Ⅱ类骨质中正畸微种植体锥度及植入角度对支抗稳定性影响的三维有限元分析

目的 探讨微种植体锥度和植入角度对Ⅱ类骨质下颌骨中支抗稳定性的影响,为临床选择微种植体最佳锥度与植入角度提供理论依据。方法 建立包含正畸微种植体的颌骨三维有限元模型,在植入角度为 30°、45°、 60°、75°、90°时分别植入不同锥度的微种植体（直径为 1.1~1.6 mm,锥度为 0~0.062 5）,分析在 2N水平力作用下颌骨应力、种植体应力和位移的变化规律。结果 植入角度对骨皮质、种植体应力和位移影响较大,植入角度为 60°时,应力和位移水平均较小;微种植体锥度的影响与植入角度相关,植入角度为 60°时D模型出现应力最小值,分别为5.013 4 MPa（骨皮质）和25.131 0 MPa（微种植体）,种植体位移与锥度变化趋势呈正比。结论 植入角度对支抗稳定性影响显著, 60°为较适宜的植入角度;微种植体锥度对稳定性的影响与植入角度相关,锥度为 0.037 5（最大直径为1.6 mm,最小直径为1.3 mm）的微种植体更加适用于Ⅱ类骨质颌骨。     

皮质骨厚度对支抗种植体-骨界面应力分布的影响

目的：研究皮质骨厚度改变对支抗种植体-骨界面应力分布的影响，供临床参考。方法：用三维有限元方法，对分别种植于皮质骨厚度为0．5mm、1．0mm、2．0mm颌骨模型中的种植体施加150g近远中方向的载荷，分析支抗种植体-骨界面应力分布情况：结果：三者种植体颈部的Von-Mises应力值分别为0．6040MPa、0．5330MPa、0．5380MPa；位移值分别为0．2110μm、0．1630μm、0．1250μm：结论：皮质骨在一定厚度内，植入体颈部皮质骨越薄，骨界面应力值就越大：但皮质骨超过一定厚度后，骨界面应力并不随其厚度的增加而做相应递减。皮质骨的厚度与界面骨的位移成反比.     

应用锥形束CT探查颧牙槽嵴处微种植钉植入的安全范围

目的:通过测量上颌第一、二磨牙间顴牙槽嵴颊侧骨皮质厚度及颊腭向最大骨厚度,探查微种植钉合适的植入位点及植入角度范围,为正畸治疗在顴牙槽嵴处安全植入微种植钉提供参考。方法:选取2010年11月～2011年11月来大连市口腔医院放射线科行锥形束CT扫描的40例成人患者,测量上颌第一、二磨牙间顴牙槽嵴处距牙槽嵴顶6、8、10mm三水平,各水平微种植钉长轴与真性水平面呈45°、60°、70°角时顴牙槽嵴颊侧骨皮质厚度及颊腭向最大骨厚度。结果:3个水平顴牙槽嵴颊侧骨皮质厚度均随着植入角度的增大而增厚。在所有颊侧骨皮质厚度测量项目中以距牙槽嵴顶6mm点微种植钉长轴与真性水平面呈70°角时最厚。在距牙槽嵴顶8、10mm水平,微种植钉长轴与真性水平面呈60°角时顴牙槽嵴颊腭向最大骨厚度均较厚。在距牙槽嵴顶8、10mm水平,3个角度的颊侧骨皮质厚度男性均大于女性。40例中有4例(占10%)上颌窦底与上颌第一、二磨牙牙根紧邻。左右对称指标相互比较无差异。结论:通过对测量数据的分析明确了上颌第一、二磨牙间顴牙槽嵴颊侧骨皮质厚度及颊腭向最大骨厚度,为正畸治疗安全植入微种植钉提供参考。     

