or thymol or essential oils e g methyl salicylate these active materials are covalently bound in a side group of the polymer e g by an acid carboxylate ester or amide group which can undergo rapid aqueous hydrolysis in the mouth such polymers also can be made by copolymerization of monomers with a comonomer such as meth acrylic acid itaconic acid vinyl acetate a maleate a fumarate vinyl pyrrolidone vinyl caprolactam vinyl sulphonic acid methacrylic acid vinyl amide alkyl vinyl ether maleic anhydride dimethylaminopropyl methacrylic acid or dimethylaminopropyl methacrylamide by esterification of carboxylic or anhydride side groups or by transesterification of ester groups in a polymer the polymer of the invention may be illustrated by the following generic formula u2014 u2014 ch 2 u2014 c u2014 u2014 is the main polymer chain or repeat unit a is h or a functional group e g carboxylate or carboxylic group and suitable x groups include alkylene alkyleneoxy amino anhydride carbonate amino acid or alkylene ester alkylene e g methylene is preferred suitable z groups are active antimicrobial flavorant or essential oil menthol is preferred suitable repeat units of the main polymer chain include alkylene with or without another functional group attached thereto e g carboxylate suitable m comonomers e g meth acrylic acid are present to solubilize the polymer in aqueous solution generally in an amount up to 95 of the polymer a preferred main monomer of the invention is the thymyl or menthyl monoester of itaconic acid u201c mi u201d whose polymer has the formula.