Kinetics of F-release from glass components of glass-ionomers

Objectives: To compare the F release from glass-ionomer glasses (GICs) into water changed periodically with release into an unchanged “sink” (Williams et al Biomater 2002;23:2191-2200). To evaluate the effect of replacing Ca wholly or partially by Sr. To compare two different methods of decomplexing F containing species. Methods: all four glasses contained Al, Si,P,O,&F. Glass A1 also had Na & Ca, C2 had Ca, B3 had Ca & Sr, and S4 had Sr. Glasses were tested:-[ R] after ball-milling, [W] after washing in dilute acid, and [P] W mixed with 35% acetic acid to form a “pseudo-cement”. F-release was from130 mg samples into 10mL of deionised water changed at 1,3,7,14, 21, 28,35,&42 days. Analysis was carried out using ISE without decomplexing F, using TISAB buffer T, and acid hydrolysis + TISAB (after Hattab) H. Results: The release rates from all glasses and treatments are linear with respect to t1/2 with r =0.97 or greater (p = <0.001). The table shows regression line slopes. F release into a “sink” showed no such correlation. The higher release rate from A is more than accounted for by its higher F content. Most F release is not complexed (except from A) whereas the “sink” study C released complexed F. For TF release, S is 26% more than C. HF>TF only for R. Conclusions: changing water produces diffusion controlled kinetics and reduces complex F formation. Replacing Ca by Sr enhances F release rate slightly. 1 AH2, 2 LG26 Advanced Healthcare Ltd; 3 LG125, 4 LG26Sr ULTRASET Project