In this study, three treatment options to replace two posterior missing teeth were investigated using three dimensional finite element analysis: two wide(${phi}5.0mm$) implants(the experimental model I), two standard(${phi}3.75mm$) implants(the experimental model II), and three standard(${phi}3.75mm$) implants(the experimental model III). Two kinds of load case were applied ; 1) perpendicular on occlusal surface(axial load), parallel on occlusal surface(lateral load). 2) perpendicular on occlusal surface(3mm lateral to central point). The results obtained from this study were as follows; value of Von-mises stress (equivalent stress) was smallest in the two wide implant among the three experimental models. It was reported that the diameter is the efficient factor than osseointegrated surface area.