J钩高位牵引压低并内收上颌前牙的三维有限元分析

目的 利用三维有限元方法探讨J钩高位牵引辅助压低并内收上颌前牙的生物力学机制,以期为临床治疗提供参考.方法 在ANSYS 14.0软件中建立包括上颌牙列、牙周膜、直丝弓矫治器及上颌骨的三维有限元模型.模拟J钩施加1.5 N力量压低内收上前牙,A组加载于侧切牙近中,B组加载于侧切牙远中.牵引方向与矢状面保持30°不变、与(牙合)平面的角度在20°～ 60°之间,每间隔5°设置1种工况,两组共18种工况.分析上前牙位移及牙周膜应力情况.结果 随着牵引角度增大,上前牙位移趋势逐渐由舌向移动为主伴压低的顺时针旋转移动,变为整体压低、内收移动,最后变为压低伴唇向倾斜的逆时针旋转移动.在侧切牙近中以35°加载或在侧切牙远中以45°加载时,上前牙出现相对均匀一致的整体压低、内收移动,整体无旋转的趋势.结论 对于唇倾度正常的上颌前牙,J钩高位牵引加载于侧切牙近中更有利于前牙的整体压低和内收,临床上应根据个体情况和治疗目标调整牵引角度.     

种植支抗整体远移上牙列的三维分析研究

目的:通过CBCT测量种植支抗整体远中移动上牙列正畸治疗后牙齿三维方向的变化,评价其移动方式及力学机制.方法:筛选满足纳入标准的23例种植支抗整体远中移动上牙列正畸成人患者,用Dolphin软件测量治疗前后牙齿三维方向上的变化,运用SPSS 23.0软件对其进行统计分析.结果:上颌第一磨牙、尖牙、切牙远中移动量分别为2.60 mm、2.66 mm、2.07 mm,远中倾斜角度分别为5.31°、5.42°、-4.68°.上颌第一磨牙颊尖和尖牙分别压低0.96 mm、0.40 mm.牙合平面顺时针旋转1.51°.第一磨牙颊向倾斜4.57°,远中旋转7.71°.尖牙区和磨牙区宽度分别增加1.18 mm、2.01 mm.结论:采用种植体支抗整体远移上牙列可以获得有效的远中移动量,远移的磨牙存在一定程度的压低、远中倾斜及远中扭转,上颌牙合平面发生顺时针旋转,尖牙区和磨牙区的宽度增加.     

摇椅弓滑动法整体内收上颌前牙的三维有限元分析

目的探讨摇椅弓应用于滑动法内收上颌前牙的力学效应。方法 应用ANSYS软件建立上牙列三维有限元模型,分别计算不同深度摇椅弓和不同高度牵引钩内收上前牙时对6个上前牙阻抗中心产生的转矩,并观察二者 联合应用时上前牙初始移动情况。结果 选择不同深度的摇椅弓可产生不同的冠唇向转矩,用以抵消摩擦力及不同高度牵引钩滑动法内收产生的冠舌向转矩,进而实现上前牙的整体移动。在上颌第二前磨牙和第一磨牙之间应用种植体支抗时,2 mm深度的摇椅弓可配合使用7.2 mm高度的牵引钩来实现上前牙的压低及整体内收。结论 摇椅弓可以有效改善内收前牙时出现的直立和舌倾状态,实现压低和转矩的双重控制。     

