The in-vitro effect of fungal dextranase on human dental plaque.

Suspensions of dental plaque from eighteen children with high caries activity were hydrolyzed in vitro by a partially purified fungal dextranase isolated from Penicillium funiculosum NRRL 1768. The dextranase preparation appeared to lack 1,4glucanhydrolase and sucrase activity. The release of reducing substances from the plaque was measured by use of a 3,5-dinitrosalicylate reagent. Hydrolysis occurred at pH 5.1 but not at pH 7.0. Approximately 20 per cent of the total carbohydrate of plaque was consumed by the dextranase (2-3 per cent of the plaque dry weight). No isomaltose was found when the hydrolysates were analysed by a thin layer chromatography procedure which could detect as little as 0.1 pg of isomaltose. The findings suggest that the quantity of dextran in these plaque samples is low.