Rose R K, Turner S J
MRC Dental Group, The Dental School, University of Bristol, UK.
Caries Res. 1998;32(3):227-32. doi: 10.1159/000016457.
It has been demonstrated that fluoride decreases the calcium-binding affinity of Streptococcus mutans and approximately doubles the calcium-binding capacity. To investigate the effect of this mechanism on calcium mobility in plaque, 45Ca flux was measured from a condensed films of S. mutans into tracer-free solution. Bacteria were suspended in pH 7.0 or 5.0 buffer including 0, 5, 10, 15 or 20 mmol/l Ca2+ carrier, with or without 5 mmol/l F- and with 45Ca and 3H-inulin. The appearance of 45Ca and 3H-inulin in carrier-containing but initially tracer-free buffer was measured and extracellular fraction (Ve) and bound calcium were calculated. As the ratio (R) of bound to free Ca2+ approached zero at high [Ca2+], the measured diffusion coefficient (rDe) approached the effective diffusion coefficient (De), such that: rDe = De/(1+R). Fluoride increased the rate of calcium diffusion by a reduction in the binding affinity. This work demonstrates that fluoride significantly increases mobility in plaque; this may increase the rate at which calcium is transported between plaque and an underlying lesion and so promote remineralization. This mechanism could also increase the penetration of bacteriocides and suggests a novel method for biofilm treatment.
已证实，氟化物会降低变形链球菌的钙结合亲和力，并使钙结合能力增加约一倍。为了研究这种机制对菌斑中钙迁移率的影响，测量了45Ca从变形链球菌浓缩膜进入无示踪剂溶液的通量。将细菌悬浮在pH 7.0或5.0的缓冲液中，缓冲液中含有0、5、10、15或20 mmol/l的Ca2+载体，有或没有5 mmol/l的F-，并含有45Ca和3H-菊粉。测量含有载体但最初无示踪剂的缓冲液中45Ca和3H-菊粉的出现情况，并计算细胞外部分（Ve）和结合钙。在高[Ca2+]时，由于结合钙与游离Ca2+的比率（R）接近零，测得的扩散系数（rDe）接近有效扩散系数（De），即：rDe = De/(1+R)。氟化物通过降低结合亲和力提高了钙的扩散速率。这项研究表明，氟化物显著增加了菌斑中的迁移率；这可能会增加钙在菌斑与潜在病变之间的运输速率，从而促进再矿化。这种机制还可能增加杀菌剂的渗透，并提示了一种生物膜治疗的新方法。
