Fluoride release/uptake from newer glass-ionomer cements used with the ARTapproach

Purpose: To determine the fluoride ion release/uptake of two conventional g lass-ionomer cements (GICs) manufactured for use with the ART approach (Fuj i IX GP, Ketac-Molar), as compared with that of a resin-modified GIC (Fuji II LC). Materials and Methods: 15 specimens of each material were prepared and placed in vials with artificial saliva and stored at 37 degreesC. The s olution was replaced weekly for 6 wks, and the fluoride ions released were measured in ppm each week. After 6 wks, the 15 specimens of each material w ere divided into three equal groups and placed into three fluoride rechargi ng agents (1.23% APF gel, 1.1% neutral NaF and 0.001% CaF2) for 4 min at 23 degreesC. Fluoride ion measurements of the recharged specimens were carrie d out at 1 day, 2 days, then weekly for another 6 wks. Results: All freshly -mixed specimens showed the highest fluoride ion release after 1 week, then the release rates dropped quickly to become largely stabilized after 3 wks . After one 4-min exposure to APF gel the initial fluoride ion release incr eased significantly for all materials. The highest rates were during the fi rst day, but then dropped very quickly to again become largely stabilized a fter usually 3 wks. Exposure to NaF and CaF2 did not usually result in sign ificantly sustained fluoride ion release by any material. The order of rele ase/uptake for all three agents was Fuji II LC > Fuji IX GP > Ketac-Molar. The mechanism of fluoride ion release after the application of different fl uoride recharging agents is not clear. It may occur partly by washout of re charge agents that are retained in the pores and cracks of the restorative materials, for APF gel is viscous and difficult to wash off completely with deionized water; by erosion of surfaces by low pH agents, or by the subseq uent release of fluoride ions from within the cement matrix.