All-ceramic restorations can solve many esthetic problems associated with implant-supported prostheses. This study evaluated stress concentration and distribution in implant abutments under normal masticatory forces using computer simulations. Two-dimensional finite element analysis was used to study four different abutment-restoration combinations using Branemark implants. The models considered two positions of the fastening screw, two positions of the crown margins, cemented versus screw-retained prostheses, and clinical loads of 200 N. Models having screws on top of abutments had the lowest stresses (3.1 to 4.8 MPa) and best stress distribution. Screw-retained prostheses and short crown margins increased overall stresses (9.9 to 11.4 MPa).