天然牙-种植体联合支持式义齿的应力分析

目的:比较以常规固定桥、固定式套筒冠和CEKA冠外精密附着体为上部结构的天然牙-种植体联合支持义齿的应力分布情况,寻求联合支持义齿上部结构的优化设计方案。方法:利用ANSYS三维有限元法,建立下颌右侧第一磨牙缺失、以下颌第二前磨牙和种植体(位于下颌第二磨牙)联合支持局部固定义齿的三维有限元模型,采用分散垂直和分散斜向(45°)两种加载方式(总加载力200N)。结果:2种加载条件下,固定式套筒冠和CEKA附着体都明显降低了种植体和天然牙周围骨组织的应力,垂直加载时,前者应力值低于后者;斜向加载时,后者低于前者,但后者会使天然牙局部应力有所增加。斜向加载时,种植体及其周围骨组织和天然牙及其周围骨组织的应力值均大于垂直加载条件下的应力值。结论:固定式套筒冠和CEKA附着体均能改善联合支持义齿的应力分布,CEKA附着体对侧向力的缓冲作用较优。     

种植体-基台连接形式对种植体周围骨组织应力分布的影响

目的分析种植体-基台连接形式对种植体周围骨组织应力分布的影响，从生物力学角度探讨平台转换连接形式防止或减少种植体周围骨吸收的可能机制。方法利用COSMOSM2．85软件包建立种植体支持的下颌第一磨牙三维有限元模型，种植体-基台的连接形式分别采用平齐对接（模型A）和平台转换（模型B）。采用垂直和斜向两种形式加载，载荷均为200N，比较两种模型种植体周围骨组织的应力分布情况以及种植体-骨界面颊舌侧相同位置的von Mises应力大小。结果不同加载条件下两种模型种植体周围骨组织应力集中在种植体颈部颊舌侧骨皮质内，斜向加载时最大von Mises应力值高于垂直加载时。模型A和模型B骨组织内最大von Mises应力值在垂直加载时，分别为11．61MPa和7．15MPa，斜向加载时分别为22．07MPa和11．87MPa。距离种植体-基台连接处越远，von Mises应力值越小，骨皮质到骨松质交界处的应力变化最明显。与模型A相比，模型B种植体-骨界面相同节点的最大von Mises应力值较小。结论与平齐对接形式相比，平台转换设计可改善种植体周围骨组织的应力分布，降低种植体颈部骨组织所受的应力。     

天然牙与种植体联合支持套简冠固定桥的骨组织应力分析

目的：研究天然牙与种植体联合支持式套筒冠固定桥牙周组织的应力分布情况。方法：选择1例左侧下颌第一磨牙缺失病例,分别设计以左侧下颌第二前磨牙与种植体（位于下颌第二磨牙）联合支持固定桥模型（模型Ⅰ）和套筒冠固定桥模型（模型Ⅱ）。在分散垂直和分散斜向2种载荷情况下,采用三维有限元法分析基牙及种植体周围骨组织的应力分布情况。结果：分散垂直载荷下,模型Ⅰ中的天然牙和种植体周围骨组织最大等效应力值分别为2．58MPa和43．92MPa;模型Ⅱ中,相应的最大等效应力值分别为2．17MPa和20．23MPa。分散斜向载荷下,模型Ⅰ中的天然牙和种植体周围骨组织最大等效应力值分别为2．23MPa和46．37MPa;模型Ⅱ中．相应的最大等效应力值分别为1．91MPa和21.19MPa。结论：套筒冠固位体能缓冲种植体周围骨组织的部分应力,但对垂直应力和侧向应力的缓冲能力差别不大。进行天然牙与种植体联合支持固定桥修复时,可在种植体端设计套筒冠固位体．以缓冲种植体周围骨组织的应力水平,防止或减轻种植体支持组织的损伤。     

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.     

