Potencial anti-cariogênico de Anacardium occidentale Linn e Psidium guajava Linn em biofilme de Streptococcus mutans

Abstract

Caries remains a major public health problem in Brazil and worldwide, and the picture is even more serious when considering inequalities between geographical regions. In order to prevent caries, mechanical control of the biofilm is the established practice, however, since it can be done improperly, it requires an adjuvant chemical control. Natural products appear as an option in formulations, since they produce secondary metabolites with proven activity against oral strains. Anacardium occidentale L and Psidium guajava L., which appear as some of the most representative plants in ethnopharmacological studies, are easily accessible, found in abundance mainly in the Brazilian Northeast and able to interfere with bacterial strains of the oral cavity. However, there are few studies regarding their action in the dynamics of biofilm. The objective of this study was to evaluate in vitro the ability of hydroalcoholic extract of Anacardium occidentale L. bark and Psidium guajava L. leaves to interfere with cariogenic properties of biofilms and demineralization of tooth enamel, using a Streptococcus mutans biofilm model. Extracts were obtained by maceration in 70% ethanol, dried and resuspended in distilled water, at a ratio of 1:10. For in vitro tests, the extracts were resuspended in sterile distilled water and filtered on filter membranes. Initially, we determined the Minimum Bactericidal Concentration (MBC) for defining the concentration that would be used in the biofilm. The biofilms were then formed on bovine enamel blocks and exposed to sucrose solution at 10% 8 times/day for 1 minute. After 48 hours of growth, the biofilm was treated 2 times/day with the following treatments: G1, Anacardium occidentale bark extract 200 mg/ml; G2, Psidium guajava leaf extract 200 mg/mL; G3, 0.9% NaCl; G4, chlorhexidine 0.12%; G5, 0.05% NaF. After three days of treatment, the biofilms were collected for quantification of bacterial viability, biomass and concentration of extra and intracellular polysaccharides. Enamel demineralization was estimated by microhardness by the percentage of demineralization loss (% PDL). The results were statistically analyzed by ANOVA with significance level set at 5%. MBC to both extracts was 50 mg/ml. For the pH Psidium guajava extract was only able to differ from the negative control after 96 hours and 120 hours (p <0.05). For bacterial viability, Psidium guajava showed an average statistically lower than the negative control (p <0.05). When analyzed mineral loss, Anacardium occidentale was able to reduce such mineral loss similarly to chlorhexidine 0.12% and 0.05% NaF (p <0.05). For insoluble extracellular polysaccharides, Anacardium occidentale and Psidium guajava differed from the negative control (p <0.05), but not between each other. Thus, extracts of the bark of Anacardium occidentale and Psidium guajava leaf, are able to interfere with the dynamics of cariogenic biofilm.