THE EFFECT OF FLUORIDE APPLICATION ON FLUORIDE RELEASE AND THE ANTIBACTERIAL ACTION OF GLASS IONOMERS

The aim of this study was to investigate whether the release of fluori de and the antimicrobial effect of freshly mixed glass ionomers could be prolonged by application of fluoride on aged material. Test slabs o f freshly mixed and aged (14 d in water) conventional and silver glass ionomer (Ketac-Fil and Ketac-Silver, Espe, Seefeld, Germany) and comp osite (Silux Plus, 3M, St. Paul, MN) were fitted into the bottom of a test tube. A layer of S. mutans Ingbritt cells was centrifuged onto th e test slabs, and the samples were incubated for 20 h in 1.7% sucrose solution. After the incubation, pH, F, and Ca contents of the fluid ph ase, and F, Mg, P, and K contents of the cells were determined. The ag ed glass-ionomer samples were then covered with toothpaste (0.1% F) or with fluoride gel (1.25% F), and the composite samples with fluoride gel. After being thoroughly rinsed, S. mutans cells were incubated on the samples as above. The pH fall was significantly inhibited by fresh ly mixed glass ionomers, and there were changes in cellular cation and phosphorus contents. Large amounts of fluoride were found in the flui d and cells. For old glass ionomers, no inhibitory effect on pH fall c ould be seen. Fluoride release had decreased to a low level. Applicati on of fluoride toothpaste on the material resulted in a small increase in the release of fluoride and slight inhibitory effects on bacteria. After application of fluoride gel, the fluoride contents of the fluid phase and cells were as high as in freshly mixed samples, and the inh ibitory effect on pH fall and electrolyte metabolism was even more pro nounced than initially. Fluoride release from old glass ionomers and t heir antimicrobial effect could be significantly increased by applicat ion of fluoride gel on the material.