A hydrogel for use in oral care. The hydrogel is ion beam cross-linked, the hydrogel is adapted to be disposed in the oral cavity and may be adapted to provide a denture fixative or may be loaded with a whitening agent for use in whitening one or more teeth and disposed on or adjacent one or more teeth and the whitening agent is slow-released to whiten the one or more teeth. Other loading materials may include materials for treatment of alveolitis or malodor, inter alia. The present invention is a new hydrophilic oral and dental cohesive hydrogel sheet designed to securely grip and cushion prosthetic devices in the human mouth with the further ability to slow release antimicrobial or other orally desirable agents. Additionally, the invention also provides a method of making an orally cohesive device that: 1) is easily adapted and applied to a removable dental prosthesis; 2) bonds well to alveolar ridge/palatal mucosa and denture acrylic materials; and 3) releases cleanly, with no tacky or thixotropic residue when the prosthesis is removed. The cohesive hydrogel gel device is a hydrogel-forming polymer mixed with water, optionally surrounding an internal scrim, and uses an electron-beam energy source to cause cross-linking. The method does not need any chemical additive to affect the cross-linking. Furthermore the beam energy can be adjusted to optimize the cohesive properties of either side of the device, as well as to compensate for addition of orally active agents, if any are chosen. The hydrogel sheets are pre-cut to fit most sizes of maxillary and mandibular full denture prostheses, but can be easily trimmed with a scissors by the end user for the ideal custom fit of any full or partial denture, in either arch.