Meng X H, Wang C J, Wang C, Wang R, Ming Y, Zheng L L
Department of Orthodontics, Stomatological Hospital of Chongqing Medical University & Chongqing Key Laboratory of Oral Diseases and Biomedical Sciences & Chongqing Municipal Key Laboratory of Oral Biomedical Engineering of Higher Education, Chongqing 401147, China.
Zhonghua Kou Qiang Yi Xue Za Zhi. 2019 Nov 9;54(11):753-759. doi: 10.3760/cma.j.issn.1002-0098.2019.11.006.
To investigate the mechanical effects during en-mass retraction of maxillary anterior teeth with clear aligner using three-dimensional finite element method. Cone-beam CT (CBCT) was used to scan a female orthodontic patient (26 years old, from Department of Orthodontics, Stomatological Hospital of Chongqing Medical University) whose maxillary first premolars were extracted and maxillary dentition had been aligned and leveled. A finite element model including maxillary teeth-periodontal ligament (PDL)-alveolar bone-clear aligner was established by using Mimics 17.0, SolidWorks 2016 and Geomagic Studio 2015 software packages. The process of 0.2 mm en-mass retraction of anterior teeth using clear aligner was simulated by using non-linear contact method of Abaqus 6.14. The trend and displacement of maxillary teeth, the stress distribution of PDL and alveolar fossae, and the deformation trend of clear aligner were obtained and analyzed. Under the experimental condition, lingual crown tipping and distal tipping movement of anterior teeth were observed, and all of them had the tendency of overbite increasing.The maximum displacement of the central incisor, lateral incisor and canine were 25.16, 50.34 and 24.98 μm, respectively. Meanwhile, the second premolar, first molar and second molar had the tendency of mesial tipping movement, and the maximum displacement of them were 33.04, 2.90 and 16.63 μm, respectively. The stress distribution both at the PDL and alveolar fossae were consistent with tooth movement pattern. It was noted that the stress in the PDL of the canine and second premolar were comparatively big, and the corresponding apical areas of alveolar fossae appeared stress concentration. Concurrently, it was found that the clear aligner showed stress concentration at the junction of adjacent teeth with a tendency of crown directional dislocation. During en-mass retraction of anterior teeth with clear aligner, attention should be paid to the overbite and torque in anterior teeth, and the anchorage protection of posterior teeth. At the same time, we should be careful of root resorption of the teeth on both sides of the extraction space.
采用三维有限元方法研究使用透明矫治器整体内收上颌前牙过程中的力学效应。使用锥形束CT（CBCT）扫描一名正畸女性患者（26岁，来自重庆医科大学附属口腔医院正畸科），该患者拔除了上颌第一前磨牙，上颌牙列已排齐整平。利用Mimics 17.0、SolidWorks 2016和Geomagic Studio 2015软件包建立了包括上颌牙齿-牙周膜（PDL）-牙槽骨-透明矫治器的有限元模型。采用Abaqus 6.14的非线性接触方法模拟使用透明矫治器整体内收前牙0.2 mm的过程。获得并分析上颌牙齿的移动趋势和位移、牙周膜和牙槽窝的应力分布以及透明矫治器的变形趋势。在实验条件下，观察到前牙舌向冠倾斜和远中倾斜移动，且均有覆合增加的趋势。中切牙、侧切牙和尖牙的最大位移分别为25.16、50.34和24.98μm。同时，第二前磨牙、第一磨牙和第二磨牙有近中倾斜移动的趋势，其最大位移分别为33.04、2.90和16.63μm。牙周膜和牙槽窝处的应力分布与牙齿移动模式一致。值得注意的是，尖牙和第二前磨牙牙周膜处的应力相对较大，牙槽窝相应根尖区域出现应力集中。同时，发现透明矫治器在相邻牙齿交界处出现应力集中，并有冠向脱位的趋势。在使用透明矫治器整体内收前牙过程中，应注意前牙的覆合和转矩，以及后牙的支抗保护。同时，应注意拔牙间隙两侧牙齿的牙根吸收情况。
