European Organization for Caries Research Workshop: Methodology for Determination of Potentially Available Fluoride in Toothpastes

Toothpastes are the most universally accepted form of fluoride delivery for caries prevention. To provide anti-caries benefits, they must be able to release fluoride during the time of tooth brushing or post brushing into the oral cavity. However, there is no standard accepted procedure to measure how much fluoride in a toothpaste may be (bio) available for release. The European Organization for Caries Research proposed and supported a workshop with experts in fluoride analysis in toothpastes and representatives from industry. The objective of the workshop was to discuss issues surrounding fluoride analysis in toothpaste and reach consensus on terminology and best practices, wherever the available evidence allowed it. Participants received a background paper and heard presentations followed by structured discussion to define the problem. The group also reviewed evidence on the validity, reliability and feasibility of each technique (namely chromatography and fluoride electroanalysis) and discussed their strengths and limitations. Participants were able to reach a consensus on terminology and were also able to identify and summarize the advantages and disadvantages of each technique. However, they agreed that most currently available methods were developed for regulatory agencies several decades ago, utilizing the best available data from clinical trials then, but require to be updated. They also agreed that although significant advances to our understanding of the mechanism of action of fluoride in toothpaste have been achieved over the past 4 decades, this clearly is an extraordinarily complex subject and more work remains to be done

Role of Fulvic Acid on Lead Bioaccumulation by Chlorella kesslerii

To better understand the relationship between lead speciation and bioavailability in natural freshwaters, the interaction of lead with the freshwater alga Chlorella kesslerii was studied in the presence of Suwannee River fulvic acid (SRFA). Special attention was paid to direct interactions of the fulvic acid on the algae, as well as potential physiol. (membrane permeability and algal metab.) influences. Lead-free ion concn. measurements were carried out using a novel ion-selective electrode. The Pb uptake decreased in the presence of SRFA with respect to noncomplexed Pb, but uptake fluxes, cellular Pb, Pb bound to the transport sites, and total adsorbed Pb were all higher than predicted from Pb2+ activities, in accordance with the free ion activity model (FIAM). The discrepancies between the obsd. values and those predicted by the FIAM in the presence and absence of synthetic ligands increased with increasing concn. of SRFA. Several hypotheses were examd. to explain the obsd. differences. No contributions of labile and(or) hydrophobic Pb-SRFA complexes were found. Furthermore, direct biol. effects, including variations in membrane permeability or algal metab., could not account for the observations. On the other hand, changes in the algal surface charge due to SRFA adsorption seemed to account, at least partially, for the obsd. increase in lead uptake in the presence of SRFA as compared to that corresponding to the same Pb2+ concn. in the presence of synthetic ligands. [on SciFinder (R)