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。     

冠外固位体义齿基牙牙周组织应力分布的三维有限元分析

目的研究下颌第一磨牙缺失、第二磨牙近中倾斜30°或45°时,用栓道附着体义齿或套筒冠义齿2种冠外固位体(extra-coronal retainer,ECR)义齿修复的基牙牙周组织应力分布。方法采用CT扫描技术和Mimics、Freeform、ANSYS软件,建立下颌第一磨牙缺失、第二磨牙近中倾斜30°或45°及ECR义齿修复后的三维有限元模型,模拟加载并计算分析基牙牙周组织应力的分布情况。结果下颌第二磨牙近中倾斜30°、45°模型,修复前第二前磨牙Von Mises应力分别是2.80 MPa、3.47 MPa,栓道附着体义齿修复后分别是19.26 MPa、25.18 MPa,套筒冠义齿修复后分别是19.47 MPa、24.48 MPa,ECR义齿修复后下颌第二前磨牙牙周组织应力明显增大;修复前第二磨牙Von Mises应力分别是20.45 MPa、20.50 MPa,栓道附着体义齿修复后分别是15.02 MPa、11.84 MPa,套筒冠义齿修复后分别是18.04 MPa、12.18 MPa,ECR义齿修复后下颌第二磨牙牙周组织应力明显减小。结论栓道附着体义齿和套筒冠义齿均能改善倾斜基牙牙周组织的应力分布,当下颌第二磨牙近中倾斜角度过大或下颌第二前磨牙牙周状况欠佳时,应该考虑增加近中端基牙数目。     

6颗种植体支持的上颌无牙颌固定义齿应力分布研究

目的:分析种植体位置变化时,6颗种植体支持的上颌无牙颌固定义齿的应力分布.方法:选择一名牙列缺失、牙槽骨中度吸收的志愿者,对其头颅部进行CBCT扫描,并利用一系列计算机软件进行数据转换,完成上颌骨三维实体模型的重建.设计8种不同位置种植体支持的固定义齿,建立8个三维有限元模型,分析种植体、上颌骨和固定义齿的应力分布情况.结果:远中没有悬臂的模型比有悬臂的模型的应力差值小;8种位点设计的模型都是应力集中在磨牙区种植体,种植体的应力集中点都是种植体颈部,且是偏向于颊侧.种植体的应力都是磨牙＞前磨牙＞前牙;在8种位点设计的模型中,种植固定义齿和颌骨位移都是集中在前牙区,种植固定义齿的位移是从前牙区向后牙区逐渐变小;8种模型的种植体应力都表现为以压应力为主.模型Ⅰ种植体(位点13、15、17、23、25、27)分散型排列,避免了远中悬臂的设计,6颗种植体的应力分布最均匀.结论:种植体植入位点于13、15、17、23、25、27,是8种方案中最佳的植入位点方案.     

隐形矫治器远移下颌第一磨牙的三维有限元研究

目的 构建隐形矫治器远移下颌第一磨牙的有限元模型,探究是否使用微种植体支抗及不同第一磨牙起始位置进行远移时的牙列移动特点。方法 使用锥形束CT (CBCT)数据构建下颌骨、牙齿、牙周膜及隐形矫治器模型,依据是否辅助微种植体弹性牵引分为无支抗组及微种植体组（第一磨牙与第二磨牙根间）,在两组中以第一磨牙起始位置分为工况1：第一磨牙距第二前磨牙0 mm;工况2：第一磨牙距第二前磨牙1 mm,工况3：第一磨牙距第二前磨牙2 mm;工况4：第一磨牙距第二前磨牙3 mm。分析各工况牙列总体位移及各方向位移的数据特点。结果 无支抗组：除第一磨牙向远中移动外,其余牙均表现为反向移动。微种植体组：除工况1中第二磨牙表现为少量近中移动,其余工况全牙列均表现为远中移动、前牙舌向移动,其中工况4第一磨牙远中位移值最大。随着第一磨牙起始位置向远中改变,第一磨牙向远中、前磨牙向近中及前牙向唇侧移动量增加,而第二磨牙向近中移动量减小。结论 微种植体能够有效保护前牙支抗,增加磨牙远移的表达率,避免第二磨牙出现往返移动,且第一磨牙移动起始位置与其远移量及其余牙齿移动量有关。     