不同前牙唇倾度及内收压低步距下隐形矫治器作用的比较：三维有限元研究

目的:应用有限元分析法探究使用隐形矫治器治疗不同前牙唇倾度以及不同内收压低移动步距下,以分步法内收前牙的牙齿移动特点。方法:建立使用隐形矫治器分步法内收上颌前牙的有限元模型,依据中切牙及侧切牙的唇倾度分为工况1:U1-SN=105°、工况2:U1-SN=115°、工况3:U1-SN=125°,牙齿移动总步距为0.2 mm,包括沿牙合平面的内收以及沿牙体长轴方向的压低,每组工况以内收量a:0.18 mm、b:0.14 mm、c:0.10 mm进行分组,分析上述不同情况下的牙齿移动特点。结果:在不同前牙唇倾度以及内收模式下,中切牙、侧切牙均表现为牙冠向舌侧、牙根向唇侧的倾斜移动,第二前磨牙至第二磨牙表现为牙冠向近中的倾斜移动。内收步距越大,前牙冠舌向位移量越大,前牙转矩改变量越大,第二前磨牙至第二磨牙牙冠近中移动量越大。结论:无托槽隐形矫治器在内收前牙时引起前牙的舌倾及伸长、后牙的近中倾斜,其移动量与内收步距呈正比,预设计的前牙绝对压低量无法抵消由牙齿内收引起的相对伸长量。     

种植体支抗辅助非拔牙矫正成人Ⅱ类2分类错牙合的临床研究

目的探讨微型种植体支抗辅助矫治成人安氏Ⅱ类2分类错牙合的临床作用机制。方法选择12例安氏Ⅱ类2分类病例,男4例,女8例,年龄18³8岁,平均21.0岁。应用微型种植体支抗牵引上牙列整体向后移动,压低上前牙,分析治疗前后患者牙齿、颌骨及软组织变化。结果上颌中切牙矢状向牙冠基本保持不动,牙根平均远中移动3.63 mm,平均倾斜比率为6050%,牙冠压低4.60 mm。上颌第一前磨牙牙冠平均远中移动3.25 mm,牙根远中移动3.65 mm,平均倾斜比率为112.3%,牙冠压低2.90 mm。上颌第一磨牙牙冠平均远中移动3.11 mm,牙根远中移动3.21 mm,平均倾斜比率为103.2%,牙冠压低1.17 mm。上颌第二磨牙牙冠平均远中移动3.22 mm,牙根平均远中移动3.15 mm,平均倾斜比率为97.8%,压低0.69 mm。结论运用微型种植体支抗可以有效地使上颌牙列整体后移、压低上前牙并改建上颌前牙区齿槽骨形态,是非拔牙矫正安氏Ⅱ类内倾型深覆牙合患者的有效方法。     

无托槽隐形矫治器整体内收上颌前牙的三维有限元分析

目的:研究无托槽隐形矫治器整体内收上颌前牙过程中上颌前牙所受的应力情况及初始移动规律.方法:采用CBCT扫描已拔除双侧上颌第一前磨牙患者,建立上牙列、牙周膜及牙槽骨的初始复合体模型.激光扫描患者牙冠外形并与初始模型三维重叠建立终模型.应用ANSYS Workbench软件分析安装无托槽隐形矫治器时上颌前牙的应力分布及初始位移趋势.结果:建立了具有高仿真度的上颌复合体三维有限元模型;上颌双侧中切牙及侧切牙初始位移趋势一致,表现为远中舌向倾斜移动,且均有伸长趋势,其牙周膜应力分布与其位移趋势相一致;上颌双侧尖牙表现为远中倾斜移动趋势.结论:无托槽隐形矫治器在整体内收上颌前牙时,上颌前牙均表现为倾斜移动,且有伸长趋势.     

托槽转矩对上颌前牙整体内收影响的三维有限元分析

目的探讨托槽转矩角度不同在内收前牙过程中对前牙冠根的控制。方法选择一例正常牙合男性样本,采用三维软件Mimics、Geomagic、Solidworks对其CT数据进行重建,在Ansys Workbench中建立包含矫治器的上颌三维有限元模型,以微种植钉为支抗、1.47 N(150 g)的矫治力整体内收上前牙,参考Damon托槽数据分别对上颌六颗前牙施加三种不同角度的位移载荷以模拟托槽的高转矩、标准转矩及低转矩,加载后求解,计算得到前牙的矢状向初始位移及牙周膜第一主应力。结果在内收前牙过程中,托槽转矩角度不同前牙冠根矢状向初始位移及牙周膜应力分布不同,对前牙的唇舌向移动方式控制不同。高转矩转矩托槽前牙移动方式为前牙唇倾;而低转矩托槽前牙发生舌侧倾斜趋势。结论通过托槽转矩角度的调整,可以在内收前牙过程中控制前牙唇舌向倾斜角度,达到更好的临床治疗效果。     

