The role of extracellular matrix material (EMM) synthesized from sucrose (S) by Streptococcus mutans IB-1600 in altering the demineralizing potential of artificial plaque was evaluated with an intraoral enamel demineralization test (IEDT). The artificial plaque samples were prepared from cells cultivated in Todd-Hewitt broth (THB) supplemented with various S concentrations and by mixing THB-grown cells with increasing proportions of EMM (heat-killed THB + 2% S-cultivated cells). The samples were also evaluated for cell density (DNA content) and acidogenicity in vitro (pH-stat), as well as for in situ pH changes during a 45-minute intra-oral test following a 10% glucose rinse. An increase in the proportion of EMM relative to cell density was associated with an increase in enamel demineralization. This trend reversed when the ratio of cells to EMM was less than 1:19. Experiments involving strains of S. mitis, S. sanguis, and S. salivarius suggested a similar effect of EMM. The intra-oral pH data suggest that the presence of EMM may enhance demineralization by altering diffusion properties of plaque.
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