Solubility of human enamel mineral.
The solubility of human enamel was investigated in dilute phosphoric acid solutions (0.07 mMols/L to 1.54 mMols/L) under controlled partial pressures of CO2 (0.005% to 3.33% in mixtures with N2) at 25 degrees C. The enamel mineral was considered as carbonatoapatite containing acid phosphate having the stoichiometry [Ca]5-x-y[HPO4]v[PO4]3-x[CO3]w[OH]l-x-y. During equilibration, a second apatitic phase precipitated, as observed under the electronmicroscope. Solubility models are advanced consistent with the adapted stoichiometry and the precipitation of the second phase. The latter appears to have a carbonate content similar to that of the enamel mineral even when precipitated under the lowest partial pressure of CO2, suggesting that a molar content of about 0.3 of carbonate stabilizes the apatitic lattice. Based on the adopted stoichiometry of enamel mineral, Ca4.34 (HPO4).08 (CO3).29 (PO4)2.63 (OH).05, its solubility product constant was calculated as Ksp = 1.74 (+/- 0.081)x10(-6), expressed as the mean activity product.
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Forsyth Dental Center, Boston, MA 02115.
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D002118:Calcium / Q000032:analysis; D002126:Calcium Hydroxide / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D002245:Carbon Dioxide / Q000737:chemistry; D003743:Dental Enamel / Q000737:chemistry; D003747:Dental Enamel Solubility; D017886:Durapatite; D006801:Humans; D006882:Hydroxyapatites / Q000737:chemistry; D008956:Models, Chemical; D010313:Partial Pressure; D010710:Phosphates / Q000032:analysis; D010756:Phosphoric Acids / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis; D013997:Time Factors
D002130:Calcium Phosphates; D006882:Hydroxyapatites; D010710:Phosphates; D010756:Phosphoric Acids; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; D002245:Carbon Dioxide; D010758:Phosphorus; C485838:calcium phosphate, monobasic, anhydrous; D017886:Durapatite; C020243:calcium phosphate; C030242:phosphoric acid; C485829:calcium phosphate, dibasic, anhydrous; D002126:Calcium Hydroxide; D002118:Calcium