三种支持类型固定义齿负载时基牙周围骨组织应力分析

目的研究三种支持形式固定义齿在载荷情况下基牙周围骨组织应力分布情况。方法选择1位右侧下颌第一磨牙缺失的志愿者,进行固定义齿修复后,建立天然牙支持式固定义齿三维有限元模型(模型Ⅰ),运用建模软件将模型Ⅰ中的天然牙根替换为种植体,分别建立天然牙与种植体联合支持式固定桥模型(模型Ⅱ)和种植体支持式固定义齿模型(模型Ⅲ)。在分散垂直和分散斜向下加载200N,采用三维有限元法分析基牙及种植体周围骨组织的应力分布情况。结果种植体支持式固定义齿种植体周围骨组织应力最高,且明显集中于种植体颈部;天然牙支持式固定义齿基牙周围骨组织应力最小,且分布较为均匀。斜向加载可以提高固定义齿基牙周围骨组织应力,并增加应力分布的集中程度。结论天然牙支持是固定义齿修复理想的支持形式,在进行各种支持形式固定义齿修复时,都应尽量减小侧向力对支持组织的破坏。     

平台转换种植体周围应力分布的三维有限元分析

目的:分析平台转换种植体周围的力学分布特点。方法:利用CATIA画图软件,建立种植体支持的上颌第一前磨牙三维模型,分析垂直向和斜向加载条件下平齐对接(PM)和平台转换(PS)种植体周围的应力分布差异;比较不同材料基台平台转换冠修复后种植体周围的应力分布差异。结果:①PS型种植体在垂直加载和斜向加载时种植体周围骨组织内最大von Mises应力值均较PM型小。②不同材料基台种植体周围应力分布云图相似,应力均集中在种植体颈部。结论:①PS种植体周围骨组织最大应力值较PM种植体小,但基台、中央螺丝、种植体的应力增大。②斜向加载较垂直向加载种植体周围应力值大大增加,特别是基台及种植体部位较为明显。③基台材料对种植体周围应力值无明显影响。     

天然牙-游离端种植牙联合支持固定桥的应力分布

目的 :揭示天然牙—种植体联合支持固定桥不同桥长度的设计时应力分布特点 ,为临床优化设计提供实验力学依据。方法 :采用三维有限元的方法研究三种长度桥体的天然牙—游离端种植牙联合支持固定桥的应力分布。结果 :天然牙—种植牙固定桥应力集中于基牙的颈部 ;种植体颈部骨组织的应力大于天然牙颈部骨组织的应力 ;集中垂直载荷时种植体颈部骨的应力分布较均匀 ;集中斜向载荷时种植体的颊舌侧骨组织有明显的应力集中区 ,并且桥体跨度增加 ,种植体周骨的最大应力值增加 ,天然牙周骨的应力值无显著变化。结论 :天然牙—种植体固定桥受集中斜向载荷易导致种植牙周骨损伤 ,尤其桥体长度增加时应减小侧向力并增加基牙数量     

动态载荷下种植体位置和直径对悬臂梁种植固定义齿应力影响的三维有限元研究

目的 应用三维有限元法分析动态加载下种植体植入位置和直径对悬臂梁种植固定义齿应力的影响。方法 建立左下颌第二前磨牙、第一磨牙、第二磨牙缺失种植固定义齿的三维有限元模型,远中种植体的位置和直径保持不变;近中种植体依次向远中移动形成中轴与第一前磨牙远中面距离D分别为5.5、8.0、10.5、13.0 mm的悬臂梁种植固定义齿,分别采用4.1和4.8 mm两种直径的种植体;以250 N 牙合力模拟咀嚼周期0.875 s的动态载荷加载于颊尖和舌尖上,应用有限元分析软件MSC.Marc和Partran分析种植体-骨组织界面的Von Mises应力情况。结果 随着近中种植体逐渐向远中移动,近远中种植体Von Mises应力均有不同程度增高,近中种植体中轴与第一前磨牙远中面距离D≤8.0 mm范围内种植体最大Von Mises应力增幅缓和,D>8.0 mm时应力急剧加大;近中种植体直径增大,则近远中种植体的应力减小;各加载阶段最大Von Mises应力均处于近远中种植体颈部与皮质骨交界处;斜向加载种植体应力显著大于垂直加载。结论 种植体植入位置是影响悬臂梁种植固定义齿应力的重要因素,悬臂梁长度不超过前磨牙宽度时行种植固定义齿设计是可行的,直径的选择要考虑骨量和悬臂梁长度双重因素。     

