<P> All fluoridation methods , including water fluoridation , create low levels of fluoride ions in saliva and plaque fluid , thus exerting a topical or surface effect . A person living in an area with fluoridated water may experience rises of fluoride concentration in saliva to about 0.04 mg / L several times during a day . Technically , this fluoride does not prevent cavities but rather controls the rate at which they develop . When fluoride ions are present in plaque fluid along with dissolved hydroxyapatite , and the pH is higher than 4.5 , a fluorapatite - like remineralized veneer is formed over the remaining surface of the enamel ; this veneer is much more acid - resistant than the original hydroxyapatite , and is formed more quickly than ordinary remineralized enamel would be . The cavity - prevention effect of fluoride is mostly due to these surface effects , which occur during and after tooth eruption . Although some systemic ( whole - body ) fluoride returns to the saliva via blood plasma , and to unerupted teeth via plasma or crypt fluid , there is little data to determine what percentages of fluoride 's anticavity effect comes from these systemic mechanisms . Also , although fluoride affects the physiology of dental bacteria , its effect on bacterial growth does not seem to be relevant to cavity prevention . </P>
where is the highest level of fluoride stored in the teeth
surface of the enamel