目的 通过改变摇椅曲的曲度和游离牵引钩的高度,分析使用种植钉配合摇椅曲整体内收前牙时该力学体系对磨牙压低作用的成因和力学机制.方法 采用螺旋CT扫描,并用Mimics 10.0建模软件建立上牙列及其支持组织,以及不同曲度摇椅曲(5°、10.、15°、20.、25°)和不同高度牵引钩(2.1、4.0、5.5 mm)的三维有限元模型,施加1.5 N向后的内收力,分析上颌各牙齿的位移趋势.结果 摇椅曲使切牙唇倾压低、远中直立和近中唇向扭转,尖牙唇倾升高、近中倾斜和近中唇向扭转,第二前磨牙和第一磨牙颊倾压低、远中直立和近中唇向扭转.随着摇椅曲曲度的增加,磨牙的位移趋势增加；但随着牵引钩高度的增加,磨牙的位移趋势减少.结论 摇椅曲曲度增加,磨牙被压低的程度增加；游离牵引钩高度增加,磨牙被压低的程度降低.5°的摇椅曲配合5.5 mm的游离牵引钩,磨牙被压低的程度最小.%Objective In order to find out the cause of molar intrusion and how to avoid molar intrusion, we analyze the movement tendency of tooth by changing the angles of upper accentuated-curve and the height of free traction hook. Methods Spiral CT scanning and Mimics 10.0 software were employed in this study to construct the three dimensional finite element model of maxillary teeth, periodontal ligaments and alveolar bone as well as the inch stainless steel upper accentuated-curve archwires with different angles (5°, 10°, 15°, 20°, 25°) and the free traction hook with different height (2.1, 4.0, 5.5 mm). By exerting 1.5 N backward force to analysis the displacement trend of maxillary tooth. Results Upper accentuated-curve archwires made the incisors labially tip, intruse, distally upright and mesi-labially torsion; made the canines labially tip, prolong, mesial-tipped and mesi-labially torsion; made the second pre-molars and the first molars buccal tip, intruse, distal upright and mesi-labially torsion. With the angle of upper accentuated-curve archwires increased, all tooth movement tendency increased; while with the height of free traction hook increased, all tooth movement tendency decreased. Conclusion When the angle of upper accentuated-curve archwires increased, the extent of molar intrusion increased, but when the height of free traction hook increased, the degree of molar intrusion decreased. The degree of molar intrusion was minimum using 5° upper accentuated-curve archwires cooperated with 5.5 mm free traction hook.
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