QuickScan Reviews in Pediatric Dentistry, March 15 2009

Background: Fluoride-releasing restorative materials are often selected because of the anti-caries effect that has been reported as a result of their fluoride release. Much of this effect has been reported as it relates to remineralization. Less work has been performed looking at the potential of fluoride released from glass-ionomer cements (GICs) to have an effect on cariogenic bacteria directly. Objective: To examine eluates from GICs and their ability to inhibit the drop in pH as well as acid production rates of the cariogenic bacteria Streptococcus mutans and Streptococcus sanguinis . Methods: A powder and liquid version of GIC (Fuji IX) was mixed according to the manufacturer's directions for 30 seconds and then placed into a cylindrical mold and allowed to set at 25C for 30 minutes. The set cement specimen was then placed into a solution of phosphate-buffered saline enriched with substances normally found in a culture medium in which bacteria are commonly grown. After storage at 37C for 24 hours, a sample of the eluate, the liquid solution now containing substances that had leached from the glass-ionomer specimen, was analyzed for the amount of fluoride and other minerals eluted from the glass-ionomer. To measure the pH fall upon sucrose challenge to bacteria, the eluate was buffered and kept at pH 7.0 to start. pH fall was monitored for 30 minutes with and without the fluoride containing glass-ionomer eluate. Separately, acid production from the 2 types of bacteria was measured with and without the glass-ionomer eluate. Results: With S. mutans , the pH started to drop in all specimens immediately after the addition of glucose. After 10 minutes, the rate of pH drop was very different depending upon the amount of fluoride in the GIC eluate. Conclusions: In specimens containing a high level of fluoride eluates from the glass-ionomer specimens, the pH drop essentially stopped after 10 minutes at pH 5.0, whereas in the controls with no fluoride eluate from the glass-ionomer, the pH continued to drop to 4.0 after 30 minutes. Reviewer's Comments: For both S. mutans and S. sanguinis , when the bacterial medium was maintained at a lower pH of 5.5, as would occur with an acid challenge in vivo, the bacterial acid production was significantly lower when there was an eluate containing a higher level of fluoride, as was produced by the specimens from the glass-ionomer group. There was minimal difference at a neutral pH. This study shows that GICs can indeed have both a slowing of the pH drop as well as a reduction in acid production effect on cariogenic bacteria.