Carbohydrates in Pooled Dental Plaque

Dental plaque was collected from approximately 3,500 schoolchildren, and immediately pooled and frozen. The lyophilized plaque was processed in several batches as follows:After an aqueous extraction the water-insoluble portion was further extracted with 1 N KOH. Both aqueous and alkaline extracts were further subfractionated by precipitation at different ethanol concentrations. Nature and composition of carbohydrates in sub-fractions were investigated using acid hydrolysis and end products were identified by gas liquid partition chromatography.29.6% of plaque dry weight, containing 6.9% carbohydrates, 1.2% nitrogen and more than 4% proteins, were water-soluble. The water-insoluble portion (67.1%), contained 11.3% carbohydrates and 7.4% nitrogen; in addition, 30.7% constituents insoluble in 1 N KOH were found. In all subfractions prepared by ethanol precipitations, substantial amounts of material other than carbohydrates were found. The sugar composition of hydrolysates showed glucose to be the main sugar constituent; however, small amounts of pentoses, other hexoses and disaccharides were also present. The water-insoluble matrix polysaccharides containing predominantly α-1,3 linkages were calculated to account for 1.35% of the plaque dry weight/ 5.6% of the plaque dry weight consisted of low molecular water-soluble carbohydrates. Glucose and oligosaccharides forming the bulk of this fraction were assumed to represent intermediates resulting from enzymatic breakdown of α-1,6-linked dextran. The high content of fermentable carbohydrates in dental plaque suggests that microbial activity is not limited by the supply of fermentable substrates.