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目的采用三维有限元法模拟不同方向牵引力内收上前牙,分析前牙位移趋势及应力分布,为临床治疗提供指导。方法研究于2012年在福建医科大学进行。建立唇侧直丝弓矫治器、6个上前牙及其牙周膜和前颌骨的三维有限元模型。模拟在0.48 mm×0.64 mm英寸主弓丝上,以种植钉为支抗、1.47 N矫治力整体内收上前牙,设定前牙区牵引钩为0-6 mm、后牙区种植钉高度分别为8和14 mm。加载后求解,计算出各前牙的位移及牙周膜第一主应力。结果滑动法整体内收上前牙时,牵引钩长度主要影响前牙的矢状向位移方式：牵引钩长度增加至6 mm的过程中,侧切牙在唇舌向上由舌向倾斜运动变为舌向整体平移和舌向控根运动外,中切牙和尖牙的三维位移只有数量的增大,趋势基本保持不变。支抗种植钉高度主要影响前牙垂直向位移：种植钉位置越高,侧切牙的压低位移增大,尖牙的伸长位移减小,即前牙整体压低的趋势更明显。结论种植支抗整体内收前牙时,单纯调整牵引钩长度和支抗种植钉高度难以实现前牙段的整体内收,有必要对前牙段增加适当的垂直向压低力量。     

无托槽隐形矫治上颌前牙分步内收和整体内收的三维有限元分析

目的通过三维有限元分析探讨无托槽隐形矫治上颌前牙分步内收和整体内收对切牙移动方式和后牙支抗的影响, 以期为临床提供参考。方法选取1例2022年6月因下颌第三磨牙阻生就诊于上海交通大学医学院附属第九人民医院口腔外科的患者(24岁, 男性, 个别正常), 使用其口腔颌面部锥形束CT构建无托槽隐形矫治三维有限元模型, 设计减数上颌第一前磨牙, 建立5组工况:分步内收-尖牙平移组、分步内收-切牙平移组、分步内收-切牙过矫治组、整体内收-切牙平移组和整体内收-切牙过矫治组。分析各组前牙和支抗后牙的初始位移。结果分步内收-尖牙平移组尖牙发生远中倾斜移动, 中切牙和侧切牙分别唇向倾斜0.18°和0.13°。分步内收-切牙平移组和分步内收-切牙过矫治组尖牙均表现为近中倾斜移动;其中, 切牙平移组中切牙和侧切牙出现不可控舌倾, 分别倾斜0.29°和0.32°;切牙过矫治组中切牙和侧切牙的舌倾角减少至0.21°和0.18°。整体内收-切牙平移组和整体内收-切牙过矫治组尖牙均表现为远中倾斜移动;其中, 切牙平移组中切牙和侧切牙仍出现不可控舌倾, 分别倾斜0.19°和0.27°;切牙过矫治组中切牙发生可控的倾...     

隐形矫治磨牙远移的三维有限元分析

目的　构建隐形矫治器上颌磨牙远移的生物力学研究模型,分析矫治体系的初始位移及应力分布特点,为该技术的临床应用提供指导。方法 建立隐形矫治上颌磨牙远移的三维有限元模型,在ANSYS软件中采用非线性有限元法通过数值仿真分析求得受力瞬间牙齿在牙周膜及周围牙槽骨等约束下的移动方式、牙套形变、牙周膜应力分布,并探索适宜的Ⅱ类牵引增强前牙支抗的必要性及适宜力值。结果 第二磨牙远移的同时伴有其牙冠远中倾斜、伸长及舌侧倾斜;其余牙表现为唇/颊倾、压低且位移量与距支抗牙距离成反比。牙周膜等效应力越靠近颈缘越大,距离第二磨牙越远越小,均小于牙周组织可承受最大应力。矫治器在第二磨牙处出现应力集中现象,位移峰值小于材料的弹性极限和拉伸极限强度。100 g Ⅱ类牵引可以有效抵抗前牙唇倾,300 g牵引力作用于牙列后超过牙周膜最大承受力值。结论 使用无托槽矫治技术远移磨牙不能实现单纯的整体移动且支抗牙有一定的支抗丧失,需要进行必要的支抗控制。100 g Ⅱ类牵引即可有效抵抗推磨牙带来的前牙支抗丧失,300 g牵引力作用下牙周膜受力过大,尽量避免使用。     

