The problem of screw stability was approached in this study by calculating the maximum occlusal forces in vito for patients with single implant restorations (which use only one screw to secure the prosthetic reconstruction to the implant). The measurements of occlusal forces together with geometric parameters for the individual patients wre used to determine the necessary holding capabilities of the screw joint. Different screw designs were tried in bench test situations and the results were compared with clinical situations. A gold alloy screw with a flat head and high tightening torque (35 Ncm) produced the best result. Keywords: occlusal force, screw design, screw stability, single tooth implants