Objective To reconstruct a three-dimensional nonlinear finite element model of mandibular teeth with three-pieces segment arch, and analyze the mechanical properties of intrusive arch and the biomechanical characteristics of three-pieces segment arch. Methods Three-dimensional nonlinear finite element model of mandible with three-pieces segment arch was reconstructed by multi-slice spiral CT scanning, Mimics, CATIA and Anasys software. Then, the mechanical properties of intrusive arch, the movement trend and stress distribution of three-pieces segment arch were calculated by Anasys software. Results In the range of 5°-25°, with the degree of intrusive arch increased, the force of intrusive arch also increased rapidly. The maximal force was 0.604 8 N in 30°; the force was about 0.59 N in 30°-65° range. In condition of three-pieces segment arch mechanics, lateral incisor tipped labially and intruded; the first moral tipped distally and rotating; other teeth did not move clearly. The largest stress distribution in the whole arch was in the one-third labial cervical area of the lateral incisor root and the root bifurcations of first moral. Conclusion Under an appropriate intrusive force, three-pieces segment arch can intrude incisors and control the extrusion of posterior teeth. It can be used to correct the deep overbite, especially with high mandibular planes, gummy smile or adult patients.%目的 建立三段式片段弓矫治技术的下颌牙列三维非线性有限元模型,分析计算压低辅弓的力学特性,初步探讨三段式片段弓矫治技术的生物力学特点.方法 利用薄层CT扫描技术,结合Mimics、CATIA、Anasys等专业软件建立含有三段式片段弓下颌牙列三维有限元模型.然后,在所建立的模型上通过Anasys软件中的非线性计算方法分析计算压低辅弓的力学特性及在三段式片段弓作用下下颌牙列的运动趋势和应力分布情况.结果 在5°～25°范围内,压低辅弓前端的力值随角度的增加而快速增大；在30°时达到最大(0.604 8N)；在30°～65°范围内,压低辅弓产生的力在0.59 N左右波动.三段式片段弓作用下,下颌侧切牙远中唇向倾斜并向龈方压入；第一磨牙则后倾明显并伴有牙冠的近中颊向远中舌向旋转；其余牙齿基本不发生移动.下颌牙列的应力集中区主要位于侧切牙根的唇侧颈1/3及第一磨牙根分叉处.结论 在适宜压入力的作用下,三段式片段弓技术能有效地压低前牙段,同时控制后牙段的伸长,有利于深覆(牙合),特别是高角、露龈笑或成年患者深覆(牙合)的矫治.
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