种植体支抗内收上颌全牙列的三维有限元分析

目的:研究在种植体支抗内收全牙列的过程中,不同的牵引钩高度对上颌全牙列的生物力学效应和影响。方法:运用螺旋CT,MIMICS、CADTIA和SOLIDWORKS软件,建立微种植体支抗内收全牙列的三维有限元模型,并计算在3 N正畸力负载下上颌全牙列在牵引钩高度为1、4、7、10 mm时的受力大小和初始位移。结果:随着牵引钩高度的增加,矢状向力逐渐增加而垂直向力逐渐减小,上牙列逐渐由顺时针变为逆时针方向旋转。结论:通过改变牵引钩的高度,可以有效地改变上牙列的移动方式;上牙列的阻抗中心的高度位于平面上方9～12 mm之间。     

Determining the center of resistance of maxillary anterior teeth subjected to retraction forces in sliding mechanics. An in vivo study

OBJECTIVE: To determine the location of center of resistance and the relationship between height of retraction force on power arm (power-arm length) and movement of anterior teeth (degree of rotation) during sliding mechanics retraction. MATERIALS AND METHODS: Three human subjects with maxillary protrusion were selected for this study. Initial tooth displacements of maxillary right central incisor under sliding mechanics with various heights of retraction forces were measured in vivo using a two-point three-dimensional displacement magnetic sensor device. By calculating the angle of rotation from the displacements measured, the location of the center of resistance was determined. RESULTS: The results suggested that different heights of retraction forces could affect the direction of anterior tooth movement. The higher the retraction force was applied, the lower the degree of rotation (crown-lingual tipping) would be. The tooth rotation was in the opposite direction (from crown-lingual to crown-labial) if the height of the force was raised above the level of the center of resistance. CONCLUSION: The location of the center of resistance of the maxillary central incisor was approximately 0.77 of the root length from the apex. During anterior tooth retraction with sliding mechanics, controlled crown-lingual tipping, bodily translation movement, and controlled crown-labial movement could be achieved by attaching a power-arm length that was lower, equivalent, or higher than the level of the center of resistance, respectively. The power-arm length could be the most easily modifiable clinical factor in determining the direction of anterior tooth movement during retraction with sliding mechanics.     

Analysis of stress in the periodontium of the maxillary first molar with a three-dimensional finite element model.

The aim of this study was to simulate the stress response in the periodontium of the maxillary first molar to different moment to force ratios, and to determine the moment to force ratio for translational movement of the tooth by means of the finite element method. The three-dimensional finite element model of the maxillary first molar consisted of 3097 nodes and 2521 isoparametric eight-node solid elements. The model was designed to dissect the periodontal ligament, root, and alveolar bone separately. The results demonstrate the sensitivity of the periodontium to load changes. The stress pattern in the periodontal ligament for a distalizing force without counterbalancing moments showed high concentration at the cervical level of the distobuccal root due to tipping and rotation of the tooth. After various counterrotation as well as countertipping moments were applied, an even distribution of low compression on the distal side of the periodontal ligament was obtained at a countertipping moment to force ratio of 9:1 and a counterrotation moment to force ratio of 5:1. This lower and uniform stress in the periodontal ligament implies that a translational tooth movement may be achieved. Furthermore, high stress concentration was observed on the root surface at the furcation level in contrast with anterior teeth reported to display high concentration at the apex. This result may suggest that the root morphology of the maxillary first molar makes it less susceptible to apical root resorption relative to anterior teeth during tooth movement. The stress patterns in the periodontal ligament corresponded with the load types; those on the root appeared to be highly affected by bending and the high stiffness of the root.     

