Objective To investigate the relationship between the displacement and stress distribution in the nasomaxillary complex and the strength of distally-directed extra-oral forces, to provide the scientific basis for the selection of orthopedic force in clinical treatment. Methods Five different sizes of distally-directed extra-oral forces were added to the model of nasomaxillary complex, using ANSYS 10.0 software to analyse the displacement and stress distribution in the nasomaxillary complex. Results When the strength of distally-directed extraoral forces increased, A point and ANS point's distal displacement was added, and N point moved to mesial, but it was displacement very potty. All of the changes were linearity and the stresses of A, ANS, and N points were added as well. Conclusion When the strength of distally-directed extraoral forces increased,the displacement and stress distribution of the nasomaxillary complex also added, and 3～5N force caused the maxilla distally displacement clearly.%目的:探讨不同大小的后方牵引力与鼻上颌复合体内部应力分布及位移的关系,以达到为临床矫治力的选择提供科学依据的目的.方法:利用有限元软件ANSYS10.0在鼻上颌复合体三维有限元模型上分析5种大小的后方牵引力对鼻上颌复合体内部应力分布和位移的影响.结果:随着后方牵引力值的增大,A点和ANS点向后位移也逐渐增大,而N点向前移动,但N点的位移量很小,变化呈线性关系.且A点、ANS点和N点的应力值也逐渐增大.结论:施加不同大小的后方牵引力,鼻上颌复合体的应力和位移随牵引力值的增大而增大,而每侧3～5N后牵引力即可引起上颌骨明显的后方移位.
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