Evaluation of the effects of different polishing systems on surface roughness and surface discoloration of various restorative materials

Aim: Surface roughness and discoloration of dental restorative materials are among the reasons for the failure of composite resins. Since proper use of polishing systems reduces surface roughness and discoloration, it is important to evaluate the use of the correct systems. The aim of this in vitro study is to assess the effect of different polishing systems on color change and surface roughness of restorative materials with different compositions. Material and Method: Using Microhybrid composite (K, Herculite Classic, Kerr), Nanohybrid composite (P, Polofil NHT, Voco), Zirconia-containing nanohybrid composite (Z, Zenit, President Dental), and Giomer (B, Beautifil II; Shofu Inc.), a total of 160 samples were obtained. The initial surface roughness values of all samples were measured with a mechanical profilometer (Mitutoyo SJ 210, Japan). AFM and SEM images were obtained from randomly selected samples from each group. Each group was then subdivided into five subgroups: OptiDisc (O, Kerr), Twist-Dia (T, Kuraray), Enhance PoGo (E, Dentsply Sirona), Lucida (L, DiaShine), and a control group (C). After polishing with the respective polishing system, surface roughness values, AFM, and SEM analyses were performed again. On day 0, color measurements were taken, and after 14 days of immersion in coffee solution for surface discoloration, color was measured again. The samples were repolished with their respective polishing systems and color values were measured for the third time Results: In post-polishing profilometer measurements, the lowest Ra values were obtained with the OptiDisc (O) polishing system for all composite groups (KO2, PO2, BO2, ZO2), and the lowest Ra value within these groups was obtained with the Z composite group (ZO2:0.33). Among the polishing system groups, the highest Ra values were obtained with L and E systems. The highest Ra value among all post-polishing measurements was observed in the PL2 group (Ra:1.70). The Ra values measured by AFM were lower than the Ra values measured by profilometer in all groups. The highest E1, E3 values for K, P, B, Z were found in C groups (p<0.05). The lowest E1 value was obtained in T groups for all composite groups, the highest E2 (4.5162) and the lowest E3 (2.8998) values were obtained in PO group. T system for B and K and O system for P and Z were found effective in removing discoloration by repolishing. Conclusion: The use of different polishing systems resulted in varying roughness values and degrees of discoloration in all the composite resins used in the study. Re-polishing is an effective method for eliminating discoloration. Keywords: Dental composite resin, polishing system, surface roughness, surface discoloration, repolishing