控根辅弓对上颌切牙转矩疗效的临床研究

目的：探讨控根辅弓对直丝弓矫治器患者的上颌切牙转矩效果。方法：选择22例安氏Ⅱ1拔牙矫治的患者,采用直丝弓矫治器矫治,在精细调整阶段配合控根辅弓对过度直立或内倾的上颌切牙进行正转矩。按主弓丝不同分为2组,14例主弓丝为0．46 mm ×0．64 mm 的不锈钢方丝,8例主弓丝为0．46 mm 的不锈钢圆丝。对22例上颌切牙转矩前后的 X 线头影测量结果采用 t 检验进行统计分析。结果：22例上颌切牙转矩后的 X 线头影测量结果显示,1-SN、UIa-NA 值增加（P ＜0．01）,控根辅弓对上切牙的正转矩效果明显;转矩的时间,主弓丝为圆丝上颌切牙转矩快于主弓丝为方丝,P ＜0．05。结论：在直丝弓矫治的精细调整阶段,配合前牙控根辅弓,是对内收后过度直立或舌倾的上颌切牙实现转矩的简单、有效的方法。     

细丝弓技术舌侧内收上颌前牙的三维有限元生物力学分析

目的 建立细丝弓舌侧内收上颌前牙的三维有限元模型,研究不同后倾曲力矩对上颌前牙牙周膜静水压以及初始位移的影响。方法 采用CT扫描法建立包含全牙列头颅的三维几何模型,用Solidworks软件生成舌侧托槽和弓丝的三维几何模型,组装并生成细丝弓舌侧内收上颌前牙的三维有限元模型。在三维有限元计算软件ANSYS中计算当颌间牵引力为0.556 N,后倾曲力矩分别为15、30、45、60、75 Nmm时上颌前牙的初始位移以及牙周膜静水压。结果 上颌中切牙、侧切牙以及尖牙的唇舌侧根尖和颈缘共产生4个应力集中区,并产生远中方向的旋转初始位移和相对压入移动;上颌尖牙牙周膜的静水压应力和初始位移均显著大于中切牙和侧切牙;随着后倾曲力矩的增加,上颌中切牙、侧切牙和尖牙垂直向的初始压入位移和牙周膜静水压应力均逐渐增加。结论 采用细丝弓技术舌侧内收上颌前牙的力系是安全可控的,通过改变弓丝后倾曲力矩的值可以有效控制牙齿移动的方式和移动量。     

方丝弓矫治技术内收上颌切牙的临床研究

本研究从临床的角度观察方丝弓矫治器内收前牙时对上颌切牙位置的控制，揭示了方丝弓矫治器控制上颌切牙唇舌向倾斜度的机理，并对上颌前牙内收时支抗磨牙及上唇突度的变化进行了观察，发现：①一般情况下，０．０２２＂系统的方丝弓矫治器内收上颌切牙关闭间隙时，在０．０１８＂×０．０２５＂方形不锈钢丝切牙段弯制３０°－３５°的扭转角度和１５°－２０°的＂人＂字形曲可以实现对上颌切牙唇舌向倾斜度和垂直位置的有效控制。②口外力是方丝弓矫治器内收前牙时加强支抗的有效措施，使用口外力后前后牙移动比例为４．３１：１。③上唇突点与上切牙切缘内收的移动比例为０．５９：１。     

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。     

转矩力作用下颌切牙及其支持组织的三维有限元分析

目的 :了解Begg细丝弓技术第三期上颌切牙及其支持组织在控根辅弓产生的舌向转矩力作用下的应力分布和牙体运动趋势。方法 :采用三维有限元法 ,计算和分析四个水平截面的主应力值和上颌切牙的位移。结果 :上颌中、侧切牙的应力分布基本相同 ;上颌中、侧切牙及其支持组织的应力分布不均匀 ,牙根部受应力最大 ,牙槽骨次之 ,牙周膜最小。牙颈部是应力主要集中区 ;牙体的运动趋势表现为牙根舌向移动、牙根远中倾斜和牙冠伸长的复合运动趋势。结论 :该结果为临床上使用控根辅弓提供了参考     