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。     

紧咬型磨牙对后牙游离端种植体周围骨组织应力分布的有限元研究

目的　采用三维有限元分析法,分析紧咬型磨牙对种植体及周围骨组织应力分布的影响。方法　采用锥体束CT扫描一成年磨牙症志愿者,通过轮廓提取、三维重建、布尔运算建立带咬合关系的游离端缺失模型。采用参数化建模,建立Ankylos C/X 4.5×11 mm种植体模型。完成模型装配后,模拟紧咬型磨牙载荷与正常咀嚼载荷对模型进行加载,分析种植体与周围骨组织的von Mises应力分布情况。结果　两种载荷下种植体、基台中应力主要集中在其颊舌侧颈部周围,种植体周围骨组织应力主要集中于与种植体颈部接触的颊舌侧骨皮质。紧咬型磨牙载荷下种植体及骨组织的von Mises峰值与高应力分布区均大于正常咀嚼载荷。紧咬型磨牙载荷与正常咀嚼载荷下第一磨牙区种植体周围骨组织von Mises峰值分别为163.27 MPa与24.02 MPa,第二磨牙区分别为135.52 MPa与16.94 MPa。结论　与正常的咀嚼负荷相比,紧咬型磨牙可能导致种植体与其周围骨组织的应力过度集中。     

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.     

Role of implant configurations supporting three‐unit fixed partial denture on mandibular bone response: biological‐data‐based finite element study

Implant‐supported fixed partial denture with cantilever extension can transfer the excessive load to the bone around implants and stress/strain concentration potentially leading to bone resorption. This study investigated the effects of implant configurations supporting three‐unit fixed partial denture (FPD) on the stress and strain distribution in the peri‐implant bone by combining clinically measured time‐dependent loading data and finite element (FE) analysis. A 3‐dimensional mandibular model was constructed based on computed tomography (CT) images. Four different configurations of implants supporting 3‐unit FPDs, namely three implant‐supported FPD, conventional three‐unit bridge FPD, distal cantilever FPD and mesial cantilever FPD, were modelled. The FPDs were virtually inserted to the molar area in the mandibular FE models. The FPDs were loaded according to time‐dependent in vivo‐measured 3‐dimensional loading data during chewing. The von Mises stress (VMS) and equivalent strain (EQS) in peri‐implant bone regions were evaluated as mechanical stimuli. During the chewing cycles, the regions near implant necks and bottom apexes experienced high VMS and EQS than the middle regions in all implant‐supported FPD configurations. Higher VMS and EQS values were also observed at the implant neck region adjacent to the cantilever extension in the cantilevered configurations. The patient‐specific dynamic loading data and CT‐based reconstruction of full 3D mandibular allowed us to model the biomechanical responses more realistically. The results provided data for clinical assessment of implant configuration to improve longevity and reliability of the implant‐supported FPD restoration.     

The influence of implant location and length on stress distribution for three-unit implant-supported posterior cantilever fixed partial dentures

STATEMENT OF THE PROBLEM: The influence of implant location for an implant-supported cantilever fixed partial denture (FPD) on stress distribution in the bone has not been sufficiently assessed. PURPOSE: This study examined the influence of location and length of implants on stress distribution for 3-unit posterior FPDs in the posterior mandibular bone. MATERIAL AND METHODS: Each 3-D finite element model included an FPD, mesial and distal implants, and supporting bone. The mesial implant with a length of 10 mm or 12 mm was placed in locations where its long axis was 3 mm to 11 mm posterior to the remaining first premolar. The distal implant with a length of 10 mm was fixed at the same distance from the premolar on each model. A buccally-oriented oblique occlusal force of 100 N was placed on each occlusal surface of the FPD. RESULTS: The maximum equivalent stresses were shown at the cervical region in the cortical bone adjacent to the mesial or the distal implants. Relatively high stresses of up to 73 MPa were shown adjacent to the mesial implant located 9 mm or more posterior to the first premolar. The use of a 12-mm-long mesial implant demonstrated a relatively weak influence on stress reduction. CONCLUSION: The implant location in the cantilever FPDs was a significant factor influencing the stress created in the bone.     

Influences of internal tapered abutment designs on bone stresses around a dental implant: three-dimensional finite element method with statistical evaluation

Background: The aim of this study is to determine the effects of various designs of internal tapered abutment joints on the stress induced in peri‐implant crestal bone by using the three‐dimensional finite element method and statistical analyses. Methods: Thirty‐six models with various internal tapered abutment–implant interface designs including different abutment diameters (3.0, 3.5, and 4.0 mm), connection depths (4, 6, and 8 mm), and tapers (2°, 4°, 6°, and 8°) were constructed. A force of 170 N was applied to the top surface of the abutment either vertically or 45° obliquely. The maximum von Mises bone‐stress values in the crestal bone surrounding the implant were statistically analyzed using analysis of variance. In addition, patterns of bone stress around the implant were examined. Results: The results demonstrate that a smaller abutment diameter and a longer abutment connection significantly reduced the bone stresses (P <0.0001) in vertical and oblique loading conditions. Moreover, when the tapered abutment–implant interfaced connection was more parallel, bone stresses under vertical loading were less (P = 0.0002), whereas the abutment taper did not show significant effects on bone stresses under oblique loading (P = 0.83). Bone stresses were mainly influenced by the abutment diameter, followed by the abutment connection depth and the abutment taper. Conclusion: For an internal tapered abutment design, it was suggested that a narrower and deeper abutment–implant interface produced the biomechanical advantage of reducing the stress concentration in the crestal region around an implant.     