上颌第一、第二磨牙间腭侧微种植支抗钉植入安全位置的CBCT研究

目的应用锥形束CT(cone beamCT,CBCT)测量在上颌第一、第二磨牙间腭侧以不同角度植入微种植支抗钉时上颌第一、第二磨牙腭根间近远中向宽度,以及微种植支抗钉植入路径的黏膜厚度和骨组织厚度,为临床选择微种植支抗钉植入位置提供参考。方法选取90例成人患者,以其颌骨进行扫描重建的CBCT资料为研究对象,在上颌腭侧,第一磨牙和第二磨牙之间选取距上颌第一磨牙腭尖12、14、16、18 mm的软组织标志点作为测量位置,分别测量与牙长轴成30°、45°、60°、90°时上颌第一、第二磨牙腭根之间的近远中向宽度及微种植支抗钉植入路径的黏膜厚度和骨组织厚度。采用SPSS 26.0软件进行单因素方差分析及LSD法两两比较。结果植入微种植支抗钉角度越大,上颌第一、第二磨牙腭根间的近远中向宽度越小,差异具有统计学意义(P<0.05),与90°方向相比,以60°方向植入时近远中向宽度更大,接触相邻牙根的概率更小;植入角度越大,黏膜厚度越小,结果具有显著性差异(P<0.001),与30°、45°方向相比,以60°方向植入时黏膜厚度更小,微种植支抗钉进入骨组织内的长度更大更稳定。植入微种植支抗钉位置越高,近远中向宽度越大,差异具有统计学意义(P<0.05),与12、14 mm位置相比,距上颌第一磨牙腭尖16 mm植入时近远中向宽度更大,接触相邻牙根的概率更小;植入位置越高,黏膜厚度越大,差异具有统计学意义(P<0.001),与18 mm位置相比,距上颌第一磨牙腭尖16 mm植入时黏膜厚度更小,微种植支抗钉进入骨组织内的长度更大,更稳定。结论在上颌第一、第二磨牙间腭侧,距上颌第一磨牙腭尖16 mm以60°方向植入微种植支抗钉较为安全。     

微型正畸支抗种植体即刻挤压植入时骨界面应力分析

目的研究微型正畸支抗种植体即刻植入时骨界面应力大小及分布,为微型支抗种植体即刻加载提供参考。方法将局部下颌骨简化成一个等腰梯形,颌骨骨块长20mm,断面高为30mm,上边宽为10mm,底边宽14mm,皮质骨厚度设定为1.6mm;微型种植体直径设定为1.2mm,长6mm。利用ANSYS9.0软件,建立局部微型种植体-骨的三维有限元模型。下颌骨材料属性设定为线性、正交各向异性,种植体-骨界面定义为完全连接。将断端处、下颌骨局部骨块面及底面的所有节点给予刚性约束。模拟种植体即刻植入时的情况,将骨界面初始位移设定为0、0.05、0.1mm,分析各指定初始位移时骨界面应力大小及分布。结果即刻加载时,0mm初始位移下,种植体骨界面无应力分布;初始位移为0.05mm时,骨界面应力集中在骨皮质内,分布较均匀,衰减幅度很小,近远中方向上的VonMises应力为1648MPa,龈向为1782MPa。初始位移为0.1mm时,近远中方向上的VonMises应力为2012MPa,龈向为2110MPa。结论微型种植体挤压植入时会产生较大的初始应力,即刻加载时,应当考虑这种初始应力。     

种植钉植入高度对隐形矫治远移下磨牙时应力分布的影响

目的 探究种植钉不同植入高度对隐形矫治配合颌内牵引远移下磨牙时所产生的生物力分布的影响,寻找有利于保护下前牙支抗的种植钉植入位置,为临床治疗方案的设计提供参考。方法 应用Mimics、Geomagic Studio 2017、SolidWorks2016、Ansys workbench建立有限元分析模型并对六种工况进行力学分析。工况一：无种植钉（对照组）;工况二至工况五：种植钉植入于下颌第一磨牙和第二磨牙之间的颊侧骨皮质,距离牙槽嵴顶分别为10 mm、7 mm、4 mm、1 mm;工况六：种植钉植入于下颌升支前缘颊舌向居中,高于平面5 mm的位置。结果 矢状向,种植支抗使所有牙齿均产生远中向位移;相较于对照组,种植钉组前磨牙远中位移量超过第二磨牙。垂直向,对照组（无种植钉）为类似后倾弯对下颌牙列产生的作用;种植钉组侧切牙、尖牙压低,中切牙、第一前磨牙伸长。冠状向,对照组（无种植钉）第二前磨牙、第一磨牙为舌向位移,种植钉组仅前磨牙及第一磨牙出现了舌向位移;所有牙齿中,尖牙的位移量受种植钉植入高度变化影响最大。结论种植钉植入位置越高,保护前牙支抗的效果越强。方案设计时应根据种植钉植入高度,...     

