Impact of dental and zygomatic implants on stress distribution in maxillary defects: a 3-dimensional finite element analysis study

The aim of this study was to evaluate the stress distribution in the bone around dental and zygomatic implants for 4 different implant-supported obturator prostheses designs in a unilaterally maxillary defect using a 3-dimensional finite element stress analysis. A 3-dimensional finite element model of the human unilateral maxillary defect was constructed. Four different implant-supported obturator prostheses were modeled; model 1 with 2 zygomatic implants and 1 dental implant, model 2 with 2 zygomatic implants and 2 dental implants, model 3 with 2 zygomatic implants and 3 dental implants, and model 4 with 1 zygomatic implant and 3 dental implants. Bar attachments were used as superstructure. A 150-N vertical load was applied in 3 different ways, and von Mises stresses in the cortical bone around implants were evaluated. When the models (model 1-3) were compared in terms of number of implants, all of the models showed similar highest stress values under the first loading condition, and these values were less than under model 4 conditions. The highest stress values of models 1-4 under the first loading condition were 8.56, 8.59, 8.32, and 11.55 Mpa, respectively. The same trend was also observed under the other loading conditions. It may be concluded that the use of a zygomatic implant on the nondefective side decreased the highest stress values, and increasing the number of dental implants between the most distal and most mesial implants on the nondefective side did not decrease the highest stress values.     

二单位式与四单位式种植牙周骨界面应力分布规律差异的三维有限元分析

为了探讨人工种植牙的数目、上部结构对种植牙周骨界面应力分布的影响，本实验应用三维有限元分析方法，对二单位和四单位式杆式覆盖种植义齿种植牙周骨界面的应力分布规律进行了探讨。结果表明：最大压应力、最大拉应力二单位式与四单位式均位于颈周密质骨，二单位式大于四单位式，两者有显著差异性，（Ｐ＜０．００１）。四单位式最大拉、压应力，远中种植牙要大于近中种植牙。最大位移运动二单位式小于四单位式，四单位式近中种植牙大于远中种植牙。二单位式与四单位式位、压应力主要集中于颈部，其它部位与颈部相比有非常显著的差异性，（Ｐ＜０．０００１）。结论：种植牙数目的增加，可以减小种植牙周颈部密质骨内的最大应力值。四单位式种植义齿颈周骨内应力要小于二单位式种植牙，从这点上看，四单位式种植义齿要优于二单位式种植义齿。多个种植牙种植时，杆的连接，改变了种植牙周骨内的应力分布规律，其应力主要由种植牙颈周密质骨来承担     

Mode superposition transient dynamic analysis for dental implants with stress-absorbing elements: a finite element analysis

The purpose of this study was to analyze the dynamic behavior of a dental implant with a stress-absorbing element, using dynamic analysis. Two model types, stress-absorbing model with a resilient stress absorber made of polyoxymethylene and non-stress-absorbing model with rigid titanium, were employed. In both model types, the implant was 4.0 mm in diameter and 13.0 mm in length and placed in the mandibular first molar region. Shapes of the finite element implant and implant-bone were modeled using computer-aided design. All calculations for the dynamic analysis were performed using the finite element method. It was found that the stress-absorbing model had a lower natural frequency than the non-stress-absorbing model. In addition, the stress-absorbing model had a higher damping effect than the non-stress-absorbing model. It was concluded that mode superposition transient dynamic analysis is a useful technique for determining dynamic behavior around dental implants.     

基于FEA的种植体个性化选择及力学性能评价

目的:使用有限元方法进行个性化种植体分析,为医师选择适合的种植体形态提供参考依据。方法:通过自行开发的口腔虚拟种植系统重建患者颌骨模型,并选择相应种植体进行虚拟种植以模拟各颌牙缺损状态下种植体植入的位置及方向,利用FEA分析咀嚼运动中不同种植体产生的应力分布,同时进行力学性能评价。结果:实现了口腔种植体的个性化选择方案。结论:所提出的口腔种植力学性能评价方法,能够从应力角度为医师选择种植体形态提供参考依据。     

种植牙即刻负载与延期负载的生物力学三维有限元分析

目的比较即刻负载和延期负载对种植体骨界面生物力学分布的影响。方法采用CT扫描和自主开发的USIS软件建模,用有限元法计算分析即刻负载和延期负载时种植体骨界面的应力、应变及种植体的位移。结果即刻负载时种植体骨界面的VonMises应力稍小于延期负载,均集中于种植体颈部骨皮质,底部骨松质次之;但VonMises应变有较明显的增加,均集中于种植体底部骨松质和螺纹部位;种植体的位移较延期负载略有增大。即刻负载种植体和延期负载种植体在受到颊舌向力时,VonMises应力、应变及位移均有不同程度的增加。结论即刻负载时种植体骨界面的生物力学分布规律与延期负载时相似,受到侧向力时应力、应变增大。种植牙即刻负载技术是可行的。     

