天然牙-种植体联合桥上部结构应力分布的三维有限元分析

目的 揭示天然牙—种植体联合桥在咀嚼过程中上部结构应力的分布规律，为临床设计该种类固定桥提供理论参考依据。方法 借助于CT扫描和计算机辅助设计手段，用三维有限元方法对天然牙一种植体联合固定桥在不同载荷下，上部结构的应力分布差异以及位移变化进行生物学分析。结果 种植体基台在斜向载荷下的最大应力值是垂直载荷下的4～6倍，且应力分布不均，有应力集中现象，以压应力为主。桥体He面的应力峰值在集中载荷下是分散载荷下的数倍，He面中1／3出现力点高度集中的压应力区，但载荷方向对其无影响。种植体基台在近远中向的最大位移明显大于天然牙颈部，固定桥整体移动方向是朝着天然牙运动。结论 天然牙—种植体联合桥可通过减少斜向力和集中力或提高基台的结构强度及桥体材料的抗挠曲强度，防止上部结构机械并发症的发生。这种固定桥是可行的。     

天然牙一种植体联合支持固定桥对种植体周骨组织应力的影响

目的 不同桥体长度结构下天然牙－牙种植体联合支持固定桥中种植体周骨组织的应力反应特点。方法 采用三维有限元方法建立不同桥长的固定桥力学模型计算分析。结果 天然牙－牙种植体联合支持固定桥中种植体颈部周围骨应力最大;长桥体固定桥在集中斜向载荷作用下种植体颈缘骨最大应力是集中垂直载荷下种植体周骨最大就力的3倍,桥体长度增加,应力值增加。结论 桥体长度对种植修复体应力分布有显著影响,桥体长度增加导致牙种植体及其周围骨应力集中程度增大,对其破坏作用增强,因此临床设计桥体不宜过长。     

种植体与天然牙联冠修复应力分布的三维有限元分析I．垂直集中载荷对种植体、天然牙骨界面应力的影响

目的：探讨种植体与天然牙联冠修复在垂直集中载荷作用下,种植体、天然牙骨界面应力分布情况及受力的相互影响,为临床优化设计提供生物力学的理论依据。方法：采用三维有限元法建立模型并计算、分析。结果：种植体与天然牙联冠修复时,种植体、天然牙骨界面颈部和根尖部出现应力集中;种植体与稳定的天然牙联合修复时种植体－骨界面应力分布较均匀。结论：种植体与天然牙可共同承担载荷;当天然牙受垂直集中载荷时,种植体未过载;种植体最好与稳定的天然牙联合修复。     

种植体-天然牙半固定桥的制作

种植体-天然牙半固定桥是指桥体一端是以天然牙为基牙，另一端是由种植体支持的联合固定修复体。由于种植体的愈合方式为骨结合，与机体组织之间缺乏牙周膜，没有生理动度，承受负荷能力较差，咬合时易对种植界面造成应力及集中，导致创伤和骨组织吸收，影响种植义齿的远期修复效果。因此，桥体的种植体侧的连接体常设计成附着体装置进行应力缓冲。     

种植体与天然牙在上颌骨复合体中应力的比较

目的：比较种植体与天然牙在上颌骨复合体中在垂直和水平载荷下的应力分布。方法：采用三维有限元法。结果：种植体与天然牙上颌骨复合体相同牙位、相同载荷下应力分布趋势相同，力的大小比较接近，垂直载荷下种植体周围应力大于天然牙。结论：骨结合种植体虽然没有牙周膜的缓冲，但其与骨连成整体，可有效地传递应力，骨结合种植体在上颌骨种植具有力学可行性。     

种植体与天然牙联合支持固定桥桥体长度的应力分析

目的 研究种植体与天然牙联合支持固定桥在不同桥体长度下的应力分布情况.方法 利用三维有限元法,建立三种桥体长度的种植体与天然牙联合支持固定桥有限元模型,进行计算分析.结果 种植体与天然牙联合支持固定桥的最大应力值位于种植体、天然牙及其周围骨组织的颈缘部位;分散斜向加载时,种植体颈缘处及其周围骨组织的最大应力值是分散垂直载荷下最大应力值的两倍以上,表现出明显的应力分布不均;无论基牙还是周围骨组织,最大应力值在桥体加长时均有明显增加.结论 种植体与天然牙联合支持固定桥主要支撑力的部位是颈缘处,桥体长度设计以一个单位以内为宜.     

