Distribution of fluoride in glass ionomer cement determined using SIMS

The uptake by glass ionomer cement of ions (particularly fluoride) from sol utions in which the cements have been immersed has been extensively reporte d. The concentrations within the cement often greatly exceed those in the i mmersing solution. The distribution of these ions has not been determined. The aim of this study is to use SIMS to investigate the levels of ions with in the cement at different depths below the immersed surface of the cement. K+ and F- were the ions studied and uptake was into a cement containing ne ither it nor F (LG30) and one containing F (AH2). The surface was analysed using a Cameca ims4f instrument employing a 14.5 keV Cs+ primary ion beam. This was calibrated on cements made from a series of glasses in which fluor ine content was systematically substituted for oxygen (without other elemen tal changes). XPS, which is very much a surface technique, was used in conf irmatory role with respect to the SIMS analysis. Cement discs were made fro m LG30- and AH2-based cements. After maturation for 72 h these were immerse d in 0.275% KF solution for 24 h. SIMS analysis indicated appreciable surfa ce F concentration on LG30 and on AH2 an enhanced F concentration. In contr ast, K was not detected on the LG30 surface and only at a low level on AH2. These results were confirmed by XPS. Using the ion beam of the SIMS to spu tter away cement enabled the F depth profile on LG30 to be measured to 10 m um Over this distance the F content drops from 6.2 mmol/g at 0.2 mum from t he surface to 0.2 mmol/g at 10 mum. No K was detected down to 13 mum from t he surface. From the results of this study, it can be concluded that SIMS i s an appropriate tool For further investigation of the distribution of ions uptaken by glass ionomer cements. (C) 2001 Elsevier Science Ltd. All right s reserved.