Abstract: Objective: To investigate the combined effects ofexogenous dextranase(Dex) and sodium fluoride (NaF) on the mature biofilm and exopolysaccharide productionof S. Mutansin different sucrose concentration medium.Materials and Methods：1)Establish S. mutansmaturemonospecies biofilm in vitro and measure the dry-weight of the biofilms. 2) The exopolysaccharide in mature biofilms labeled with 14C and were determined by means of scintillation counting; 3) The structure of the mature biofilm was detected by scanning electron microscope (SEM).Results:1)Thedry-weight of S. mutansmature biofilmsreduced after treated with Dex and NaF (p<0.05). 2) Combined use of Dex and NaFcould decrease the exopolysaccharideproduction(p<0.05). 3) Dex and NaFcould destroy the mature S. mutans biofilms(p<0.05). 4) The effect of Dex and NaF on biofilms and exopolysaccharidestrengthened with the increase of sucrose concentration. Conclusions: The combined use of Dex and NaFcould significantly destroy S. mutans mature biofilms and decrease the exopolysaccharideproduction, and their effects had positive relation with the medium sucrose concentration.

Key words: Streptococcus mutans, biofilm, dextranase, NaF, exopolysaccharide