Metastable Equilibrium Solubility Distribution of Carbonated Apatite as a Function of Solution Composition

Metastable Equilibrium Solubility Behavior of Carbonated Apatites in the Presence of Solution Fluoride

“…In order to minimize changes in solution composition and the consequent changes in the solution ion activity products during equilibration, a large solution-to-solid ratio has been used in previous studies (31,32). Accordingly, 10 mg of CAP was equilibrated with 2000 ml of buffer solution with stirring (300 rpm) for 48 h at 30…”

“…Recently, the MES concept has been extended to the determination of the functional form of the dissolution driving force, which is hypothesized to be associated with surface complex formation on dissolving apatite crystal surfaces (31,32). It is envisioned that surface complex formation occurs on the dissolving apatite crystal surface with a composition responsive to the ions in the ambient solution.…”

“…It is envisioned that surface complex formation occurs on the dissolving apatite crystal surface with a composition responsive to the ions in the ambient solution. The results of MES studies in a series of solutions with varying composition have demonstrated that in the absence of solution fluoride the metastable equilibrium solubility (MES) distributions of CAPs are best described by a surface complex possessing the stoichiometry of hydroxyapatite (HAP) (31).…”

Use of Dicalcium Phosphate Dihydrate as a Probe in an Approach for Accurate Calculations of Solution Equilibria in Buffered Calcium Phosphate Systems

“…A pH-dependent surface charge on enamel surfaces was also hypothesized to be the cause for the variable solubility behavior of dental enamel by Larsen and Jensen (4). All of these theories and others (3,(11)(12)(13) remain controversial and are discussed in greater detail in our accompanying manuscript dealing with the solubility behavior of the carbonated apatites (CAPs) (14). Research in our laboratory (15) demonstrated that human dental enamel and CAPs in general exhibit the phenomenon of metastable equilibrium solubility (MES) distribution in acetate buffers.…”

“…Hsu et al (16) further demonstrated that this solubility distribution phenomenon was consistent with the dissolution kinetics of CAP. In a recent study (14), the metastable equilibrium solubility system established by Hsu et al (15) was investigated with the goal of accurately deducing the composition of the surface complex which controls the dissolution of CAP. In that study, MES distributions of CAPs were determined over a wide range of solution composition after a 2-day equilibration period and the stoichiometry of the surface complex was sought directly from the MES data by comparing these results with predictions based upon the possible surface complex stoichiometries, such as HAP, DCPD, octacalcium phosphate, tricalcium phosphate, etc.…”