Combined Effects Of Exogenous Dextranase And Sodium Fluoride On The Mono-species Biofilm Of Streptococcus Mutans 25175

Aims: To elucidate the effects of exogenous dextranase and sodium fluoride on the formation of mono-species biofilm of Streptococcus mutans, and the effects of the two agents on the preformed biofilms of S.mutans. To approach whether the combined effects exist between the two agents and analyze the potential mechanism. Materials and methods: 1. After stained with fluorescent BOBO^TM-3 and Calcofluor^TM, the biofilms of S. mutans formed on the glasses were visualized by Confocal laser scanning microscope(CLSM) to observe the effects of exogenous dextranase and sodium fluoride(alone or combined) on the early formation of biofilm and the mature biofilm of S. mutans. 2. S. mutans were labeled with ³H-TdR to survey the influences of the former two agents (alone or combined) on the adhesion of bacteria; anthrone method was applied to determine the amounts of exopolysaccharide in the mature biofilms after treated by dextranase and sodium fluoride (alone or combined). Results: 1. The early formation of biofilm from S. mutans was inhibited by dextranase while sodium fluoride of subinhibitory concentration has little effect. Dextranse in combination with sodium fluoride can make less adhesion of S. mutans than single one, resulting in the loss of typical tree-like structure of biofilm and deprivation of cross linkages among the colonies. 2. Sodium fluoride of subinhibitory concentration does not work on the preformed biofilm of S. mutans alone, while dextranse can partly destroy it. When applied together, the two agents make greatly degradation of the mature biofilm in which the cross linkages among the colonies decrease even disappear and the amounts of soluble and insoluble exopolysaccharide were reduced much more. Conclusion: Dextranase can inhibit the formation of biofilm from S. mutans and partly resolve excellular polysaccharide in the mature biofilm inducing the destruction of biofilm's structure, while sodium fluoride of subinhibitory concentration has little effect on the biofilm. Some extent synergic effects exist between dextranse and sodium fluoride.