The relation between eccentricity loading and implant diameter and the reaction force versus implant diameter were analyzed. Under distributed loading, the stress was larger at the abutment/fixture interface and in the crestal bone, compared to the stress pattern under vertical loading. The amount of stress at the superstructure was similar regardless of the length, diameter, and platform shape of a fixture. Finite element models were constructed in mandible having single screw-type implant fixture connected to the premolar superstructure; this was done in order to evaluate how the length, diameter, and platform shape of a screw-type fixture influence the stress in the supporting tissue around fixtures.