颊舌减径对固定修复后基牙牙周受力影响的三维有限元研究

目的：以不同程度地减少固定桥桥体的颊舌径,观察固定桥基牙牙周膜的受力情况,了解桥体的颊舌减径是否可以减少固定桥基牙牙周的受力.方法：采用三维激光扫描与Marc软件结合的方式,建立双端固定桥桥体颊舌径分别为正常时的100%（M1）、90%（M2）、66.7%（M3）和50%（M4）的4个三维有限元模型,施加载荷,计算并分析牙周膜支持组织中的应力分布状况.结果：垂直均布加载时基牙牙周膜的受力随着咬合面积的减小而呈规律性的下降,但在垂直集中加载和斜向加载时牙周膜受力变化不显著.结论：单纯的颊舌减径并不能有效地起到降低牙周受力的作用.     

下颌固定桥基牙牙槽骨单侧吸收对基牙应力分布的影响

目的:研究双端固定桥基牙牙槽骨单侧吸收对基牙应力分布的影响。方法:采用螺旋CT扫描获取健康人下颌骨、牙齿、牙周支持组织的二维图像,通过图像合成软件建立三维数字模型,并应用三维有限元分析软件生成下颌后牙三单位固定桥的三维有限元分析模型。在相同垂直和水平载荷情况下,分析基牙牙槽骨单侧吸收时固定桥各基牙的应力分布。结果:当前磨牙端基牙牙槽骨单侧吸收达25%、磨牙端基牙牙槽骨无吸收时,前磨牙端基牙开始出现应力集中;当磨牙端基牙牙槽骨单侧吸收达35%、前磨牙端基牙牙槽骨无吸收时,磨牙端基牙开始出现应力集中。结论:下颌后牙双端固定桥基牙应力分布与基牙牙槽骨吸收形式密切相关,但二者之间不是线性关系而是存在临界区,基牙牙槽骨单侧吸收的程度对基牙应力分布的影响弱于多侧吸收。     

用光弹性方法对固定桥基牙牙槽骨受力的实验研究

本文采用平面光弹性方法对下颌第一磨牙缺失的两基牙双端固定桥、半固定桥、三基牙双端固定桥、有邻牙的两基牙双端固定桥以及未修复牙的受力情况进行了实验研究,得出了固定桥基牙垂直支反力的分配比例和各类修复体基牙牙槽骨的应力条纹图。结果表明:     

上颌切牙缺失两基牙双端固定桥修复的生物力学分析

目的 :研究上颌切牙缺失两基牙双端固定桥修复的应力分布。方法 :采用CT扫描获取健康成人上颌牙及其支持组织的二维图像 ,通过计算机重建技术建立三维立体图像 ,并获得了上颌切牙缺失后的两基牙双端固定桥的三维有限元数学模型 ,在相同垂直载荷和水平载荷下分析了基牙牙槽骨高度对固定桥应力分布的影响。结果 :当基牙牙槽骨无吸收时固定桥两基牙应力分布均匀 ;当基牙牙槽骨吸收 >15 %时固定桥两基牙出现应力集中。结论 :上颌切牙缺失后选择尖牙两基牙双端固定桥修复是合理的 ,但其前提是基牙牙槽骨吸收较少。     

固定桥双基牙侧牙槽骨吸收对基牙应力分布的影响

目的:探讨固定桥双基牙侧牙槽骨有不同程度水平吸收时,基牙牙周膜的等效应力值和分布的变化,以指导临床固定桥的合理设计。方法:采用螺旋CT扫描技术与Mimics、Ansys软件相结合建立双基牙侧牙槽骨有不同程度水平吸收后的三基牙双端固定桥的三维有限元模型,施加垂直和斜向45°载荷,分析双基牙侧牙周膜的应力分布状况。结果:①斜向载荷下各模型应力值均大于垂直向载荷时的应力,应力集中现象也较垂直向载荷时明显;②在垂直或倾斜载荷下,有牙槽骨吸收的第二前磨牙侧增加牙周组织健康的第一前磨牙时,应力均变大以分担牙合力;若增加的第一前磨牙有不同程度的牙槽骨吸收,垂直载荷时应力值变化不大,斜向载荷时应力值减小,但应力集中现象较无吸收时明显。结论:增加牙槽骨有不同程度吸收的基牙不能有效地发挥分散牙合力的作用,不适合做固定桥基牙。加载方向是影响应力分布的重要因素,应注意防止产生过大的侧向力。     

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。     

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摘要：目的 探讨斜向载荷下采用不同基牙数目时下颌后牙双侧游离缺损冠外附着体义齿支持组织的应力分布情况。方法 2005年选取一成年健康男性志愿者的头部CT（取下颌牙槽骨部分）和离体尖牙、第一双尖牙、第二双尖牙、第一磨牙、第二磨牙的CT扫描图片。建立下颌KennedyⅠ类牙列缺损冠外附着体义齿修复的三维有限元模型,分析在斜向载荷作用下采用不同基牙数目时,基牙牙周组织及缺牙区牙槽嵴的Von Mises应力分布。结果 斜向载荷下,末端基牙牙周膜应力集中区主要位于颊舌侧的牙颈部,随着基牙数目的增加,基牙牙周组织及缺牙区牙嵴的最大应力值都呈下降趋势,基牙由1颗增加至2颗时,应力明显下降,当基牙增加至3颗时,应力的下降量明显减少。结论 在下颌游离缺损修复中,斜向载荷下冠外附着体义齿支持组织应力的减少与基牙数目的增加不完全成比例,在临床上应根据具体的情况确定联合基牙的数目。     

