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.[12] Technically, this fluoride does not prevent cavities but rather controls the rate at which they develop making them take a lot longer and making them easier to prevent via normal brushing as it will take a higher amount of acid, usually built up over a number of days, to destroy the created fluorapatite.[13] When fluoride ions are present in plaque fluid along with dissolved hydroxyapatite, and the pH is higher than 4.5,[14] a fluorapatite-like remineralised 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 remineralised enamel would be.[4] The cavity-prevention effect of fluoride is partly due to these surface effects, which occur during and after tooth eruption.[15] Fluoride interferes with the process of tooth decay as fluoride intake during the period of enamel development for up to 7 years of age; the fluoride alters the structure of the developing enamel making it more resistant to acid attack.