Determining low levels of fluoride released from resin based dental materials

Fluoride release determinations were made on two resin matrix dentine bonding systems using an ion-selective electrode and ion chromatography. Calibrations were made on serially diluted samples of standard fluoride solutions. The electrode method consistently gave higher values than the chromatographic method for one of the materials, and this was considered to be due to the use of total ionic strength adjustment buffer in electrode determinations. The lower limit of fluoride determination using the electrode was 0.5-0.1 p.p.m. Below this concentration the output from the electrode became meaningless. The chromatographic method gave meaningful results down to 0.001 p.p.m. The fluoride release results for the meter were meaningful only for the first 2 d for one test material and for up to 10 d for the other material. Using chromatography, fluoride release could be monitored for the full 44 d of the trial for both materials. Over the range of concentrations where fluoride determinations were possible by both methods, the values were correlated (R = 0.98). Ion chromatography appears to have an advantage over the ion-selective electrode for measuring low levels of fluoride release from dental materials.