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Purpose

To determine the effect of zinc on the in vitro formation of calcium phosphates and its relevance to calculus inhibition.

Materials and methods

Different types of calcium phosphate phases (amorphous calcium phosphate, ACP; dicalcium phosphate dihydrate, DCPD; octacalcium phosphate, OCP; and carbonate hydoxyapatite, CHA) were precipitated from solutions containing increasing concentrations of zinc (Zn) ions. The precipitates were characterized using x-ray diffraction, infrared absorption spectroscopy, and scanning electron microscopy.

Results

The presence of Zn ions affected the type and amount of calcium phosphate phases formed. Zn, even at concentrations as low as 0.1 mM/L, inhibited the crystal growth of DCPD, OCP and AP; and, at higher concentrations (0.5 mM to 2 mM/L), promoted the formation of amorphous calcium phosphate, ACP, or Zn-substituted tricalcium phosphate (beta-TCP) depending on the reaction pH and temperature.