured via a contact profilometer. To assess bacterial adhesion, Streptococcus mutans ( S. mutans ) adhesion was quantified by colony-forming unit (CFU) counting. The color change (Δ E ₀₀ ) of specimens polished using different polishing systems and immersed in a coffee solution for 12 days was calculated using a spectrophotometer with the CIEDE2000 formula. Additionally, one specimen from each subgroup was fabricated for examination under a scanning electron microscope (SEM). Data were analyzed using two-way analysis of variance (ANOVA). CME exhibited the least discoloration among the CRs ( p < 0.001). The greatest discoloration in all tested composites was observed in the C subgroups ( p < 0.001), while no statistically significant differences were found among the OG, OD, and CT polishing systems. OMN demonstrated the lowest surface roughness among the CRs ( p < 0.001). Examining the bacterial adhesion results, the highest values were observed in the C subgroups for all CR groups ( p < 0.001). The polishing systems tested had a significant effect on the surface roughness values of the CRs. Application of polishing systems to the CRs resulted in a reduction in both discoloration and bacterial adhesion values compared to the control group. Within the limitations of this in vitro study, the results may provide clinicians with preliminary guidance in selecting polishing systems for contemporary composite resins. However, clinical extrapolation should be made with caution, as intraoral conditions cannot be fully simulated in vitro.