使用三维有限元方法，研究不同加载方式对种植钉压低高角Ⅱ类骨面型患者上颌后牙的生物力学影响，为正畸临床提供参考。

建立1例高角Ⅱ类骨面型患者的含有上牙列、牙槽骨和牙周膜及临床矫治器的压低上颌后牙的三维有限元模型，设置不同加载工况。工况1：在第一与第二磨牙之间的颊腭侧各放置1枚种植钉；工况2：在第一与第二磨牙之间的颊侧放置1枚种植钉，左右两侧第一磨牙通过横腭杆连接；工况3：在第一与第二磨牙之间的颊侧放置1枚种植钉，左右两侧第一磨牙通过横腭杆连接，第二磨牙腭侧设计一由腭杆伸出的牵引钩；工况4：在第一磨牙对应的腭中缝处植入1枚种植钉，左右两侧第一磨牙通过横腭杆连接，在两侧腭杆中点处设计一牵引钩；工况5：在第一磨牙对应的腭中缝处植入1枚种植钉，左右两侧第一磨牙通过横腭杆连接，第二磨牙腭侧设计一由腭杆伸出的牵引钩，在两侧腭杆中点处设计一牵引钩，研究不同工况下后牙的牙周膜应力分布与位移趋势。

工况1第二前磨牙、第一磨牙与第二磨牙的应力梯度（颈缘区应力均值与根尖区应力均值的比值）在5种工况中最小，分别为2.10、2.09和2.26，且应力分布最为均匀，能最大程度地避免后牙的颊腭侧倾斜与近远中倾斜，其次是工况4。工况3中第二磨牙腭侧设计的牵引钩能抑制其颊侧倾斜，工况5中第二磨牙腭侧设计的牵引钩会加重其腭侧倾斜程度。

在上颌第一与第二磨牙之间的颊腭侧均植入种植钉是最理想的压低上颌后牙方式，其次是腭中缝植入种植钉搭配横腭杆。使用颊侧种植钉搭配横腭杆压低上颌后牙时，需在第二磨牙腭侧设计牵引钩以抑制其颊倾；使用腭中缝植入种植钉搭配横腭杆可无需在第二磨牙腭侧再设计牵引钩。

This study utilized a three-dimensional finite element method to investigate the biomechanical effects of various loading modalities on the intrusion of maxillary posterior teeth using orthodontic miniscrews in a patient with high-angle Class Ⅱ skeletal pattern, aiming to provide guidance for clinical orthodontic practice.

A three-dimensional finite element model was developed for a patient with a high-angle Class Ⅱ skeletal pattern, incorporating the maxillary dentition, alveolar bone, periodontal ligament, and clinical orthodontic appliances for the maxillary posterior teeth. The following loading conditions were configured: Condition 1: One miniscrew was placed on both the buccal and palatal sides between the first and second molars. Condition 2: One miniscrew was placed on the buccal side between the first and second molars, and the left and right first molars were connected via a transpalatal arch. Condition 3: One miniscrew was placed on the buccal side between the first and second molars, the left and right first molars were connected via a transpalatal arch, and a traction hook was designed extending from the palatal bar on the palatal sides of the second molars. Condition 4: One miniscrew was placed at the midpalatal suture region corresponding to the first molars, the left and right first molars were connected via a transpalatal arch, and midpoint traction hooks were designed on both sides of the palatal bar. Condition 5: One miniscrew was placed at the midpalatal suture region corresponding to the first molars, the left and right first molars were connected via a transpalatal arch, a traction hook was designed extending from the palatal bar on the palatal sides of the second molars, and midpoint traction hooks were added on both sides of the palatal bar. The stress distribution in the periodontal ligament and the displacement trends of the posterior teeth were investigated under these conditions.

In Condition 1, the stress gradients (defined as the ratio of mean stress in the cervical region to that in the apical region) for the second premolar, first molar, and second molar were 2.10, 2.09, and 2.26, respectively, the lowest among the five conditions. This setup exhibited the most uniform stress distribution and minimized the buccopalatal and mesiodistal inclination of the posterior teeth to the greatest extent, followed by Condition 4. In Condition 3, the hook designed on the palatal side of the second molar helped restrain its buccal inclinations, whereas in Condition 5, the palatally designed hook aggravated the degree of palatal inclination.

The most ideal method for intruding the maxillary posterior teeth is to place miniscrews on both the buccal and palatal sides between the maxillary first and second molars, followed by the use of a transpalatal arch combined with miniscrews placed in the midpalatal suture. When intruding the maxillary posterior teeth using buccal miniscrews with a transpalatal arch, a hook should be designed on the palatal side of the second molar to restrain buccal inclination. However, when using a midpalatal suture miniscrew with a transpalatal arch, it is unnecessary to design an additional hook on the palatal side of the second molar.