牙周膜厚度对舌侧矫治中下颌第1磨牙近中移动的影响

目的 研究舌侧矫治中下颌第1磨牙近中移动过程，牙周膜厚度因素对牙齿及牙周组织应力和位移的影响。方法 基于逆向工程技术的方法，分别建立牙周膜厚度为0.15、0.2、0.25、0.3、0.35 mm的等牙槽骨高度的牙齿—牙周膜—牙槽骨三维模型，在舌侧矫治中倾斜、旋转及整体移动载荷作用下，分析牙周膜、牙根及牙槽骨表面的应力和位移状况。结果 由牙周膜厚度差异引起的牙周膜、牙根以及牙槽骨表面最大应力极大值与极小值之比分别为1.46、2.06、6.72，牙根、牙槽骨表面的最大位移极大值与极小值之比分别为1.65、1.50；对应不同的牙周膜厚度值，牙根及牙周组织最大应力部位在牙根、根分叉以及牙颈间变动。结论 临床治疗中，应注意观察牙颈、根分叉以及牙根部位的变化，针对牙周膜厚度较小的患者，整体移动更有利于牙齿及牙周组织的健康。

Effects of periodontal ligament thickness on mesial movement of mandibular first molar in lingual orthodontics

Objective To study the effects of the various thickness of periodontal ligament on stress and displacement of mandibular first molar and periodontal tissues during mesial movement of tooth in lingual orthodontics. Methods Based on the reverse engineering technology, the three-dimensional assembly models of the teeth, periodontal ligament and alveolar bone with the same height of alveolar bone were constructed, and thicknesses of the periodontal ligament was 0.15, 0.2, 0.25, 0.3 and 0.35 mm, respectively. The stress and displacement of periodontal ligament, root and surface of alveolar bone were analyzed under the condition of lingual tipping, rotation and translation movements. Results For the maximum stress of periodontal ligament, root and surface of alveolar bone due to different periodontal ligament thickness, the ratio of the maximum value to the minimum value was 1.46, 2.06 and 6.72, respectively. For the maximum displacement of root and the surface of alveolar bone, the ratio of the maximum value to the minimum value was 1.65 and 1.50, respectively. Corresponding with different thickness of periodontal ligament, the location of the maximum stress of root and periodontal tissues would change at root, periodontal furcation and tooth neck. Conclusions In clinical practice, changes of tooth neck, periodontal furcation and root should be observed carefully, and the translation movement is more conducive to the health of teeth and periodontal tissues for patients with thin thickness of periodontic ligament.