Rose R K, Shellis R P, Lee A R
MRC Dental Group, Dental School, Bristol, UK.
Caries Res. 1996;30(6):458-64. doi: 10.1159/000262360.
The cation-bridged fluoride binding model proposed previously was tested by measuring fluoride binding to Streptococcus mutans R9 in the presence and absence of calcium, magnesium or zinc ions. The dissociation constant for fluoride binding to washed cells was 8.4 +/- 7.9 mmol/l and the binding capacity was 4.3 +/- 1.7 mumol/g wet weight. Binding was largely accounted for by residual bound divalent magnesium, with a small contribution from calcium. In the presence of 5 mmol/l divalent cation, dissociation constants for fluoride (mmol/l) were: 12.2 +/- 3.8 (calcium), 9.9 +/- 0.4 (magnesium) and 14.4 +/- 0.5 (zinc). Binding capacities (mumol/g wet weight) were: 122 +/- 26 (calcium), 130 +/- 90 (magnesium) and 142 +/- 56 (zinc). Fluoride produced a marked reduction in calcium binding affinity and approximately doubled the calcium binding capacity. In the absence of fluoride, divalent cation binding to plaque is bidentate. It is suggested that fluoride, by competing with macromolecular anionic groups, causes binding to become monodentate. This allows the binding of double the quantity of cations (and of further fluoride). Release of fluoride, bound by calcium bridging, into plaque fluid, as a result of fluoride clearance into saliva, or of a fall in pH, will always be accompanied by a release of calcium which will potentiate the cariostatic effect of fluoride.
通过测量在有或没有钙、镁或锌离子存在的情况下氟化物与变形链球菌R9的结合，对先前提出的阳离子桥连氟化物结合模型进行了测试。氟化物与洗涤过的细胞结合的解离常数为8.4±7.9 mmol/L，结合容量为4.3±1.7 μmol/g湿重。结合主要由残留的结合二价镁引起，钙的贡献较小。在存在5 mmol/L二价阳离子的情况下，氟化物的解离常数（mmol/L）为：12.2±3.8（钙）、9.9±0.4（镁）和14.4±0.5（锌）。结合容量（μmol/g湿重）为：122±26（钙）、130±90（镁）和142±56（锌）。氟化物使钙结合亲和力显著降低，并使钙结合容量增加约一倍。在没有氟化物的情况下，二价阳离子与牙菌斑的结合是双齿的。有人提出，氟化物通过与大分子阴离子基团竞争，导致结合变为单齿。这使得阳离子（以及更多氟化物）的结合量增加一倍。由于氟化物清除到唾液中或pH值下降，通过钙桥连结合的氟化物释放到牙菌斑液中时，总是会伴随着钙的释放，这将增强氟化物的抑龋作用。
