In vitro investigation of the impact of contemporary restorative materials on cariogenic bacteria counts and gene expression

Objectives: The aim of this study was to compare the antibacterial effect of different fluoride-containing and bioactive restorative materials, and their effect on the expression of specific biofilm-associated genes and therefore the caries process. Materials and methods: The restorative materials utilized in this study included: 1. Filtek Z250, 2. Fuji II LC, 3. Beautifil II, 4. ACTIVA, and 5. Biodentine. For each material, disc-shaped specimens were prepared. The inhibitory effects against Streptococcus mutans, Lactobacillus acidophilus, and Leptotrichia shahii were tested. After incubation for 24 h and 1 week, colony-forming units (CFUs) were enumerated. From the plates dedicated for biomass quantification and RNA purification, the target glucosyltransferase B (gtfB) and glucan-binding protein B (gbpB) genes were chosen for S. mutans. For L. acidophilus, a gene involved in exopolysaccharide synthesis (epsB) was chosen. Results: Except for Filtek Z250, all four materials showed statistically significant inhibitory effects on the biofilms of all three species. When biofilms were grown in the presence of the same four materials, the expression of S. mutans gtfB and gbpB genes, was significantly reduced. For L. acidophilus, the decrease in the expression of gtfB gene in the presence of ACTIVA was the highest change seen. The epsB gene expression also decreased. Compared to fluoride-releasing materials, bioactive materials had more inhibitory effect against L. acidophilus, both at 24 h and 1 week. Conclusions: Both fluoride releasing and bioactive materials exhibited a significant inhibitory effect on the biofilm growth. The expression of the targeted biofilm-associated genes was downregulated by both material groups. Clinical significance: The findings from this study give insight into the antibacterial effect of fluoride-containing and bioactive materials which would help to reduce the chances for secondary caries and therefore increase the lifetime of dental restorations placed for patients.