下颌骨典型牙位圆柱状牙种植体周围骨应力分布的三维有限元分析

目的：生理加载下不同牙位种植体周围骨应力有明显差异，采用有限方法计算，其结果是种植体设计和临床使用的重要依据，但可靠性依赖于模型和加载条件的准确性。方法：本文基于下颌骨四个典型牙位的CT数据，结合各牙位咬舍关系的测量结果，建立了三维有限元模型，并对圆柱状种植体周围骨的应力分布进行有限元分析：结果：种植体沿长轴植入时。各牙位应力分布差异较大，颊、舌侧应力分布明显不对称，应力均主要集中在种植体颈部与牙槽骨界面顶端的舌侧，且舌侧极大值为颊侧的2～3倍：结论：在种植体一骨界面上的最大应力不超过20MPa的条件下，各牙位能承受的最大袷力分别为：第二磨牙100N、第二前磨牙300N、尖牙180N、中切牙120N。第二磨牙采用牙槽骨垂直方向植入时，可承受约250N的He力.     

不同载荷下天然牙一种植牙联合桥基牙应力分布

目的：揭示天然牙一种植体联合支持固定桥在不同载荷下基牙的应力反应规律,指导临床优化设计。方法：采用三维有限元方法建模计算、分析。结果：斜向载荷下种植体的最大应力值是天然牙的2－2．5倍,集中斜向载荷与分散斜向载荷下种植体最大应力值无明显差异,是垂载荷下种植最大应力值2－2．5倍。集中垂直载荷下天然牙、种植体的最大应力值高于分散垂直载荷下的最大应力值,天然牙集中斜向载荷下最大应力值大于分散斜向载荷下的最大应力值。结论：天然牙一种植体联桥受侧向力的能力弱,种植体应具有高强度,天然牙根应粗大,减小侧向力,集中载荷比分散载荷破坏作用大,桥体与基牙的He面咬合接触点分布均匀,建立多点咬合接触。     

天然牙—种植体共同支持式固定义齿的生物力学研究I.垂直集中载荷对种植体、天然牙骨界面应力的影响

目的：通过对天然牙-种植体共同支持式固定义齿受垂直集中载荷时，种植体、天然牙骨界面应力分布情况进行测试，为临床能否使用该方式修复牙列缺损提供生物力学的理论依据。方法：应用电阻应变计电测技术的方法。结果：天然牙-种植体共同支持式固定义齿修复时，在垂直集中载荷下，随着载荷的不断加大，天然牙-种植体与骨组织界面处的应力值不断加大，最大应力出现在种植体、天然牙根颈部区，种植体与稳固的天然牙共同支持式固定修复时，天然牙与骨界面应力分布较均匀。结论：从生物力学的角度来看，在优化临床设计的前提下，天然牙-种植体共同支持式固定义齿是临床可采用的特殊固定义齿，尤其适用于末端游离缺牙的患者。     

天然牙——末端骨内种植体固定桥的临床修复设计

目的：讨论游离端由种植体和天然牙支持的桥体的修复设计。方法：１６例磨牙缺失牙患者植入３４枚两段式种植体，修复３２个缺失后牙，采用天然牙－末端骨种植体上端烤瓷固定桥修复体的设计。结果：经定期复诊随访，追踪临床观察２年，其中１例因种植体颈部螺栓折断而失败。１例因种植体松动而拔除外，其余取得良好效果（８７．５％）。结论：天然牙－末端骨内种植体混合支持上部固定修复设计是可行的，但是应充分考虑种植体所在的颌     

不同连接设计种植全口义齿的三维光弹应力分析

目的：研究常规半口义齿、种植杆卡覆盖义齿及种植固定义齿在牙合力作用下其支持组织——牙槽骨及种植体周围的应力分布状况。方法：用三维光弹应力冻结切片法,对在牙合力作用下的应力状况进行应力冻结,并分别在切牙区、尖牙区、前磨牙区、第一磨牙区、第二磨牙区作３ｍｍ厚切片;并在４颗种植体周围作包含种植体的５ｍｍ厚切片,分析其内部的应力分布状况。结果：种植覆盖义齿的种植体周围骨界面,牙槽骨的应力值均比常规义齿及种植固定义齿低,无论是哪种形式的种植义齿,都易发生远中种植体受力过大而松动。结论：种植覆盖义齿具有良好的力学特性;在义齿设计时应采取措施保护远中种植体。     

Analysis of stress on a fixed partial denture with a blade-vent implant abutment.

Using a two-dimensional finite element method, a study was made that compared the behavior of a model mandibular posterior fixed partial denture constructed on the second premolar abutment and a blade-vent implant imbedded at the site of the second molar with the behavior of a fixed partial denture constructed on the second premolar and second molar abutments. The following were the results: 1. Deflections of the implant fixed partial denture were less than those of the natural tooth fixed partial denture in vertical and inclined loads. 2. Stress concentration was markedly found in the pontic and the mesial and distal parts of the premolar retainer in both restorations and the implant neck in the implant fixed partial denture. 3. In the implant fixed partial denture, stresses induced in the surrounding bone became higher around the posterior abutment and became lower around the premolar retainer than the stresses produced with the natural tooth fixed partial denture. 4. Therefore it was suggested that, to relieve stress to the surrounding bone around the implant abutment, occlusal forces loaded to the implant fixed partial denture have to be more concentrated on the premolar abutment than do forces loaded to the natural tooth fixed partial denture.     

