This invention relates to a class of .alpha.1,3 glucan 3-glucanohydrolase named mutanase. The .alpha.1,3 glucosidic bonded polysaccharides hydrolyzed by these enzymes, herein termed mutan, forms part of the matrix material of dental plaque.Mutanase may be produced by culturing microorganisms such as, Trichoderma, Penicillium, or Streptococcus on a glucan characterized by at least 50% alpha -1, 3 glucosidic bonds.Mutanase containing compositions are adapted for disintegrating in vivo essential structural components of dental plaque.