Comparative Evaluation of Color Stability and Surface Roughness of Bulk-Fill and Nanohybrid Composites Following Long-Term Mouthrinse Exposure: An In Vitro Study.

INTRODUCTION

Composite resin restorations are widely used in restorative dentistry; however, their long-term aesthetic success depends on color stability and surface integrity. Daily exposure to mouthwashes may influence these properties. This study aimed to evaluate and compare the effects of different mouthwash formulations on the color stability and surface roughness of Tetric N-Ceram Nanohybrid (Ivoclar Vivadent, Schaan, Liechtenstein) and Tetric N-Ceram Bulk-Fill (, Ivoclar Vivadent, Schaan, Liechtenstein) composites.

MATERIALS AND METHODS

80 disc-shaped specimens (n = 40/group) of nanohybrid (Tetric N-Ceram), and bulk-fill composite (Tetric N-Ceram) were fabricated and polished according to the manufacturer's instructions. Each group was further divided into four subgroups (n = 10): control (distilled water), Listerine Cool Mint® (alcohol-based mouthwash, Johnson & Johnson, New Brunswick, USA), Phos-Flur® (fluoride-based mouthwash, Colgate-Palmolive, New York, USA), and Rexidine® (0.2% chlorhexidine-based mouthwash, Indoco Remedies Ltd., Mumbai, India). Specimens were immersed in 30 mL of the respective solution for five min per cycle, three times daily, for 60 days, simulating one year of clinical exposure. The color change (ΔE) was measured using a VITA Easyshade® V spectrophotometer (VITA Zahnfabrik, Bad Säckingen, Germany), and the surface roughness (Ra) was assessed using a contact profilometer (Zeiss, Oberkochen, Germany). Scanning electron microscopy (SEM) (Zeiss, Oberkochen, Germany) analysis with 3D surface plots using ImageJ software (National Institutes of Health, Bethesda, Maryland, USA) provided a complementary morphological evaluation. Data were analyzed using one-way analysis of variance (ANOVA) and post-hoc Tukey's test (p < 0.05).

RESULTS

Significant color changes were observed in both composites, with Listerine causing the highest ΔE values, particularly in the bulk-fill group. Rexidine caused notable discoloration, whereas Phos-Flur had minimal effects. The surface roughness increased significantly in both materials after exposure, with the nanohybrid composites showing greater sensitivity to surface alterations.

CONCLUSION

The mouthwash formulation significantly affected the aesthetic and surface characteristics of composite resins. Nanohybrid composites demonstrated better color stability, but were more susceptible to surface roughness changes than bulk-fill composites.