Effect of Bleaching on the Surface Roughness of Restorative Materials Evaluated by Atomic Force Microscopy (AFM)

Background/Objectives: This study aimed to compare the effects of two bleaching techniques—light-activated (Zoom) and laser-activated—on the surface roughness of nanohybrid and microhybrid composites, using atomic force microscopy (AFM) for topographic evaluation. Methods: Sixty composite resin discs were fabricated, with 30 nanohybrid and 30 microhybrid samples. Each type was divided into three subgroups: control, Zoom bleaching, and laser bleaching (n = 10 per group). Zoom bleaching employed 40% hydrogen peroxide activated by Philips Zoom light, while laser bleaching used a diode laser (940 nm) with QuickLase gel. Surface roughness parameters (Sa, Sq, Sz) were measured using AFM, and statistical analysis was performed. Results: Both bleaching protocols increased surface roughness compared to controls. Microhybrid composites showed higher roughness after Zoom (103.12 ± 19.25 nm) and laser bleaching (106.16 ± 25.21 nm), while nanohybrid composites had lower values after Zoom (57.77 ± 13.88 nm) and laser (78.13 ± 23.29 nm). Significant differences were found between composite types post-bleaching (p < 0.001 for Zoom; p = 0.019 for laser). However, differences between bleaching methods within the same composite were not significant. Conclusions: Both Zoom and laser bleaching negatively affect composite surfaces, with laser showing a greater impact. Nanohybrid composites demonstrated superior resistance to surface alteration, suggesting better clinical durability. These results highlight the importance of material selection when bleaching patients with existing composite restorations.