Selection of optimal dental implant diameter and length in type IV bone: a three-dimensional finite element analysis

This study aimed to create a 3D finite element model for continuous variation of implant diameter and length, thereby identifying their optimal range in type IV bone under biomechanical consideration. Implant diameter ranged from 3.0 to 5.0 mm, and implant length ranged from 6.0 to 14.0 mm. The results suggest that under axial load, the maximum Von Mises stresses in cortical and cancellous bones decrease by 50% and 27%, respectively; and under buccolingual load, by 52% and 60%, respectively. Under these two loads, the maximum displacements of implant-abutment complex decrease by 39% and 43%, respectively. These results indicate that in type IV bone, implant length is more crucial in reducing bone stress and enhancing the stability of implant-abutment complex than implant diameter. Biomechanically, implant diameter exceeding 4.0 mm and implant length exceeding 9.0 mm are the combination with optimal properties for a screwed implant in type IV bone.     

Selection of the distraction implant length with improved biomechanical properties by three‐dimensional finite element analysis

Summary In this study, the distraction length of distraction implant was set as input variable which ranged from 2 to 10 mm. The effect of distraction length on the maximum Von Mises stress in the jaw bones and the implant were evaluated by a finite element method. The results showed that under axial load, the maximum equivalent stresses in cortical bone, cancellous bone, and distraction screw decreased by 5·8%, 8·6%, and 11·0%, respectively, with the changing of distraction length, and under buccolingual load those decreased by 0·3%, 18·0%, and 13·0%, respectively. The data indicate that cancellous bone is more sensitive to distraction length than the cortical bone. Under both loads, the central distraction screw was subjected to the stress concentration and more easily damaged by buccolingual force than by axial force. Distraction implant with distraction length exceeding 8 mm showed relatively better biomechanical behaviour.     

圆柱状种植体螺纹的双目标稳健分析

目的:探讨圆柱状V形螺纹种植体螺纹参数变化对骨组织应力大小的影响,为临床设计和选择最佳的螺纹参数提供理论依据。方法:建立了包含圆柱状V形螺纹种植体的颌骨骨块三维有限元模型,设定螺纹齿高(H)范围为0.20-0.60mm,螺纹宽度(W)范围为0.10-0.40mm。在修复体正中分别进行垂直向100N和450颊舌向50N的力学加载。观察H和W变化对颌骨平均主应力(EQV)峰值的影响,同时进行变量对颌骨的敏感度分析。结果:在垂直向加载中皮质骨和松质骨的EQV应力峰值增幅分别为4.3%和63.0%;在颊舌向加载中皮质骨和松质骨的增幅分别为19.3%和118.0%;在各种加载情况下,当变量H位于0.34mm-0.50mm之间,同时变量W位于0.18mm-0.30mm之间时,对颌骨的EQV应力峰值响应曲线的切线斜率位于-1和1之间;变量H比W对颌骨的EQV应力峰值的影响更明显。结论:松质骨的应力大小更易受到螺纹的影响;螺纹对侧向力加载时的力学传递影响更明显;给予生物力学方面的考虑,圆柱状螺纹种植体最佳的螺纹设计为螺纹高度介于0.34mm-0.50mm之间,螺纹宽度介于0.18mm-0.30mm之间;在圆柱状螺纹种植体设计中,相对于螺纹宽度而言应更重视螺纹高度的设计。     

种植体直径和长度在Ⅰ类骨质中的优化选择

目的:应用Ansys DesignXplorer模块,研究圆柱形种植体直径和长度同时连续变化对Ⅰ类骨质的颌骨应力影响,为临床选择和设计种植体提供理论依据。方法:建立包含圆柱状种植体的下颌骨Ⅰ类骨质骨块的三维有限元模型,设定种植体直径(D)变化范围为3.0~5.0mm,种植体长度(L)变化范围为6.0~16.0mm,观察D和L变化对颌骨Von Mises应力峰值的影响。同时进行颌骨Von Mises应力峰值对变量的敏感度分析。结果:随着D和L的增加,垂直向加载时,皮、松质骨的EQV应力峰值分别降低了54.5%和70.2%,颊舌向加载时,皮、松质骨的EQV应力峰值分别降低了73.5%和75.1%;当D大于3.8mm同时L大于9.0mm时,应力峰值的响应曲线的切斜率位于-1和0之间;在垂直向加载和颊舌向加载时,变量D比L更易影响皮质骨的EQV应力峰值。结论:种植体的直径比长度更易影响皮质骨的应力大小。从生物力学角度而言,对于Ⅰ类骨质,在临床上选择种植体时,种植体的直径应不小于3.8mm,种植体的长度应不小于9.0mm。     

