氧化锆瓷基台与钛种植体联合应用中不同连接体设计的有限元分析

目的：分析不同氧化锆基台对基台自身及钛种植体周围骨组织应力的影响,为氧化锆基台设计提供理论依据。方法：采用计算机辅助设计建立5种不同设计的氧化锆基台模型,并根据不同的基台模型设计了与之对应的种植体、牙槽骨及全瓷冠模型。用三维有限元方法对每个模型进行100N的斜向加载,分析不同氧化锆基台的设计对基台自身及牙槽骨应力分布及应力峰值的影响。结果：5种设计的等效应力的分布基本一致,基台的应力主集中在基台颈部连接体上方,皮质骨及松质骨的应力主集中于骨与种植体连接的最上方。5种设计等效应力的峰值不同,圆形连接体设计时氧化锆基台,皮质骨及松质骨的等效应力峰值均小于其他各设计组。结论：圆形连接体设计是本研究5种设计中氧化锆基台与钛种植体相连的最佳设计形式。     

Effect of different restorative crown and customized abutment materials on stress distribution in single implants and peripheral bone: A three-dimensional finite element analysis study

Statement of problem

In recent years, the use of resin-matrix ceramics and polyetheretherketone (PEEK) abutments has been suggested to absorb excessive stresses on dental implants. However, only a few studies have evaluated the effect of these materials on stress distribution in implants and peripheral bone structure.

种植体-基台连接设计对基台与基台螺丝受力影响的三维有限元分析

目的: 研究锥形固位、平台转移种植体的不同连接设计对基台及基台螺丝受力情况的影响。方法: 建立平台转移量分别为0.2、0.4、0.6、0.8、1.0 mm并对应基台锥度分别为6°、8°、10°的种植体模型,分析各组模型受不同载荷时,基台及基台螺丝von-Mises应力及应变情况。结果: 随着平台转移量增大,基台与基台螺丝峰值von-Mises应力及应变增大,且平台转移量≥0.8 mm的模型在水平向力作用下,其峰值von-Mises应力高于690 MPa。水平向加力时,应力与应变随平台转移量增大的幅度最大,斜向加力时次之,垂直向加力时最小。81.67%的模型基台应力集中于基台颈部;所有模型基台螺丝应力均集中于基台螺丝头部与体部转折处。结论: 平台转移量增大使基台与基台螺丝在咬合过程中受力增大。为了减少种植修复后机械并发症的发生,建议在一定范围内选用平台转移量小的种植体。当平台转移量≥0.8 mm时,基台与基台螺丝最大应力超过纯钛的屈服强度,临床上应慎用该设计。     

Effect of bone quality and bone loss level around internal and external connection implants: A finite element analysis study

Statement of problemA consensus regarding the biomechanical effects of vertical bone loss in normal and osteoporotic bone tissue according to different implant-abutment interfaces is lacking.PurposeThe purpose of this finite element analysis study was to evaluate the effect of vertical bone loss (without bone loss; with 1.5-mm bone loss; with 3-mm bone loss; and with 4.5-mm bone loss) in normal and osteoporotic bone that received a Ø4×10-mm implant with different implant-abutment connections (external connection [external hexagon] and internal connection [Morse taper]) by using 3D finite element analysis.Material and methodsSixteen 3D models were simulated. Axial and oblique forces of 200 N and 100 N, respectively, were applied on the occlusal surfaces of the prostheses. Maximum principal stress and microstrain were determined from the bone tissue of each model. von Mises stress analysis was used to evaluate the stress distribution in implants and prosthetic components (fixation screws, abutment, and crown).ResultsThe results showed higher stress concentrations in models with bone loss as increased vertical bone loss contributed to higher stress and microstrain in the bone tissue, regardless of the quality of bone and implant-abutment connection. Osteoporotic bone contributed to increase in microstrain in the trabecular bone. The internal connection showed lower stress than the external connection implants only in models without marginal bone loss. Furthermore, higher stress concentrations were observed in the implants and fixation screws in models with increased bone loss and external connection implants, mainly under oblique loading. Osteoporotic bone did not affect stress distribution in the implants and prosthetic components.ConclusionsProgressive bone loss contributed to higher stress in the bone tissue, implants, and prosthetic components. The osteoporotic bone affects only the microstrain in the trabecular bone, but not the stress in the implants and prosthetic components. The internal connection implants showed lower stress in the cortical bone only in models without bone loss, while external connection implants exhibited higher stress in the implants and screws under oblique loading.     