下颌骨各向异性材质模型对种植牙有限元分析的影响

目的 建立含螺纹种植体各向异性的完整下颌骨有限元模型,研究各向异性材质模型模拟对牙种植体有限元分析的影响.方法 采用薄层CT扫描和自主开发的软件分别建立各向异性和等效各向同性的完整下颌骨三维有限元模型,其中在后牙区植入两枚牙种植体,分析在颊舌向、斜向加载时,种植体-骨界面主应力和主应变值的变化.结果 在各向异性下颌骨模型中,除骨皮质第一最小主应力减小6.3%～7.6%和骨松质第三最小主应力减小8.7%～46.0%外,骨界面绝大多数主应力和所有主应变值均大于各向同性;骨皮质主应力增加2.1%～74.1%,主应变增加4.7%～57.3%;骨松质主应力增加10.3%～71.4%,主应变值增加19.5%～63.4%,而且骨松质应力的增加比骨皮质明显.结论 下颌骨种植牙有限元分析时,下颌骨各向异性模拟会明显影响骨界面应力和应变值,并以增加为主.在生物力学研究中应更注重下颌骨各向异性的材质力学特性.     

Analysis of stress and strain around orthodontically loaded implants: an animal study

PURPOSE: The aim of this study was to describe the stress and strain fields around orthodontically loaded dental implants using the finite element method and to evaluate the relationship between the generated strain and the biologic reaction expressed through histomorphometric parameters. Finally, this study aimed to evaluate the interaction between the orthodontic loading and the deformation generated by normal occlusal function. MATERIALS AND METHODS: Sixteen titanium dental implants were inserted in extraction sockets after the removal of the second premolars and first molars of 4 adult Macaca fascicularis monkeys. After 17 weeks of healing, the implants were loaded by a pair of Sentalloy springs (50 cN) for 16 weeks. After sacrifice, tissue blocks including the implants and surrounding bone were excised. Five tissue blocks were scanned with a synchrotron radiation-based microtomography (microCT) scanner and sample-specific finite element models were generated. Subsequently all samples were prepared for histomorphometric analysis. RESULTS: All implants were osseointegrated, although the surrounding alveolar bone differed from sample to sample. As a consequence the finite element analyses showed that the stresses and strains in the peri-implant alveolar bone greatly varied among the samples. A high level of remodeling activity was found close to the implants. Discussion: Individual differences between the receptors (in this case, the monkeys) have a large effect on both the biologic and morphologic parameters. These variations were indeed found to have a substantial impact on the (re)modeling dynamics and the load transfer mechanisms around the implants. CONCLUSIONS: By integrating different analysis techniques to evaluate bone (re)modeling around orthodontically loaded implants, this study has demonstrated the complexity and case-specific character of alveolar adaptation to orthodontic loading. Furthermore, stresses generated by combined functional and orthodontic forces should not be neglected.     

种植体穿通下颌骨对骨界面应力分布的影响

目的：为了探讨下颌种植牙穿通下颌骨后对骨界面应力分布的影响。方法：采用三维有限元方法,通过单个穿下颌螺旋型种植体的种植,了解穿下颌种植后对骨界面应力分布的影响。结果：穿下颌种植减小了颈周密质骨内的应力,加大了根端侧穿下颌骨下缘处的应力,减小了骨界面的位移。结论：穿下颌种植,改变了骨界面的最大应力分布部位,使最大应力位于根端侧下颌骨下缘处。     

上切牙区双端悬臂梁种植固定桥的应力分析

目的：通过分析双端悬臂梁种植义齿修复上颌切牙区牙列缺损的种植体在不同加载条件下的周围骨应力分布及位移量,进而探讨临床修复的可行性。方法：应用CT断层扫描技术对上颌骨及上颌牙列的大致轮廓进行三维重建,后于上中切牙区植入种植体,完成牙冠修复并建立模型。通过三维有限元技术模拟载荷,比较不同加载条件下种植体的周围骨组织应力分布及位移量。结果：经统计学分析,种植体-骨界面的皮质骨唇侧、舌侧、近中、远中、根尖部五个部位应力值的差异有统计学意义（P〈0.001）,五个部位的位移量的差异也有统计学意义（P〈0.001）。模型在各种加载条件下的应力分布及位移量的特征大致相同,且变化趋势相似,种植体颈部及周围骨皮质为应力集中区。在各种不同的加载条件中,30°加载角度时种植体周围骨应力分布更为科学。结论：在适当的负重条件下,双端悬臂梁种植义齿是临床修复切牙区缺失可供选择的一种设计方案。     

