Fluoride release profiles of restorative glass ionomer formulations

Objectives. The amounts of fluoride released by different glass ionomer formulations were compared on the basis of individual fluoride release profiles in order to derive the effect of the physical and chemical formulation on the fluoride release process. Methods. The fluoride release profiles of each of five specimens of ten glass ionomer cements setting by an acid-base reaction were investigated. The profiles were obtained by determining the amount of fluoride released [F] after equilibrating the samples at 37°C in distilled water for 140 d. The {[F],t}-profiles were compared with a Multivariate Data Analysis on the basis of a Principal Component Analysis. Results. The Multivariate Data Analysis reveals that eight of the ten glass ionomers can be classified into four distinct groups. When the cumulative amount of fluoride released by each sample, [F]c, is calculated and fitted as a function of dime, a regression analysis (r>0.99) reveals that [F]c for all samples is most adequately represented by [F]c = ([F].t)/(t+t1/2) + β·√t, indicating that two kinetic processes are responsible for the fluoride release profiles. Significance. A comparison of the parameters of this equation shows that the physicochemical rationale for the classification of the glass ionomers conforms to differences in the kinetics of these processes which are determined by the qualitative and quantitative chemical composition as well as by the presentation (hand-mixed vs. capsules) of the glass ionomer. From the classification, it becomes apparent that different formulations can result in the same fluoride release profiles.