Influence of Composite Polishing Pastes on Surface Roughness and Their Stability After Simulated Tooth Brushing

<b>Background/Objectives:</b> Achieving and maintaining a smooth restoration surface is clinically significant, as surface roughness is linked to plaque accumulation, staining, and wear. This study aimed to evaluate in vitro the effect of different polishing paste systems on reducing surface roughness and to assess their performance after simulated post-operative maintenance through toothbrushing. <b>Methods:</b> A total of 128 cylindrical, flat-surface specimens were fabricated from a nanohybrid composite (Filtek Supreme XTE, 3M, USA) using a standardized metal mold. All specimens were finished with silicon carbide paper and polished with a two-step rubber disc system (Hi-Luster, Kerr, USA). They were then randomly assigned to 16 groups (<i>n</i> = 8) according to the polishing protocol. One group was polished with a prophylaxis paste, while the other fifteen groups were treated with pastes indicated for composite and/or ceramic materials. Polishing was performed with a flat buff wheel. To simulate clinical maintenance, specimens underwent a standardized toothbrushing cycle equivalent to three months of use. Surface roughness parameters (Sa and Sq) were measured at three stages with an optical profilometer: after initial polishing, after paste application, and after simulated toothbrushing. <b>Results:</b> Mean Sa values ranged from 0.065 to 0.560 and Sq values from 0.075 to 0.676. Significant differences were found among pastes for both parameters (<i>p</i> < 0.05). Two-way ANOVA revealed significant differences after polishing paste application, both before and after toothbrushing (<i>p</i> < 0.05). Toothbrushing increased roughness in most groups (<i>p</i> < 0.05), although no significant deterioration was observed for nine pastes in Sa and eight in Sq (<i>p</i> ≥ 0.05). <b>Conclusions:</b> Polishing pastes vary in effectiveness, and not all produce measurable improvements in surface smoothness. Their efficiency appears to be unrelated to the abrasive or the number of steps. Simulated toothbrushing over a three-month period may reduce the initial benefits, emphasizing the importance of careful clinical selection.