下颌牙种植体即刻加载三维有限元模型的建立

目的:建立包含即刻加载螺纹种植体的下颌骨三维有限元模型,以深入研究牙种植体即刻加载骨界面的力学分布规律。方法:以女性无牙牙合下颌骨为标本,采用螺旋CT扫描,DICOM格式保存。将DICOM数据导入计算机,用自主开发的通用外科手术集成系统(UniversalSurgicalIntegrationSystem,USIS)和ANSYS软件进行划分单元建模,并模拟ITI螺纹种植体的真实形态,在下颌骨前牙区植入3颗种植体,模拟种植体即刻加载的状态,将种植体骨界面定义为滑动摩擦。结果:建立了结构精确的含即刻加载螺纹种植体的下颌骨三维有限元模型,牙种植体螺纹螺旋形态连续一致。结论:本实验建立的有限元模型的几何相似性、生物力学相似性及临床适应性均达到实验要求,为进一步研究牙种植体即刻加载的骨界面力学分布提供了良好的基础。     

A biomechanical study of the mechanical stress transmission of dental implants using finite element analysis. Part II. Experiments

In the first part of this two-part study the possible uses of finite element analysis in studying the stress transmission of dental implants were reviewed. In the present second part our own experiments are presented. In the first series the effect of the geometric parameters and load types on mechanical stresses arising around cylindrical implants in bone were studied with 2D and 3D finite element analysis. In the second series the stress transmissions of various implant geometries were compared and an attempt was made to determine the optimal implant shape from the point of view of stress transmission.     

带凹槽螺纹种植体三维有限元模型的建立

目的：利用CAD软件的自适应功能建立包含Branemark TiUniteTM型带凹槽种植体骨块三维有限元模型。方法：应用pro/E软件根据种植体相关参数,建立牙种植体、冠修复体、松质骨和皮质骨三维实体模型,利用自适应功能生成装配体,导入Ansys Workbench10.0CAE软件中,进行单元划分建立有限元模型,应力加载后进行模型准确性的检测。结果：建立了包含真实螺纹种植体的下颌骨骨块三维有限元模型。结论：应用Pro/E软件自适应功能建立包含种植体的下颌骨骨块的三维有限元模型,为种植修复三维有限元分析提供了一种准确、灵活、快速的平台。     

种植牙即刻负重的生物力学的三维有限元分析

目的 用三维有限元的方法分析牙种植体不同角度即刻负重的骨界面应力分布规律.方法 选成人无牙下颌骨进行薄层螺旋CT扫描,将扫描图像导入通用外科手术集成系统,建立下颌骨三维网格模型.模拟标准的螺纹实心种植体,建立种植体一下颌骨即刻负重的三维有限元模型.以150 N的力轴向加载和分别10.、20.、30.侧向加载,应用ANS...     

Effects of overdenture attachment systems with different working principles on stress transmission: A three-dimensional finite element study

PURPOSEThe aim of the present study was to compare the stress distributions on the dental implants, abutments, and bone caused by different overdenture attachment types under functional chewing forces.MATERIALS AND METHODSThe 3D finite element models of the mandible, dental implants, attachment types, and prostheses were prepared. In accordance with a conventional dental implant supported overdenture design, the dental implants were positioned at the bone level in the canine teeth region bilaterally. A total of eight models using eight different attachment systems were used in this study. All the models were loaded to simulate chewing forces generated during the centric relationship (450 N), lateral movement (400 N), protrusive movement (400 N), and also in the presence of a food mass unilaterally (200 N). Stress outputs were obtained as the maximum principal stress and the equivalent von-Mises stress.RESULTSIn all attachment types, higher stress values were observed in the abutments, dental implants, and bone in the magnet attachments in different loading conditions. The highest stress values were observed among the magnet systems in the components of the Titanmagnetics model in all loading conditions (stresses were 15.4, 17.7, and 33.1 MPa on abutment, dental implant, and bone, respectively). The lowest stress value was observed in the models of Zest and O-Ring attachments.CONCLUSIONThe results of the present study implied that attachment types permitting rotation and tolerating various angles created lower stresses on the bone, dental implants, and abutments.     

