The human tooth minerals are impure non-stoichiometric forms of calcium hydroxy apatite, ideally, Ca10(PO4)6(OH)2. The 'impurities' are present as minor constitutents (eg, CO3=, Mg2+) and as trace elements (eg, F-,Sr2+,Li+) and are nebulously associated with the apatite and with dental caries. Except for the well-documented cariostatic effect of ingested and topical F-, the cariogenic/cariostatic properties attributed to many trace elements are conflicting and circumstantial. ---The goal of this research is to define the role of trace elements on the formation (==mineralization/remineralization) and on the chemical stability (==caries resistance/susceptibility) of dental apatites. Based on he qualitative data obtained to date, this study will provide quantitative experimental evidence showing that the effect of F- and of other trace elements on the chemical stability is, to a significant degree, a consequence of their effects on the structural/physical properties (size, morphology, strain/defects, stoichiometry, composition) of the apatite. ---The specific aims are: (1) to determine the effects of a series of cationic and anionic elements on the formation of apatites; (2) to define the manner of association, whether incorporated or surface bound, thus providing insights as to the possible mechanisms by which an effect is manifested; (3) if incorporated, to determine their effects on the structural/physical properties; (4) to determine synergistic effects with F- or CO3=; (5) to determine physico-chemical properties of dental apatites: (a) enamel of known trace element conc; (b) enamel from teeth of known ages, (c) 'white spot' and 'sound' enamel; (d) fluorosed enamel(e) fluoridated and non-fluoridated apatites; (6) to determine effects of dissolution properties when element is a substituent in the apatite and when a component of the solution. ---Studies on dental apatites will be paralleled with studies on synthetic apatites prepared by precipitation or by hydrolysis of CaHPO4/CaHPO4. 2H2O in solutions containing the trace elements in identical conc., pH (5 and 7.5) and temp. (37 and 100C). ---The physico-chemical techniques will include: chemical analyses (atomic absorption), x-ray diffraction, infrared, electron microscopy, thermo-gravimetric anal, dissolution in acetate buffer (pH 5, 37C, exposure times, 10 to 120 min). --The long term goal is to provide quantitative information which will be useful in developing effective formulations of topical and remineralizing agents for preventive dentistry.

National Institute of Health (NIH)
National Institute of Dental & Craniofacial Research (NIDCR)
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New York University
Schools of Dentistry/Oral Hygn
New York
United States
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