不同结构氧化锆瓷基台及种植体周骨壁应力的有限元分析

目的 研究不同结构氧化锆瓷基台及种植体周骨壁应力的分布情况,为临床应用提供理论指导.方法 采用建模软件Altair Hypermesh建立三维有限元模型,应用Altair Hyperview后处理软件对模型中不同载荷条件下的三种不同结构氧化锆瓷基台及种植体周骨壁应力的分布情况进行分析,并与常规钛基台进行比较.结果 Replace基台模型的种植体周骨壁应力明显小于Lifecore实心基台模型和Lifecore螺栓固定基台模型的种植体周骨壁应力,而Replace基台模型的基台等效应力明显大于Lifecore实心基台模型和Lifecore螺栓固定基台模型的基台等效应力,Replace基台模型的螺栓等效应力峰值明显大于Lifecore螺栓固定基台的模型的螺栓等效应力峰值;Lifecore实心基台模型的种植体周骨壁应力略小于Lifecore螺栓固定基台模型的种植体周骨壁应力,而Lifecore实心基台模型的基台等效应力略大于Lifecore螺栓固定基台模型的基台等效应力;氧化锆基台模型与钛基台模型比较,两者无明显差异.结论 基台与种植体连接方式的不同对氧化锆瓷基台及种植体周骨壁应力的分布有影响,提示临床上应该根据患者情况选择最合适的基台;基台材料的改变对应力分布无明显影响,从生物力学考虑可以放心使用氧化锆瓷基台.     

Experimental evaluation of stress distribution with narrow diameter implants: A finite element analysis

Statement of problem

Narrow diameter implants were developed to allow placement in narrow alveolar ridges. Clinicians may have concerns about the durability and function of such implants.

A three-dimensional finite element analysis of the stress distribution on morse taper implants surface

PurposeThis finite element analysis (FEA) compared stress distribution on external surface of different morse taper implants, varying implant bodies length and dimensions of metal-ceramic crowns in order to maintain the occlusal alignment.MethodsThree-dimensional finite element (FE) models were designed representing a posterior left side segment of the mandible: group 0, 3 implants of 11 mm length; group 1, implants of 13 mm, 11 mm and 5 mm length; group 2, 1 implant of 11 mm and 2 implants of 5 mm length; group 3, 3 implants of 5 mm length. The abutments heights were 3.5 mm for 13 mm and 11 mm implants (regular) and 0.8 mm for 5 mm implants (short). Evaluation was performed on a computer program (Ansys software), with oblique loads of 365 N for molars and 200 N for premolars, applied on ridges of cusps and grooves.ResultsAbutments with 0.8 mm height generated less von Mises stresses compared with 3.5 mm height. The use of short implants associated with bigger crowns concentrated higher stress distribution and stress values on the surface implants, principally on the vestibular side (oblique direction of the loads). The more distal implant concentrated higher stress.ConclusionsMoreover, these 5 mm implants were positioned at the cortical bone level, which has higher elastic modulus and may have influenced at the stress distribution. However, despite the higher stresses, these implants were well able to withstand the applied forces.     

