Objective: To observe the exopolysaccharides produced by biofilm cells of clinical strains 593 and 18 and the difference between the two strains.Methods:① Streptococcus mutans biofilms formed on polystyrene plastic sheets in 3

12 and 20 hours respectively

exopolysaccharides distribution

after fluorescein isothiocyanate-conjugated concanavalin A staining

were visualized by confocal scanning laser microscopy.② The amounts of exopolysaccharides by adhesive streptococcus mutans in different culture time were determined by the anthrone method.Results: After combining with the fluorescent stain

the exopolysaccharides showed green light.Strain 593 in biofilm possessed stronger ability to synthesize exopolysaccharides than strain 18

especially the amount of water soluble glucans in 3～20 h and water insoluble glucans in 3～16 h(P<0.05).Conclusion: The stronger ability of biofilm strain 593 to synthesize exopolysaccharides in the early biofilm formation stage during the 3～16 h may be the reason for its higher cariogenic ability.