The effect of amine fluoride preparations on the formation and viability of oral bacterial biofilms

In this study, the anti-plaque activities of amine and tin fluorides were investigated in laboratory models that were designed to simulate specific components of microbial ecology in the oral cavity. The efficacy of the agents applied topically in the form of a solution was determined. The influence of growth mode and sucrose on the bactericidal activity towards Streptococcus sanguis was determined using a constant depth film fermenter (CDFF). S. sanguis cultures growing as biofilms were less susceptible to the amine fluorides than planktonic cultures. When sucrose was added to the growth medium, the susceptibility of both planktonic and biofilm cultures were reduced. The smallest kills, which were measured in sucrose-grown biofilms, were not significantly different from control groups. Inorganic fluorides had no bactericidal effect on S. sanguis biofilms regardless of the presence of sucrose in the growth medium. The CDFF was also used to investigate the effect of olaflur/tin fluoride on the formation of microcosm biofilms over a 12 hour period. In the absence of sucrose, the structures of control and test group biofilms were observably different. A parallel flow cell system was developed to investigate the anti-adhesion properties of the amine and tin fluorides. The effect on the net adhesion of S. sanguis to mucin-conditioned surfaces over a one hour period was determined. Only one of the amine fluorides tested was able to reduce the net adhesion of S. sanguis over a one hour period. Tin (II) and tin (IV) fluorides were found to reduce the net adhesion after one hour of culture flow. The flow cell system was also used to investigate the effects of olaflur/tin fluoride on bacterial desorption and co-adhesion. The amine/tin combination had no effect on either the level of Streptococcus gordonii desorption, or the co-adhesion of the streptococci with Actinomyces naeslundii. In summary, the study has shown that the CDFF model was useful in determining the effect of anti-plaque agents on the susceptibility of intact biofilms of oral bacteria. The parallel flow cell system was a good model for investigating processes involved in adhesion of oral bacteria to conditioned surfaces and enabled the determination of the effects of the anti-plaque agents on bacterial adhesion, desorption and co-adhesion. Additionally, the system allowed the comparison of the substantivity of the different anti-plaque agents