Micromotion and stress distribution of immediate loaded implants: a finite element analysis

Background: Primary stability and micromotion of the implant fixture is mostly influenced by its macrodesign.
Purpose: To assess and compare the peri-implant stress distribution and micromotion of two types of immediate loading implants, immediate loaded screw (ILS) Nisastan and Xive (DENTSPLY/Friadent, Monnheim, Germany), and to determine the best macrodesign of these two implants by finite element analysis.
Methods: In this experimental study, the accurate pictures of two fixtures (ILS: height = 13, diameter = 4 mm and Xive: height = 13, diameter = 3.8 mm) were taken by a new digital camera (Nikon Coolpix 5700 [Nikon, Japan], resolution = 5.24 megapixel, lens = 8× optical, 4× digital zoom). Following accurate measurements, the three-dimensional finite element computer model was simulated and inserted in simulated mandibular bone (D₂) in SolidWorks 2003 (SolidWork Corp., MA, USA) and Ansys 7.1 (Ansys, Inc., Canonsburg, PA, USA). After loading (500 N, 75° above horizon), the displacement was displayed and von Mises stress was recorded.
Results: It was found that the primary stability of ILS was greater (152 µm) than Xive (284 µm). ILS exhibited more favorable stress distribution. Maximum stress concentration found in periapical bone around Xive (≈30 MPa) was lesser than Nisastan (≈37 MPa).
Conclusions: Macrodesign of ILS leads to better primary stability and stress distribution. Maximum stress around Xive was less.     

A finite element analysis of two different dental implants: stress distribution in the prosthesis, abutment, implant, and supporting bone

This study evaluates the influence of 2 commercially available dental implant systems on stress distribution in the prosthesis, abutment, implant, and supporting alveolar bone under simulated occlusal forces, employing a finite element analysis. The implants and abutments evaluated consisted of a stepped cylinder implant connected to a screw-retained, internal, hexagonal abutment (system 1) and a conical implant connected to a solid, internal, conical abutment (system 2). A porcelain-covered, silver-palladium alloy was used as a crown. In each case, a simulated, 100-N vertical load was applied to the buccal cusp. A finite element model was created based on the physical properties of each component, and the values of the von Mises stresses generated in the prosthesis, abutment, implant, and supporting alveolar bone were calculated. In the prostheses, the maximum von Mises stresses were concentrated at the points of load application in both systems, and they were greater in system 1 (148 N/mm2) than in system 2 (55 N/mm2). Stress was greater on the abutment of system 2 than of system 1 on both the buccal (342 N/mm2 x 294 N/mm2) and lingual (294 N/mm2 x 148 N/ mm2) faces. Stress in the cortical, alveolar bone crest was greater in system 1 than in system 2 (buccal: 99.5 N/mm2 x 55 N/mm2, lingual: 55 N/mm2 x 24.5 N/mm2, respectively). Within the limits of this investigation, the stepped cylinder implant connected to a screw-retained, internal hexagonal abutment produces greater stresses on the alveolar bone and prosthesis and lower stresses on the abutment complex. In contrast, the conical implant connected to a solid, internal, conical abutment furnishes lower stresses on the alveolar bone and prosthesis and greater stresses on the abutment.     

Influence of implant abutment type on stress distribution in bone under various loading conditions using finite element analysis

PURPOSE: The purpose of this study was to investigate the effect of 3 different abutment types on the stress distribution in bone with inclined loads using finite element analysis. MATERIALS AND METHODS: The 1-body, internal-hex, and external-hex implant systems were modeled to study the effect of abutment type on stress distribution in bone. The bone model used in this study comprised compact and spongious bone assumed to be homogeneous, isotropic, and linearly elastic. RESULTS: In the case of the 1-piece implant, the load was transferred evenly not only in the implant system but also in bone. However, the maximum Von Mises stress generated in bone with the 1-piece implant was always higher than that generated with the internal-hex implant, regardless of load angle inclination. In the case of the internal-hex implant, the contact condition with friction between abutment and implant in the tapered joints and at abutment neck reduced the effect of bending caused by horizontal component of inclined load. The maximum Von Mises stress in bone was the highest for the external-hex implant. DISCUSSION: It was found that the internal-hex implant system generated the lowest maximum Von Mises stresses for all loading conditions because of reduction of the bending effect by sliding in the tapered joints between the implant and abutment. CONCLUSIONS: It was concluded that abutment type has significant influence on the stress distribution in bone because of different load transfer mechanisms and the differences in size of the contact area between the abutment and implant.     

