Author
W M Hoffman
Bio: W M Hoffman is an academic researcher from United States Department of Agriculture. The author has contributed to research in topics: Phosphorus & Ammonium molybdate. The author has an hindex of 2, co-authored 13 publications receiving 35 citations.
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26 Oct 2015
162 citations
TL;DR: A structural mechanism for the incorporation of impurities during hydrolysis of octacalcium phosphate is presented, of particular importance since the presence of carbonate in human enamel appears to be related to caries susceptibility.
Abstract: Octacalcium phosphate (Ca8H2(PO4)6·5H2O) is considered to be a precursor in the formation of apatite in bones and teeth; a crucial step for incorporation of impurities appears to occur during its hydrolysis. The present study examines the role that octacalcium phosphate plays in the process of incorporation of carbonate into apatite. Chemical, X-ray diffraction, and infrared techniques were used.
147 citations
TL;DR: Solubility of human dental enamel in H3PO4 was studied in the pH range of 4.5 to 7.6 and the ion activity product, (Ca2+)5(PO4 3-)3 (OH-), for hydroxyapatite varied depending on the cumulative amount of the dissolution in a series of repetitive sequences of solubility experiments.
Abstract: Solubility of human dental enamel in H3PO4 was studied in the pH range of 4.5 to 7.6. Thermodynamic solubility of the enamel mineral was calculated in terms of the ion activity product, (Ca2+)5(PO4 3-)3 (OH-), for hydroxyapatite. The solubility product varied from 7.2 × 10-53 to 6.4 × 10-58 mol9 liter-9 depending on the cumulative amount of the dissolution of the solid in a series of repetitive sequences of solubility experiments.
111 citations
TL;DR: The thermodynamic analysis of the solution composition data suggests that ACP converts into a nonstoichiometric apatite when the OCP-like intermediary is formed, and a stoichiometric Apatite is formed when no O CP- like intermediary is involved.
Abstract: The hydrolysis of previously prepared amorphous calcium phosphate (ACP) was studied in a solution “saturated” with ACP; this eliminated the initial consumption of acid due to ACP dissolution. The procedure established that conversion of a high-concentration ACP slurry to an apatite involves two processes: the first process consumes acid and indicates the formation of a more acidic calcium phosphate intermediary with the solubility of octacalcium phosphate (OCP); the second process consumes base and indicates the conversion of the intermediary to apatite and, possibly, direct conversion of ACP to apatite. The thermodynamic analysis of the solution composition data suggests that ACP converts into a nonstoichiometric apatite when the OCP-like intermediary is formed, and a stoichiometric apatite is formed when no OCP-like intermediary is involved.
105 citations
TL;DR: Etude de la solubilite de l'OCP, important intermediaire dans la formation des dents et des os as mentioned in this paper, influence d'une atmosphere riche en CO 2
Abstract: Etude de la solubilite de l'OCP, important intermediaire dans la formation des dents et des os. Influence d'une atmosphere riche en CO 2
105 citations