OPA-K平直弓丝矫治技术排齐阶段的临床研究

目的：研究平直弓丝矫治技术排齐阶段使用弹性链状圈远中移动尖牙的效果及其对前牙、尖牙、后牙的影响。方法：15例拔除4个第一双尖牙的正畸病例，使用日本TOMY公司生产的OPA-K平直弓丝矫治器进行矫治，排齐前后利用模型测量和X线头影测量进行统计学分析。结果：第一磨牙近中倾斜但前移不明显且牙冠近中舌向旋转；双尖牙及磨牙区牙弓缩窄；尖牙远中倾斜移动，牙尖间宽度增大；上下切牙舌向倾斜移动，前牙覆He加深。结论：平直弓丝矫治技术排齐阶段使用弹性链状圈远中移动尖牙配合弓丝末端回弯，可有效预防切牙唇倾，加快排齐的速度。应采取必要的增强支抗及控制前牙覆He的措施，预防此期中出现的不利变化。     

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。     

舌侧活动翼矫治器联合微种植钉内收上前牙的生物力学研究

目的探讨舌侧活动翼矫治器内收上前牙过程中, 双弓丝体系联合腭中缝微种植钉支抗时, 上颌牙齿的生物力学效应。方法选取1例双颌前突患者的锥形束CT数据, 分别建立单、双弓丝体系;有、无种植钉内收上前牙的4个三维有限元模型。在模型上加力内收上前牙, 分析对比上牙列的初始位移趋势和牙周膜应力分布。结果单、双弓丝体系对比组中, 第一磨牙牙冠的矢状向位移量分别为-3.62E-4 mm、-2.64E-4 mm, 上中切牙冠根位移差值分别为8.64E-3 mm、6.23E-3 mm。联合微种植钉, 第一磨牙牙冠水平向、矢状向、垂直向位移量为6.96E-10 mm、5.46E-10 mm、2.28E-10 mm, 上中切牙冠根位移差为1.20E-2 mm。结论双弓丝体系, 更有利于后牙支抗的保护和前牙转矩的控制。联合微种植钉后, 后牙支抗控制更好, "拱形效应"减弱, 前牙转矩控制相对减弱。     

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。     

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。     

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.     

The effects of increasing the reverse curve of Spee in a lower archwire examined using a dynamic photo-elastic gelatine model.

This paper describes the development and testing of a dynamic in vitro photo-elastic model for evaluating the effects of orthodontic mechanics on an entire arch of teeth. A model of a mandibular arch was made and the teeth were embedded in a gelatine material with a high level of mechanical creep which permitted tooth movement in response to orthodontic forces. The excellent photo-elastic properties of this material also facilitated the analysis of the stress distribution around the roots of the teeth. The model of a mandibular arch was used to investigate the tooth movements and stress distributions produced by increasing the reverse curve of Spee in a 0.018 x 0.025-inch stainless steel archwire. The results revealed that a 1-mm reverse curve of Spee increased the arch length by 1.6 mm, but increasing the reverse curve of Spee to 5 mm did not increase arch length further. Photo-elastic analysis showed an increased stress distribution around the roots of the incisors and molars as the reverse curve of Spee was increased in the archwire.     

无托槽隐形矫治器联合微种植体内收并压低上前牙的三维有限元分析

目的 运用三维有限元技术研究无托槽隐形矫治器联合微种植体内收并且压低上前牙时,使用不同方式的微种植体牵引的治疗效果差异。 方法 获取患者上颌骨及牙体等锥形束CT数据,使用Mimics、Geomagic、Solidworks和Ansys软件建立所需要的三维有限元模型以及无托槽隐形矫治器。根据微种植体的设计不同,分为4个实验组。第1组为空白对照组;第2组在上颌双侧第二前磨牙和第一磨牙之间各植入一颗微种植体,在双侧尖牙牙套上沿内收方向加0.98 N的力;第3组在第2组基础上,在中切牙之间植入一颗微种植体加力0.98 N压低上前牙;第4组在第2组基础上,在双侧中切牙和侧切牙之间各植入一颗微种植体加力0.56 N压低上前牙。对各组进行受力分析,比较不同位点植入微种植体牵引加力时前牙转矩的改变、运动趋势以及应力分布。 结果 4组中所有上颌切牙皆表现出内收和压低的趋势,且伴有不同程度的转矩改变。第3组上颌中切牙及侧切牙在矢状向冠根位移差最小,第4组上颌中切牙及侧切牙压低值最大,第2组最大应力集中值最大。 结论 将微种植体植入上颌中切牙之间进行牵引更利于转矩控制;而植入上颌中切牙与侧切牙之间并联合前牙垂直牵引时更利于单纯压低,在一定程度上避免了“过山车”效应。     

