Dextrans are high-molecular weight polymers of D-glucose produced via the action of enzymes called glucosyltransferases on the cell surface of some lactic acid bacteria. Lactic acid bacteria are important causes of tooth decay, because they live and reproduce in the mouth. These bacteria form dextrans from the metabolism of sucrose. Dextrans then deposit onto the tooth enamel. Dextrans are part of what we call "plaque". Plaque is responsible for tooth decay, because plaque enables bacteria to adhere to the tooth surface. Other substances can also adhere to plaque, contributing to the decay of teeth. Be careful not to confuse dextrans with dextrin !