The lower denture is only supported by the bone where your teeth used to be; whereas, the upper dentures create suction by covering the top palate. The bones in the mouth are constantly shrinking when we lose our teeth. This means that the denture has less bone to support itself. Sometimes some retention can be created for the lower denture if there is a large bone. Other efforts to create permanent stability would involve the placement of implants. Dental implants greatly improve the retention and function of a lower denture.