[Inhibition of water insoluble glucan formation by eluate from amalgams]

The effect of the eluate from amalgam on glucan synthesis was investigated in this study in order to elucidate the mechanisms by which plaque accumulation is inhibited on amalgam but not on enamel or composite. Glucosyltransferase (GTase) was prepared from a cultured supernatant of Streptococcus mutans B 13 by the ammonium sulfate precipitation method. Five commercial amalgams were tested. The eluate from amalgams was prepared by immersing the amalgam discs (10 mm dia. x2 mm thick.) into distilled water for 2 weeks. A glucan synthesizing system was compounded using GTase (50 microliters), [14C]-sucrose (100 microliters), distilled water, and the eluate (350 microliters). After 18 h incubation at 37 degrees C, the formed water insoluble glucan was collected on glass fiber filters and its radioactivity was counted. Moreover, concentrations of zinc (Zn) and copper (Cu) in the eluates were determined by atomic absorption spectrophotometry. The eluates from Dispersalloy and Fluor alloy, which eluted Zn, were the most inhibitory for glucan synthesis. Sybraloy, which released Cu to a much greater degree than the other amalgams and its eluate showed intermediate antienzymatic activity. The other amalgams, Hi-atomic M and Spherical-D, did not effect GTase at all. The results indicated that various amalgams strongly impact inhibition rates of glucan formation.