Sucrose Metabolism in Resting-Cell Suspensions of Caries-Associated and Non-Caries-Associated Dental Plaque

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Small specimens of cariogenic plaque (CP) and non-cariogenic plaque (NCP) from the same tooth were individually dispersed in buffer, divided equally, and incubated for 45 min with [14C]sucrose uniformly labeled either in the glucosyl moiety or the fructosyl moiety. Sucrose metabolism was analyzed periodically during an anaerobic incubation at 37°C. Radiochemical techniques were devised to analyze formation of lactic acid, soluble extracellular polysaccharide, total cell-bound and insoluble products, intracellular polysaccharide, lactic acid from intracellular polysaccharide catabolism, insoluble extracellular glucan, CO2, total volatile acids, individual volatile acids, and rates of sucrose consumption. The contribution of the glucosyl and fructosyl moieties of sucrose to each metabolic by-product was determined. All of the metabolic data were adjusted to the size of the plaque specimens as determined by colony-forming units, Coulter counter particle counts, and fluorometric protein analyses. Both types of dental plaque transformed from 70 to 80% of the consumed sucrose into lactic acid and cell-bound and insoluble products, primarily intracellular polysaccharide and extracellular glucan. Volatile acids accounted for most of the remaining by-products. CP metabolized significantly more sucrose than NCP and consequently produced significantly higher levels of each metabolic by-product. High levels of Streptococcus mutans were found in CP (averaging 40% of colony-forming units), whereas it was virtually absent in NCP. Actinomyces and S. sanguis levels were distinctly higher in NCP. NCP harbored more anaerobes and dextranase-forming microorganisms than CP.

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