"Examples of monomers containing hydrophilic Y group are acrylic acid, methacrylic acid, alpha-ethylacrylic acid, beta-methylacrylic acid, alpha, beta-dimethylacrylic acid, orally acceptable salts of these acids, for example those containing such cations as alkali metal (e.g., sodium and potassium), ammonium, C1-18 mono-, di- and tri-substituted ammonium (e.g., alkanol substituted such as mono-, di" . . . . . .