Sinus lift and augmentation procedures with simultaneous insertion of cylindrical root form implants can be used to treat the atrophic posterior maxilla. The long-term use of a second stage provisional prosthesis is emphasized. The recommended metal-reinforced acrylic resin provisional restoration allows treatment and/or removal of a failing implant and progressive loading before fabrication of the definitive prosthesis. Modifications in prosthesis fabrication after sinus lift surgery and augmentation procedures are discussed. (Implant Dent 1994;3:24—28)