only a depth of a few nanometres, which has raised doubts whether the mechanism really relies on the formation of fluorapatite. Synthesis The synthesis of olaflur starts from cattle's tallow. The contained fatty acids, mainly stearic acid (C17H35COOH), are obtained by hydrolysis, and then converted to the corresponding amides, which in turn are reduced catalytically to the primary amines (largely octadecylamine). Addition of acrylonitrile, followed by another reduction, yields N''-alkyl-1,3-propanediamines. The two nitrogen atoms react with ethylene oxide to form tertiary amines. Finally, hydrofluoric acid is added to give the end product. Because olaflur is produced from a mixture of fatty acids, some molecules have side chains that are longer or shorter than 18 carbon atoms. Other byproducts of the reaction include hydroxyethyl ethers resulting from addition of ethylene oxide to the free hydroxyl groups. The presence of these side products is clinically irrelevant. See also Fluoride therapy Remineralisation of teeth References Dental materials Fluorides Amines Cationic surfactants