In the case of posterior single tooth missing, four clinical treatment options of implant restoration have been designed to give an optimal stress distribution to the surrounding bone. In this study, three treatment options were investigated using three dimensional finite element analysis. First, single standard(zero, slash 3.75mm) implant was used to replace a posterior single tooth. Second, single wide(zero, slash 5.0mm) implant was used. Third, two small(zero, slash 3.25mm) implants were used. 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 ; The value of Von-mises stress (equivalent stress) was smallest in the wide implant among the three experimental models. It was reported that the diameter is the efficient factor than osseointegrated surface area.