Temperature and thermal stress analysis of a crowned maxillary second premolar tooth using three-dimensional finite element method

The purpose of this study was to calculate the temperature and thermal stress distribution as a result of hot/cold liquid in the mouth. This numerical study was carried out using three-dimensional finite element models and the tooth model was crowned with Au-Pd alloy, Ni-Cr alloy and porcelain. In the first part of the study, temperature changes as a result of hot/cold liquid in the mouth were calculated. In the second part, the thermal stresses caused by temperature changes were obtained. The tooth was assumed isotropic, homogenous, elastic and unsymmetrical. The authors using fortran 77 prepared all calculation programs. The distribution of temperature and thermal stress were plotted for some critical points.     

Stress distribution in a post-restored tooth using the three-dimensional finite element method

Clinicians are opting ever more frequently for restorative materials which have an elastic modulus similar to that of dentin when reconstructing endodontically treated teeth. Metallic posts, which are capable of causing dangerous and non-homogenous stresses in root dentin, are slowly being abandoned. Ideal posts may be those made of various types of fibre (carbon, mineral and glass) and which are adhesively luted into the canal. Among the different methods for evaluating the mechanical behaviour of posts in root canals (progressive loads and photo-elastic technique) the finite element method (FEM) presents many advantages. The aim of this paper is to evaluate, utilizing three-dimensional analysis of the finite elements, what the effect of material rigidity, depth of insertion and post diameter could be on the stress distribution in the different components of the single tooth-post-core reconstruction unit. The results of the FEM analyses, expressed as the distribution of Von Mises stress values, has allowed us to conclude that (i) fibreglass-reinforced composite distributes stress better than titanium alloy or stainless steel; (ii) fibreglass-reinforced composite posts should be inserted as deeply as possible (but maintaining 5-6 mm of gutta-percha apical seal); (iii) fibreglass-reinforced composite post diameter does not affect stress distribution, therefore, as much radicular dentin as possible should be preserved.     

Stress analysis in a post-restored tooth utilizing the finite element method

This study utilized the finite element method (FEM) to predict distribution of stresses in dentin of an endodontically treated tooth, restored with cast post and cores. For this investigation an axisymmetric model of a maxillary second pre-molar that included an alveolar bone was analysed. The three tooth models evaluated were Ti-Ti alloy, NiCr-AuPd alloy and Ti-NiCr alloy as post-material and crown material with porcelain. A load of 200 N at an angle of 45 degrees to the longitudinal axis was applied on the occlusal margin of each model. The tooth was assumed isotropic, homogenous and elastic. The author prepared a calculation program using fortran 77. Investigation of the stress distributions was made in five regions; namely bottom of post, top of post, cole, metal-cement interface and metal-porcelain interface. The distributions of radial and axial stresses were plotted with length of radial.     

Stress distribution associated with loaded acrylic-metal-cement crowns by using finite element method

The axisymmetrical finite element method (FEM) was used to compare stress distribution in a maxillary second premolar restored tooth. The three models were evaluated by crowning the tooth with Au-Pd alloy, Ni-Cr alloy and Ti alloy with acrylic. A longitudinal static force, 200 N in magnitude at an angle of 45 degrees was applied on the occlusal margin of each model. The tooth was assumed isotropic, homogenous and elastic. This numerical study was carried out using axisymmetric finite element models and calculation programmes were prepared by the authors using FORTRAN 77. Comparison of stress distributions was made in four regions of apex, cole, dentin-metal interface and metal-acrylic interface. The highest stress values were obtained when NiCr alloy with acrylic was used.     

Effect of temperature and stress distribution on all-ceramic restorations by using a three-dimensional finite element analysis

summary   This study presents the stress analysis of the mandibular first premolar tooth restored with an all-ceramic crown under thermal loading as a result of hot/cold liquid intake to the mouth using the three-dimensional (3D) finite element analysis (FEA). In the first step of the study, the temperature changes as a result of hot/cold liquid intake were calculated. The thermal stress distributions because of the temperature changes were then obtained. Thermal loads ranging from 60 to 15 °C were applied on all prepared models. The distribution of temperature and stress were plotted for some critical points which were the transition points of strain to tension or tension to strain when hot or cold liquids were consumed. The changes in oral temperature cause thermal fatigue and the material stability might be negatively affected. According to the thermal tension results in the present study, IPS Empress, Carrara press ceramic and Ceramco FAC all-ceramic materials exhibited different values while IPS Empress 2 material showed similar properties to that of enamel.     