I类骨质中正畸微种植体支抗直径和长度的优化设计

目的：探讨正畸微种植体支抗长度和直径对I类骨质下颌骨的应力和微种植体稳定性的影响,为临床设计I类骨质中微种植体支抗的最佳长度和直径提供理论依据。方法：建立包含正畸微种植体支抗的颌骨骨块的三维有限元模型,设定微种植体的直径和长度为变量,直径变化范围1.0～1.8mm,长度变化范围5.0～11.0mm。设定颌骨平均主应力峰值和正畸微种植体支抗位移峰值为目标函数。观察设计变量变化对目标函数的影响。结果：随着直径的增加,皮质骨、松质骨应力峰值和种植体位移分别降低了67.98%,64.06%,78.55%;随着长度变化皮质骨、松质骨的应力峰值和种植体位移分别降低了13.94%,61.32%,0.01%。结论：种植体支抗的直径对I类骨质颌骨的应力和种植体支抗稳定性的影响更显著。长度对I类骨质颌骨的应力和种植体支抗稳定性的影响并不显著。从生物力学角度而言,直径大于1.4mm种植体支抗更加适用于I类骨质的颌骨。     

应用锥形束CT探究上颌前牙区颌骨微种植支抗钉植入的安全区

目的:对上颌前牙区颌骨的骨量及唇侧骨皮质厚度进行测量分析,为正畸治疗植入微种植支抗钉的安全区提供参考。方法:对25例成人患者上颌前牙区行锥形束CT扫描及三维重建,测量距上颌牙槽嵴顶3、6、9、12 mm水平上颌中切牙、侧切牙、尖牙根间区近远中向、唇腭向的距离以及唇侧骨皮质厚度。结果:在距上颌牙槽嵴顶3、6、9 mm水平中切牙根间近远中向距离均最宽,唇侧骨皮质均最薄;在距牙槽嵴顶9mm水平中切牙与侧切牙根间近远中向距离最窄;在4个测量水平侧切牙与尖牙根间唇侧骨皮质均最厚;唇腭向在距牙槽嵴顶9 mm及以上水平,中切牙根间骨厚度最薄,中切牙与侧切牙根间骨厚度最厚。25例中仅3例前牙区各牙根长度超过12 mm,在距牙槽嵴顶12 mm水平测出的根间近远中向距离均较宽。结论:通过对扫描后颌骨影像的分析,明确了前牙区颌骨的骨量及唇侧骨皮质厚度,为植入微种植支抗钉的安全区提供参考。     

植入角度及深度对种植体支抗稳定性影响的三维有限元研究

目的 分析不同植入角度和植入深度下支抗种植体受力后的位移变化。方法 利用pro/E软件自适应功能建立包含不同植入角度和植入深度支抗种植体和上颌骨块的三维有限元模型,在种植体顶部中央点模拟施加水平方向(与颌骨面平行,近远中方向)的正畸作用力,分析该点位移与力值变化受植入角度和植入深度影响的规律。结果 ①当植入深度是11mm,以30°、60°、90°植入时,需要力值分别是1 041.07、735.71、623.11 N;②当植入深度是10 mm,以30°、60°、90°植入时,需要力值分别是486.72、518.66、456.98 N;③当植入深度是9 mm,以30°、60°、90°植入时,需要力值分别是306.12、384.49、362.61N;④在本研究设计的9种工况作用下,以30°、11 mm深度植入支抗种植体时,种植体最稳定。结论 深度对种植体稳定性的影响远大于角度对种植体的影响;60°倾斜度相对于90°和30°来说更加稳定。?     

