Effects of fluoride on caries development and progression in vivo.

The dissolution rate of calcium-fluoride-like material from the enamel surface in vivo appears to be much slower than previously thought. This could be due to adsorption of phosphate ions and/or protein molecules to the surface of the calcium-fluoride-like particles. During cariogenic challenges, the phosphate/protein coating is released, resulting in increased solubility rate of the calcium-fluoride-like material. Due to this mechanism, calcium-fluoride-like material may be a major aspect of the cariostatic mechanism of topically applied fluoride. Topically applied neutral fluoride agents are able to inhibit caries development in enamel but not completely stop lesion development. A fluoride solution at low pH has been found to be more effective in caries model studies than neutral fluoride agents, which might be due to the formation of a larger depot of calcium fluoride. Data from fluoridated areas indicate that the fluoride ion as such has a limited effect on lesion development, and a major mechanism of the cariostatic effect may be reformation of apatite (remineralization). The product of lesion consolidation (a fluoridated apatite) may have a limited effect, since intra-oral caries model studies show that even pure fluorapatite, in the form of shark enamel, demineralizes. In fissures and around orthodontic appliances, conventional fluoride agents appear to have only a small effect.