Abstract: Reliability and stability of implant-bone collision are of great importance in evaluations of dental implant life time. Implant thread is a fundamental factor in force and stress transmission from implant to bone. In this study, by applying static load, effects of thread shape and dimensions on stress distribution in the implant and the marginal bone are analyzed. A three-dimensional finite element analysis has been performed via simulations in ABAQUS commercial software. Changing the values of height, thread pitch and surface angle in trapezoidal and triangular thread types, the maximum stress values are compared. Furthermore while accounting for the osseointegration phenomenon, a thread with shape and dimensions optimized for implant-a length of 13 mm and diameter of 3.9 mm is suggested. After modeling and stress simulation, it is concluded that compared to triangular threads, a trapezoidal thread with a height of 0.4 mm and pitch of 0.8 mm creates a better stress distribution both in the implant and in the marginal bone.