[Does the application of a fluoride lacquer modify the de- and remineralization of initial carious lesions in vitro?]

Bovine enamel specimens with artificial initial lesions were fluoridated with a fluoride lacquer (Duraphat) for 6 hours. Subsequently artificial plaque (Streptococcus mutans, FA1) was grown on the enamel blocks in an artificial mouth. During the experimental period (23 days) the specimens were continuously rinsed with synthetic saliva and with sucrose twice daily. Nonfluoridated specimens served as controls. At the end of the experiment microhardness was evaluated in three levels parallel to the enamel surface. In addition, the concentration of KOH-soluble and structurally bound fluoride was determined. In the fluoridated specimens microhardness increased in levels near the surface of the lesion, but decreased in the next two lower levels. However, in the nonfluoridated enamel specimens microhardness decreased in all three levels and was more pronounced compared to the fluoridated specimens. At the end of the experiment no KOH-soluble fluoride could be determined on the surfaces of the artificial lesion. In contrast, structurally bound fluoride was significantly increased in the fluoridated specimens. A single application of the fluoride lacquer on initial enamel lesions resulted in remineralization of the outer enamel layers even under persisting cariogenic conditions. However, lesion progression could not be inhibited totally.