Biochemical Studies on the Formation and Composition of Dental Plaque in Relation to Dental Caries:

Similar polysaccharides were extracted by dilute alkali from the matrix of the dental plaque of rats fed diets containing different sugars. The fructose components of the extracellular polysaccharides produced from sucrose by either of two streptococci or by the mixed oral flora were labile in the presence of oral bacteria. It is now generally accepted that the major carbohydrate components in the matrix of human dental plaque are not a result of denaturation of the salivary mucin, but rather are a product of the reaction between certain bacterial enzymes and dietary sugar, particularly sucrose. ' The major and minor carbohydrate components of this matrix have been considered to be made up of the polysaccharides dextran and levan, re-spectively, for the following reasons: (1) the characteristic carbohydrate components of salivary mucin were absent from the plaque."12 (2) Extraction of the plaque matrix with dilute alkali followed by sub-sequent hydrolysis in acid yielded glucose as the major and fructose as the minor sugars, respectively.3 (3) Smith degradation of these extracted polysaccharides produced primarily glycerol. This is compatible with the initial glycosidic linkages composed of the 1:6 and 1:2 hexopyranoside and 2:6 ketofuranoside types, which are typical of the glycosidic linkages of these polymers.3 (4) Several typical oral bacteria have been shown to produce dextran and levan in culture media containing sucrose.4-7 At the present time, little else is known of either the structure or the function of these polysaccharides as they actually occu