垂直负荷对种植体边缘骨应力分布的影响

目的　比较不同部位施加不同的垂直负荷对种植体边缘骨的应力分布的影响。方法采用电阻应变片法测试单个种植牙和 2个种植体支持的固定桥在垂直负荷时种植体边缘骨的应力。结果　负荷大小、负荷点以及二者的交互作用都可影响应力分布。单个种植牙的应力集中在种植体的颈部和根尖部 ,2个种植体支持的固定桥应力易集中在种植体近负荷点侧的根尖部、颈部 ,尤其是近负荷点的种植体。在游离端施加负荷时 ,应力与负荷大小、悬臂长度成正比。结论　减小咬合力、避免使用游离端种植义齿可以减小种植体边缘骨的应力 ,尤其是远中种植体。     

Nonlinear finite element analysis of a splinted implant with various connectors and occlusal forces

PURPOSE: The aim of this study was to analyze the biomechanics in an implant/tooth-supported system under different occlusal forces with rigid and nonrigid connectors by adopting a nonlinear finite element (FE) approach. MATERIALS AND METHODS: A model containing 1 Frialit-2 implant (placed in the second molar position) splinted to the mandibular second premolar was constructed. Nonlinear contact elements were used to simulate a realistic interface fixation between the implant body and abutment screw and the sliding keyway stress-breaker function. Stress distributions in the splinting system with rigid and nonrigid connectors were observed when vertical forces were applied to the tooth, pontic, implant abutment, or complete prosthesis in 10 simulated models. RESULTS: The displacement obtained from the natural tooth increased 11 times than that of the implant, and the peak stress values within the implant system (sigmaI, max) increased significantly when vertical forces acted only on the premolar of a fixed prosthesis with a rigid connector. The sigmaI, max values seen in the splinting prosthesis were not significantly different when vertical forces (50 N) were applied to the pontic, molar (implant) only, or the entire prosthesis, respectively, regardless of whether rigid or nonrigid connectors were used. Moreover, the peak stress values in the implant system and prosthesis were significantly reduced in single- or multiple-contact situations once vertical forces on the pontic were decreased. DISCUSSION: The compensatory mechanism between the implant components and keyway sliding function of the implant/tooth-supported prosthesis could be realistically simulated using nonlinear contact FE analysis. The nonrigid connector (keyway device) significantly exploited its function only when the splinting system received light occlusal forces. CONCLUSION: Minimization of the occlusal loading force on the pontic area through occlusal adjustment procedures to redistribute stress within the implant system in the maximum intercuspation position for an implant/tooth-supported prosthesis is recommended.     

Finite element analysis on dental implant–supported prostheses without passive fit

PURPOSE: The purpose of this study is to use finite element analysis to investigate the effect of misfit prostheses, cantilever prostheses, and various occlusal forces on the stress distribution in the prostheses, implant components, and surrounding bone. MATERIALS AND METHODS: Two 3-dimensional finite element models were constructed: (1) a 2-implant-supported, 2-unit fixed partial denture and (2) a 2-implant-supported, 2-unit fixed partial denture with a distal cantilever. Variations of the standard finite element models were made by placing a 111-microm gap between the gold cylinder on either the mesial or distal implant. The effects of load of 100 N were tested on all models. Subsequently, loads of 50 N, 200 N, and 300 N were evaluated on the cantilever model. RESULTS: When the gap was positioned near to the applied force, the stress in both models increased significantly in the implant components and surrounding bone. The stress increase in each component ranged from 8% to 64% in the non-cantilever models and 43% to 85% in the cantilever models. The greatest stress was found in the distal gold screw. The effect of the gap was clearly shown by the pattern of stress distribution in both models. Additionally, the presence of a cantilever and excessive occlusal force amplified the effect of prosthesis misfit. CONCLUSIONS: Prosthesis misfit influenced the pattern and magnitude of stress distribution in the prosthesis, implant components, and surrounding bone, and the presence of the cantilever or greater occlusal force amplified the effect of misfit.     

