牙种植体即刻负载骨界面应力分布的三维有限元分析

目的：用三维有限元法分析牙种植体即刻负载骨界面的力学特性。方法：采用CT扫描和自主开发的USIS软件建立螺纹种植体即刻负载的三维有限元下颌骨模型，用ANSYS计算垂直加载、颊舌向450及近远中向45°加载150N力时种植体骨界面的Yon Mises应力、应变值。结果：垂直加载时骨界面的Yon Mises应力集中于颈部舌侧骨皮质，应变分布均匀，以颈部骨皮质、底部颊侧骨松质及颊侧螺纹接触部位的松质骨较为集中：颊舌向加载时骨界面的Yon Mises应力也集中于颈部舌侧骨皮质，但最大值是垂直加载时的4．15倍，应变分布不均匀，主要集中于颈部舌侧骨皮质，最大值是垂直加载时的3．98倍；近远中斜向加载时骨界面的Yon Mises应力集中于颈部远中侧骨皮质，最大值是垂直加载时的3．72倍，应变集中于底部近中侧骨松质，最大值是垂直加载时的1．51倍。结论：即刻垂直加载时，种植体周围骨质应力及应变无明显集中，分布较均匀，颊舌向及近远中向加载时应力、应变明显增大，分布不均匀。     

种植体长度对即刻负载种植体骨界面生物力学分布的影响

目的:建立包含不同长度标准直径种植体的下颌骨三维有限元模型,分析不同长度种植体对即刻负载种植体骨界面应力应变分布的影响.方法:采用薄层CT扫描下颌骨和自主开发的USIS软件建立直径4.1mm不同长度螺纹种植体即刻负载的三维有限元模型,用ANSYS软件分析长度分别为6、8、10、12、14mm的种植体,在垂直和颊舌向45o加载150N力时种植体骨界面的von Mises应力、应变值.结果:随着种植体长度的增加,种植体骨界面的应力和应变值均呈下降趋势.种植体骨界面应力值在长度从6mm增加到8mm时下降最明显,尤其是颊舌向加载时;而种植体长度从8mm增加到10mm及从10mm增加到12mm和从12mm增加到14mm时,骨界面应力值下降并不很明显.种植体骨界面应变值也是在长度从6mm增加到8mm及8mm增加到10mm时下降最明显.结论:种植体长度的增加能降低骨界面应力和应变值,呈负相关关系;但只在长度从6mm增加到8mm时应力值降低才较明显.这提示临床上尽量不要采用长度为6mm的种植体,并应适当地选择足够长度的种植体.     

微型正畸支抗种植体即刻挤压植入时骨界面应力分析

目的研究微型正畸支抗种植体即刻植入时骨界面应力大小及分布,为微型支抗种植体即刻加载提供参考。方法将局部下颌骨简化成一个等腰梯形,颌骨骨块长20mm,断面高为30mm,上边宽为10mm,底边宽14mm,皮质骨厚度设定为1.6mm;微型种植体直径设定为1.2mm,长6mm。利用ANSYS9.0软件,建立局部微型种植体-骨的三维有限元模型。下颌骨材料属性设定为线性、正交各向异性,种植体-骨界面定义为完全连接。将断端处、下颌骨局部骨块面及底面的所有节点给予刚性约束。模拟种植体即刻植入时的情况,将骨界面初始位移设定为0、0.05、0.1mm,分析各指定初始位移时骨界面应力大小及分布。结果即刻加载时,0mm初始位移下,种植体骨界面无应力分布;初始位移为0.05mm时,骨界面应力集中在骨皮质内,分布较均匀,衰减幅度很小,近远中方向上的VonMises应力为1648MPa,龈向为1782MPa。初始位移为0.1mm时,近远中方向上的VonMises应力为2012MPa,龈向为2110MPa。结论微型种植体挤压植入时会产生较大的初始应力,即刻加载时,应当考虑这种初始应力。     

倾斜角度对种植体骨界面生物力学影响的三维有限元分析

目的 :分析不同倾斜种植对种植体界面应力、应变及位移分布状况的影响。方法 :在第一磨牙区分别垂直及向舌侧倾斜10°、20°、30°植入种植体 ,建立下颌骨三维有限元模型。模拟咀嚼肌力加载 ,分析在正中咬合情况下种植体骨界面应力、应变及位移分布情况。结果 :随着倾斜角度的增大 ,种植体骨界面应力、应变及位移均增加。倾斜30°种植时 ,种植体骨界面应力显著性增大(P<0.01)。结论 :种植体倾斜角度应小于30°。     

