Cases demonstrating complications in osseointegrated implant supported prostheses are described. These complications occurred in the prostheses framework or veneer, in the fixation screw, in the abutment post or screw as well as in the implant body. The two main reasons for the complications were lack of passive fitting between the restoration and the abutment; and destructive occlusal contacts. The destructive occlusal contacts may develop during the time of wear of the prostheses material or by changes in the opposite restoration. Overloading or bending moments exerted on the prostheses via these occlusal contacts resulted in loosening or fracture in one of the implant-prostheses components. The benefit of acrylic resin or composite material in reducing stresses in the light of the possible long-term, harmful occlusal changes that might develop as a result of their wear should be considered.