A fixed case is in reference to the final prosthesis (denture/teeth) that will be screwed in the abutments on top of the dental implants. A fixed case is screwed in and can only be removed by a dentist for cleaning, hygiene, or repair. A removable case is where the denture is able to be removed by the patient. The prosthesis or denture will snap in or out and can be removed at night for sleeping and cleaning. Removable dentures usually have the palate and will cover the roof of your mouth. Fixed prosthesis will be like real teeth and will not cover the roof of your mouth.