Thermodynamic solubility product of human tooth enamel: powdered sample.

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(PO43-)3(OH-), for hydroxyapatite. The solubility product varied from 7.2 times 10(-53) to 6.4 times 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.