不同种植方式修复下颌后部游离缺失的三维有限元分析

目的 比较不同的种植体植入位置对下颌后牙种植固定桥应力分布的影响。方法 利用三维机械制图专用软件UG7.0绘制不同种植体植入位置的种植固定桥有限元模型,分别为:A模型:4567;B模型:×567;C模型:4×67;D模型:45×7;E模型:456×;对每个模型都进行垂直向及斜向加载负荷,并利用Ansys Workbench12.0对各模型受力后Von Mises应力分布情况进行比较分析。结果 各载荷条件下,种植体骨界面Von Mises应力均集中于种植体颈部骨皮质处;斜向载荷下各模型Von Mises应力明显提高;单端固定桥出现明显的应力集中,应力分布不均;双端固定桥应力分布较为合理。结论 种植固定桥修复应尽量避免单端固定桥设计,而双端固定桥两端基牙的支持力应相对均衡,45×7的设计方案应力分布更为合理。     

不同直径种植体与天然牙联合支持固定桥的应力分析

目的:通过三维有限元方法研究种植体直径对天然牙种植体联合固定桥周围骨组织应力的影响。方法:CT扫描获得志愿者DICOM数据,通过Mimics软件、Imageware逆向工程软件及ANSYS软件处理,先建立左侧下颌第二前磨牙和第二磨牙支持的天然牙固定桥三维有限元模型,用不同直径种植体替换下颌第二磨牙得到一系列种植体-天然牙联合支持式固定桥的三维有限元模型。分别在垂直向和斜向45°集中加载下,对比分析天然牙及种植体周围的应力分布情况。结果:相同加载条件下,不同模型的第二前磨牙(天然牙)颈部应力无明显区别。对联合支持式固定桥,当种植体直径由3.5 mm增加为4.3 mm时,种植体颈部和基台的应力明显降低(近1/2);随种植体直径增加,2处应力也继续降低,但降低的幅度明显放缓。结论:随着种植体直径的增大,种植体颈缘处骨组织及基台的von Mises应力逐渐减小,但对天然牙周围的应力影响较小。斜向载荷时,天然牙、种植体周围骨组织及基台受到的von Mises应力显著增大,更易导致固定桥修复的失败。     

全下颌改良杆卡式种植覆盖义齿不同加载部位对其应力分布的影响

分析全下颌改良杆卡式种植覆盖义齿种植体固位杆上加载义齿人工牙上加载的应力分布。方法：三维各向异性有限元法。结果：种植体界面骨组织的最大应力出现在种植体颈部周围的骨质界面;种植体的最大应力位于种植外段的近,远中面;两种加载条件下,种植体的应力峰值有一定差别,种植体骨界面的应力峰值差别不大,,但二者的应力分布着差异;牙弓后都牙槽嵴粘膜中的应力峰值及应力分布均有差别。结论义齿上加载与固位杆上加载的应 布     

附着体义齿修复近中倾斜30°基牙的牙周组织应力分析

目的研究两种附着体义齿（栓道附着体义齿和套筒冠固定义齿）修复下颌第一磨牙缺失伴下颌第二磨牙近中倾斜30°的基牙的牙周组织应力分布。方法在已经建立的下颌第一磨牙缺失伴下颌第二磨牙近中倾斜30°修复前及两种附着体义齿修复后的三维有限元模型上,将200N垂直负荷和斜向负荷分别模拟加载于下颌第二磨牙,计算分析基牙牙周组织的应力情况。结果在下颌第二磨牙近中倾斜30°时,两种附着体义齿修复后倾斜基牙应力主要集中在其颈部牙槽骨或根分叉区。斜向加载下,栓道附着体义齿修复后倾斜基牙牙周组织应力小于套筒冠义齿修复。斜向加载下,下颌第二前磨牙和第二磨牙牙周组织应力远远大于垂直加载。结论在下颌第二磨牙近中倾斜30°时,栓道附着体义齿修复在改善倾斜基牙牙周组织应力方面更优于套筒冠义齿修复。斜向加载时,下颌第二前磨牙和第二磨牙牙周组织中产生较大的应力集中。     