种植体根尖部与上颌窦底皮质骨的关系对上颌后牙区种植影响的三维有限元分析

目的    利用三维有限元分析方法评估种植体根尖部与上颌窦底皮质骨的关系对上颌后牙区种植的生物力学影响。方法    应用计算机辅助设计（computer assisted design,CAD）软件建立标准种植体及上颌后牙区三维有限元模型（M1 ~ M6）,皮质骨厚度均为1 mm,依据牙槽骨高度不同（10 ~ 14 mm）,种植体根尖部与上颌窦底皮质骨的关系如下。M1：种植体根尖部穿通上颌窦底皮质骨（窦底皮质骨的上表面与种植体根尖部位于同一平面）;M2：种植体根尖部进入窦底皮质骨厚度的一半;M3：种植体根尖部恰好接触窦底皮质骨的下表面;M4 ~ M6：种植体根尖部分别距离窦底皮质骨的下表面1、2、3 mm。采用129 N斜向加载,分别置于即刻负载与常规负载条件下,计算其应力分布、最大von Mises应力、种植体的最大位移和共振频率。结果    除M1即刻负载外,最大von Mises应力均集中于种植体颈部周围的牙槽嵴顶皮质骨表面。无论即刻负载或常规负载下,种植体根尖部进入或穿通窦底皮质骨时,牙槽嵴顶皮质骨的最大von Mises应力降低,窦底皮质骨的最大von Mises应力增加,种植体的轴向共振频率显著增加,颊舌向共振频率显著降低。即刻负载条件下,当种植体进入或穿通窦底皮质骨时,其最大位移尤其是根尖部的最大位移小于其他情况下的最大位移。常规负载条件下,种植体颈部与根尖部的最大位移几乎不受种植体根尖部位置的影响。结论    种植体根尖部与上颌窦底皮质骨的相对位置关系对种植体周围组织的应力分布、种植体的最大位移以及共振频率均有一定影响。种植体根尖部进入或穿通上颌窦底皮质骨有利于改善应力分布,减少种植体根尖部的位移,增加种植体的稳定性,尤其在即刻负载下作用显著。     

不同(牙合)特征对后牙种植单冠生物力学影响的有限元分析

目的 通过有限元方法探究即刻负荷状态下不同■特征对后牙种植单冠种植体-骨界面生物力学变化的影响,以期为临床■特征的选择提供参考。方法 利用过盈配合法建立即刻负荷种植义齿及周围骨组织有限元模型后,参照天然牙设计6种不同的■特征,使用Ansys Workbench 2021 R2软件分别进行轴向200 N静态加载分析,对所有数据进行对比分析后,评估不同■特征对种植体-骨界面位移、Von Mises应力等的影响。结果 A-B-C咬合接触可获得最小的种植体及周围骨皮质和骨松质的位移（10.52μm、5.67μm、9.34μm）;修复平台咬合（3点）接触产生了最大的种植体、骨皮质、骨松质位移（15.24μm、8.94μm、12.15μm）。与其他■接触类型相比,A-B咬合接触产生了最大的种植体Von Mises应力（71.91 MPa）,明显降低了骨皮质和骨松质的最大Von Mises应力（18.04 MPa,17.81 MPa）。结论 即刻负荷状态下不同的■特征显著影响种植体-骨界面的位移及Von Mises应力分布,改变了应力集中位点;A-B-C咬合接触有利于减小种植体及周围骨组织的...     

下颌骨各向异性材质模型对种植牙有限元分析的影响

目的 建立含螺纹种植体各向异性的完整下颌骨有限元模型,研究各向异性材质模型模拟对牙种植体有限元分析的影响.方法 采用薄层CT扫描和自主开发的软件分别建立各向异性和等效各向同性的完整下颌骨三维有限元模型,其中在后牙区植入两枚牙种植体,分析在颊舌向、斜向加载时,种植体-骨界面主应力和主应变值的变化.结果 在各向异性下颌骨模型中,除骨皮质第一最小主应力减小6.3%～7.6%和骨松质第三最小主应力减小8.7%～46.0%外,骨界面绝大多数主应力和所有主应变值均大于各向同性;骨皮质主应力增加2.1%～74.1%,主应变增加4.7%～57.3%;骨松质主应力增加10.3%～71.4%,主应变值增加19.5%～63.4%,而且骨松质应力的增加比骨皮质明显.结论 下颌骨种植牙有限元分析时,下颌骨各向异性模拟会明显影响骨界面应力和应变值,并以增加为主.在生物力学研究中应更注重下颌骨各向异性的材质力学特性.     