弓丝形变对微种植体舌侧内收上前牙影响的三维有限元分析

目的:对舌侧矫治系统中,内收弓丝形变及微种植体植入位置对上前牙三维方向移动的影响进行生物力学评价。方法:建立舌侧矫治三维有限元模型,当弓丝为可变形体及刚性体滑动法内收时,微种植体的植入位置设置为距离第二前磨牙与第一磨牙之间的牙槽嵴顶0、3、5、7 mm,分析上前牙的初始位移和牙周膜静水压的大小。结果:舌侧矫治系统中,使用可变形体弓丝内收上前牙,加力瞬间弓丝发生形变,牙初始位移受弓丝形变的作用发生舌向倾斜移动;随着微种植体高度的增加,上颌侧切牙牙冠的初始位移増大。弓丝为刚性体内收时,上前牙发生冠舌向倾斜移动;随着微种植体高度的增加,其位移趋势未发生明显变化。弓丝为可变形体时,上前牙的牙周膜静水压值超过毛细血管压的上限值。弓丝为刚性体时,上前牙的牙周膜静水压值小于毛细血管压的上限值。结论:弓丝形变对牙初始位移及牙周膜静水压影响较大。临床上可考虑使用刚性高的内收弓丝并减小内收力值,以降低牙根吸收风险。     

Locating the center of resistance of maxillary anterior teeth retracted by Double J Retractor with palatal miniscrews

Objective:To locate the center of resistance of six maxillary anterior teeth retracted by the Double J Retractor (DJR) and to find the optimal position of palatal miniscrews.Materials and Methods:The three-dimensional (3D) finite element model included 12 teeth with two first premolars extracted. The DJR was modeled as a 3D beam element. The miniscrew was sagittally placed between the second premolar and the first molar, and the vertical position of the miniscrew was established at five conditions: 6, 7, 8, 9, and 10 mm apically from the cervical line of the first molar. The length of the retraction lever arm was determined according to the position of the miniscrew, for the direction of retraction force to be parallel to the maxillary occlusal plane. The 3D finite element method was used to determine the location of the center of resistance of the maxillary anterior teeth by visualizing the tooth displacement and stress distribution.Results:As the miniscrew was located apically, the stress spread out to the root apex and the adjacent alveolar bone. At the 8-mm level of miniscrews, a bodily-like parallel retraction could be obtained with DJR.Conclusion:In this study, the center of resistance of the six maxillary anterior teeth retracted by DJR with palatal miniscrews was estimated to be 12.2 mm apically from the incisal edge of the central incisor.     

微植体支抗滑动法内收上颌前牙的三维有限元研究

目的探讨不同微螺钉种植体植入高度以及不同牵引钩高度对微植体支抗滑动法内收上颌前牙的生物力学效应的影响。方法采用高精度螺旋CT扫描结合MIMICS快速三维重建的方法建立微植体－直丝弓上颌前牙内收力系的三维有限元模型,并在准确构建托槽、牙齿、弓丝、微种植体的力学关系基础上计算当微种植体植入高度为4、8 mm时以及牵引钩高度为1、4、7、10 mm时上颌前牙的初始移动情况。结果随着牵引钩高度的增加,上颌前牙内收时逐渐从冠舌向倾斜移动变为冠唇向移动;微种植体高位植入更有利于上颌前牙内收时的压入移动。结论通过微种植体植入高度和牵引钩高度的变化可以有效控制上颌前牙内收的牙齿移动方式。     

Dentoalveolar and skeletal changes associated with the pendulum appliance.

