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.     

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.     

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。     

Influence of marginal bone resorption on stress around an implant--a three-dimensional finite element analysis

Average marginal bone resorption of about 1 mm after the first year of functional loading, which is followed by an annual loss of approximately 0.1 mm, has been reported in stable implants. However, finite element analyses on bone stress around implants have been limited to analysing the bone stress in the absence of any bone resorption. Thus, a three-dimensional finite element analysis was performed to compare the bone stresses in a non-resorption model with those in four models with bone resorption of two depths (1.3 and 2.6 mm) and types (horizontal resorption and angular defects). Axial and bucco-lingual forces were separately applied to the center of the superstructure and the maximum equivalent stress was calculated. The main tendencies of bone stress (highest stress concentration around implant neck, higher stresses under bucco-lingual than axial load, as well as in the cortical than cancellous bone) were the same in the non-resorption and resorption models. Bone stress distributions were similar in the non-resorption and horizontal resorption models, but differed from those in the angular defect models. Moreover, the changes of the bone stress values with resorption depth differed for the two resorption types. Thus, in FEA, accurate simulation of the marginal bone shape in the implant neck region is advisable.     

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.     

A conical implant-abutment interface at the level of the marginal bone improves the distribution of stresses in the supporting bone. An axisymmetric finite element analysis

It has been hypothesized that marginal bone resorption may result from microdamage accumulation in the bone. In light of this, a dental implant should be designed such that the peak stresses arising in the bone are minimized. The load on an implant can be divided into its vertical and horizontal components. In earlier studies, it was found that the peak bone stresses resulting from vertical load components and those resulting from horizontal load components arise at the top of the marginal bone, and that they coincide spatially. These peak stresses added together produce a risk of stress-induced bone resorption. Using axisymmetric finite element analysis it was found that, with a conical implant-abutment interface at the level of the marginal bone, in combination with retention elements at the implant neck, and with suitable values of implant wall thickness and modulus of elasticity, the peak bone stresses resulting from an axial load arose further down in the bone. This meant that they were spatially separated from the peak stresses resulting from horizontal loads. If the same implant-abutment interface was located 2 mm more coronally, these benefits disappeared. This also resulted in substantially increased peak bone stresses.     

种植牙即刻负载与延期负载的生物力学三维有限元分析

目的比较即刻负载和延期负载对种植体骨界面生物力学分布的影响。方法采用CT扫描和自主开发的USIS软件建模,用有限元法计算分析即刻负载和延期负载时种植体骨界面的应力、应变及种植体的位移。结果即刻负载时种植体骨界面的VonMises应力稍小于延期负载,均集中于种植体颈部骨皮质,底部骨松质次之;但VonMises应变有较明显的增加,均集中于种植体底部骨松质和螺纹部位;种植体的位移较延期负载略有增大。即刻负载种植体和延期负载种植体在受到颊舌向力时,VonMises应力、应变及位移均有不同程度的增加。结论即刻负载时种植体骨界面的生物力学分布规律与延期负载时相似,受到侧向力时应力、应变增大。种植牙即刻负载技术是可行的。     

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.     

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.     

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.     

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.     

骨吸收对平台转换种植体周围骨组织内部应力的影响

目的:观察骨吸收对平台转换设计种植体周围骨组织内部应力的影响。方法:利用COSMOS 2.85软件包建立不同程度骨吸收的种植体支持下颌第一磨牙金属冠三维有限元模型共10个。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)设计,模型又分为无骨吸收(A0,B0)和骨吸收的深度分别为0.5mm(A1,B1)、1.0mm(A2,B2)、1.5mm(A3,B3)和2.0mm(A4,B4)5种。采用垂直和斜向两种形式加载,载荷均为200N。观察骨吸收程度对种植体周围骨组织内部应力的影响,并比较不同程度骨吸收时两种设计种植体周围骨组织内部应力的不同。结果:平台转换种植体和平齐对接种植体周围骨组织内部的应力分布相似,应力主要集中在种植体颈部。随着骨吸收程度的增加,应力集中的范围增大;当皮质骨完全吸收后,种植体根部也出现应力集中的趋势。种植体周围骨组织内部的最大等效应力随着骨吸收程度的增加而减小,当皮质骨完全吸收后改变最明显。同等程度骨吸收时,平台转换设计种植体周围骨组织内部的最大等效应力小于平齐对接设计;随着骨吸收程度的增加,两者的差距逐渐减小。结论:骨吸收会导致种植体周围骨组织内部应力集中的范围加大而最大等效应力减小;骨吸收后平台转换设计改善种植体周围骨组织应力分布的作用变得不明显。     

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。     

Two-dimensional FEM analysis of hydroxyapatite implants: diameter effects on stress distribution

The effect of the diameter of hydroxyapatite (HAP) implants on stress distribution in alveolar bone was analyzed by two-dimensional finite element methods (FEM), with use of a 100-N vertical and lateral load. Since HAP is considered a bioactive material, the alveolar bone was assumed to be bonded directly to the HAP implant in the FEM model. The analysis showed that the stresses in cortical bone were generally higher than those in cancellous bone, and that the stress concentration occurred mainly in cortical bone around the neck of the implant with both vertical and lateral load. The stresses in cortical bone with lateral load were especially high-twice those in vertical load. Stresses in cortical bone decrease in inverse proportion to the increase in implant diameter with both vertical and lateral load. The results suggested that an implant with a large diameter is favorable from the standpoint of stress distribution.     

