Enamel conditioning for fluoride treatments

One of the limiting factors of the fluoride-enamel reaction is the close proximity of the enamel crystals. We proposed to loosen the structure of enamel somewhat to cause a favorable reaction with fluoride. The final phase of the process, for which the name enamel conditioning is proposed, is the re-tightening of the enamel structure (triggered by fluoride ions) and the incorporation of fluoride into the enamel crystals. The possibility of a topicalt fluoride mech-anism for reducing the incidence of dental caries was predicted by Bibby ' in the early forties and was confirmed thereafter in numerous studies. When sodium fluoride is applied to sound enamel, electron micro-scope,2A electron diffraction,56 and X-ray diffraction'7 studies show that the principle chemical product of the reaction is calcium fluoride. This reaction is pH dependent: at neutral or near neutral pH there is practi-cally no observable reaction, whereas at a pH of 4.0 or below, the reaction proceeds rapidly.5'6 The reaction occurs mainly on the surface of the enamel and is probably limited by the close proximity of the crys-tals and the formation of calcium fluoride. Fluoride can also react with calcium ions adsorbed on the surface of the apatite crys-tals, or present in their hydration layer, with an end product, again, of calcium fluoride. When fluorides other than sodium fluoride are used, the reaction(s) between the cation and tooth components must be considered. For instance, with stannous fluoride, the fluoride moiety reacts as indicated to for