The effect of saliva on fluoride release by a glass-ionomer filling material

The initial aim of this study was to investigate the effect of saliva and t he formation of pellicle on the fluoride release in vitro of the glass-iono mer filling material, Chemfil Superior(R). For the first study glass-ionome r discs of 6 mm in diameter and 1.5 mm thick were made. Ten discs were imme rsed in whole stimulated saliva each day for 10 min and 10 control discs we re immersed in deionized water. For the remaining 23 h and 50 min of each d ay, over the 20-day experimental period, both test and control discs were p laced in deionized water. A considerable amount of fluoride was released on the first day (14.5 ppm F control and 13.3 ppm F test). The concentration of fluoride released on the second day fell sharply to 5.3 ppm F for contro ls and 4.9 ppm F for tests. This release had almost reached a plateau by da y 10 and at day 20 the pellets continued to release low levels of fluoride. The concentration of fluoride released was only slightly higher for contro ls than for test discs when both were immersed in deionized water until day 20. However, during the 10-min period between 1.5 and 2 times as much fluo ride was released into the deionized water as into saliva until day 20 when the ratio fell to 1.2:1. The second experiment assessed fluoride release w hen specimens were incubated for Ih using an identical protocol. Again, les s fluoride was released from the saliva-coated specimens compared with the controls (17%), which was not substantially different to the comparable 10- min samples (13%). This study indicates that saliva retards the release of fluoride from glass-ionomer and that this retarding effect is still present when discs are subsequently immersed Fn water compared with those that wer e placed in water alone. This suggests that salivary deposits have formed w ithin minutes of immersion in saliva. This retarding effect was observed th roughout the study period with the exception of the 20-day samples which ha d been incubated in saliva for 10 min.