Oral absorption of radioactive fluoride and iodide in rats

The bio-availability of fluoride from black tea

OBJECTIVES

To investigate the oral retention of fluoride from tea and its association with the tooth surface and acquired pellicle.

METHODS

Oral retention of fluoride after rinsing in vivo was assessed from expectorated samples with an ion specific electrode methodology. Interaction of fluoride with the tooth surface and acquired pellicle was examined in situ with enamel blocks mounted on partial removable appliances. In vitro models were used to examine fluoride binding to enamel particles.

RESULTS

Thirty four percent of the fluoride was retained in the oral cavity after rinsing with tea. Differences in retention at the tooth surface in the presence and absence of an acquired pellicle were not statistically significant at incisor or molar sites. Fluoride from tea showed strong binding to enamel particles, which was only partially dissociated by solutions of ionic strength considerably greater than that of saliva. Binding studies demonstrated strong avidity of enamel for tea and salivary pellicle components.

CONCLUSIONS

This study has demonstrated that tea can provide an effective vehicle for fluoride delivery to the oral cavity where it may interact with the oral tissues and their surface integuments. This may lead to local topical effects of the ingested fluoride as well as systemic effects following oral and gastro-intestinal absorption.

Fluoride absorption through the hamster cheek pouch: a pH-dependent event

The fractional absorptions of fluoride, 3H2O, 125I and 14C-DMO from the hamster cheek pouch were determined as functions of solution pH. When the pH was less than 5, fluoride absorption rate was inversely related to pH. The absorption rates of the other substances were not influenced by pH. The fractional absorptions of fluoride and 3H2O were independent of fluoride concentrations over the range 1-53 mM. The data indicate that the absorption of fluoride through this keratinized epithelium occurs mainly by the diffusion of non-ionic HF.