三维有限元法对下颌种植覆盖义齿应力分布的分析

目的：分析种植义齿不同连接方式、即刻载荷式种植义齿、设置缓冲间隙对下颌种植覆盖总义齿应力分布的影响。方法：应用三维有限元法模拟正中开闭口运动中下颌种植覆盖总义齿的受力情况,分析种植义齿不同连接方法、即刻载荷式种植义齿、冲击载荷下缓冲间隙的设置对义齿应力分布的影响。结果：缓冲间隙的设置可以降低种植体内部、种植体软硬组织界面和义齿基托内应力的峰值,最易引起种植体侧方界面骨吸收的压应力峰值降低了约52%。螺丝固定的种植全口固定义齿有助于远期修复效果,即刻载荷式种植义齿初期稳定性尚待研究。结论：螺丝固定的种植全口固定义齿对设置缓冲间隙有利于保护种植体界面软硬组织的健康,防止义齿基托折裂,提高种植义齿的远期成功率。即刻载荷式种植义齿对种植义齿的远期成功率有一定的影响。     

种植体钛基台和全瓷冠间粘接界面的三维有限元应力分析

目的：观察钛基台支持时四种粘接剂和3种全瓷冠间不同粘接界面的应力分布情况。方法：建立下颌第一磨牙种植体局部结构的三维有限元模型,模拟最大咬力在冠咬面加载水平和垂直力。结果：磷酸锌粘接界面的应力最大;铸瓷冠可以降低粘接界面的应力大小;粘接界面的应力受粘接剂的影响最大;水平加载最大应力远大于垂直加载;弹性应变主要集中在基台与种植体和冠颈部连接处。结论：粘接界面应力过大应首先考虑更换粘接剂,其次考虑面侧向力过大或不平衡,最后考虑修复冠材料。基台与种植体和冠颈部连接处最可能发生折断。三维有限元法应力分析可以为种植修复提供较准确的理论依据,对临床工作准备和预期都具有重要的指导意义。     

上颌全口义齿的加强结构对基托下黏膜应力分布的影响

目的：分析上颌全口义齿加强前后及不同的加强设计，对基托下黏膜应力分布的影响。方法：采用三维有限元法，建立无加强（BS），铸造结构加强BA，BD和BDr等4种上颌全口义齿三维有限元模型。设定P1，M1，PMc和PMe等4种垂直加载条件，加载力合计98N。对全口义齿基托下黏膜的应力分布进行分析。结果：在相同加载条件下，黏膜应力峰值表示为按BS，BA，BD，BDr的顺序依次减小。BDr基托下黏膜应力峰值最小，应力分布更均匀和广泛。结论：使用覆盖牙槽嵴顶及后堤区的铸造加强结构的上颌全口义齿能够使基托下黏膜应力分布更均匀和广泛，有利于保护基托下黏膜组织。     

牙齿磨耗后颞下颌关节应力分布的三维有限元研究

目的：计算机模拟牙齿不同程度磨耗、颌垂直距离减小时，三维有限元分析颞下颌关节内的应力分布变化。方法：应用以往研究所建正常颞下颌关节三维有限元模型，分别将下牙列分层删除从上至下1／3、1／2及全部的单元，并改变咀嚼肌加力方向。应用ANSYS6．1分析颞下颌关节内的应力变化。结果：随着磨耗程度的加重，髁状突表面的应力增加较多。关节盘等效应力增加的速度较髁状突、关节窝要大；关节盘的后带后缘，还有关节盘中带、后带的中间、外侧区有应力集中表现；磨耗越重，变形越大，关节盘越薄。颞骨关节窝不但应力值增加，最大应力的位置也由关节结节后斜面向顶部移动。结论：牙齿磨耗可造成颞下颌关节应力的明显增加及特定的应力集中区。     

正常颞下颌关节应力分布的三维有限元研究

目的:探讨正常人牙尖交错位紧咬牙时颞下颌关节内的应力分布情况,了解生理状况下TMJ生物力学特点。方法:应用ANSYS 6.1对以往研究所建正常颞下颌关节三维有限元模型进行分析。加载情况接近正常生理。由ANSYS 6.1进行求解。在后处理器中研究分析应力分布与形变。结果:正常人牙尖交错位紧咬牙时颞下颌关节内拉压应力并存,存在剪切应力,分布较均匀,无特别明显应力集中表现。髁突前斜面等效应力值高于后斜面,而前斜面外侧区的应力值又明显高于内侧、中间区。关节盘腹面平均应力值大于背面,且背面应力分布较腹面均匀。腹面应力分布,外侧区最高,最大应力值0.244位于后带与双板区交界处;后带与中间带差别不大,但都明显大于前带。关节盘的变形量明显大于髁突及颞骨关节窝。颞骨关节窝前部即关节结节后斜面等效应力较大。结论:正常牙尖交错位紧咬牙时颞下颌关节内的应力分布,与髁突、关节盘、颞骨关节窝的解剖生理之间,具有良好的功能适应性。     

