The Chemistry of Caries Inhibition Problems and Challenges in Topical Treatments

¹ Forsyth Dental Center and Harvard University School of Dental Medicine, Boston, Massachusetts

Evidence has been presented in support of the view that the effectiveness of known topical agents is dependent on their ability to deposit F as fluorapatite in the surface enamel. Stannous tin depresses the deposition of F, and there is no indication that presence of tin compounds in enamel increases caries resistance. A portion of the F acquired during topical treatments leaches away during the first few hours. The lost F represents unreacted F and CaF₂. The retained F appears to be present as fluorapatite and is permanently fixed due to super-saturation of saliva in respect to fluorapatite. Several coating materials applied to the enamel immediately after topical treatments have been shown to noticeably increase the amount of retained fluoride after 24 hours. The clinical significance of this finding is discussed.