Relining and rebasing dentures involves resurfacing or replacing the base material to reestablish correct tissue fit and occlusion. Relining refits the tissue side while rebasing replaces the entire base. It is done for issues like retention loss, changed occlusion, or tissue changes. Methods include direct chairside relining or indirect lab relining, with indirect offering more durability. Procedures prepare the tissues and denture, add soft or hard relining materials, and ensure proper fit on reinsertion.