Initial forces experienced by the anterior and posterior teeth during dental-anchored or skeletal-anchored en masse retraction in vitro

Objective:To investigate initial forces acting on teeth around the arch during en masse retraction using an in vitro Orthodontic SIMulator (OSIM).Materials and Methods:The OSIM was used to represent the full maxillary arch in a case wherein both first premolars had been extracted. Dental and skeletal anchorage to a posted archwire and skeletal anchorage to a 10-mm power arm were all simulated. A 0.019 × 0.025-inch stainless steel archwire was used in all cases, and 15-mm light nickel-titanium springs were activated to approximately 150 g on both sides of the arch. A sample size of n = 40 springs were tested for each of the three groups. Multivariate analysis of variance (α = 0.05) was used to determine differences between treatment groups.Results:In the anterior segment, it was found that skeletal anchorage with power arms generated the largest retraction force (P < .001). The largest vertical forces on the unit were generated using skeletal anchorage, followed by skeletal anchorage with power arms, and finally dental anchorage. Power arms were found to generate larger intrusive forces on the lateral incisors and extrusive forces on the canines than on other groups. For the posterior anchorage unit, dental anchorage generated the largest protraction and palatal forces. Negligible forces were measured for both skeletal anchorage groups. Vertical forces on the posterior unit were minimal in all cases (<0.1 N).Conclusions:All retraction methods produced sufficient forces to retract the anterior teeth during en masse retraction. Skeletal anchorage reduced forces on the posterior teeth but introduced greater vertical forces on the anterior teeth.     

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.     

Comparison of anterior retraction and anchorage control between en masse retraction and two-step retraction: A randomized prospective clinical trial

Objectives:The purpose of this two-arm parallel trial was to compare en masse (ER) and two-step retraction (TSR) during space closure.Materials and Methods:Forty-eight adult patients with bimaxillary protrusion who were planned for treatment with extraction of four first premolars were enrolled. All patients were randomly allocated in a 1:1 ratio to either the ER (n = 24) group or the TSR (n = 24) group. The main outcome was the amount of posterior anchorage loss in the molars and the retraction of the incisors between ER and TSR; the difference in incisor and molar inclination was a secondary outcome. Lateral cephalometric radiographs and oblique cephalometric radiographs at 45° were taken before retraction (T1) and after space closure (T2). Cephalograms were digitized and superimposed on the anatomic best fit of the maxilla and mandible by one operator who was blinded to the treatment group.Results:Neither incisor nor molar crown movements showed any significant differences between the ER and TSR. There were no significant differences in the tipping of incisors and molars between the two groups.Conclusions:No significant differences existed in the amount of retraction of incisors and anchorage loss of molars between ER and TSR. Changes in incisor and molar tipping were similar, with the crowns showing more movement than the apex.     

Mechanical environment for lower canine T-loop retraction compared to en-masse space closure with a power-arm attached to either the canine bracket or the archwire

ObjectivesTo assess the mechanical environment for three fixed appliances designed to retract the lower anterior segment.Materials and MethodsA cone-beam computed tomography scan provided three-dimensional morphology to construct finite element models for three common methods of lower anterior retraction into first premolar extraction spaces: (1) canine retraction with a T-loop, (2) en-masse space closure with the power-arm on the canine bracket (PAB), and (3) power-arm directly attached to the archwire mesial to the canine (PAW). Half of the symmetric mandibular arch was modeled as a linear, isotropic composite material containing five teeth: central incisors (L1), lateral incisor (L2), canine (L3), second premolar (L4), and first molar (L5). Bonded brackets had 0.022-in slots. Archwire and power-arm components were 0.016 × 0.022 in. An initial retraction force of 125 cN was used for all three appliances. Displacements were calculated. Periodontal ligament (PDL) stresses and distributions were calculated for four invariants: maximum principal, minimum principal, von Mises, and dilatational stresses.ResultsThe PDL stress distributions for the four invariants corresponded to the displacement patterns for each appliance. T-loop tipped the canine(s) and incisors distally. PAB rotated L3 distal in, intruded L2, and extruded L1. PAW distorted the archwire resulting in L3 extrusion as well as lingual tipping of L1 and L2. Maximum stress levels in the PDL were up to 5× greater for the PAW than the T-loop and PAB methods.ConclusionsT-loop of this type is more predictable because power-arms can have rotational and archwire distortion effects that result in undesirable paths of tooth movement.     