基底冠结构变化对金属烤瓷冠应力分布影响的三维有限元分析

目的探讨基底冠结构变化对后牙金属烤瓷冠应力分布的影响,为基底冠的结构设计提供理论指导。方法将金属基底冠设计为均匀厚度形、蝶形和水平形三种结构型,建立金属烤瓷冠三维有限元模型,模拟加载1N垂直载荷时的应力分布。结果瓷层最大主应力主要集中于金瓷界面,蝶形结构型和水平结构型的瓷层最大主应力峰值明显低于均匀厚度型,而最小主应力峰值则明显高于均匀厚度型。蝶形结构型和水平结构型的基底冠von-Mises应力峰值明显低于均匀厚度型。结论蝶形结构型和水平结构型基底冠设计,能有效优化金属烤瓷冠的应力分布,提高瓷层的抗拉强度,增强金属烤瓷冠的结构强度。     

支抗力作用下上颌第一磨牙牙周膜应力的三维有限元分析

目的研究上颌第一磨牙在支抗力作用下牙周膜的应力分布情况。方法应用薄层CT技术以及ANSYS10.0有限元分析软件建立上颌第一磨牙及其牙周膜、牙槽骨的有限元模型。模拟3种不同大小的支抗力对模型中的上颌第一磨牙进行加载,应用三维有限元法分析上颌第一磨牙在支抗力作用下牙周膜的应力分布情况。结果当上颌第一磨牙颊侧中心受到近中水平向支抗力时,近颊根的颊侧近中颈部、近中颈部和腭侧根的近中颈部主要受压应力,远颊根的远中颊侧颈部主要受拉应力,牙周膜表面的最大应力值出现在近颊根的近中颈部。牙周膜有向近中腭侧转动的趋势。随着加载力的增加,牙周膜表面的应力值也随之增大。结论在临床正畸治疗时,应考虑第一磨牙颊侧是否能提供足够的支抗。     

非均匀的粘结剂层的厚度对全瓷冠应力分布的影响

目的:探讨非均匀的粘结剂层的厚度对轴向加载的全瓷冠应力分布的影响。方法:建立四个轴对称的二维有限元的In-Ceram全瓷冠模型,粘结剂层的厚度分别为均匀厚度25μm组,100μm组,咬合面25μm轴壁和肩台100μm组及咬合面100μm轴壁和肩台25μm组。通过轴向均匀加载540牛顿对全瓷冠的各组分的应力大小和分布进行分析。结果:只有当粘结剂层为均匀厚度100μm时,饰面瓷的拉应力峰值比均匀厚度25μm时降低12%;只有当粘结剂层为均匀厚度100μm和咬合面厚度25μm、轴壁肩台厚度100μm时,粘结剂层的拉应力峰值较均匀厚度25μm分别降低了33.3%和33.1%;核瓷所受的拉应力水平最高。当咬合面粘结剂层的厚度为25μm时,核瓷拉应力峰值降低。饰面瓷的拉应力峰值存在于朝向核瓷侧的咬合面线角区,应力值较低;核瓷的拉应力峰值存在于咬合面线角区的内面上,而粘结剂的拉应力峰值则位于轴龈线角并向轴壁抬起处。结论:从材料的机械性能角度分析,粘结剂层在修复体各部位对全瓷修复体的应力所起到的作用是不同的,要结合修复材料的机械性能和受到的应力水平来决定修复体粘结剂层的厚度。     