植入位点不同对颧骨种植义齿种植体周骨应力分布影响的研究

目的探讨植入位点不同时颧骨种植义齿种植体-骨界面的应力分布规律。方法计算机模拟建立上颌后牙区重度萎缩三维有限元模型,分别在第一前磨牙区、第二前磨牙区、第一磨牙区和第二磨牙区模拟颧骨种植义齿修复。进行垂直向、颊向30°和舌向30°加载100 N,统计分析植入位点不同时颧骨种植义齿种植体-骨界面的应力。结果1）第一前磨牙区颧骨种植体颊侧暴露较多,与临床不符。2）上颌后牙区拉应力峰值比较：选择第二磨牙区植入时最大,第二前磨牙区次之,第一磨牙区最小。上颌后牙区压应力峰值比较：选择第二磨牙区植入时最大,第一磨牙区次之,第二前磨牙区最小。颧骨区拉应力及压应力峰值比较：选择第二前磨牙区植入时最大,第一磨牙区次之,第二磨牙区最小。结论选择第一磨牙区颧骨种植义齿修复较好。     

植入部位对种植固定桥受力影响的三维有限元分析

目的:采用三维有限元方法比较种植体不同植入部位对下颌后牙四单位种植固定桥应力分布的影响.方法:建立4种不同植入部位四单位种植同定桥的有限元模型,分别为456X、45X7、4X67、X567,采用分散垂直、分散斜向、集中垂直、集中斜向4种加载方式,利用ABAQUS有限元分析软件,分析各种载荷下的应力分布情况.结果:分散载荷下,不管是垂直向还是斜向,4种植入方案的最大Von Mises应力均位于种植体颈部-皮质骨界面处;斜向载荷的Von Mises应力在皮质骨和种植体上明显增高,为垂直向的2.9～5.6倍.集中载荷下,4种植入方案的最大VonMises应力都位于邻近桥体的种植体颈部皮质骨处.远中悬臂设计应力集中最为明显.结论:四单位种植固定桥应避免远中悬臂456X设计方案,在本实验所假设的条件下,45X7植入方案力学分布更为均匀.     

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.     

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.     

动态载荷下不同骨质对天然牙-种植体联合修复应力分布的影响

目的 利用有限元方法探索下颌后牙区天然牙-种植体联合修复在不同骨质内的应力分布情况,以评定出适宜行联合修复所需的骨质类型。方法 采用三维有限元分析法,分别对骨质为Ⅰ、Ⅱ、Ⅲ、Ⅳ类颌骨类型中的天然牙-种植体联合修复体施加动态载荷,并对各界面所承受的Von Mises应力进行分析。结果 皮质骨所受最大Von Mises应力值从Ⅰ类骨到Ⅳ类骨逐渐增大,最大等效应力分别为89.229、91.860、125.840、158.420 MPa。松质骨所受最大Von Mises应力值从Ⅰ类骨到Ⅳ类骨均逐渐减小,最大等效应力分别为58.584、43.645、21.688、18.249 MPa。在同一类模型中,松质骨和皮质骨的最大Von Mises应力值均为舌颊向加载>颊舌向加载>垂直向加载。结论 骨质的类型对修复体周围骨的应力分布有重要的影响,Ⅰ、Ⅱ类骨较Ⅲ、Ⅳ类骨更适合行种植体-天然牙联合修复。     

The influence of occlusal loading location on stresses transferred to implant-supported prostheses and supporting bone: A three-dimensional finite element study