下颌侧切牙缺失固定桥设计基牙受力情况的实验研究

目的比较双端及单端固定桥修复下颌侧切牙缺失时基牙的受力情况。方法应用ANSYS软件,通过三维有限元法建立4种固定桥模型,分别以中切牙和尖牙、中切牙、尖牙、尖牙和第一前磨牙为基牙模拟下颌侧切牙缺失,分析基牙最大受力部位和大小。结果单端固定桥修复模型中,以中切牙作为单一基牙时,基牙根尖受力值最大;双基牙单端桥基牙根尖受力最小;双端固定桥两基牙根尖受力分布最均匀。结论下颌侧切牙缺失患者以双端固定桥修复时,基牙受力最合理;单基牙单端桥设计,中切牙受力大于尖牙,而双基牙的单端桥修复形式较单基牙理想。     

固定桥不同桥体龈端形态修复下颌第一磨牙的三维有限元分析

目的 应用三维有限元分析法探讨不同桥体龈端形态对固定桥基牙及牙周膜应力分布的影响.方法 利用健康成人牙列的锥形束CT(CBCT)原始数据,通过三维建模软件建立下颌第一磨牙缺失,第二前磨牙与第二磨牙为基牙的双端固定桥,并模拟三种不同桥体龈端形态,即改良鞍式、改良盖嵴式、船底式.利用Ansys 17.0对已建立的三种不同龈...     

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     

Evaluation of the effect of the residual bone angulation on implant-supported fixed prosthesis in mandibular posterior edentulism. Part II: 3-D finite element stress analysis

Buccolingual angulation of the mandibular posterior edentulous region may affect the prosthetic load conditions, so as to cause high stress concentrated areas that may easily lead to failure. The aim of this study was to evaluate the effect of various predetermined buccolingual angulation values on stress distribution in the mandibular posterior edentulous region restored with implant-supported fixed partial dentures, using three-dimensional finite element analysis. Stress analyses were performed applying 400N oblique force to implant-supported fixed prosthesis. Stress analyses indicated tensile stress values on the buccal surface and compressive stress values on the lingual surface of cortical bone were increased as the angulation of the edentulous bone increased (especially corresponding to the cervical region of the implants). Compressive stress values, observed where two implants were placed at the second premolar and second molar regions (5-7 design) and first and second molar regions (6-7 design), respectively, were very close to or even exceeded the ultimate compressive strength of bone. It is concluded that when a definite buccolingual angulation is added to other existing risk factors such as bruxism, placing an implant for every missing tooth might reduce the high stress concentration areas.     

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.     

Stresses induced by different loadings around weak abutments

Stresses and deflections of abutments induced by various loadings were analyzed with a two-dimensional finite element model. The biomechanic system consisted of the mandibular posterior three-unit fixed partial denture (FPD). Four different loading types were analyzed: (1) a distributed force of 600 N; (2) concentrated nonaxial and (3) axial 300 N forces at the marginal ridge of the molar; and (4) a concentrated vertical 300 N force at the center of the pontic. All computations were conducted for three different alveolar bone levels. The premolar exerted a greater pressure during occlusal loadings (except axially) on the alveolar bone than the molar. According to the stresses induced in the alveolar bone, the most critical loading was the distributed force. With diminishing periodontal support, stresses elevated in the biomechanic system and critical increases were noted for the concentrated nonaxial load on the molar.     

下颌第一磨牙斜向受力时下颌骨的有限元分析

目的：采用有限元方法分析下颌第一磨牙颊舌向45＆#176;受力时,下颌骨局部以及整体应力变化,为寻找下颌第一磨牙的最佳临床修复方法提供生物力学依据。方法：基于CT扫描1例正常的成年人的下颌骨, Mim-ics14.11软件建立下颌骨模型,下颌第一磨牙咬合面给予50N的颊舌向45＆#176;力,有限元分析软件ABAQUS6.9-3分析整个下颌骨应力应变的变化。结果：当下颌第一磨牙颊舌向45＆#176;受力时,下颌第一磨牙周围骨质应力应变最大处为底部偏向颊侧;整个下颌骨受力分析中,应力应变主要集中在受力的下颌第一磨牙处,其次在对侧的下颌角位置,应力应变也沿着下颌骨外斜线方向传导。结论：有限元分析方法可以用来进行下颌第一磨牙的受力分析,揭示引起局部以及整体因素导致的生理病理过程中生物力学机制。     

