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– Test specimens of seven different glass ionomer filling materials and one fissure sealant were exposed to running water for 2 yr. One amalgam and one composite, both containing fluoride, were included for comparison. The fluoride release from the specimens was measured periodically after storing the specimens for 24 h or 1 wk in a small amount of water. The fluoride release From the glass ionomers decreased with time and a constant level was reached for most products during the 2‐yr period. The release was increased by lowering the pH of the storage solution. The release from the glass ionomers was clearly greater than from the amalgam and the composite.

Forsten L: Fluoride release and uptake by glass ionomers. ScandJ Dent Res 1991; 99: 241-5.Abstract -The aim was to study the fiuoride release 1) from 7 and 15-month-old glass ionomer specimens after treating them wilh fluoride; 2) from fresh compared with matured material; and 3) from specimens stored for 29 months in running water. Glass ionomer test specimens which had been in running water for first 7 then 15 months were treated with a 50 ppm fluoride solution after which the specimens were again exposed to running water for first 24 h and then 1 wk. The fiuoride release was measured after each of the two periods of time. The fiuoride treated specimens released more fiuoride than the nontreated ones. This effect was not observed with composite resin specimens which were studied for comparison. Fluoride release from fresh glass ionomer specimens was observed to be 3-10 fold compared to specimens that had matured for 3 days. The release of fluoride from specimens that had been in running water for 29 months was measured and the results were compared with those of earlier measurements. It was found that the release reached a constant level for all tested glass ionomers during the second year.

The release of fluoride from a glass ionomer cement (ASPA®) was compared with that from a silicate cement. Test specimens were shaken in a solution with hydroxyapatite for 7 weeks. The solution was changed every week and the fluoride taken up by the hydroxyapatite measured. The specimens released considerably more fluoride during each of the first 2 weeks than during each of the subsequent 5 weeks. The continued release did not decrease very much with time. Slightly more fluoride was released from the glass ionomer ceinent than from the silicate.A glass ionomer cement which adheres chenjically to enamel and dentin has been • developed for filling gingival toothbrush abrasions and preventively opened "sticky" fissures. In these cases especially, a fluoride effect like that of silicate cement would be desirable. The glass ionomer cement contains fluoride but the solubility of the material in the oral fluids is less than tliat of silicate cement (KENT, LEWIS k WILSON 1973),, which may have an influence on the release of fluoride. The purpose of the present study was to determine the release of fluoride in vitro from a glass ionomer cement compared with that from a silicate cement. Materiai and methodsTest specimens [measuring 2 x 2 x 12 mm') were made of the glass ionomer ASPA* (Amalgamated Dental, London, England) and of silicate cement (Biocap*, Gebr. De Trey A.G., Zurich, Switzerland) according to a method described earlier (FORSTEN & VALIAHO 19V1). The materials were handled according to the manufacturer's instructions and after hardening the specimens were covered with a layer of vaseline to prevent dehydration. The determination of the fluoride content of the powders and the release of fluoride from the specimens has been described earlier in detail (FORSTEN & PAUNJO 1972). To recapitulate, the specimens were shaken in a 10-mI 0.01 M phosphate buffer solution (pH 6.8) together with 100 mg synthetic hydroxyapatite. The solution with the hydroxyapatite was changed every week, and the apatite was analyzed for fluoride. No fluoride could be found in the supernatant (FORSTEN 1976). Six samples were made of each material and the results were compared using the Student's (-test. ResultsThe Huoride content of the silicate powder was 73.6 jig/mg and of the glass ionomer powder 132ng/mg.

The aim was to study the short- and long-term fluoride release from resin-modified glass ionomer cements (GIC). The aim was also to determine the effect of fluoride treatment of 9-month-old specimens, consistency of the mix, and pH of the environment on the fluoride release. GIC test specimens were continually exposed to running water, and the fluoride release was measured periodically by storing the specimens in 5 ml deionized water for 1 week and measuring the fluoride content of the solution. After 24 h, 1 month, 9 months, and 11 months in running water four of the six resin-modified GICs released as much as or more fluoride than the auto-curing GIC tested for comparison. Fluoride treatment after 9 months also increased the fluoride release of these four brands, as was the case with the conventional GIC. At 24 h and 1 month two of the resin-modified GICs released smaller amounts of fluoride than the other materials, and the fluoride treatment used on those had no or only a minimal effect. Thin consistency of a mix resulted in higher fluoride release for one resin-modified material than a thick mix. Low pH increased the fluoride release for all materials.