F Levels as low as 1ppm have been shown to be effective at reducing lesion formation, but F must be present at the time of the acid challenge
Elevated levels of F close to the tooth surface help change the dynamics of the demineralization process, preventing dissolution of HAP crystals
Fluoridated water and fluoridated dentifrice and mouthrinse help deliver low levels of F to the saliva, enabling residual F to build up in plaque, pellicle and calculus
Thus, fluoride changes the remineralization process by acting as a mineral growth catalyst. The action of fluoride accelerates the rebuilding of enamel and can stop or even reverse the progression of dental decay. More importantly, the incorporation of fluoride into the tooth mineral along with calcium and phosphate makes enamel more resistant to acid demineralization then it was originally.
The processes of remineralization and demineralization are similar on any tooth surface upon which they are occurring (enamel pits, fissures, smooth surfaces). However, some surfaces tend to have higher incidence of lesion formation compared to others. This is primarily a function of a combination of tooth morphology and accessibility for cleaning, with pit and fissure along with interproximal sites experiencing the highest rates of lesion formation.