This study used photoelastic stress analysis to compare the location and magnitude of periradicular stresses created by load application directed through two anatomically different natural teeth and three different implant designs. Also studied was the contribution made by the periodontal ligament in the transfer of these stresses. Within the limits of this study, results suggest that the abutment structures with the greatest amount of periodontal support tend to distribute stresses in the most favorable manner. Also, the conical shape of the tooth root, with its large cervical area, has a distinctly positive effect on stress distribution.