Effect of pH of amine fluoride containing toothpastes on enamel remineralization in vitro

A 5 × 5 mm window on the enamel surface of 40 caries free extracted human premolars was demineralized in a hydroxyethylcellulose solution at pH 4.8. The teeth were divided into 8 groups and the lower half of the window was covered with varnish serving as control. Each group was then immersed in toothpaste slurry containing amine fluoride (1400 ppm) at pH 4.1, 4.5, 5.1 and 6.9 or control toothpaste slurry without fluoride at pH 4.3, 4.7, 5.3 and 7.0. Serial sections were cut through the lesions and investigated with polarization light microscopy and quantitative EDX element analysis.The PLM results showed a decreased porous volume of the body of the lesion after incubation with fluoridated toothpaste at pH 4.53 and 5.16. No differences between the experimental window and the control window were found in the other groups. The quantitative element analysis showed no differences in the element content of any of the groups.From the results it can be concluded that slightly acidified fluoridated dentifrices may have a certain positive effect on enamel remineralization.Dental caries progression or reversal depends upon the balance between demineralization and remineralization [1]. This balance is depended from several factors e.g. salivary Ca and P concentration, bioavailability of fluoride and pH. Remineralization occurs when the pH raises and Ca and P from saliva together with fluoride are forming new hydroxyapatite crystals on the enamel surface and the body of the lesion [2,3]. Mineral loss of incipient caries lesions is inversely proportional to the degree of saturation of Ca and P ions and the pH of the solution The critical pH range for demineralization and remineralization is between 4.3 and 5.0 where lesions with well defined surface layers occur whereas at pH levels around 6.0 no surface layers are forming [4].Fluoride plays an important role in the remineralization process. Although a dose-response effect of fluoride enhancing enamel remineralization has been fo