The anticariogenic effect of amine fluorides on Streptococcus sobrinus and glucosyltransferase in biofilms

Dental caries is a chronic infectious disease caused by the accumulation of bacterial plaque (biofilm) on tooth surfaces. Antibacterial agents, in addition to other preventive measures, can control dental plaque accumulation. Amine fluorides (AmF) are known anticaries agents for over 30 years. The purpose of our study was to assess the adsorption and desorption of AmF to experimental dental biofilm and to evaluate the effect of AmF on Streptococcus sobrinus 6715 and glucosyltransferase (GTF) activity in experimental dental biofilms. The experimental plaque model used in this study consists of hydroxyapatite beads coated with human saliva (sHA), followed by adsorption of S. sobrinus and synthesis of in situ polysaccharides. Our results show that the viability of S. sobrinus in biofilm decreased as the concentration of AmF and chlorhexidine (CHX) increased. The concentration of AmF and CHX required to kill S. sobrinus adherent to sHA is about 100 times greater than the concentration required to kill the same amount of planktonic bacteria. Adsorption of AmF to surfaces was more than 90% and the desorption of AmF from our experimental model was limited. Pre-adsorption of AmF on the surface increased adhesion of S. sobrinus but also resulted in surface killing of the adsorbed bacteria. At low concentrations AmF increased GTF activity in solution by about 10%, but at concentrations above 0.1 mM it inhibited GTF activity. Inhibition of GTF on the surface required about 100 times more AmF than in solution. Our results show that AmF retains its anticariogenic effects in solution and in biofilm systems.