Cheng Bihuan，Bai Ding，Luo Songjiao.

    Shenzhen Dental Center，518001.

    【Abstract】 Objective The purpose of this study was to find the relationship between stress characteristic of the canine root surface and the type of tooth movement during a long-term movement of distal movement in the maxilˉlary canine.Methods The model was implemented numerically by means of the finite element method(FEM)and was used to simulate both translation and tip movements in orthodontic tooth movements.The finite element model was loaded with the two kinds of defined force systems.And the stress values of the nodes were calculated in root surface in different stages during a long-term movement of the canine retraction.Results There was difference of the stress distribution between the two types of the canine movement.The stress of the translation in the root surface seemed to be more evenly and lower stress level comparing to that of the tip movement.And the stress degradation in the tip movement contributed a further decreasing in stress value than that in the translation movement during the long-term movement.Conclusion There was close relationship between the types of the canine movement and the stress distriˉbution in the root surface.And the results of the present study may do help to the orthodontist to select the appropriate device of the force systems to control the initial loading while the orthodontic treatment planning was proposed. ......