个性化舌侧上颌前牙滑动内收三维有限元构建与分析

目的： 以牙槽性前突患者为研究对象,应用逆向工程软件构建个性化舌侧正畸滑动内收阶段上颌牙列的三维有限元模型,运用有限元分析软件进行不同滑动内收加力模式的模拟,探讨前牙转矩控制和牙弓形态的变化,为临床舌侧正畸提供理论依据和数据基础。方法： 选择牙槽性前突成年女性患者1例,采用eBrace个性化舌侧技术拔牙矫正,获取该患者滑动内收前颌面部锥形束CT（CBCT）数据,使用Mimics 15.0软件进行三维重建。采用Pro/E 4.0软件对三维模型进行修整,生成牙周膜、舌侧托槽、舌侧弓丝、种植钉及其他附件的模拟结构。使用Geomagic Studio 13.0软件将模型整合,建立复合结构三维实体模型。将实体模型导入Ansys Workbench 15.0软件平台进行网格划分,设定材料属性和接触性质,完成三维有限元模型的构建。结果： 三维有限元系统包括4组模型,即①不同内收加力模式的力学模型—种植钉分别放置于第二前磨牙与第一磨牙之间,以及第一、第二磨牙之间; ②不同弓丝尺寸的力学模型—分别建立0.016英寸×0.022英寸、0.017英寸×0.022英寸、0.016英寸×0.024英寸及0.017英寸×0.025英寸弓丝的加力模拟;③不同弓丝截面形态的加力模型—分别建立扁平弓及带状弓2种弓丝形态的加力模拟;④不同转矩预置的力学模型—在右侧上颌中切牙舌侧托槽中分别预置0°、4°、7°、10°及13°的转矩量,建立不同转矩状态下的加力模拟。结论： 根据牙槽性前突患者的CBCT数据,建立了4组个性化舌侧正畸滑动内收阶段的三维有限元模型,用于分析不同内收模式、不同补偿设计时的力学差异。所建立的模型几何相似性强,能模拟内收阶段前牙转矩控制和牙弓形态的变化趋势。     

附件对隐形矫治器内收上前牙影响的三维有限元分析

目的    通过拔除上颌第一前磨牙后前牙内收的隐形矫治三维有限元模型,分析切牙上设置附件对牙齿移动方式的影响。方法    基于1例成年患者颌骨的锥形束CT影像数据,按照切牙上有无附件,构建4组拔除第一前磨牙的上颌隐形矫治模型,分别为切牙无附件组、侧切牙单附件组、中切牙单附件组和双附件组;导入Ansys Workbench三维有限元软件,设置4个上切牙控根压入内收的隐形矫治过程,分析牙列初始位移和附件的应力分布。结果    切牙无附件组及中切牙单附件组均发生4个切牙的舌向倾斜移动,后牙产生不同程度的近中倾斜移动,尖牙近中倾斜伴有伸长;侧切牙单附件组及双附件组切牙呈整体内收压入移动趋势,切牙附件的龈方可观测到压应力集中。结论    隐形矫治内收上前牙时,在侧切牙放置附件有助于切牙整体内收的表达,而中切牙附件对牙移动方式的影响较小。     

“摇椅形”方弓配合前牙区垂直牵引作用下牙齿应力分布与移动趋势的光弹性研究

目的利用三维光弹应力分析法研究"摇椅形"方弓配合前牙区垂直牵引作用下,下颌牙齿牙槽骨的应力分布规律和移动趋势。方法制作上下颌三维光弹模型,对模型加载"摇椅形"不锈钢方丝配合前牙区垂直牵引力,将下颌实验模型单颗牙进行三维方向冻结切片,利用三维切力差法,计算单颗牙牙槽骨各点应力值。结果在"摇椅形"方弓配合前牙区垂直牵引作用下,各牙齿均未受到较大正畸力。17整体龈向压低,颊向移动,冠向远中旋转,近中颊向远中舌向扭转。16整体龈向压低,颊向移动,冠向远中旋转。15整体向伸长,冠向远中旋转,冠颊向根舌向转矩。13整体向伸长,冠唇向根舌向转矩。12为向伸长,冠唇向根舌向转矩。结论"摇椅形"方弓配合前牙区垂直牵引可以用来矫治开,随着弓丝直径增加,摇椅角度要减小。对于采用拔除双尖牙矫治的开患者,利用"摇椅形"不锈钢方丝配合前牙区垂直牵引关闭拔牙间隙可以满足开矫治机理的五个方面。