Current concepts on the theories of the mechanism of action of fluoride

The caries-preventive effect of flue ride is mainly attributed to the effec ts on demineralization/remineralization at dic tooth oral fluids interface. Sub ppm levels of fluoride in saliva are effective in shifting the balance from demineralization, leading to caries, to remineralization. This is att ributed to the fluoride-enhanced precipitation of calcium phosphates, and t he formation of fluorhydroxyapatite in the dental tissues. Low; fluoride le vels are found in saliva after toothbrushing with fluoride containing denti frices. Similar concentrations are ineffective in interfering with processe s of growth and metabolism of bacteria, and also do nor result ill a signif icantly reduced dissolution of tooth mineral as a result of (firmly bound) fluoride incorporation. Comparative studies of fluoride efficacy have shown that higher concentrations in solution are needed in pH-c) cling studies o f dentine than in enamel to maintain the mineral balance or to induce remin eralization. This is attributed to the greater solubility of the dentine an d the smaller size of the dentine crystallites compared to enamel. Fluoride slow-release devices, in the form of fluoride-releasing restorative materi als, may serve to increase the fluoride levels in saliva and plaque to leve ls at which caries can be prevented, also in high-risk patient. Research qu estions for the next millennium and Future perspectives for fluoride applic ations should be found in the retention and slow release of fluoride after various combinations of fluoride treatment, the combination of fluoride and anti-microbial treatment, the individualization of cal ies prevention. and the combination of preventive schemes with new developments in caries diag nosis.