Topical application of titanium tetrafluoride has shown promise as an effective chemotherapeutic agent in combating tooth decay. The mechanism of action of such topically applied fluorides probably has both a chemical and a biological component. It is the objective of this project to investigate the chemical aspect of the mechanism of action of titanium tetrafluoride. The initial approach will be to study the reactions of titanium tetrafluoride with powdered hydroxyapatite in aqueous media. When the products of this reaction are identified, powdered dental enamel and enamel slabs will be treated with titanium tetrafluoride and the reaction products studied. The poducts of these reactions will be identified by application of x-ray diffraction, infrared, atomic absorption, and wet chemical analytical methods.