圆柱种植体直径和长度的双因素分析

目的应用Ansys DesignXplorer模块,进行圆柱形种植体直径和长度的双目标稳健分析,为临床选择和设计种植体提供理论依据。方法建立包含圆柱状种植体的颌骨骨块三维有限元模型,设定种植体的直径（D）为2.5～5.0 mm,种植体长度（L）为6.0～16.0 mm,观察D和L变化对颌骨Von Mises应力峰值的影响,同时进行颌骨VonMises应力峰值对变量的敏感度分析。结果在一个变量取中间值时,垂直向加载情况下,随着D的增加,皮、松质骨的EQV应力峰值分别降低了44.66%和51.45%,随着L的增加,皮、松质骨的EQV应力峰值分别降低45.97%和52.15%;颊舌向加载情况下,随着D的增加,皮、松质骨的EQV应力峰值分别降低71.32%和58.50%,随着L的增加,皮、松质骨的EQV应力峰值分别降低21.66%和37.75%。在两种加载情况下,当D>3.7 mm且L>10.0 mm时,颌骨的EQV应力峰值对D和L的响应曲线曲率位于- 1和0之间;变量D比L对颌骨的EQV应力峰值的影响更明显。结论种植体直径的增大有利于改善颊舌向力的力学分布,长度的增大有利于改善垂直向力的力学分布;临床选择种植体时,只要骨量允许,种植体直径应不小于3.7 mm,长度应不小于10.0 mm;相对于长度而言,应更重视圆柱形种植体直径的选择和设计,而改善颌骨的宽度比改善颌骨的高度在缓和颌骨的应力分布中可能更有意义。     

种植体直径和长度在Ⅲ类骨质中的优化选择

目的应用Ansys DesignXplorer模块，分析圆柱形种植体直径和长度同时连续变化时对Ⅲ类骨质的颌骨应力的影响，为临床选择和设计种植体提供理论依据。方法建立包含圆柱状种植体的下颌骨Ⅲ类骨质的骨块三维有限元模型，设定种植体直径变化范围为3．0～5．0mm，种植体长度变化范围为6．0～16．0mm，观察直径和长度变化对颌骨Von Mises应力峰值的影响。同时进行颌骨Von Mises应力峰值对变量的敏感度分析。结果随着直径和长度的增加，垂直向加载时，皮、松质骨的EQV应力峰值分别降低了65．3％和76．8％；颊舌向加载时，皮、松质骨的VonMises应力峰值分别降低了76．1％和78．0％；当直径大于3．95mm，同时长度大于10．5mm时，应力峰值响应曲线的切斜率位于-1和0之间；在垂直向加载和颊舌向加载时，长度和直径分别对皮质骨EQV应力峰值的影响更明显。结论种植体直径增加更有利于改善颌骨颊舌向加载下的应力分布，种植体长度的增加更有利于改善颌骨垂直加载下的应力分布。从生物力学角度而言，对于m类骨质在临床上选择种植体时，种植体的直径应不小于3．95mm。种植体的长度应不小于10．5mm。     

