Studies on the Effect of Fluoride Released by Glass Ionomers in the Oral Cavity

Abstract

Numerous in vitro studies have shown that fluoride released by glass ionomers can have effects on enamel, dentin, and plaque adjacent to the material. However, the action of fluoride in vivo may be different from that found in vitro. The aim of the present series of studies was to investigate the effects of glass ionomers in oral conditions. This was tested in clinical experiments conducted on adults who had freshly made or old glass ionomers in their mouths. The results of the studies showed that fluoride released by glass ionomers may increase the fluoride content of plaque close to the material. Fluoride content decreased rapidly with decreasing fluoride release from glass ionomer, but it was increased slightly even in plaque growing on three-year-old fillings. However, the effect appeared to be very local, and no increase in salivary fluoride content due to glass-ionomer fillings was found. Although the growth of plaque was not inhibited, the proportion of mutans streptococci was significantly reduced in plaque growing on glass ionomer during the six weeks after placement of the material. No such effect, however, could be seen in the case of three-year-old glass-ionomer fillings. Although in vitro studies have shown that glass ionomers can take up fluoride and subsequently release it, applying fluoride gel to old glass-ionomer fillings did not result in an increased fluoride concentration of plaque growing on the fillings in vivo. Further studies are needed to find out whether the recharging of glass ionomers with fluoride has clinical significance.