Propolis antimicrobial activity on streptococci mutans strains and dental plaque

Composition and biological properties of propolis vary extensively according to source, processing and storage conditions and need to be studied previously to its use in caries control. Objectives: to determine in vitro antimicrobial activity on mutans streptococci strains and efficacy of a propolis from Zacatecas, México, to reduce dental plaque and oral microflora in children. Methods: Streptococcus mutans ATCC35668 and twelve clinical isolates, four of them mutacin producers, were used. Inhibitory assays were performed by diffusion method in brain heart agar plates inoculated with overnight cultures of each strain. 100 µl of propolis hydroalcoholic extract (10%), and 10-2, 10-3, 10-4 aqueous dilutions were tested. Plates were incubated at 37°C, in CO2 5%, during 24 h. Strains susceptibility was defined according to inhibition zone size. Eighty children were assigned to one of 5 groups: G1, tooth brushing and chlorhexidine mouthrinse; G2, chlorhexidine mouthrinse; G3, tooth brushing and propolis mouthrinse; G4, propolis mouthrinse, and G5, tooth brushing and placebo. Dental plaque index and mutans streptococci, lactobacilli, and yeast counts in stimulated saliva, were determined before, 8 and 15 days after treatment beginning. Results: Inhibition zone sized from 2 to18 mm. Reference and mutacin producer strains were more resistant. Mutans streptococci counts diminished in all groups but clorhexidine showed the greatest effect (94% in G1). Lactobacilli concentration decreased in 50% of children in groups 3, 4 and 5, while yeasts showed a less significant decrease in G2 and G4. Dental plaque index was lower en 82.4% of children in G3; 80% in G4; 76.5% in G1 and 42.9% in G2. Conclusions: Propolis showed antibacterial activity on all mutans streptococci strains, but susceptibility pattern was specific for each one. Tooth brushing increased mouthrinses effectiveness. Chlorhexidine was more effective to reduce mutans streptococci, and propolis showed better results in reducing dental plaque.