Osstell^TM换能器变幅杆方向对牙种植体扭转振动行为影响的三维有限元研究

目的：利用三维有限元分析方法,研究Osstell^TM换能器变幅杆方向对牙种植体扭转振动行为的影响。方法：采用UGS NX和ANSYS软件建立骨-种植体-换能器系统三维有限元模型,分析Osstell^TM换能器变幅杆方向对牙种植体扭转振动模态、共振频率及整个系统变形程度的影响。结果：4种骨质类型中换能器变幅杆在0°～90°不同方向影响下,扭转振动模态共振频率增加趋势较弱,而种植体、骨块的最大位移呈明显减小趋势。结论：Osstell^TM换能器变幅杆方向变化对骨-种植体-换能器系统扭转振动共振频率的影响不明显,而当换能器变幅杆垂直于牙槽嵴长轴时,扭转振动行为对骨块和种植体变形的影响较小。     

牙种植体的生物力学研究

目前牙种植体的生物力学研究主要集中于种植体-骨结合界面及种植牙内各个部件连接界面的力学损伤及增强机制,以及如何获得更好的牙种植体-基台复合体的整体机械强度和服役寿命等方面的研究。目前有关生物力学的研究,主要通过电阻应力测试方法、光弹应力分析法、数字图像相关分析法、有限元分析法、种植体-骨结合强度力学测试和机械性能测试法对实验样本进行综合评价。目前有限元分析法是最常见的牙种植体应力分布研究法,而静态压力实验和疲劳实验是最常见的机械强度测试研究方法。本文通过对这些研究方法的原理、应用范围及特点的介绍和对实验结果影响因素的梳理,给相关领域研究者们提供方法学的指导,并可拓展种植体的设计思路。     

隧道开放式种植模板的制作与应用

目的:观察隧道开放式模板在牙种植手术中的作用。方法:对13例缺牙患者取模后灌制工作模型,雕蜡牙,恢复牙列的完整性,在蜡牙上制作开放式植入隧道;二次取模灌模型后,采用热压成型技术制作隧道开放式模板。手术时按隧道方向钻孔并植入种植体。结果:12例患者的工作模型及X线片显示,植入位置和方向与预定方向基本一致,并取得了较好的修复效果。结论:使用隧道开放式种植模板,能使术者较准确地把握牙种植体植入的位置与方向,制作简单,使用方便。     

A comparison of three finite element models of an edentulous mandible provided with implants

The stress distribution in an edentulous mandible provided with two implants in the interforaminal region was calculated by means of three different finite element models. The implants were connected with a bar or remained solitary. The first model was a three-dimensional representation of the entire mandible, the second model of the interforaminal region of this same mandible, whilst the third model was a two-dimensional representation of the interforaminal region. The differences in stress distribution around the connected implants and the solitary implants between these three models were analysed.
It can be concluded that for a parameter study the stress distribution around the dental implants following from a three-dimensional finite element model of only the interforaminal region of an edentulous mandible can be used. For such studies therefore, benefit can be gained from the advantages of reduced modelling and calculation time.     

人工种植牙直径对骨界面应力分布的影响

本文应用二维有限元方法，对３ｍｍ、４ｍｍ、５ｍｍ三种不同直径的螺旋型种植牙进行了对比分析，实验结果表明：螺旋型种植牙直径的增加，对骨界面的总体应力分布规律影响不大，应力值均以根端部皮质骨为最大，其次为根侧部皮质骨，再以颈部皮质骨，最小的为松质骨，但随着种植牙直径的增加，各部位骨界面应力随之降低，种植牙－骨界面的相对位移运动也相应减小，有利于骨界面的应力分布。提示临床种植时，根据颌骨的具体解剖形态，尽可能选择直径稍粗一些的种植牙，可减小骨界面的应力分布及位移运动，取得更好的临床种植效果。     

The implant neck: smooth or provided with retention elements. A biomechanical approach.

A combined three-dimensional and axisymmetric finite element analysis was made of the effect upon the peak interfacial shear stress of providing an axially loaded mandibular dental implant with retention elements all the way up to the crest of the implant as opposed to a smooth neck. The effect of increased wall thickness of the implant and of using bi-cortical fixation as opposed to unicortical fixation was also studied. Retention elements at the implant neck were found to bring about a major decrease in the peak interfacial shear stress. Increased wall thickness and bi-cortical fixation also resulted in decreased peak interfacial shear stress but this effect was minor. The interpretation of this was that all these three measures increase the capacity of the implant to carry axial loads. Thus from a biomechanical viewpoint it appears to be advantageous to provide the neck of screw-shaped implants with retention elements, for example a rough surface of suitable micro-architecture and/or a microbhyphen;thread. It is furthermore suggested that retention elements at the implant neck will counteract marginal bone resorption in accordance with Wolff's law. This paper is a revision of: Hansson, S. (1997) Some steps to improve the capacity of dental implants to resist axial loads. In: Hansson, S., ed. Towards an optimized dental implant and implant bridge design: A bio-mechanical approach. Thesis. Göteborg; Chalmers University of Technology.