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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.

Three animal studies were performed to investigate the influence of the macromolecular structure of milk casein on caries incidence and the possible ecological changes of the oral microbiota by such casein fractions. Towards this end, rats were infected with mixed bacterial suspensions of Streptococcus sobrinus OMZ 176 and Actinomyces viscosus Ny1. Various milk protein fractions were incorporated into carefully balanced powdered cariogenic diets to constitute the sole major protein component. Diets containing micellar casein had a pronounced and highly significant effect on almost all clinical and microbiological parameters examined. Both the formation of advanced dentinal fissure (B) and smooth surface (E) caries lesions was inhibited by diets containing micellar casein; this caries–inhibiting effect appeared to be due mainly to modifications within the plaque microbiota. The proportion of S. sobrinus in the oral cavity of rats was reduced (73–80%) by micellar casein–containing preparations, whereas the A. viscosus population was increased. Both these microbiological parameters were always negatively correlated. This appears to be the first example of a food component other than dietary sugars, selectively modifying the composition of the dental plaque microbiota of rats in such a way as to reduce its pathogenic potential. It also demonstrates the importance of establishing a molecular basis for the role of food components, which prove to be beneficial to oral health.

In vitro, xylitol was not fermented by S. mutans and A. viscosus and had no effect on cell growth. Xylitol neither interfered with the utilization of sucrose by the two bacterial species nor inhibited bacterial colonization of rat molar surfaces in sucrose-containing broth. In a rat caries test, xylitol added to starch diets and starch-sucrose diets did not affect formation of bacterial agglomerates on rat molars. Rinsing with 10% xylitol solutions did not interfere with early plaque formation in young adults consuming their habitual diet. Telemetric recordings of interdental plaque pH showed that 10% xylitol rinses and xylitol chewing gum were non-acidogenic. Xylitol did not prevent rapid sucrose glycolysis. In a 40-day rat caries test, xylitol was non-cariogenic and seemed to reduce the cariogenic potential of sucrose administered simultaneously, however, the animals consuming xylitol diets suffered from severe diarrhoea and gained less weight. In another experiment, rats drank less when xylitol was added to the drinking water.