Fluoride ions adverse effects

With stannous fluoride, the mechanism of action appears to be related to an alteration of bacterial aggregation and metabolism. In summarizing the properties of this agent, it can be stated that it has moderate substantivity, that the antibacterial activity may be related to the tin ion, and that a 0.4% concentration may be the most effective. Stannous fluoride is the most toxic of the products considered and has the shortest shelf life. Adverse effects have been taste and black stain lines on teeth. Usage of once or twice daily favors compliance. Stannous fluoride is most often available as an aqueous gel. 

Evidence exists that certain trace elements can reduce the incidence of caries. Systemically administered fluoride appears to favour the deposition of apatite with a reduced solubility in acid (page 429) and also to be essential for maturation of the enamel and the remineralization of an early carious lesion (page 511). Even after the teeth are fully developed, the presence of fluoride in the oral fluids is beneficial because fluoride ions are adsorbed on the enamel surface and have an adverse effect on bacterial metabolism (page 500). 

In fact, the presence of such inorganic arsenic (As(V/III)), fluoride (F ) and uranium (U(VI)) species (mostly ions) in groundwater (and to less extent in surface water) is a critical global issue, and has created severe health impacts for decades. Bioaccumulation and adverse effects on human health by intake of these ions via drinking water have been well documented (e.g., Fawell et al., 2006 Qrloff et al., 2004 Smedley and Kinniburgh, 2002). 

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