【作者】 何艳；

【导师】 李晓智；

【作者基本信息】 重庆医科大学 ， 口腔临床医学， 2007， 硕士

【摘要】 目的探索一种快速高效的建模方法,建立上颌前牙段牙齿及其牙周组织的高质量三维有限元模型,研究其在不同角度磨牙后倾曲作用下的受力情况,为临床前牙打开咬合使用合适矫治力系统提供一定理论依据。方法1、对一健康青年女性上颌骨行CT扫描,将所得截面影像数据直接传输、处理,并生成三维模型,划分网格,赋予其材料力学参数,建立可分析用的上颌前牙段牙齿及其牙周组织的三维有限元模型。2、按照方程Y=4.0491E-5X4+3.3263E-2X2 (上颌),建立弓丝的二维坐标,并将弓丝的XY平面沿YZ平面旋转一定角度,形成三种角度磨牙后倾曲的有限元模型。对模型进行加载和约束,计算求得不同角度弓丝施以托槽反力。将所得结果分别加载到上颌前牙段各个牙齿上,观察牙周膜三个应力指标(S1、S3及Von mises应力)的分布情况。结果1、建立了精度较高的上颌前牙段及其牙周组织(包括牙周膜、牙槽骨)的三维有限元模型,共形成640396个单元,117889个节点。2、在磨牙后倾曲作用下,前后牙垂直向受力结果显示:1)对上颌前牙段牙齿均产生压入力,且呈不均匀分布。其中尖牙所受压入力最大,侧切牙其次,中切牙最小。与此同时,磨牙近中受到伸长力,而远中受到压入力,并且伸长力大于压入力。2)前牙段各个牙齿所受的压入力随磨牙后倾曲加载角度增加而成倍增大,且不均匀分布的趋势也增大。与此同时,磨牙所受净伸长力也逐渐增加。3、在磨牙后倾曲作用下,上颌前牙段牙周膜不同节点三个应力指标(S1、S3及Von mises应力)变化显示:1)整个上颌前牙段牙周膜主要受压,唇侧总体受力较舌侧大,中1/3处受力相对较小,近远中面应力分布相对均匀;应力峰值集中区域位于唇、舌侧的颈缘及根尖。其中尖牙牙周膜总体受力最小,而侧切牙最大。2)牙周膜各个节点所受应力随磨牙后倾曲加载角度增加而增大,应力值峰值区域也越来越集中,呈现倾斜移动的分布特点。结论1、本研究所采用的建模方法为今后牙齿及牙周等复杂组织的快速精确建模提供了借鉴。同时,所建模型为进一步研究上颌前牙段单个牙齿或节段牙弓生物力学变化规律奠定了基础。2、进一步印证:差动牙移动技术打开咬合是牙齿差别压入的过程。本研究认为,差动牙移动技术第一期打开咬合时,宜采用30度左右的磨牙后倾曲。3、在磨牙后倾曲作用下,整个上颌前牙段表现为唇向倾斜移动的趋势,并且这种趋势随加载角度的增加而增大。因此,为达到前牙段整体压入,临床上应采取必要措施(如同时配合使用II颌间牵引)以建立打开咬合的有效力系。更多还原

【Abstract】 Objective To search a new rapid and effective method for model construction,and establish a highly precision 3D finite element analysis model of maxillary anterior dentition and its periodontal tissues, investigate its stress distribution with the effect of the molar tip-back bend in different angles,in order to provide academic evidence for how to use orthodontic force systems becomingly when it needs bite opening .Method1. The maxilla of a healthy young female was scanned with spiral CT in order to obtain the CT tomographic images which were transfered and disposed to build the 3D reconstruction model . The finite element analysis models were created after being meshed and checked.2.The two dimensional coordinates of archwire were established according to the formula[Y=4.0491E-5X4+3.3263E-2X2 ( maxilla) ]. The three-dimentional model was established after being rotated along YZ plane. Setting 3 different angles of molar tip-back bends in order to simulate the bite opening instance and investigate the stress distribution of maxillary anterior dentition and its periodontal tissues .Results1.The high quality model consisted of maxillary anterior dentition segment and periodontal tissues (including periodontal ligament and alveolar bone),which had 640396 elements and 117889 nodes.2. The force results of anterior tooth and molar which were loaded by the molar tip-back bend:1)Originaly the maxillary anterior teeth were pressured by the effect of molar tip-back bends,but the force distribution was uneven. Canine was pressed into the biggest, followed by lateral incisor, the smallest incisor . Meanwhile, the anchorage molar was loaded on the force which was extended medially and intruded distally, and the extend force outweighting the intrusive one.2)The pressures on each teeth of the anterior dentition and uneven distribution trend increased with the increase of loading angle.The net elongation force on molar also increased.3. The changes of three stress index(S1、S3、Von mises) of PDL’s different nodes indiciated :1)The periodontal ligament of maxillary anterior dentition were pressured maining.Generally the stresses on the labial side were bigger than the lingual ones , the peak value were on the cervical edge and root tine of labial and lingual side. Generally the maximum stress was on the canine PDL ,and the minimum stress was on the lateral incisor.2 ) With the increasing loading angles of tip-back bend, the stress of each nodes has also increased, and more and more concentrated.It presented the distribution characteristics of incline movement.Conclusion1.The new method was easy to use,especially fit for the construction of complex tissues.Meanwhile,the model provided a good foundation for the research of the biomechanics behavior of maxillary anterior dentition.2. It proved that the instrusion of anterior dentition was also a different teeth movement. The results of this research suggest that, the optimum molar tip-back bend is 30°while on stage I bite opening .3. Maxillary anterior dentition which was loaded by the molar tip-back bend presented a trend of incline movement and the trend increased with the increase of loading angle.In order to achieve bodily instrusion of anterior dentition and establish the efficient force system of bite opening , the class II elastic was necessary at the same time on the clinic.更多还原