ELUTIONS OF METAL-IONS FROM DENTAL CASTING ALLOYS AND THEIR EFFECT ON CALCIUM-PHOSPHATE PRECIPITATION AND TRANSFORMATION

The elution characteristics of metal ions from dental casting alloys were studied in vitro. Large amounts of nickel (0.12-4.94 mg/cm(2)) and chromium (<0.01-0.63 mg/cm(2)) were solubilized from the surface of seven brands of nickel-chromium alloy in either 1% lactic acid or 0.05% hydrochloric acid solutions. The elution of chromium from two brands of cobalt-chromium alloys in both eluents was below the detection limit or less than 0.01 mg/cm(2). The elution of tin, copper, and zinc from a gold-palladium-silver alloy in both eluents was below the detection limit or less than 0.01 and 0.04 mg/cm(2). Some amounts of tin (0.19-1.92 mg/cm(2)) and zinc (0.56-1.73 mg/cm(2)) were eluted from a silver alloy in both eluents. The effects of five eluting metal ions, i.e., nickel, chromium, tin, copper, and zinc, on the conversion of amorphous calcium phosphate (ACP) to hydroxyapatite (HAP) in vitro also were studied by a pH drop method. All divalent cations except for chromium decreased the rate of HAP transformation and elongated the induction time. Nickel had an inhibitory effect comparable to 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP) on the rate of HAP transformation. Tin, copper, and zinc inhibited similarly, but the inhibition was weaker than that by nickel. Chromium did not inhibit these reactions. (C) 1994 John Wiley and Sons, Inc.