螺纹种植体螺距的优化设计和应力分析

目的应用Ansys Workbench DesignXplorer优化设计模块,探讨圆柱状V形螺纹种植体螺距变化对颌骨和
种植体应力大小的影响,为临床设计和选择最佳的螺纹参数提供理论依据。方法建立了包含圆柱状V形螺纹种植
体的颌骨骨块三维有限元模型,设定螺纹螺距（ P）范围为0.5～1.6 mm,观察P变化对颌骨和种植体Equivale（nt EQV）
应力峰值的影响。结果在垂直向加载中皮质骨、松质骨和种植体的EQV应力峰值增幅分别为7.1%、123.4%和
28.7%;在颊舌向加载中皮质骨、松质骨和种植体的EQV增幅分别为2.8%、28.8%和14.9%;在各种加载情况下,当
变量P大于0.8 mm时,对颌骨及种植体的EQV应力峰值响应曲线曲率位于- 1和1之间。结论松质骨的应力大小更
易受到螺距的影响;螺纹对垂直加载时的力学传递影响更明显;螺距在保护种植体垂直受力时起着更为重要的作
用;圆柱状螺纹种植体螺距最佳设计应不小于0.8 mm,但同时应避免过大的螺距。     

Evaluation of the cylinder implant thread height and width: a 3-dimensional finite element analysis

PURPOSE: To evaluate continuous and simultaneous variations of thread height and width for an experimental screw-type implant. MATERIALS AND METHODS: A finite element model of an implant with a V-shaped thread was created. The range of thread height was set at 0.20 to 0.60 mm, and the range of thread width was set at 0.10 to 0.40 mm. Forces of 100 N and 50 N were applied along the implant axis (AX) and an angle of 45 degrees in a buccolingual direction (45-degree BL), respectively. The maximum von Mises stresses in jawbone were evaluated, and the sensitivity of the stress in jawbone to the variables was also evaluated. RESULTS: Under AX load, the maximum von Mises stresses in cortical and cancellous bones increased by 4.3% and 63.0%, respectively, as thread parameters changed. Under 45-degree BL load, maximum von Mises stresses in cortical and cancellous bones increased by 19.3% and 118.0%, respectively. When thread height was from 0.34 to 0.50 mm and thread width was 0.18 to 0.30 mm, the tangent slope of the maximum von Mises stress response curve ranged from -1 to 1. The variation of the maximum von Mises stresses in jawbone was more sensitive to thread height than to thread width. CONCLUSIONS: Stress in cancellous bone is more likely to be influenced by thread parameters than stress in cortical bone. A 45-degree BL force is more likely to be influenced by thread parameters than an axial force. A thread height of 0.34 to 0.50 mm and a thread width of 0.18 to 0.30 mm is optimal from a biomechanical point of view. In the design of a screw-type implant, thread height is more important than thread width for the reduction of stress within the bone.     

反支撑形螺纹种植体即刻负载时应力分布的三维有限元分析

目的:利用三维有限元模型,探讨圆柱状反支撑形螺纹种植体螺纹形态变化对周围骨组织应力大小的影响,为临床设计和选择最佳的种植体螺纹参数提供理论依据.方法:利用包含圆柱状反支撑形螺纹种植体的颌骨三维有限元模型,分别设定螺纹宽度恒定(W=0.2)螺纹齿高(H)变化范围为0.2-0.6mm,或螺纹齿高恒定(H=0.4)螺纹宽度(W)范围为0.1-0.4mm.在种植体正中分别加载垂直向100N和颊舌向45°50N的作用力进行分析.观察H和W变化对颌骨平均应力Von-Mises峰值的影响.结果:即刻负载时,垂直向加载(F1)时,齿高及宽度变化时种植体Von-Mises应力峰值增幅分别为68.39％和20.90％;侧向加载(F2)时,种植体应力峰值变化增幅为42.28％和32.51％;结合两种作用力,当螺纹宽度恒定,齿高为0.3-0.5mm时,即刻负载情况下种植体对颌骨产生的应力峰值相对较小;齿高恒定,宽度设计为0.1-0.3mm时,种植体对颌骨产生的应力峰值相对较小.结论:在生物力学方面研究表示,圆柱状反支撑形螺纹种植体最佳的螺纹设计为螺纹齿高在0.3-0.5mm之间,螺纹宽度在0.1-0.3之间;相对于种植体螺纹宽度而言种植体螺纹齿高对应力分布影响更大,种植体螺纹设计时更应重视齿高的设计.     