The purpose of the study was to examine the dentoalveolar and skeletal effects of the pendulum appliance in Class II patients at varying stages of dental development and with varying facial patterns (high, neutral, and low mandibular plane angles). Specifically, the amount and nature of the "distalization" of the maxillary first molars and the reciprocal effects on the anchoring maxillary first premolars and incisors were studied, as were skeletal changes in the sagittal and vertical dimensions of the face. Pretreatment and posttreatment cephalometric radiographs obtained from 13 practitioners were used to document the treatment of 101 patients (45 boys and 56 girls). The average maxillary first molar distalization was 5.7 mm, with a distal tipping of 10.6 degrees. The anchoring anterior teeth moved mesially, as indicated by the 1.8-mm anterior movement of the upper first premolars, with a mesial tipping of 1.5 degrees. The maxillary first molars intruded 0.7 mm, and the first premolars extruded 1.0 mm. Lower anterior facial height increased 2.2 mm; there was no significant difference in lower anterior facial height increase between patients of high, neutral, or low mandibular plane angles. In patients with erupted maxillary second molars, there was a slightly greater increase in lower anterior face height and in the mandibular plane angle and a slightly greater decrease in overbite in comparison to patients with unerupted second molars. Similar findings were observed in patients with second premolar anchorage versus those with second deciduous molar anchorage. The results of this study suggest that the pendulum appliance is effective in moving maxillary molars posteriorly during orthodontic treatment. For maximum maxillary first molar distalization with minimal increase in lower anterior facial height, this appliance is used most effectively in patients with deciduous maxillary second molars for anchorage and unerupted permanent maxillary second molars, although significant bite opening was not a concern in any patient in this study.     

Treatment of open bite with microscrew implant anchorage.

Open bite treatment with microscrew implant anchorage is discussed in relation to vertical control of the posterior dentoalvelar dimension. Maxillary microscrew implants provided anchorage for intruding the posterior teeth and retracting the anterior teeth; mandibular microscrew implants were used to apply intrusion force distal to the mandibular first molars to prevent mesial tipping of the posterior teeth during space closure. Closing the mandibular plane after intruding the maxillary posterior teeth and bodily mesial movement of the mandibular posterior teeth contributed to facial profile improvement. The efficacy and potency of microscrew implants in open bite treatment are discussed.     

改良型Ⅱ类颌间牵引致下颌支抗牙受力变化分析

目的 研究改良型Ⅱ类颌间牵引的支抗磨牙受力情况及移动特点,分析其相关影响因素.方法 参考Typodont模型原理,设汁制作出结构简化的实验牙受力、移位测量装置.实验对象依受力点、受力大小及受力角度不同分为4个实验组,每组3颗样本牙.1组:受力点位于下颌实验牙近中舌侧尖,力值150g;2组:受力点位于下颌实验牙远中舌侧尖,力值150g;3组:受力点位于下颌实验牙近中舌侧尖,力值100 g;以上3组上颌受力点均位于上颌尖牙,施力角度约30°.4组:受力点位于下颌实验牙近中舌侧尖,力值100 g,上颌受力点位于上颌双尖牙,施力角度约60°.选取实验牙近中颊尖、远中尖、近中舌尖、远中舌尖最高点为固定标志点,以测量装置上的基准点线为参照点线,测量实验前后下颌实验牙标志点与基准点线间的距离,对所得数据进行t检验分析.结果 4组下颌实验牙在牵引力作用下均有明显的近中向及颊向移位,同时伴(牙合)向伸长.近中向位移值范围为0.50～3.33 mm,颊向位移值范围为2.67 ～6.17 mm,垂直向位移值范围为0.22 ～4.00 mm.位移大小与牵引力大小有关,1组和3组差异有统计学意义(P＜0.05).牵引力角度的变化可影响实验牙移动模式,角度增加,实验牙以颊向及(牙合)向移位为主,同时冠远中向旋转减轻.结论 改良型Ⅱ类颌间牵引力引起下颌实验牙三维移动,以近中及颊向移位为主,受力点的位置、牵引力的大小与角度可影响支抗牙的移动模式.