Investigation of the Effects of Mouthwashes on the Microhardness and Color Stability of Bulk-fill Composite Resins

Objective: The current study aimed to investigate the effects of mouthwashes on the microhardness and discoloration of bulk-fill resin composites by comparison with a conventional resin composite. Methods: In the study, 22 disc-shaped samples (8*2 mm) were prepared from four different composite resins, Clearfil Majesty Esthetic (CME), Estelite Bulk-fill Flow (EBF), Filtek One Bulk-fill Restorative (FBF) and SonicFill-2 (SF2). Half of the samples for each material were stored in Listerine Cool Mint and the other half in Colgate Optic White mouthwashes for 24 hours (n=11). The color and microhardness of the samples were measured baseline and after 24 h incubation in mouthwashes. After calculating color change (∆E00) and microhardness changes (∆VHN), the obtained data were analyzed in SPSS software at α=.05 by Two-Way ANOVA, One-Way ANOVA, Post-hoc Tukey, Independent and Paired-Samples t test. Results: The effect of composite material type (p=.016) and mouthwash type (p=.008) on color change was statistically significant. All materials were more colored in Listerine Cool Mint than in Colgate Optic White but statistically significant only for FBF (p=.017). Discoloration of the materials in both mouthwashes didn’t exceed the 50:50% acceptability threshold (∆EAT=1.8). For all materials, microhardness decreased significantly after storage in mouthwashes compared to baseline state (p.05). Conclusion: Although the discolorations of materials were at an acceptable threshold for the tested mouthwashes, a significant decrease in microhardness is very important for long-term clinical success of the materials. The uncontrolled use of mouthwash should be avoided.