Abstract
Aim: To investigate the effects of selected alcohol-free mouthwashes with different formulations (zinc-hydroxyapatite, hydrogen peroxide, and sodium fluoride) on the surface microhardness of a single-shade universal resin composite.
Materials and Methods: Forty disc-shaped specimens (8 x 2 mm) from the universal resin composite (Omnichroma (R)), and a nano-hybrid composite (Tetric (R) N-Ceram) were prepared. After polymerization, baseline surface microhardness values were recorded using Vickers microhardness tester. The samples from each material were randomly assigned to 4 groups (n = 10) and immersed in 20 ml of the mouthwashes: Biorepair (R), Listerine (R), Colgate (R) Optic White, and distilled water (control). The samples were kept in the immersion solutions for 24 hours, and post-immersion microhardness values were recorded. Data were analyzed with one-way ANOVA and paired sample t-tests at p < .05.
Results: Significant reduction in microhardness was observed in all resin composite groups after immersion in the mouthwashes compared to baseline values (p < .0001). The highest microhardness reduction in Omnichroma (R) group was observed after immersion in Colgate (R) Optic White; and Tetrie N-Ceram group after immersion in Listerine (R) mouthwash. For both materials, the least reduction in microhardness was observed after immersion in Biorepair (R). Microhardness values for Omnichroma were significantly higher than Tetric (R) N-Ceram (p < .0001). However, Omnichroma exhibited a significantly greater reduction in microhardness after immersion in the tested mouthwashes.
Conclusion: In vitro simulated use of the investigated mouthwashes negatively affected the surface microhardness of both tested resin composites. The observed effects were both mouthwash and material dependent.