Influence of Sodium Chloride on Fluoride Reactions with Dental Tissues

Abstract

Owing to previous findings of an enhanced fluoride (F) uptake by enamel surfaces in the presence of elevated NaCl concentrations, accompanying solubility changes were studied on homologous pairs of extracted premolar teeth and on powdered enamel and dentine. The enamel surfaces and the enamel and dentine powders were exposed to solutions of NaCl and NaF, the NaCl concentrations corresponding to either F-salted food or saliva, the NaF concentrations to either F-salted food or fluoridated water. Subsequently, the surfaces and powders were exposed to 0.2 M acetate buffer, pH 4. The slight dissolving effect of the NaCl-NaF solutions was investigated by calcium analysis and the loss of F from solution to tooth substance was determined. The subsequent dissolution in acetate buffer was studied by calcium and F analyses and by determination of the weight losses and the levels of F remaining in the enamel and dentine powders. The results showed (1) that intact enamel surfaces were moderately affected by 175 mM NaCl when F was present in a proportion corresponding to fluoridated salt; (2) that this chloride concentration had a dissolving effect on the fine-crystalline dentine apatite; (3) that the enamel and dentine solubility in acid was reduced nearly as much by the lower as by the higher F concentrations studied; (4) that F dissolved by acid seemed to counteract simultaneous calcium dissolution, and (5) that dissolved F was recombined to a great extent by apatite present in a fine-crystalline form.

Single Fluoride Doses and Enamel Fluorosis in the Rat

“…We hypothesize that, fol lowing an acute and relatively large dose of F, the ion is slowly released by ex change and remodelling from the bone ad jacent to the enamel organ thus producing locally elevated F concentrations in the extracellular and cellular fluids surround ing the developing enamel. This hypothe sis is supported by Findings of Zipkin [1972] and Ericsson [1982] who reported reFixation of dissolved F in adjacent hard tissue. The hypothesis might be supported by the earlier Findings of Lindemann [1967] who noted pigmental evidence of rat incisor fluorosis for several months af ter halting high F doses via drinking wa ter.…”

Effect of fluoride-containing alginates and gels on the acid resistance of demineralized human enamel

“…This may indicate that part of the F dissolved in acetate buffer was refixed to the demineralized enamel surface. Evidence supporting this phenomenon has previously been reported (22,23). I t might, therefore, be concluded that the F dissolved in the acidic buffer did not represent the original F concentration in the enamel layer biopsied.…”

Enamel and Dentin Fluoride Levels and Fluorosis following Single Fluoride Doses: A Nuclear Microprobe Study

“…In this way, locally elevated F concentrations, sufficient to adversely affect ame logenesis, are produced in the extracellular and cellu lar fluids surrounding the developing enamel. The hy pothesis is also supported by findings of Zipkin [1972] and Ericsson [1982] who reported that fluoride dis solved from bone could be taken up by adjacent hard tissue.…”

“…It was hypothesized that, following an acute and relatively large dose of F, the ion would be released slowly by exchange and remodelling from the bone adjacent to the enamel organ, thus producing locally elevated F concentrations in the extracellular and cellular fluids surrounding the developing enamel. This hypothesis was supported by the findings of Zipkin [1972] and Ericsson [1982] who reported refixation of dissolved F in adjacent hard tissue. Further, it has been sug gested that the F of developing enamel is not irreversi bly bound therein, but is recycled throughout the life of the tooth [Weatherell et al, 1977].…”