Evaluation of implant abutment screw tightening protocols on reverse tightening values: An in vitro study

Statement of problemImplant abutment screw loosening is a common prosthetic complication of implant-supported crowns. However, reports that have objectively evaluated the effectiveness of different tightening protocols on reverse tightening values are sparse.PurposeThe purpose of this in vitro study was to determine the optimal tightening protocol for implant abutment screws.Material and methodsFifty Neoss implants were randomly distributed to 5 groups (n=10). The implants received a cover screw and mounted, and the impression coping was tightened. Tightening was measured by using a digital measuring device. Then, the implant abutments were placed and tightened to 32 Ncm by using a Crystaloc screw. In Group 2T10I, the screws were tightened twice with an interval of 10 minutes between the first and second tightening. In Group 2T0I, the screws were tightened twice with no interval time. In Group 1T, the screws were tightened 1 time only. In Group TCT, the screws were tightened, counter-tightened, and then tightened again. In Group TCTCT, the abutment screws were tightened, counter-tightened, tightened, counter-tightened, and then tightened again. All the mounted implants were left in the same environment for 3 hours, and the reverse tightening values were then measured.ResultsThe mean reverse tightening values of the first 4 groups ranged from 21.49 Ncm to 22.57 Ncm, whereas the reverse tightening value for the fifth group was 25.51 Ncm. A significant difference was found among the groups (P<.05) with reverse tightening data.ConclusionsNo significant difference was found in tightening the abutment screw 2 times with a 10-minute interval time, no interval time, or tightening it 1 time only. However, a significant difference was found in reverse tightening in the 3-time tightening and counter-tightening group.     

氧化锆角度基台及种植体周骨壁应力分布的有限元分析

目的研究氧化锆角度基台及种植体周骨壁应力的分布情况,为临床应用提供参考。方法采用三维有限元分析方法,对氧化锆直基台、15°、20°基台修复时的种植体基台、固定螺丝及种植体周骨壁应力的分布进行分析,并与常规钛基台进行比较。结果角度基台模型的基台、螺丝、种植体周骨壁的等效应力大于直基台;20°基台模型的基台、螺丝、种植体周骨壁等效应力远远大于15°基台模型;氧化锆基台模型与钛基台模型相比,2组无显著差异。结论基台角度对应力分布有影响,并随角度的增大而增大,提示临床上应注意种植体植入方向,尽量使用直基台或小角度基台,以减少种植体颈部骨吸收及修复并发症的发生;基台材料改变对基台、螺丝、种植体周骨壁的应力分布无显著影响,从生物力学考虑,临床上可以放心选用氧化锆角度基台。     

3D finite element analysis to detect stress distribution: spiral family implants

Aim  

Spiral family implants are a root-form fixtures with increasing thickness of tread. This characteristic gives a self-tapping and self-condensing bone properties to implants. To study spiral family implant inserted in different bone quality and connected with abutments of different angulations a Finite Element Analysis (FEA) was performed. Once drawn the systems that were object of the study by CAD (Computer Aided Design), the FEA discretized solids composing the system in many infinitesimal little elementary solids defined finite elements. This lead to a mesh formation where the single finite elements were connected among them by nodes. For the 3 units bone-implant-abutments several thousand of tetrahedral elements having 10 parabolic nodes were employed.     