不同肩台宽度的下前牙全瓷联冠的有限元分析

目的: 采取有限元分析研究肩台宽度变化对3种不同全瓷材料的下颌中切牙联冠修复的影响。方法: 利用下颌中切牙全瓷联冠的三维有限元模型, 对3种不同全瓷材料以及肩台宽度变化的全瓷联冠进行垂直向和唇向45°大面积加载120 N, 并采用Abaqus 6.11软件包对数据进行力学分析。结果: 利用CBCT、Mimics10.01软件及Abaqus 6.11软件建立了下颌中切牙全瓷联冠、基牙、牙周膜和牙槽骨的三维有限元模型。 不同全瓷材料和肩台宽度对牙周膜、牙槽骨的等效应力峰值几乎无影响。 同一肩台宽度下, 大面积加载120 N时, 3种全瓷联冠中冠受到的拉应力最大为In-Ceram Alumina, 其次为In-Ceram Zirconia, 最小为IPS.Empress2。唇向45°大面积加载120 N时, IPS.Empress2随着肩台宽度增加, 冠边缘的最大拉应力值上升。结论: 建立的三维有限元模型具有很好的几何相似度, 在所设定的条件范围内, 全瓷材料的弹性模量越大, 联冠受到的拉应力也越大。     

三维有限元分析法在根管治疗中的应用

三维有限元分析法是研究口腔生物力学的重要手段之一.采用三维有限元分析法对牙体组织和充填材料的应力分布进行分析和计算机模拟是指导牙体牙髓病学临床应用的重要内容,很多学者对根管治疗过程中根管预备和根管充填等方面进行了应力分析影响的研究,本文就近几年其应用和研究进展作一综述.     

下颌第一磨牙分根后单冠与联冠修复的有限元分析

目的：研究下颌第一磨牙分根后2种修复方式对磨牙应力分布的影响。方法：利用锥形束CT(CBCT)扫描和Mimics、Geomagic、UG处理图像,建立下颌第一磨牙分根术后单冠和联冠修复的三维有限元模型。分别进行垂直和斜向加载,计算正常下颌第一磨牙及2种修复方式下牙体和牙周组织的应力。结果：垂直载荷时,2种修复模型与正常磨牙牙体、牙周应力分布相似;牙体应力极值和牙周膜最大主应力值均增加,单冠模型增幅较大。斜向载荷时,联冠模型与正常磨牙牙体、牙周应力分布相似,单冠模型远中根及牙周膜颊侧根下半部应力集中区增大;牙体应力极值和牙周膜最大主应力值均增加,单冠模型增幅较大。结论：下颌第一磨牙分根术后选择联冠修复更为合理。     

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.     

钴铬合金和钛基台与全瓷冠间粘接界面的三维有限元应力分析

目的 对比观察钴铬合金基台和钛基台支持时与氧化锆全瓷冠、氧化铝全瓷冠和铸造全瓷冠间复合树脂粘接界面的应力分布情况,分析钴铬合金基台的特性.方法 建立右下颌第一磨牙种植体局部结构的三维有限元模型,在冠咬合面加载水半和垂直力,以模拟最大咬合力的侧向水平分力和垂直分力.结果 钻铬合金基台粘接界面应力最大数值小于钛基台粘接界,...     

种植体周围骨内应力分布的三维有限元分析

目的针对不同类型的牙槽骨科学地选用种植体,提高种植体临床疗效,延长使用寿命。方法采用三维有限元分析方法,将圆柱状、螺纹状和台阶状种植体分别植入4类骨质结构中,对此12种情况进行应力分析。结果在同种骨质模型中,圆柱状种植体颈部周围骨内的应力集中最小;就同种形态种植体而言,较低的骨质密度不利于种植体的应力分布。结论圆柱状是一种最有利于降低颈部骨质吸收的形态结构。螺纹状种植体周围骨内应力最大值大于圆柱状,而螺纹自身非力学优势极大的拓展了该型种植体的使用范围,但螺纹尖端处的高应力区域和螺纹之间的低应力区域是影响其长期使用效果的潜在不利因素。台阶状种植体相对较适合骨质好的情况,其根部出现局部高应力区域,若应力处于骨生理承受范围之内,将有利于减少根部骨质疏松。     

有限元法分析犬下颌不全截骨牵张时特定标志点应力状况

目的:利用犬不完全截骨牵张成骨有限元模型计算牵张过程中下颌骨特定点受力状况。方法:有限元模型模拟不完全截骨(截骨处剩1mm舌侧皮质骨),观察下颌骨特定标志点所受最大主应力和Von Mises应力。结果:犬下颌不全截骨牵张时,在牵张侧下颌角、喙突受到较大应力,第五臼齿、髁状突前斜面前缘中点和髁状突后斜面后缘中点VonMises应力分别为:0.3726 MPa、0.2408 MPa、0.1051 MPa,并且前两点所受最大主应力为压应力、后缘中点为拉应力,在非牵张侧应力为0。结论:犬下颌骨不全截骨牵张成骨时,牵张侧受到不同程度应力影响,在非牵张侧不受应力影响。