In vitro fluoride uptake by enamel and dentin. A comparative study of two varnishes

Influence of fluoride concentration and ethanol pre-treatment on the reduction of the acid susceptibility of enamel

OBJECTIVE

To determine the association between KOH-soluble and structurally bound fluoride uptake and the erosion resistance of enamel, respectively. Additionally, the effect of enamel pre-treatment with ethanol before fluoridation was assessed.

METHODS

Sixty bovine incisors (4 specimens/tooth) were randomly allocated to six groups (A-F). Samples 1 and 2 remained untreated, serving as control at baseline. Pre-treatment of the samples was performed for 5 min with 99% ethanol (groups A, B and C) or physiologic saline (groups D, E and F). Samples 3 and 4 were treated either with 0.5% (groups A and D), 1.0% (groups B and E) or 1.5% (groups C and F) fluoride solution. In samples 1 and 3, uptake of KOH-soluble and structurally bound fluoride was determined. Samples 2 and 4 were used for the determination of acid susceptibility by immersion in 1 ml HCl for 30s. Calcium release into HCl was assessed by atomic absorption spectroscopy. Differences between the groups were calculated by unpaired t-tests (p<0.05).

RESULTS

Mode of pre-treatment showed no influence on fluoride acquisition. KOH-soluble and structurally fluoride uptake increased with increasing fluoride concentrations. Highest acid resistance was observed after treatment with 1% fluoride solution for both kinds of pre-treatment followed by 1.5% and 0.5% fluoride solution.

CONCLUSION

Dose-dependency was observed for enamel fluoride acquisition but not for acid resistance.

Laser-fluoride effect on root demineralization

Although the individual cariostatic effects of laser and fluoride have been shown, the combined effect of CO(2) laser and fluoride on root demineralization remains uncertain and was the main aim of this study. By using a pH-cycling system and Polarized Light Microscopy, we demonstrated the synergistic effect of fluoride combined with CO(2) laser treatment on reducing root demineralization. The mean lesion depths (in microm) for each group were 160 +/- 14 (Control), 113 +/- 8 (Laser treatment alone), 111 +/- 6 (Fluoride treatment alone), and 25 +/- 7 (Fluoride followed by laser treatment). A significant laser-enhanced fluoride uptake, characterized by the ToF-SIMS analysis, was revealed by the 37% and 400% increments in loosely and firmly bound fluorides (both p < 0.002) in laser-irradiated areas, compared with the non-irradiated controls. In conclusion, there is a significant synergistic effect of combined CO(2) laser and fluoride treatment on the inhibition of root demineralization, possibly due to laser-enhanced fluoride uptake in the root.

Fluoride varnishes. A review of their clinical use, cariostatic mechanism, efficacy and safety

BACKGROUND

This is a review of the clinical use, cariostatic mechanism, efficacy, safety and toxicity of fluoride varnishes.

TYPES OF STUDIES REVIEWED

The authors reviewed and summarized in vitro, in vivo and in situ studies; clinical trials; demonstration programs; position papers; and editorials published in English in the biomedical literature since 1966.

RESULTS

Extensive laboratory research and clinical trials conducted in Europe and elsewhere show that fluoride varnishes are as efficacious as other caries-preventive agents. Fluoride varnishes are widely used in European caries-preventive programs. The U.S. Food and Drug Administration has cleared these products only as medical devices to be used as cavity liners and for the treatment of hypersensitive teeth. These products have not yet been cleared for marketing in the United States as caries-preventive agents.

CLINICAL IMPLICATIONS

Three fluoride varnishes are currently available in the United States. Semiannual applications are the most proven treatment regimen. Varnishes are safe and easy to apply and set in contact with intraoral moisture.

Influence of tooth surface conditions on enamel fluoride uptake after topical application of TiF4 in vitro

Three groups of extracted human teeth were sectioned longitudinally into experimental and control halves. The enamel surfaces of the three groups of teeth were pretreated with 37% H3PO4 for 1 min, 0.5 M NaClO3 for 2 h, or water rinsing for 10 min. The experimental halves of the three groups received an application of 1% TiF4 for 1 min and were washed with deionized water. The tooth specimens were then immersed in synthetic saliva for 24 h at 37 degrees C before sampling for measurement of fluoride uptake. An acid etching technique was used to determine the uptake of fluoride by measuring both fluoride and calcium concentrations in the solution collected from each etched sample. A significantly higher uptake of fluoride was found in teeth rinsed in water and etched with 37% H3PO4 than in teeth pretreated in 0.5 M NaClO3. It seems that the organic components in enamel play an important role in the fluoride uptake after the topical application of TiF4.