Dental plaque is a biofilm, formed by bacteria, salivary glycoproteins and sticky glucose polymers of bacterial origin that adhere to tooth surfaces. To verify the possibility of reducing or preventing such glucan formation, a number of commercial certified food-grade enzymic preparations, were tested. Among these, two commercial enzyme preparations (Dextranase 50 L and Dextrozyme) were chosen for prevention and degradation experiments of water-insoluble glucans. Dextranase 50 L, in the concentration range 3.75 x 10(-2) 1.5 x 10(-1) U/l, was capable of blocking in vitro synthesis of the glucans catalysed by glucosyltransferases of Streptococcus sobrinus. With small amounts of the enzyme, a limited production of glucans was observed, but the synthesised polysaccharides showed no adhesive properties. Dextranase 50 L was also able to degrade partially (about 20%) pre-synthesised glucans. When Dextrozyme (concentration range 9.05 x 10(-1)-7.25 U/l) was used, in vitro synthesis of glucans occurred, but the polymer lost its adhesive properties. Dextrozyme was not capable of degrading glucans which were already formed. The stability characterisation of the two enzymic preparations in commercial mouthwash without ethanol and at physiological temperature (37 degreesC) showed that it is possible to use Dextranase 50 L as a dental plaque control agent. (C) 2002 Elsevier Science Ltd. All rights reserved.