The relining of complete dentures involves solving all of the problems encountered in the construction of new dentures, except positioning individual teeth. The first and most important problem is to achieve a healthy condition of the tissues of the basal seat for the dentures. To do this, the patient must be without his dentures for at least 24 hours before the impressions are made. The dentist looks for errors in the occlusion, the occlusal vertical dimension, and for whatever other changes should be made. A posterior palatal seal is formed in modeling compound on the upper denture before any other change is made on the impression surface. The modeling compound is reheated and the denture is reseated in the mouth to perfect the form of the posterior palatal seal. After each heating, the compound is tempered and placed in the patient’s mouth; slight pressure is applied near the distal end of the denture, and the cheeks are pulled in to mold the compound around the distal ends of the buccal flanges. The width of the posterior palatal seal is reduced to about 2mm.—the width of the area between the bead on the denture and the endof the denture. Space is provided inside the denture for the new impression material by grinding about a 1.0 mm. thickness of resin from the entire palatal surface. All undercuts removed from the labial and buccal flanges. The borders are shortened 1.0 mm. to allow space for the impression material to form a new border. The labial notch is broadened and deepened so it will not interfere with the labial frenum. The lower denture is prepared for the reline impression in exactly the same way as a tray would be prepared for making a new denture. The buccal surfaces of the lingual flanges are ground to minimize the pressure against the mylohyoid ridges and between the tissues of the floor of the mouth and the buccal sides of the lingual flanges. The lingual flange between the premylohyoid eminences is shortened 1 mm. The labial flange between the buccal notches is shortened 1 mm. Shortening the flanges provides space so the impression material canform new borders. Nothing is removed from the buccal flanges, but grooves are cut on the buccal sides of the lingual flanges to facilitate removal of the retromylohyoid eminences