PubMed · 4534662
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F Crossay. [Continuing homeopathy].. https://pubmed.ncbi.nlm.nih.gov/4534662/
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Fluoride-mediated inhibition of peroxidase potential activity in human saliva was investigated using NaF, NH4F, CaF2, Na2PO3F (MFP), SnF2 and TiF4. At pH 5.5 and for a 20 mM F concentration, the inhibition percentages increased from 2% for MFP and 5% for CaF2 to 61% for NaF and 65% for NH4F, while a 100% inhibition was observed at 10 mM for TiF4 and at 5 mM for SnF2. The inhibition was enhanced at acid pH and removed at pH 7. The inhibition could be attributed to ionized F-, except for SnF2 and TiF4, in which part of the inhibition could be imputed to the cations.
As calcium fluoride formation following topical application of fluoride may be responsible for at least some of the caries-reducing effect of fluoride, the concentration of fluoride necessary to induce its formation were examined. The aim was to determine the degree of supersaturation with respect to calcium fluoride necessary for inducing its spontaneous precipitation, with close reference to its possible formation and retention on dental hard tissue when topical fluoride solutions are used clinically. Powdered enamel or brushite were suspended for 4 h in aqueous solutions buffered at pH 7.2 and 5.0. After the equilibration, ion concentrations were determined and degrees of saturation with respect to apatite and brushite were calculated. In aqueous solutions at pH 7.2 and 5.0 with similar concentrations as those found in the equilibrated suspensions the fluoride concentration was adjusted to from 5 to 500 parts/10(6). After 2 h of gentle agitation the supernatant was analysed, the precipitate (if any) isolated and examined by X-ray diffraction. Initiation of spontaneous calcium fluoride formation required a calcium fluoride ion-activity product of 10(-7.6) or more, 300 parts/10(6) fluoride were necessary to initiate calcium fluoride formation in neutral solution saturated with enamel, and the increased solubility of enamel apatite at low pH allowed calcium fluoride formation from solutions with as low as 100 parts/10(6) fluoride. When phosphate was present in the solution a competing apatite formation could mask the calcium fluoride formation. In neutral solutions saturated with respect to brushite, spontaneous fluorapatite formation was initiated by 100 pats/10(6) fluoride. With 200 parts/10(6) fluoride a further competing formation of calcium fluoride occurred.
All currently used topical fluoride agents deposit soluble fluoride as calcium fluoride on enamel or in lesions. Calcium fluoride serves as a source of fluoride for the formation of fluorapatite. The latter phase is formed when pH drops in plaque, not during topical application. The potential for calcium fluoride formation should probably be increased in topical fluoride agents. In countries with low caries prevalence, the clinical recommendations for topical fluoride need to be reconsidered. Toothpaste is the basic fluoride regimen recommended for everybody. The need for additional fluoride supplementation depends on caries activity. There is no distinct difference in the caries-preventive effects of concentrated fluoride solutions, gels, or varnishes. Thus, the choice of method depends on costs, convenience, patient acceptance, and safety. The use of fluoride varnishes has proven to be a feasible and safe method of fluoride application. With fluoride varnishes, the amounts of fluoride exposure can be better controlled, and less chair-time is required compared with conventional solutions and gels. No dose-response effect to concentrated fluoride agents is apparent, and the benefit of frequent application is not clearly established. In individuals with the most severe cariogenic challenge, combinations of fluoride and antimicrobials may give better clinical effects than fluoride alone.