For esthetic and functional implant prosthesis, the retention type of implant should be selected considering the oral condition of the patient. However, studies on the differences in biomechanical stability of the retention type are scarce. The purpose of this study was to evaluate the biomechanical effects between retention types in implant prosthesis using 3- dimensional finite element analysis. Two retention types (Cement and Screw-Cement) were considered for the implant complex consisting of the ComOcta abutment, SS type implant, and screw all implanted in the mandibular segment of the bone block. Static finite element analysis was performed under external loads of 200 N (Vertical Load) and 100 N (Oblique Load) to each cusp tip. We measured the von-Mises stress fields in abutment and implant, and the principal strain distribution of the mandibular bone to evaluate the risk of fatigue failure in the bone. Separations between the implant components were also evaluated. The results show that with the ComOcta abutment Cement type provided enhanced stability.