Diffusion Of Fluoride Research Articles

Diffusion of fluorides in human dental enamel in vitro

The diffusion of fluoride (F) from sodium fluoride, sodium fluorosilicate, and sodium monoflurophosphate solutions (containing 0.1 per cent F in physiological saline) was studied using a two-chamber diffusion cell separated by enamel membrane. The diffusion coefficient, D in cm 2s −1, of F was determined under steady-state conditions over 3 weeks. The D value of F for NaF was significantly higher than for Na 2SiF 6 and Na 2PO 3F ( p < 0.001;unpaired t-test). F for acidic Na 2SiF 6 diffused more rapidly than for Na 2PO 3F ( p ⩽ 0.001), presumably as HF molecule. Despite the F in the tested solutions being in different forms, i.e. simple ion in NaF or mainly complex ions as in Na 2SiF 6 and Na 2PO 3F, the diffusivity of the F in enamel for these compounds was of the same order of magnitude ( D = 10 −9cm 2s −1). The findings support the concept that enamel can behave as an ion-selective membrane with certain molecular-sieve effects.

Diffusion of fluoride from alginate compared with other topical fluoride agents

A two-chamber diffusion cell has been employed to monitor the diffusion of fluoride (F) from F-containing agents. The F which diffused from fluoridated alginate-base formula, F-containing gel (Gelution) and varnish (Duraphat) was determined within the first 6 or 20 min in unstirred conditions. A comparative analysis of the data showed that the alginate-base formula was efficient in releasing F. The results also indicate that the diffused F was not directly related to the total F content in the products or the bulkiness of the test specimens. It is obvious that the physicochemical properties of the products play a determining role in the release of F.

Effect of zinc citrate on fluoride uptake by artificial caries lesions.

Artificial caries lesions were treated three times with dentifrice slurries or aqueous solutions of sodium monofluorophosphate with and without zinc citrate. Analysis of the treated lesions showed that the presence of zinc citrate reduced fluoride uptake by 60%. Very high levels of zinc were found at the lesion surface, suggesting that zinc precipitates prevented diffusion of fluoride into the lesion.

Enamel microhardness and fluoride uptake underneath fermenting and non-fermenting artificial plaque.

Washed cells of Streptococcus sanguis were used to form artificial plaque on the surface of bovine enamel and incubated underneath buffer solutions, initial pH 6, for 36 h at 37 degrees C. The decrease in the microhardness of the enamel surface under fermenting "plaque" could be prevented with fluoride. Enamel under a fermenting "plaque" took up significantly more (P less than 0.0u) fluoride than enamel under a non-fermenting "plaque" (initial F- in buffer: 10 parts/10(6)). The artificial plaque did not accumulate fluoride. Within fermenting "plaques/, the pH decreased significantly more without flouride (P less than 0.01) than with fluoride. Fluoride combined with sucrose more than negated the softening of the enamel caused by sucrose fermentation, i.e. it increased the hardness above the original values. The diffusion of fluoride through the fermenting artificial plaque was more rapid than through a non-fermenting plaque. These findings suggest that caries-conducive circumstances may promote fluoride uptake by enamel compared with non-caries-conducive circumstances.

A histological, chemical and X-ray diffraction study on contemporary ( Carcharias glaucus) and fossilized ( Macrota odontaspis) shark teeth

It is well known that the fluoride content of contemporary shark teeth is nearly as high as that of pure fluorapatite (3.77 per cent). The purpose of this study was to compare the structure and chemical composition of contemporary and fossilized shark teeth (30 million years old). Microradiographical studies revealed that the fossil shark teeth were denser than the contemporary ones. On the basis of chemical analyses and X-ray diffraction studies it is suggested that contemporary shark teeth consist partly of fluorapatite with a small F − component replaced by OH − or H 2O, and partly of amorphous Ca 3(PO 4) 2 or defect apatite with a low Ca:P-ratio. The study supports the hypothesis that the fluoride content in dental hard tissues can increase owing to the diffusion of fluoride from the environment.

Incorporation of fluoride by human enamel. II. An exothermic chemical process.

The conversion of hydroxyapatite to fluorapatite and the diffusion of fluoride into enamel from acidulated phosphate-fluoride solutions are both exothermic chemical processes. Thus, the postulate that these topical fluoride applications to enamel tend to form fluorapatite is sound thermodynamically.

The diffusion of fluoride with hexamethyldisiloxane

Several acids, when saturated with hexamethyldisiloxane, induce the diffusion of fluoride at ambient temperatures. Observations with plant and soil suspensions which contain a mixture of complex fluorides including organically combined fluorine show that siliconed acids may not diffuse as much fluoride as does perchloric acid containing silver sulphate at 60°.

Effect of silicone grease on diffusion of fluoride.

Effect of silicone grease on diffusion of fluoride.