Bivariate Evaluation of Cylinder Implant Diameter and Length: A Three-Dimensional Finite Element Analysis

Purpose: To evaluate continuous and simultaneous variations of implant diameter and length for an experimental cylinder implant.
Materials and Methods: A finite element model of a mandible segment with implant was created. The range of implant diameter (D) was set from 2.5 to 5.0 mm, and that of implant length (L) from 6.0 to 16.0 mm. The maximum Von Mises stresses in the mandible were evaluated, and the sensitivity of the stresses in the mandible to the variables was also evaluated.
Results: Under axial load, the maximum von Mises stresses in cortical and cancellous bones decreased by 73.3% and 69.4%, respectively, with D and L increasing. Under buccolingual load, those decreased 83.8% and 79.2%, respectively. When D exceeded 3.9 mm and L exceeded 10.0 mm, the tangent slope rate of the maximum von Mises stress response curve ranged from −1 to 0. The variation of the maximum von Mises stresses in the mandible was more sensitive to D than to L.
Conclusions: Buccolingual force is apt to be influenced by the two implant parameters; implant diameter and length favor stress distribution in cortical bone and cancellous bone, respectively. Implant diameter exceeding 3.9 mm and implant length exceeding 10.0 mm are the optimal choice for type B/2 bone in a cylinder implant. The implant diameter is more important than length in reducing bone stress.     

Influence of implant design and bone quality on stress/strain distribution in bone around implants: a 3-dimensional finite element analysis

PURPOSE: A 3-dimensional finite element analysis was performed to evaluate the influence of implant type and length, as well as that of bone quality, on the stress/strain in bone and implant. MATERIALS AND METHODS: Two types (screw and cylinder) and 4 lengths (9.2, 10.8, 12.4, and 14.0 mm) of titanium implants were buried in 4 types of bone modeled by varying the elastic modulus for cancellous bone. Axial and buccolingual forces were applied to the occlusal node at the center of the abutment. RESULTS: Regardless of load direction, maximum equivalent stress/strain in bone increased with a decrease in cancellous bone density. Under axial load, especially in the low-density bone models, maximum equivalent strain in cancellous bone was lower with the screw-type implant than with the cylinder-type implant. It was also lower with the longer implants than with the shorter implants. Under buccolingual load, equivalent stress/strain was influenced mainly by bone density. DISCUSSION: This study confirms the importance of bone quality and its presurgical diagnosis for implant long-term prognosis. Implant length and type can also influence bone strain, especially in low-density bone. CONCLUSIONS: The results of this study suggest that cancellous bone of higher rather than lower density might ensure a better biomechanical environment for implants. Moreover, longer screw-type implants could be a better choice in a jaw with cancellous bone of low density.     

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.     

眶部种植体长度对骨界面应力影响的三维有限元研究

目的 探讨不同长度的眶部种植体对骨界面应力分布的影响。方法 建立直径3.75 mm,长度分别为3、4、6、10 mm的眶部种植体-颅颌面骨三维有限元模型,分别给予沿种植体轴向和与轴向成45°的载荷,载荷大小20 N,记录两种方向载荷下种植体及骨界面的Von-Mises应力峰值和位移峰值,分析其应力分布。结果 施加沿种植体轴向载荷时,种植体周围应力集中于根部,种植体受力大于骨面;施加与轴向成45°载荷时,应力集中于种植体颈部与第一螺纹之间,种植体受力大于骨面。施加两个方向的载荷时,3 mm种植体的应力峰值明显大于其他长度种植体,而位移峰值无明显变化。在相同长度下,施加沿种植体轴向载荷时的应力峰值及位移峰值均明显低于与轴向成45°载荷时,载荷方式对界面应力分布有明显的影响。结论 临床上尽量选择4 mm以上的眶部种植体;应用3 mm种植体时,应选择骨密质较厚的区域植入。     

密质骨厚度影响牙种植体稳定性的有限元固有频率分析

目的：用有限元方法研究密质骨厚度对牙种植体初期稳定性的影响。方法：建立牙种植体、局部下颌骨块三维有限元模型，利用ABAQUS有限元软件，分析不同密质骨厚度对种植体颊舌向、轴向一阶振动固有频率的影响。结果：随着密质骨厚度由缺如逐渐增加至3．0mm，种植体颊舌向、轴向振动的固有频率值均逐渐增加，其中颊舌向固有频率最大增幅达97．61％，而轴向固有频率最大值仅增加了11．06％。结论：种植体周密质骨厚度主要增加了种植体颊舌向稳定性，而对种植体轴向稳定性的增加有限。     