桥基牙为种植牙与天然牙时的固定修复对种植体稳定性的影响探讨

目的:探讨种植牙与天然牙联合作为桥基牙的固定修复对种植体稳定性的影响。方法:对2001年到2007年就诊于口腔科的42例进行种植修复的患者,考虑到患者的口腔条件、缺牙数目的多少、经济条件、对义齿的要求等因素,调整种植体与天然牙的距离,然后进行种植牙与天然牙联合作为桥基牙的固定修复方式进行修复。结果:当种植体与天然牙相近时,易导致种植体的松动;当种植体与天然牙相远时,不会导致种植体的松动。结论:种植体远离天然牙设计固定修复是可行的。     

栓道式混合支持型种植固定义齿

由于种植体与自然牙支持组织的差异，种植学界对自然牙和种植体混合支持式固定义齿有较多争议。作者在自然牙人造冠设计栓体，在种植体支持的冠式桥体上设计栓道。种植义齿通过栓体栓道与自然基牙上的人造冠形成混合支持式义齿。当义齿承负力时，自然基牙与种植义齿又可有相对独立运动，使应力中断。临床应用表明，这种设计可以有效地解决自然牙和种植体支持组织的不均衡及在力作用下弹性变形不均衡，导致自然基牙松动，及种植体骨界面损害的问题；又可使义齿保持可折邻结构，便于种植体的清洁和护理。作者认为这种混合支持式义齿的咬合面颊舌径应为自然牙列的３／５至２／３为宜。     

Comparative evaluation of peri-implant stress distribution in implant protected occlusion and cuspally loaded occlusion on a 3 unit implant supported fixed partial denture: A 3D finite element analysis study

PURPOSETo assess peri-implant stress distribution using finite element analysis in implant supported fixed partial denture with occlusal schemes of cuspally loaded occlusion and implant protected occlusion.MATERIALS AND METHODSA 3-D finite element model of mandible with D2 bone with partially edentulism with unilateral distal extension was made. Two Ti alloy identical implants with 4.2 mm diameter and 10 mm length were placed in the mandibular second premolar and the mandibular second molar region and prosthesis was given with the mandibular first molar pontic. Vertical load of 100 N and and oblique load of 70 N was applied on occlusal surface of prosthesis. Group 1 was cuspally loaded occlusion with total 8 contact points and Group 2 was implant protected occlusion with 3 contact points.RESULTSIn Group 1 for vertical load , maximum stress was generated over implant having 14.3552 Mpa. While for oblique load, overall stress generated was 28.0732 Mpa. In Group 2 for vertical load, maximum stress was generated over crown and overall stress was 16.7682 Mpa. But for oblique load, crown stress and overall stress was maximum 22.7561 Mpa. When Group 1 is compared to Group 2, harmful oblique load caused maximum overall stress 28.0732 Mpa in Group 1.CONCLUSIONIn Group 1, vertical load generated high implant stress, and oblique load generated high overall stresses, cortical stresses and crown stresses compared to vertical load. In Group 2, oblique load generated more overall stresses, cortical stresses, and crown stresses compared to vertical load. Implant protected occlusion generated lesser harmful oblique implant, crown, bone and overall stresses compared to cuspally loaded occlusion.     

Photoelastic stress analysis of implant-tooth connected prostheses with segmented and nonsegmented abutments

STATEMENT OF PROBLEM: There is some question about whether implant abutment selection affects the transfer of load between connected implants and natural teeth. PURPOSE: The purpose of this study was to compare stress transfer patterns with either 1 or 2 posterior implants connected to a single anteriorly located simulated natural tooth with either 1 or 2 segmented and nonsegmented implant abutments under relevant functional loads by use of the photoelastic stress analysis technique. MATERIAL AND METHODS: A model of a human left mandible, edentulous posterior to the first premolar, with two 3.75-mm x 13-mm screw-type implants embedded within the edentulous area, was fabricated from photoelastic materials. The implants were in the first and second molar positions. Two fixed partial denture prosthetic restorations were fabricated with either segmented conical abutments or nonsegmented UCLA abutments. Vertical occlusal loads were applied at fixed locations on the restorations. The photoelastic stress fringes that developed in the supporting mandible were monitored visually and recorded photographically. The stress intensity (number of fringes), stress concentrations (closeness of fringes), and their locations were subjectively compared. RESULTS: Loading on the restoration over the simulated tooth generated apical stresses of similar intensity (fringe order) at the tooth and the first molar implant for both abutment types. Low-level stress was transferred to the second molar implant. Loading directed on the implant-supported region of the restoration demonstrated low transfer of stress to the simulated tooth. Nonvertical stress transfer with slightly higher intensity was observed for the nonsegmented abutment. CONCLUSION: Within the limitations of this simulation study, stress distribution and intensity for the 2 implant conditions was similar for segmented and nonsegmented abutment designs. Magnitude of stresses observed for both abutment designs was similar for the single implant condition. Vertical loading produced more nonaxial stresses away from the force applied for the 1 implant condition with the nonsegmented abutment. Direct loading results were similar for both abutment designs. Specific recommendations for selection of implant abutment and application should be based on clinical criteria.