Implant–Bone Interface Stress Distribution in Immediately Loaded Implants of Different Diameters: A Three-Dimensional Finite Element Analysis

Purpose: To establish a 3D finite element model of a mandible with dental implants for immediate loading and to analyze stress distribution in bone around implants of different diameters. Materials and Methods: Three mandible models, embedded with thread implants (ITI, Straumann, Switzerland) with diameters of 3.3, 4.1, and 4.8 mm, respectively, were developed using CT scanning and self‐developed Universal Surgical Integration System software. The von Mises stress and strain of the implant–bone interface were calculated with the ANSYS software when implants were loaded with 150 N vertical or buccolingual forces. Results: When the implants were loaded with vertical force, the von Mises stress concentrated on the mesial and distal surfaces of cortical bone around the neck of implants, with peak values of 25.0, 17.6 and 11.6 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains (5854, 4903, 4344 μ?) were located on the buccal cancellous bone around the implant bottom and threads of implants. The stress and strain were significantly lower (p < 0.05) with the increased diameter of implant. When the implants were loaded with buccolingual force, the peak von Mises stress values occurred on the buccal surface of cortical bone around the implant neck, with values of 131.1, 78.7, and 68.1 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains occurred on the buccal surface of cancellous bone adjacent to the implant neck, with peak values of 14,218, 12,706, and 11,504 μm, respectively. The stress of the 4.1‐mm diameter implants was significantly lower (p < 0.05) than those of 3.3‐mm diameter implants, but not statistically different from that of the 4.8 mm implant. Conclusions: With an increase of implant diameter, stress and strain on the implant–bone interfaces significantly decreased, especially when the diameter increased from 3.3 to 4.1 mm. It appears that dental implants of 10 mm in length for immediate loading should be at least 4.1 mm in diameter, and uniaxial loading to dental implants should be avoided or minimized.     

下颌固定义齿基牙齿槽骨降低时不同受载的三维有限元分析

目的 研究下颌后牙固定义齿在齿槽骨降低后受载的三维有限元应力分布情况。方法在建立的下颌固定义齿三维有限元模型的基础上，选取桥体、两侧基牙的咬合面施加不同方向的载荷，利用MARC有限元分析软件计算并绘制各种载荷下的应力分布图像。结果 固定义齿受垂直载荷时基牙的牙周支持组织的应力分布集中在根尖部位，以压应力为主。斜向载荷使基牙支持组织的应力增加且分布不均匀，颈部的应力增加较多。齿槽骨的降低使固定义齿基牙支持组织的应力增加，但分布规律不变。结论 齿槽骨的降低使固定义齿基牙支持组织的应力增加，此类修复体的设计应特别注意基牙牙周组织的健康。     

The influence of medial implant location in three-unit posterior cantilever fixed partial dentures on stress distribution in surrounding mandibular bone

This study examined the influence of medial implant location in three-unit posterior cantilever fixed partial dentures (FPDs) on stress distribution in mandibular bone surrounding two implants. A three-dimensional finite element model that included three-unit FPD and two cylindrical-type implants (4 mm in diameter and 10 mm in length) osseointegrated in the posterior mandible, was digitized. Five different models were created according to the medial implant location between the missing second premolar and the first molar location. The distal implant was fixed at the missing second molar location. Oblique bite force of 100 N at 30 degrees buccal to the vertical direction was directed on each of three artificial teeth, respectively and simultaneously, while the lower surface of the mandible was fixed. The maximum equivalent stress in the cortical and the trabecular bone generally increased as the medial implant shifted to a distal position. Under the simultaneous bite force, relatively low maximum stresses within the cortical bone: between 55 MPa and 57 MPa, were shown in the models with the medial implant placed within the range of one implant diameter from the most medial position, while higher maximum stresses: between 64 MPa and 73 MPa, were demonstrated with more distally placed medial implants. The results suggest that reasonably low mechanical stress in the surrounding bone may be assured when the medial implant is placed in the range between the missing second premolar position and one implant diameter distal from that location.