Effect of repolishing on the discoloration of indirect composite block, nanohybrid, and microhybrid resin composites.

Purpose: To comparatively assess the color stability of indirect composite block, nanohybrid, and microhybrid resin composites after immersion in red wine and repolishing.

Materials and methods: Specimens (2x7x12 mm) were prepared using an indirect composite block (Cerasmart), a nanohybrid (Ceram X), and a microhybrid (Charisma Smart) resin composite. The specimens' color was recorded based on the CIE L*a*b* system in a spectrophotometer (Spectroshade). After recording the initial color, the specimens were immersed in red wine for 3 hours per day for 15 days. The color measurement was done again. The specimens were repolished with a multistep polishing system (SuperSnap). The color was measured for the third time. The color change values (ΔE) were calculated with the L*, a*, and b* coordinates obtained at baseline, after the immersion procedure, and after repolishing. Statistical analyses were performed with one-way ANOVA, Tukey's post hoc, and paired t-tests (p=0.05).

Results: The composite block presented the lowest ΔE value (p <0.05). No statistically significant difference was found between the ΔE values of the nanohybrid and microhybrid resin composites. The repolishing promoted a decrease in the color change of all three materials (p<0.05). The ΔE value of the composite block was clinically acceptable after repolishing.

Conclusion: The composite block showed higher color stability. The staining resistance of the nanohybrid and microhybrid resin composites was not different. The repolishing decreased the discoloration of all three materials.