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目的对上颌前牙区颌骨的骨量及唇侧骨皮质厚度进行测量分析,为正畸治疗植入微种植支抗钉的安全区提供参考依据。方法对2010年9月至2011年6月来大连市口腔医院就诊的25例成人患者行锥形束CT扫描及三维重建,测量距上颌牙槽嵴顶3、6、9、12mm4个水平上颌中切牙、侧切牙、尖牙根间区近远中向、唇腭向的距离以及唇侧骨皮质厚度。结果 (1)在距上颌牙槽嵴顶3、6、9mm水平中切牙根间近远中向距离均最宽,唇侧骨皮质均最薄;(2)在距牙槽嵴顶9mm水平中切牙与侧切牙根间近远中向距离最窄;(3)在4个测量水平侧切牙与尖牙根间唇侧骨皮质均最厚;(4)唇腭向在距牙槽嵴顶9mm及以上水平,中切牙根间骨厚度最薄,中切牙与侧切牙根间骨厚度最厚。25例中仅3例前牙区各牙根长度超过12mm,在距牙槽嵴顶12mm水平能测出根间近远中向距离,均较宽。结论通过对扫描后颌骨影像的分析,明确了前牙区颌骨的骨量及唇侧骨皮质厚度,为植入微种植支抗钉的安全区提供参考依据。     

不同矢状骨面型成年患者磨牙后三角及下颌升支前缘骨骼特征的CBCT分析

目的 通过CBCT评估不同矢状骨面型成年患者磨牙后三角及下颌升支前缘骨骼特征,并分析微种植体的植入风险.方法 选取2016—2020年就诊于南京医科大学附属口腔医院正畸科的150例成年患者,按照矢状骨面型分为三类.在矢状面上高于牙合平面2 mm及4 mm处绘制与牙合平面平行和成45°的参考线,测量参考线上的有效骨量和骨皮质厚度.结果 所有测量的植入部位平均有效骨量超过10 mm,平均骨皮质厚度1.7～2.4 mm;与牙合平面平行处测得的有效骨量和骨皮质厚度的平均值大于与牙合平面成45°处测得的有效骨量和骨皮质厚度的平均值,差异具有统计学意义(P<0.05);骨性Ⅲ类患者有效骨量最小,骨性Ⅱ患者有效骨量最大,差异具有统计学意义(P<0.05).结论 不同矢状骨面型成年患者磨牙后三角及下颌升支前缘具有足够的有效骨量和骨皮质厚度,可以安全地植入微种植体.     

不同垂直骨面型成人微螺钉种植体常植入区骨皮质厚度分析

目的 探讨不同垂直骨面型成人上下颌骨后牙区微螺钉种植体拟植入部位的骨皮质厚度,为临床植入微螺钉种植体提供参考.方法 57例正畸成人患者,髙角组20例、均角组22例、低角组15例;拍摄头颅CBCT,在三维重建模型上测量上颌骨颊、腭侧及下颌骨颊侧骨皮质厚度,进行统计学分析.结果 3组间多数测量部位平均骨皮质厚度的差异均有统计学意义(P<0.05),且高角组的平均骨皮质厚度最小,低角组的平均骨皮质厚度最大.结论 髙角患者在上颌后牙区植入微螺钉种植体需谨慎.     

Histomorphometric Evaluation of Cortical Bone Thickness Surrounding Miniscrew for Orthodontic Anchorage

Background: Recently, the use of miniscrews as an anchorage device has become a routine approach in the orthodontic field. However, there is no report that has analyzed the healing process of the miniscrew, such as the thickness of the cortical bone, in the past. Purpose: In the present study, to histologically assess the healing process of the osseous tissue surrounding miniscrews used as an orthodontic anchorage, the change in the thickness of the cortical bone was analyzed after 3, 6, and 12 weeks after the placement. Furthermore, the change in the bone‐implant contact in different regions of the miniscrew during the initial healing period was also investigated. Materials and Methods: Ninety‐six miniscrews were placed in eight beagle dogs. After 3, 6, and 12 weeks of healing, a force of 200–300 g was applied to the force‐applied groups for 12 weeks. Non‐forced groups remained in the jaw without force application. Results: In the non‐forced groups, a significant amount of cortical bone was formed at the head of the miniscrew at the initial stage of the healing process in the maxilla. However, less cortical bone formation was observed in the mandible. After the force application, increased bone formation was observed within 1 mm of the miniscrew compared to other regions in both jaws. In the mandible, significantly less cortical bone was observed 3 and 6 weeks after the force application. Bone‐implant contact revealed that the osseous tissue surrounding the miniscrew matured from the apex toward the head of the miniscrew. Conclusion: We suggest that this sufficient amount of cortical bone at the initial stage of healing enables the immediate loading in miniscrews to resist against orthodontic force. Furthermore, less amount of cortical bone formed at the head of the miniscrew may be one reason for the higher failure rate in the mandible.     

