Effects of polyphosphates on the solubility and mineralization of HA: relevance to a rationale for anticaries activity.

Preexposure of hydroxyapatite (HA) to polyphosphate reduced the near-equilibrium acid solubility of HA, the mineralization of HA, and the exchange of PO4 between medium and HA. Appreciably longer exposure times were required for maximal effects of trimetaphosphate (TMP) than of pyrophosphate (PP), tripolyphosphate (TPP), and hexametaphosphate (HMP). Calcifying solution solubilized small amounts of the HA-bound polyphosphates. This occurred to the smallest extent in the case of TMP, a fact which could have relevance for the superior anticaries effect of TMP.