US Patent No. 9,408,780 B2; Combe Incorporated has patented a denture adhesive hydrogel comprising a mixed salt of a copolymer of alkyl vinyl ether, and maleic anhydride or maleic acid, a dry tack enhancing agent being polyvinylpyrrolidone, and optionally one or both of polyethylene oxide and a cellulose derivative and water. The mixed salt comprises monovalent and multivalent cationic salts selected from the group consisting of sodium, calcium, zinc, strontium, ferric and mixtures thereof....