种植体颈部微螺纹结构对种植稳定性影响的三维有限元分析

目的：通过分析种植体颈部螺纹结构,以及Von-Mises应力和应变分布情况,为种植体结构设计提供生物力学实验数据和理论参考依据。方法：本文通过运用三维计算机辅助设计CAD软件,设计建立颈部有螺纹和无螺纹三维种植体模型,利用CT扫描数据重建下颌骨三维模型,牙齿咬合面与上颌骨长轴面形成的倾角为45。,沿此方向施加120N的力作用在牙冠顶部,以模拟实际咬合状态受力。利用有限元分析软件模拟即刻负荷（即骨一种植体之间摩擦系数0．3）和骨愈合后期（即骨一种植体之间为绑定接触）两种加载情况下种植体与周围骨组织之间Von-Mises应力和应变峰值大小及分布状况进行比较和分析。结果：在即刻负荷的条件下,Von-Mises应力、应变在颈部光滑的种植体与皮质骨之间分布均匀,峰值分别为28．654MPa、0．01334mm;而颈部有螺纹种植体与皮质骨之间的Von-Mises应力、应变峰值分别为52．630MPa、0．015864mm。在骨愈合后期,颈部光滑的种植体,在相同咬合力作用下,皮质骨Von-Mises应力、应变峰值分别为36．975MPa、0．010272mm;而具有颈部螺纹设计的种植体所引起的Von-Mises应力、应变峰值分别为35．857MPa、0．010234mm。在骨愈合后期,增加种植体颈部的螺纹设计使得皮质骨所受Von-Mises应力减小1．118MPa、应变峰值也有减小的趋势。结论：即刻负载种植时,增加种植体颈部螺纹结构,在种植体一骨愈合后期,颈部的微螺纹结构可使种植体一骨接触界面的Von-Mises应力和应变峰值有所减小,并且有效改善了接触界面的应力分布状况,有助于其长期稳定性及种植成功率的提高。     

支抗种植体外形影响骨界面应力分布的研究

目的探讨种植体外形差异对骨界面应力分布的影响，并筛选出最佳支抗种植体外形。方法应用三维有限元分析方法对刃状螺纹型、矩形螺纹型及光滑型种植体进行骨界面应力和位移分析。结果刃状螺纹型种植体做支抗体时其骨界面第一、第二及第三主应力分别为6.67MPa、1.47MPa及0.52MPa，并且VonMises应力为7.22MPa，在三种种植体中应力值最小。而3种种植体颈部牙槽骨的DMX位移值分别为0.11×10     

弹性模量和初始应力对种植体骨界面应力分布影响的三维有限元分析

目的:分析种植体弹性模量与骨界面应力分布的关系。方法:用三维有限元的方法对不同弹性模量种植体在各种载荷下骨界面的应力大小和分布进行分析。结果:种植体周围界面骨组织应力强度随着材料弹性模量的增大而增大。结论:低弹性模量的钛合金材料作为种植材料时具有更好的生物力学相容性。初始应力在分析种植体骨界面应力分布时必须加以考虑。     

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.     

Evaluation of the mechanical characteristics of the implant-abutment complex of a reduced-diameter morse-taper implant. A nonlinear finite element stress analysis

The purpose of this study was to evaluate the mechanical characteristics of the implant-abutment connection of a reduced-diameter ITI dental implant. A finite element model of a slashed circle 3.3 mm x 10 mm ITI solid-screw implant and a 6 degrees solid abutment 4 mm in height was constructed, and the implant-abutment complex was embedded vertically in the center of a slashed circle 1.5 cm x 1.5 cm acrylic cylinder. Static vertical and oblique loads of 300 N were applied in separate load cases. The contact area was defined between the implant-abutment connection and nonlinear finite element stress analysis was performed. The magnitude and distribution of Von Mises stresses and displacement characteristics were evaluated. In vertical loading, Von Mises stresses concentrated around the implant-abutment connection at the stem of the screw and around the implant collar. Oblique loading resulted in a 2-fold increase in stresses at the implant collar, which was close to the yield strength of titanium. Displacement values under both loading conditions were negligible. We conclude that, in a reduced-diameter ITI dental implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. The neck of this implant is a potential zone for fracture when subjected to high bending forces. The reduced-diameter ITI dental implant might benefit from reinforcement of this region.     

