Reactions of Fluoride Ion with Hydroxyapatite by Harold

A problem of long standing in the study of dentin and enamel is the exact nature and structure of the inorganic material in these tissues. A review of these studies from the time of Berzelius in 1845 up to 1949 has been published by Armstrong (1). In general the mineral component of teeth as well as bones consists chiefly of a basic calcium phosphate which is most probably hydroxyapatite (2, 3). Hydroxyapatites may be synthesized in the laboratory and their basic chemistry and reactions studied directly. The use of a synthetic hydroxyapatite instead of the natural hydroxyapatites, as may be found in teeth and bones, avoids possible complications introduced by extraneous chemicals present. in the natural materials. Chemical methods devised to study the synthetic apatites may then be adapted for study of natural tooth substance. At the same time information is obtained concerning basic chemical reactions which take place and the effects of varying conditions on these basic reactions. In these experiments we have been concerned for obvious reasons (4, 5) primarily with reactions between the fluoride ion and synthetic hydroxyapatite.