Selection of the implant transgingival height for optimal biomechanical properties: a three-dimensional finite element analysis

We evaluated the effects of the transgingival height of an implant on the maximum equivalent stress in jaw bones and the maximum displacement in implant-abutment complex by a finite element method. The transgingival height ranged from 1.0-4.0 mm. Under axial load, the maximum equivalent stress in the cortical bone could be reduced by up to 4.7%, and under a buccolingual load, the maximum equivalent stresses in the cortical and the cancellous bones could be reduced by 17.3% and 18.5%, respectively. The maximum displacement of the implant-abutment complex could be reduced by 4.1% and 48.9% under axial and buccolingual loads, respectively. When the transgingival height was in the range of 1.7-2.8 mm, there was minimum stress in the jaw bones and minimum displacement in the implant-abutment complex. Data indicated that transgingival height played a more important part in protecting a dental implant under a buccolingual load than under an axial load; and transgingival heights ranging from 1.7-2.8 mm were biomechanically optimal for a screwed implant.     

Biomechanical effect of a zirconia dental implant-crown system: a three-dimensional finite element analysis

Purpose: The objective of this study was to analyze and compare the stresses in two different bone-implant interface conditions in anisotropic three-dimensional finite element models (FEMs) of an osseointegrated implant of either commercially pure titanium or yttrium-partially stabilized zirconia (Y-PSZ) in combination with different superstructures (gold alloy or Y-PSZ crown) in the posterior maxilla. Materials and Methods: Three-dimensional FEMs were created of a first molar section of the maxilla into which was embedded an implant, connected to an abutment and superstructure, using commercial software. Two versions of the FEM were constructed; these allowed varying assignment of properties (either a bonded and or a contact interface), so that all experimental variables could be investigated in eight groups. Compact and cancellous bone were modeled as fully orthotropic and transversely isotropic, respectively. Oblique (200-N vertical and 40-N horizontal) occlusal loading was applied at the central and distal fossae of the crown. Results: Maximum von Mises and compressive stresses in the compact bone in the two interfaces were lower in the zirconia implant groups than in the titanium implant groups. A similar pattern of stress distribution in cancellous bone was observed, not only on the palatal side of the platform but also in the apical area of both types of implants. Conclusion: The biomechanical parameters of the new zirconia implant generated a performance similar to that of the titanium implant in terms of displacement, stresses on the implant, and the bone-implant interface; therefore, it may be a viable alternative, especially for esthetic regions.     

Tension More种植体骨界面的光弹应力分析

目的 研究不同锥度设计的Tension More（TM）种植体对种植体骨界面应力分布的影响。方法 医用纯钛制作5组种植体,分别为圆柱状螺纹种植体、上1/3 TM种植体（锥度长度为3 mm）、中1/2 TM种植体（锥度长度为5 mm）、下1/3 TM种植体（锥度长度为7 mm）、全长变化TM种植体（锥度长度为10 mm）。每组种植体各自包埋于由松质骨及1 mm皮质骨构成的复合光弹模型中,共建立5个复合光弹模型。每一模型先后分别予以垂直及斜向（45°）静态加载力。利用光弹应力分析法比较5组种植体骨界面的生物力学特征。结果 垂直加载下,上1/3 TM种植体、中1/2 TM种植体、下1/3 TM种植体比圆柱状螺纹种植体在皮质骨区及松质骨区的局部应力集中小;斜向加载下,4组TM种植体皮质骨区局部应力集中均低于圆柱状螺纹种植体。无论在垂直、斜向加载下,上1/3 TM种植体皮质骨区局部应力集中均最小。结论 合理锥度设计的TM种植体周围皮质骨、松质骨应力分布均匀合理,在不同载荷条件下,上1/3 TM种植体骨界面生物力学表现最优。     

单个种植体周围两种形状垂直骨吸收稳定期的骨内应力比较研究

目的:对单个种植体周围牙槽骨发生碟形和楔形垂直吸收并处于稳定期时的骨内应力变化状况,进行比较研究。方法:应用MSC-NASTRAN软件建立种植体周围不同形状、不同深度骨缺损的垂直骨吸收稳定期三维有限元模型,在垂直及斜向载荷下进行计算分析。结果:单个种植体周围牙槽骨发生少量垂直吸收后并处于稳定期时,随着骨缺损深度的增加,垂直载荷下骨内最大Von-Mises应力值有很小幅度的波动;斜向载荷下骨内最大Von-Mises应力值会增大,但幅度不大。同等骨缺损深度的碟形和楔形吸收的骨内应力情况相差较小。结论:在骨皮质保持完整及种植体不松动的情况下,种植体周围骨组织发生少量的垂直吸收时,骨内应力情况随缺损深度增加变化不大;而且相同条件下两种形状垂直骨吸收的骨内应力情况较相近。     

纳米羟基磷灰石/聚醚醚酮复合种植体受力的三维有限元分析

目的:评价纳米羟基磷灰石/聚醚醚酮(Nano-hydroxyapatite/Polyetheretherketone ,n-HA/PEEK)仿生种植材料受力时种植体及其周围骨组织的应力特征,为该种植材料的临床运用提供生物力学依据。方法:根据CT扫描数据及种植体产品数据建立包括牙槽骨、种植体的三维有限元模型,比较在150N垂直加载条件下n-HA/PEEK和钛种植体周围骨皮质及骨松质的应力分布。结果:两种材料应力分布规律:紧邻种植体颈部的骨皮质应力最大远离处逐渐减小,皮质骨内两种材料的表面最大应力有显著性差异(P<0.05)。负重时钛金属种植体其表面应力波动变化范围增大,容易形成应力集中。同骨组织具有相似弹性模量的n-HA/PEEK材料表面应力分布更均匀。结论:n-HA/PEEK材料更有利于将种植体所受载荷以应力的形式传递到周围骨组织中去,有利于保持骨结合面的长期稳定。