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。     

不同螺距种植体集中载荷的有限元分析

目的:用三维有限元方法分析不同螺距种植体-骨界面应力分布状况,确定利于应力均匀分布的最佳螺纹参数设计.方法:建立包含上部结构的牙种植体、局部下颌骨块三维有限元模型,利用Cosmos/works软件分析在垂直、斜向45° 2 种集中载荷下螺距分别为0.6、 0.8、 1.0 mm的3 种种植体与骨界面的应力分布状况.结果:螺距为0.8 mm种植体周围Von-Mises应力、拉应力、压应力峰值较小,应力分布最均匀;同一螺距种植体斜向载荷下应力显著高于垂直载荷;应力集中主要出现于种植体颈部、皮质骨上缘和种植体末端最下一个螺纹处.结论:螺纹种植体螺距影响骨界面的应力分布和(牙合)力传导,为避免应力集中种植体末端螺纹应进行适当的截齿处理,种植义齿设计和修复时应尽可能减小或避免非轴向力.     

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。     

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??Objective    To evaluate the biomechanical influence of the relationship between implant tip and sinus ?oor cortical bone on posterior maxilla implantation by means of 3-dimensional??3-D??finite element??FE??analysis. Methods        Six 3-D FE models ??M1 to M6?? of standard implants and posterior maxillary region were constructed using CAD software. The thickness of both crestal cortical bone and sinus floor cortical bone were 1mm??according to different heights of the alveolar bone??the relationship between implant tip and sinus floor cortical bone was as follows. M1??the implant tip just broke through sinus cortical bone??the upper surface of sinus cortical bone and the apical surface of the implant were at the same level????M2??the implant tip broke through half the thickness of sinus ?oor cortical bone??M3??the implant tip just made contact with the lower surface of sinus ?oor cortical bone??for the remaining models??the implant tips were 1mm??2mm and 3mm apart from sinus floor??respectively. An inclined force of 129N was applied under immediate loading and conventional loading. The maximum von Mises stress??stress distribution??implant displacement and resonance frequencies were calculated using CAD software. Results    Except the M1 under immediate loading??the maximum von Mises stress of all models were concentrated on the surface of the crestal cortical bone around the implant neck. When the implant tip broke into or through sinus floor cortical bone??the maximum von Mises stress of crestal cortical bone reduced while that of sinus cortical bone increased??and the occlusional resonance frequencies of implants increased significantly while horizontal frequencies decreased??whether under immediate loading or conventional loading. Under immediate laoding??the maximum displacement of implant??especially the maximum displacement of the implant tip??was lower than the other models when the implant tip broke into or through the sinus cortical bone. However??the maximum displacements of both implant neck and tip were  hardly affected by the association between implant tip or sinus floor cortical bone under conventional loading. Conclusion    The association between implant tip and sinus floor cortical bone has effects both on stress distribution of the bone tissues around implant and on the maximum displacement and resonance frequencies of implants. Making the implant tip break into or through the sinus floor cortical bone??bi-cortical anchorage??is beneficial to improve the stress distribution and reduce the maximum displacement of implant??increasing the stability of the implant??especially under immediate loading.     

Stress Distribution Around Single Short Dental Implants: A Finite Element Study

Bone height restrictions are more common in the posterior regions of the mandible, because of either bone resorption resulting from tooth loss or even anatomic limitations, such as the position of the inferior alveolar nerve. In situations where adequate bone height is not available in the posterior mandible region, smaller lengths of implants may have to be used but it has been reported that the use of long implants (length ≥10 mm) is a positive factor in osseointegration and authors have reported failures with short implants. Hence knowledge about the stress generated on the bone with different lengths of implants needs scientific evaluation. The purpose of this study was to compare and evaluate the influence of different lengths of implants on stress upon bone in mandibular posterior area. A 3 D finite element model was made of the posterior mandible using the details from a CT scan, using computer software (ANSYS 12). Four simulated implants with lengths 6 mm, 8 mm, 10 mm and 13 mm were placed in the centre of the bone. A static vertical force of 250 N and a static horizontal force of 100 N were applied. The stress generated in the cortical and cancellous bone around the implant were recorded and evaluated with the help of ANSYS. In this study, Von Mises stress on a 6 mm implant under a static vertical load of 250 N appeared to be almost in the same range of 8 and 10 mm implant which were more as compared to 13 mm implant. Von Mises stress on a 6mm implant under a static horizontal load of 100 N appeared to be less when compared to 8, 10 and 13 mm implants. From the results obtained it may be inferred that under static horizontal loading conditions, shorter implants receive lesser load and thus may tend to transfer more stresses to the surrounding bone. While under static vertical loading the shorter implants bear more loads and comparatively transmit lesser load to the surrounding bone.

     

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.