Ⅱ类骨质平台转换连接种植体植入深度对皮质骨应力的影响

目的研究Ⅱ类骨质平台转换连接种植体不同植入深度对皮质骨应力的影响。方法于2010年3月在滨州医学院(烟台校区)参照Ankylos种植系统种植体和实心基台的真实数据,利用Solidworks2007制图软件,模拟不同植入深度时平台转换连接种植体-基台-Ⅱ类骨质模型,导入Ansys workbench有限元软件,采用垂直向200N和斜向100N加载,分析不同植入深度时的应力分布。结果不同植入深度间皮质骨最大应力差异有统计学意义(P<0.01);当植入深度在皮质骨下2mm范围内时皮质骨最大应力在各向加载时均较稳定。结论为避免应力在骨组织中的过度集中,Ⅱ类骨质植入深度应控制在皮质骨下2mm范围内。     

��ֲ����ⲿ�������Ƥ�ʹǵĹ�ϵ������������ֲӰ�����ά����Ԫ����

??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.     

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。     

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。     

上颌窦底提升不同高度对种植义齿受力影响的三维有限元分析

目的:研究上颌窦底提升后种植义齿修复时,不同提升高度对种植体-骨界面应力状况的影响,为其临床应用提供生物力学参考依据。方法:采用健康志愿者的CT扫描数据,通过Mimics 11.0软件,建立上颌第一磨牙缺失、含上颌窦的上颌骨三维有限元模型,并模拟植入10 mm长标准种植体1枚。模拟上颌骨骨量不足,建立上颌窦底分别提升2、4、6 mm的种植义齿模型,并以无需窦底提升的种植义齿模型为对照。分别从垂直、颊向30°和舌向30°三个方向,对种植义齿上部结构牙冠咬合面中心点施加100 N的集中载荷,用三维有限元分析方法对不同模型的种植体-骨界面进行应力分析。结果:各模型在同一加载条件下,皮质骨的应力最大,松质骨和人工骨的应力值接近。随着窦底提升高度的增高,种植体颈部周围骨组织的应力总体呈先降后升的趋势,在提升高度为4 mm时最小。颊舌向加载时产生的应力远大于垂直载荷下产生的应力。结论:上颌骨后部骨量不足时,上颌窦底提升植骨可以大大改善种植体-骨界面内应力,植骨高度为4 mm时,种植体-骨界面应力总体最小;垂直载荷更有利于种植体-骨界面的应力分布状况,在临床设计种植义齿上部结构时应尽量减小或避免斜向载荷。     

Influence of maxillary cortical bone thickness,implant design and implant diameter on stress around implants: A three-dimensional finite element analysis

PurposeThere is no clear evidence of the factors that could improve implant biomechanics in the posterior maxilla. Thus, a finite element analysis was performed to investigate the effect of maxillary cortical bone thickness, implant design and diameter on stress around implants.MethodsA total of 12 models of the posterior maxilla with implant were computer-simulated by varying the thickness of the alveolar cortical bone (1.5, 1.0, 0.5 or 0 mm) and implant characteristics (cylindrical implant of 4.1-mm diameter, screw-type implants of 4.1-mm or 4.8-mm outer diameters). On top of each implant, forces were separately applied axially (100 N) and buccolingually (50 N), and the von Mises stresses were calculated.ResultsRegardless of load direction, implant design and diameter, cortical and cancellous bone stresses increased with the decrease of crestal cortical bone thickness. In the absence of crestal cortical bone, cancellous bone stresses were highest and, under axial load, were transferred to the sinus floor. Implant design and diameter influenced stress to a less extent, especially under buccolingual load and in the presence of crestal cortical bone.ConclusionsFrom a biomechanical viewpoint, to improve implant success odds in the posterior maxilla, rather than implant selection, careful preoperative evaluation of the cortical bone at the planned implant site is recommended. If this cortical bone is very thin or even lacking, implant treatment should be carried on with caution by progressive loading in the range of functional loads.