Factors affecting stresses in cortical bone around miniscrew implants

Abstract Objective: To evaluate various types of stress in cortical bone around miniscrew implants using finite element analysis. Materials and Methods: Twenty-six three-dimensional assemblies of miniscrew models placed in alveolar bone blocks were constructed using Abaqus (Dassault Systèmes Simulia Corp, Providence, RI), a commercial finite element analysis software package. The model variables included implant design factors and bone-related factors. All miniscrew implants were loaded in the mesial direction with a linear force equal to 2 N. Peak von Mises and principal stress values in cortical bone were compared between the different models for each factor. Results: The results demonstrated that some factors affected the stresses in bone (implant diameter, implant head length, thread size, and elastic modulus of cancellous bone), while other factors did not (thread shape, thread pitch, and cortical bone thickness). Conclusions: Miniscrew implant diameter, head length, and thread size as well as the elastic modulus of cancellous bone affect the stresses in cortical bone layer surrounding the miniscrew implant and may therefore affect its stability.     

Factors affecting stresses in cortical bone around miniscrew implants: A three-dimensional finite element study

Objective:To evaluate various types of stress in cortical bone around miniscrew implants using finite element analysis.Materials and Methods:Twenty-six three-dimensional assemblies of miniscrew models placed in alveolar bone blocks were constructed using Abaqus (Dassault Systèmes Simulia Corp, Providence, RI), a commercial finite element analysis software package. The model variables included implant design factors and bone-related factors. All miniscrew implants were loaded in the mesial direction with a linear force equal to 2 N. Peak von Mises and principal stress values in cortical bone were compared between the different models for each factor.Results:The results demonstrated that some factors affected the stresses in bone (implant diameter, implant head length, thread size, and elastic modulus of cancellous bone), while other factors did not (thread shape, thread pitch, and cortical bone thickness).Conclusions:Miniscrew implant diameter, head length, and thread size as well as the elastic modulus of cancellous bone affect the stresses in cortical bone layer surrounding the miniscrew implant and may therefore affect its stability.     

Buccal cortical bone thickness in different sagittal skeletal relationship

Purpose

To assess buccal cortical bone thickness of the alveolar process in the maxilla and mandible in subjects with different skeletal relationship as an aid in orthodontic miniscrew placement.

Optimal Palatal Configuration for Miniscrew Applications

Objective:To test the hypothesis that palatal bone is not able to support titanium miniscrews (11 mm in length and 2 mm in diameter) when subjected to forces normally generated during orthodontic treatment.Materials and Methods:The miniscrew–palatal bone system was modeled and analyzed using the commercial finite element method software ANSYS Multiphysics 10.0; tests were done in both a state of total osseointegration and in the absence of it. Calculations were carried out in both cases in configurations where the miniscrew was inserted into two different palatal regions: in the first it was anchored in one layer of cortical bone and in the underlying trabecular bone; in the second, two layers of cortical bone and the trabecular bone in between were involved. Two different loads were taken into account, 240 g_f and 480 g_f, both of which are within the normal range for orthodontic treatment, and applied to the miniscrew heads.Results:The results demonstrated that the miniscrew inserted into the palate can be anchored to bone and loaded within normal orthodontic force range without exceeding the stress levels that lead to bone fracture. The osseointegrated system was characterized by a lower level of stress than the nonosseointegrated one, but anchorage within the second layer of cortical bone markedly reduced the stress on the trabecular bone, thereby improving the stability of the implant, also in the absence of osseointegration.Conclusions:The hypothesis is rejected. Miniscrews loaded within the normal orthodontic force range do not exceed the stress levels that lead to bone fracture.     