STATEMENT OF PROBLEM: Information about the influence of occlusal loading by location on the stress distribution in an implant-supported fixed partial denture and supporting bone tissue is limited. PURPOSE: The purpose of this study was to investigate the effect of loading at 1 to 3 different locations on the occlusal surface of a tooth on the stress distributions in an implant-supported mandibular fixed partial denture (FPD) and surrounding bone, using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-dimensional finite element model of a mandibular section of bone (Type 2) with missing second premolar and its superstructures were used in this study. A 1-piece 4.1 x 10-mm screw-shape ITI dental implant system (solid implant) was modeled for this study. Cobalt-Chromium (Wiron 99) was used as the crown framework material and porcelain was used for occlusal surface.The implant and its superstructure were simulated in a Pro/Engineer 2000i program. Total loads at 300 N were applied at the following locations: 1) tip of buccal cusp (300 N); 2) tip of buccal cusp (150 N) and distal fossa (150 N); or 3) tip of buccal cusp (100 N), distal fossa (100 N), and mesial fossa (100 N). RESULTS: The results demonstrated that vertical loading at 1 location resulted in high stress values within the bone and implant. Close stress levels were observed within the bone for loading at 2 locations and 3 locations; the former created the most extreme stresses and the latter the most even stresses within the bone. With loading at 2 or 3 locations, stresses were concentrated on the framework and occlusal surface of the FPD, and low stresses were distributed to the bone. CONCLUSION: For the loading conditions investigated, the optimal combination of vertical loading was found to be loading at 2 or 3 locations which decreased the stresses within the bone. In this situation, von Mises stresses were concentrated on the framework and occlusal surface of the FPD.     

Comparative evaluation of the effect of diameter, length and number of implants supporting three-unit fixed partial prostheses on stress distribution in the bone.

OBJECTIVES: The purpose of this study was to compare the effects of the diameter, the length and the number of implants on stress distribution in the bone around the implants supporting three-unit fixed partial prostheses in the mandibular posterior edentulism. MATERIALS AND METHOD: A mandibular Kennedy II three-dimensional finite element model was constructed. Four fixed partial prostheses with two terminal implant supports of various lengths and diameters, and two fixed partial prostheses with three implant supports of various lengths were designed. In separate load cases, 400 N oblique, 200 N vertical, and 57 N horizontal forces were simulated. The tensile and the compressive stress values in the cortical bone around the collar of the implants and Von Mises stresses in the implants were evaluated. RESULTS: Although the change in the length of implants did not decrease the stress levels, lower tensile and compressive stress values were observed in the bone for wider implant placement configurations. Similar stress distributions and close stress levels were observed for two wider implant supports in comparison with the three-implant-supported fixed partial prostheses. CONCLUSION: With the use of two implants of 4.1-mm diameter and 10-mm length as terminal supports for three-unit fixed prostheses, the magnitude and the distribution of stresses in the cortical bone around the implant collar is within the normal physiological limits.     

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.     

Finite element analysis of fixed partial denture replacement

The purpose of this study was to investigate, by means of the finite element method the mechanical behaviour of three designs of fixed partial denture (FPD) for the replacement of the maxillary first premolar in shortened dental arch therapy. Two-dimensional, linear, static finite element analyses were carried out to investigate the biomechanics of the FPDs and their supporting structures under different scenarios of occlusal loading. Displacement and stress distribution for each design of FPD were examined, with particular attention being paid to the stress variations along the retainer-abutment--and the periodontal ligament-bone interfaces. The results indicated that displacement and maximum principal stresses in the fixed-fixed, three-unit FPD were substantially less than those in the two-unit cantilever FPDs. Of the two cantilever FPDs investigated, the distal cantilever design was found to suffer less displacement and stresses than the mesial cantilever design under similar conditions of loading. The highest values for maximum principal stress in the cantilever FPDs were found within the connector between the pontic and the retainer, and within the periodontal ligament and adjacent bone on the aspect of the retainer away from the pontic.