My Dad had the same thing happen with his oral cancer. He had Stage 4 Retromolar cancer, surgicallly- a radical neck dissection and a pectoral flap to rebuild his jaw. He has been G tube dependent since 2002. He produces no saliva- a side effect of radiation, and it never did return. He got used to it. He uses oral swabs, and wet washcloths to keep the oral cavity moist.

Best of luck to you