骨性Ⅰ、Ⅱ类不同垂直骨面型患者下颌前牙区皮质骨厚度与下切牙牙根位置的CBCT研究

目的:比较骨性Ⅰ、Ⅱ类不同垂直向个体下颌前牙区皮质骨厚度和下切牙牙根位置的差异。方法:本研究为回顾性观察性研究。共收集324例个体，其中男性141例，女性183例。测量个体下颌前牙区皮质骨厚度和下切牙牙根位置，使用单因素方差分析比较不同骨型个体下颌前牙区皮质骨厚度与下切牙牙根位置，使用线性相关分析研究骨性Ⅱ类患者随着下颌平面角增加皮质骨厚度变化趋势。结果:高角患者下颌前牙区皮质骨较均角和低角患者更薄，男、女性Ⅰ类高角根中唇舌侧厚度分别为0.50 mm、1.27 mm和0.35 mm、1.16 mm，低角为0.58 mm、1.82 mm和0.62 mm、1.77 mm( P<0.05， P<0.01)，Ⅱ类高角根中唇舌侧厚度分别为0.38 mm、1.14 mm和0.51 mm、1.35 mm，低角为0.83 mm、2.28 mm和0.97 mm、1.93 mm( P<0.001)。且高角患者牙根距离唇舌侧皮质骨距离更近( P<0.05， P<0.01， P<0.001)。在骨性Ⅱ类患者中，随着下颌平面角增加，骨皮质厚度变薄( P<0.001)。 结论:高角患者下颌前牙区皮质骨较薄，骨性Ⅱ类患者尤其明显，因此临床上应防止骨开裂和骨开窗的发生。     

骨性Ⅰ、Ⅱ类不同垂直骨面型患者下颌前牙区皮质骨厚度与下切牙牙根位置的CBCT研究

目的:比较骨性Ⅰ、Ⅱ类不同垂直向个体下颌前牙区皮质骨厚度和下切牙牙根位置的差异。方法:本研究为回顾性观察性研究。共收集324例个体,其中男性141例,女性183例。测量个体下颌前牙区皮质骨厚度和下切牙牙根位置,使用单因素方差分析比较不同骨型个体下颌前牙区皮质骨厚度与下切牙牙根位置,使用线性相关分析研究骨性Ⅱ类患者随着下颌平面角增加皮质骨厚度变化趋势。结果:高角患者下颌前牙区皮质骨较均角和低角患者更薄,男、女性Ⅰ类高角根中唇舌侧厚度分别为0.50 mm、1.27 mm和0.35 mm、1.16 mm,低角为0.58 mm、1.82 mm和0.62 mm、1.77 mm( P<0.05, P<0.01),Ⅱ类高角根中唇舌侧厚度分别为0.38 mm、1.14 mm和0.51 mm、1.35 mm,低角为0.83 mm、2.28 mm和0.97 mm、1.93 mm( P<0.001)。且高角患者牙根距离唇舌侧皮质骨距离更近( P<0.05, P<0.01, P<0.001)。在骨性Ⅱ类患者中,随着下颌平面角增加,骨皮质厚度变薄( P<0.001)。 结论:高角患者下颌前牙区皮质骨较薄,骨性Ⅱ类患者尤其明显,因此临床上应防止骨开裂和骨开窗的发生。     

Is miniscrew primary stability influenced by bone density?

Primary stability is absence of mobility in the bone bed after mini-implant placement and depends on bone quality among other factors. Bone quality is a subjective term frequently considered as bone density. The aim of this preliminary study was to evaluate bone density in two bovine pelvic regions and verify the primary stability of miniscrews inserted into them. Forty bone blocks were extracted from bovine pelvic bones, 20 from iliac and 20 from pubic bone, all of them containing cortical bone about 1 mm thick. Half of the sections extracted from each bone were designated for histological evaluation of bone density (trabecular bone area - TBA) and the other half for bone mineral density (BMD) evaluation by means of central dual-energy X-ray absorptiometry (DEXA). Then, twenty self-drilling miniscrews (INP?, S?o Paulo, Brazil) 1.4 mm in diameter and 6 mm long were inserted into the bone blocks used for BMD evaluation. Peak implant insertion torque (IT) and pull-out strength (PS) were used for primary stability evaluation. It was found that iliac and pubic bones present different bone densities, iliac bone being less dense considering BMD and TBA values (P > 0.05). However, the miniscrew primary stability was not different when varying the bone type (P < 0.05). IT and PS were not influenced by these differences in bone density when cortical thickness was about 1 mm thick.