台阶式垂直闭合曲内收上颌切牙的三维有限元分析

目的 研究台阶式垂直闭合曲在三维空间内对上颌切牙位置的控制作用.方法 选择一名正常 志愿者,对其上颌牙列和牙槽骨进行三维螺旋CT扫描,只对上颌右侧中、侧切牙及牙槽骨进行建模和数据计算,利用Ansys软件生成右侧弓丝-托槽-上颌切牙段及牙周支持组织的三维有限元模型,最后根据镜像对称原理建立弓丝-托槽-上颌切牙段及牙周支持组织的三维有限元模型.模拟台阶式垂直闭合曲在临床上的使用情况加力,分析上颌切牙的位移趋势以及牙周支持组织中的应力分布规律.结果 台阶式垂直闭合曲作用下,上颌中切牙舌向、唇向最大位移分别为5.29×10-2和0.71×10-2 mm;龈向、向最大位移分别为10.47×10-3和10.20×10-3 mm;近中、远中最大位移分别为10.26×10-3和1.63×10-3 mm;侧切牙舌向、唇向最大位移分别为3.31×10-2和0.41×10-2 mm;龈向、向最大位移分别为10.52×10-3 和5.10×10-3 mm;近中、远中最大位移分别为6.29×10-3 和4.64×10-3 mm;二者均表现为舌向、龈向的近似整体移动趋势.中切牙牙齿、牙周膜、牙槽骨的最大应力值分别为31.35、2.52、4.64 MPa;侧切牙牙齿、牙周膜、牙槽骨的最大应力值分别为19.59、1.28、4.12 MPa;二者的应力分布规律相似,牙周膜对应力起缓冲作用.结论 台阶式垂直闭合曲在上颌切牙内收阶段可控制其在三维方向上的位置,对抗"钟摆效应",对临床实践具有一定参考意义.

Abstract：

Objective To investigate the displacement and stress distribution of upper incisors in three-dimensional(3D) space controlled by step-shaped vertical closing loop. Methods The maxillary teeth and alveolar bone of a volunteer with normal occlusion were scanned with 3D spiral CT. Modeling and calculation were only carried out on right upper central incisor, lateral incisor and their alveolar bone in order to simplify the procedures. A 3D finite element model of archwire-brackets-upper incisors and periodontal tissues was developed using Ansys finite element package. Finally, a 3D finite element model of archwire-brackets-upper incisors and periodontal tissues was established based on mirror symmetry principle. The displacement of maxillary incisors and stress distribution in periodontal tissues were analyzed. ResultsWhen step-shaped vertical closing loop was simply drew back 1 mm, the maximum displacement of upper central incisor in labial and lingual direction were 5.29×10-2 and 0.71×10-2 mm; 10.47×10-3 and 10.20×10-3 mm in gingival and occlusal direction, 10.26×10-3 and 1.63×10-3 mm in medial and distal direction; the maximum displacement of upper lateral incisor in labial and lingual direction were 3.31×10-2 and 0.41×10-2 mm, 10.52×10-3 and 5.10×10-3 mm in gingival and occlusal direction, 6.29×10-3 and 4.64×10-3 mm in medial and distal direction, the displacement trend of them were moving lingually and gingivally similar to bodily movement. The stress peach of upper central incisor, periodontal ligament and alveolar bone were 31.35, 2.52 and 4.64 MPa, the stress peach of upper lateral incisor, periodontal ligament and alveolar bone were 19.59, 1.28 and 4.12 Mpa, the stress distribution of them were similar and the periodontal ligament buffered the stress imposed on the tooth. Conclusions The position of upper incisors in 3D space could be controlled by step-shaped vertical closing loop and the pendulum effect could be confronted.

Three-dimensional finite element analysis of maxillary incisor retraction with step-shaped vertical closing loop

Objective To investigate the displacement and stress distribution of upper incisors in three-dimensional(3D) space controlled by step-shaped vertical closing loop. Methods The maxillary teeth and alveolar bone of a volunteer with normal occlusion were scanned with 3D spiral CT. Modeling and calculation were only carried out on right upper central incisor, lateral incisor and their alveolar bone in order to simplify the procedures. A 3D finite element model of archwire-brackets-upper incisors and periodontal tissues was developed using Ansys finite element package. Finally, a 3D finite element model of archwire-brackets-upper incisors and periodontal tissues was established based on mirror symmetry principle. The displacement of maxillary incisors and stress distribution in periodontal tissues were analyzed. ResultsWhen step-shaped vertical closing loop was simply drew back 1 mm, the maximum displacement of upper central incisor in labial and lingual direction were 5.29×10-2 and 0.71×10-2 mm; 10.47×10-3 and 10.20×10-3 mm in gingival and occlusal direction, 10.26×10-3 and 1.63×10-3 mm in medial and distal direction; the maximum displacement of upper lateral incisor in labial and lingual direction were 3.31×10-2 and 0.41×10-2 mm, 10.52×10-3 and 5.10×10-3 mm in gingival and occlusal direction, 6.29×10-3 and 4.64×10-3 mm in medial and distal direction, the displacement trend of them were moving lingually and gingivally similar to bodily movement. The stress peach of upper central incisor, periodontal ligament and alveolar bone were 31.35, 2.52 and 4.64 MPa, the stress peach of upper lateral incisor, periodontal ligament and alveolar bone were 19.59, 1.28 and 4.12 Mpa, the stress distribution of them were similar and the periodontal ligament buffered the stress imposed on the tooth. Conclusions The position of upper incisors in 3D space could be controlled by step-shaped vertical closing loop and the pendulum effect could be confronted.