METHODS: Two-fold serial micro-dilution method was used to measure minimal inhibitory concentration (MIC) of aqueous extracts of Gt, Sp and their combinations. Adsorption to hexadecane was used to determine the cell surface hydrophobicity (CSH) of bacterial cells. Glass beads were used to mimic the hard tissue surfaces, and were coated with saliva to develop experimental pellicles for the adhesion of the primary colonizing bacteria.
RESULTS: Gt aqueous extracts exhibited better anti-plaque effect than Sp aqueous extracts. Their combination, equivalent to 1/4 and 1/2 of MIC values of Gt and Sp extracts respectively, showed synergistic anti-plaque properties with fractional inhibitory concentration (FIC) equal to 0.75. This combination was found to significantly reduce CSH (p<0.05) and lower the adherence ability (p<0.003) towards experimental pellicles.
CONCLUSION: Combination between Gt and Sp aqueous extracts exhibited synergistic anti-plaque activity, and could be used as a useful active agent to produce oral health care products.
METHODS: Saliva-coated glass beads (sGB) were used as substratum for the adhesion of a mixed-bacterial suspension of Streptococcus mutans, Streptococcus sanguinis and Streptococcus mitis. Biofilms formed on sGB at 3h and 24h represented the early and established-plaque models. The biofilms were exposed to three doses of the sweeteners (10%), introduced at three intervals to simulate the exposure of dental plaque to sugar during three consecutive food intakes. The treated sGB were (i) examined under the SEM and (ii) collected for turbidity reading. The absorbance indicated the amount of plaque mass produced. Analysis was performed comparative to sucrose as control.
RESULTS: Higher rate of bacterial adherence was determined during the early compared to established phases of formation. Comparative to the sweeteners, sucrose showed a 40% increase in bacterial adherence and produced 70% more plaque-mass. Bacterial counts and SEM micrographs exhibited absence of matrix in all the sweetener-treated biofilms at the early phase of formation. At the established phase, presence of matrix was detected but at significantly lower degree compared to sucrose (p<0.05).
CONCLUSION: Alternatives sweeteners promoted the formation of oral biofilm with lighter mass and lower bacterial adherence. Hence, suggesting alternative sweeteners as potential antiplaque agents.
DESIGN: Here, we have investigated these individual plant extracts and its synergistic mixture (PEM) for its anti-cariogenic effect to reduce populations of single and mixed-species of Streptococcus sanguinis and Streptococcus mutans in a planktonic or/and biofilm and their others reduced virulence. Bacterial populations in the biofilm after 24 h, hydrophobic cell surface activity to n-hexadecane and pH changes at 5 min' intervals until 90 min of incubation were recorded. Total phenolic content and bioactive compounds in the crude aqueous plant extracts were analysed. Regulatory gene expressions of S. mutans adhesins genes (gtfB, gtfC, gbpB and spaP) upon treatment with PEM were investigated in planktonic and biofilm conditions.
RESULTS: All plant extracts strongly reduced S. mutans in the biofilm compared to S. sanguinis in single and mixed-species. PEM reduced S. mutans by 84% with S. sanguinis 87% in the mixed population. Psidium sp. and PEM highly reduced cell-surface hydrophobicity of the two bacteria thus reducing adherence and biofilm formation. PEM and Mangifera sp. lowered initial pH change in the mixed populations of S. sanguinis and S. mutans. PEM downregulated the S. mutans gtfB gene expression in the single species planktonic and mixed-species biofilms.
CONCLUSIONS: The effectiveness of PEM in reducing S. mutans within the biofilm, cell-surface hydrophobicity, acid production and adhesin gene (gtfB) expression in mixed-species with S. sanguinis indicates its potential as an antibacterial agent against dental caries. This is attributed to the phenolic content in the PEM.