锥形束CT对微螺钉植入后牙安全区域的分析

目的通过锥形束CT（CBCT）测量上下颌后牙区不同高度牙槽骨近远中向及颊舌（腭）向的骨量,分析微螺钉种植体植入的安全区域。方法选取30例CBCT扫描的成人影像资料为研究对象,对颌骨进行扫描重建,从第前磨牙远中开始向后,在每个牙根间区域（包括上颌结节）距离牙槽嵴顶2、4、6、8、10 mm处,分别测量颊舌（腭）向宽度和近远中宽度。采用SPSS 16.0软件进行单因素方差分析和LSD法比较。结果1）上颌后牙区近远中骨量在同一高度不同位置间均存在统计学差异（P<0.05）,最大近远中骨量位于第二前磨牙和第一磨牙腭侧根间;颊腭向骨量在不同位置、高度间均有统计学差异（P<0.05）,最大颊腭向骨量位于第一磨牙和第二磨牙之间。2）下颌后牙区近远中骨量在不同位置、高度间均有统计学差异（P<0.05）,颊舌向骨量在同一位置不同高度间均存在统计学差异（P<0.05）,最大近远中骨量和最大颊舌向骨量均位于第一磨牙和第二磨牙之间。结论经CBCT获取了上下颌骨后牙段植入微螺钉种植体的安全区域,为后续临床应用提供了有价值的参考。     

正常人群下颌管的三维定位测量研究

目的：应用CT进行下颌管的三维定位测量研究,为牙种植术等提供临床解剖学依据。方法：对50例正常人下颌骨进行螺旋CT扫描,在预定截面上测量下颌管至颊、舌、牙槽嵴顶以及下颌骨下缘的距离,测量结果采用SPSS13.0软件进行统计学分析。结果：下颌骨左右两侧各组测量结果无显著性差异;下颌管至舌侧骨板的距离比下颌管外缘至颊侧骨板距离小,两者差异有显著性（P〈0.05）;下颌管上缘至牙槽嵴顶的距离较下颌管下缘至下颌骨下缘的距离大,两者差异有显著性（P〈0.05）。结论：下颌管在下颌骨后牙区走行中偏向舌侧骨板,而且距离下颌骨下缘较近。当下颌骨的垂直高度不足时,下颌管的颊舌向位置就十分重要,第二磨牙区种植一般伤及下牙槽神经的风险较小。     

牙槽骨降低对牙周膜内应力的影响

为了解牙齿的牙槽骨降低对牙周膜内应力的大小和分布的影响规律,本文建立了一包括第二双尖牙和第二磨牙的下颌骨段的三维有限元模型,模拟牙齿在咀嚼时的受力状况进行加载,计算分析了牙槽骨为五种不同的高度水平时牙周膜内的应力值。计算结果表明:牙周膜内的应力随牙槽骨降低而逐渐增大,但在牙周膜的不同部位应力增加的幅度不同。牙周膜内应力的增加与牙槽骨降低之间的关系不是线性的,牙槽骨吸收在根长的20％以内时应力的增长较平缓,牙槽骨吸收超过根长的20％以后应力的增加幅度明显加大。     

Finite element analysis of three- and four-unit bridges

A two-dimensional finite element model of a mandibular quadrant was used to examine differences in magnitude of the principal stresses from the placement of three- and four-unit bridges. The area of interest spanned the first premolar to the second molar. Loading conditions were (i) vertical and distributed and (ii) 30 degrees to the vertical and concentrated. The principal stresses were calculated and compared for: (i) the first molar removed with the remaining bone either cancellous or cancellous surrounded by a cortical shell; (ii) as in (i) but with the second premolar and first molar removed; (iii) a three-unit bridge spanning the second premolar to the second molar; and (iv) a four-unit bridge spanning the first premolar to the second molar. Each tooth was supported by periodontal ligaments, cortical and cancellous bone with each assigned the appropriate physical constants. Removal of the first molar resulted in considerable variation of the stresses especially when the cortical shell was replaced by cancellous bone. Because of the lower modulus of cancellous bone and its lower load-bearing capabilities the stresses were three to ten times lower and more uniform within the cancellous bone. Generally, the addition of a bridge resulted in lower and better distributed sigma min stresses. The bridge also resulted in higher tensile stresses distal to the abutment teeth which theoretically could result in bone deposition. No significant differences in magnitude were observed between the three- and four-unit bridge. From a stress standpoint the bridges resulted in more uniform stress distribution around the abutments and an increase in the tensile stress distal to the abutments. Such findings support the placement of a fixed bridge to maintain bone in an edentulous area.     

第三磨牙倾斜不同角度对下颌双端固定桥应力的影响

目的:下颌第一二磨牙缺失三基牙双端固定桥修复的条件下,分析近中倾斜不同角度的第三磨牙作为基牙后受力时修复体、牙体组织及牙周膜的应力分布情况,为临床修复提供理论依据.方法:在已建好的第一二磨牙缺失三基牙双端固定桥修复的三维有限元模型基础上,将第三磨牙近中倾斜0°、10°、20°、30°和40°,通过Ansys软件分析修复...