下颌后牙区不同骨质内种植体即刻负载的三维有限元分析

Objective To assess and compare the peri-implant stress distribution of three posterior implants under immediate loading with 4 different bone qualities using three dimensional (3D) finite element (FE) analysis. Methods A 3D finite element model representing three implants in a portion of mandible at the 654-| region was developed, and three implants received a crown each. Four types of bone qualities (B1,B2, B3 and B4) were designed for the model. Load of 100 N was applied on the occlusal surfaces of the crowns at a 45° angle to the vertical axis of the implants. Results Von Mises stresses in the peri-implant bone of4-| in bone quality from B1 to B4 were ( 13. 17 ± 9. 32), ( 12. 95 ± 9. 14), ( 15. 00 ± 9. 44 ), and(16.81 ±10.74) MPa, and those of 5-| were (15.51 ± 10.32), (14.73 ±8.96), (16.79 ±8.40), and(18. 34 ±8.45) MPa. Stress in bone quality B4 showed the highest value, followed by B3 bone, the loweststress were found in B1 and B2 bone. It was significantly different (P ＜0. 05). However, von Mises stresses in different quality of bone around 6-| [(42.45 ±25.71), (41.66 ±25.29), (42.70 ±23.24), (42.06 ±23.66) MPa] were close to each other, and were as twice or three times as those of 4-| and 5-| , irrespective of different bone qualities. Conclusions The stress distribution around implant under immediate loading was not only affected by different bone qualities, but also by the direction of loading, and the latter may have a greater impact when a severe load delivered.     

下颌固定义齿不同松动度基牙应力分布的三维有限元分析

目的建立不同动度基牙的下颌固定义齿模型,探讨松动牙作为固定义齿基牙的合理性,以期为进一步的临床应用提供实验依据和指导。方法采用螺旋CT扫描,应用PHOTOSHOP CS2与ANSYS 11.0软件相结合建立下颌复合式固定桥模型。结果当3Ⅰ°松动时各基牙应力值显著增大且能观察到明显应力集中现象;当5或7松动时各基牙应力值也有不同程度的增加,但应力变化过程中并未观察到突然的应力增大现象。结论复合固定桥当两端基牙松动时,尤其是单根牙松动时,对基牙应力分布影响较大不宜单独作为基牙;而多根牙对应力分布的影响较小,可单独作为基牙;复合固定桥中间基牙有松动时,其松动度不论是Ⅰ度还是Ⅱ度都不会引起明显的应力集中,可选作基牙。     

下颌后牙区不同骨质内种植体即刻负载的三维有限元分析

目的 采用三维有限元分析探讨种植体在下颌后牙区不同骨质条件下即刻负载的应力分布,以期为即刻负载的应用选择提供参考.方法 建立下颌后牙区654-|种植体及上部牙冠和牙槽骨的即刻负载模型,根据骨皮质和骨松质比例构成不同分为B1(颌骨完全由均质的骨皮质构成)、B2(3 mm厚骨皮质包绕致密骨松质)、B3(1.5 mm厚骨皮质包绕致密骨松质)、B4(1.5 mm厚骨皮质包绕疏松骨松质)4种骨质条件,模拟颊舌向45°、100 N的力在修复体中心集中加载,分析各种植体在不同骨质内的von Mises应力分布.结果 颊舌向加载后von Mises应力主要集中于种植体颈部舌侧骨皮质,由B1至B4种植体4-|颈周骨内应力平均值[分别为(13.17±9.32)、(12.95±9.14)、(15.00±9.44)、(16.81±10.74)N]和种植体5-|颈周骨内应力平均值[分别为(15.51±10.32)、(14.73±8.96)、(16.79±8.40)、(18.34±8.45)N]的改变趋势一致,B3应力明显高于B1、B2,B4应力明显高于B3(P＜0.05).从B1～B4种植体6-|颈周骨内应力平均值[分别为(42.45±25.71)、(41.66±25.29)、(42.70±23.24)、(42.06±23.66)N]随骨质改变不大,但均显著高于相应骨质内4-|、5-|颈周骨内应力(P＜0.05).结论 在本项实验条件下进行即刻负载,种植体周围应力分布不仅受颌骨骨质的影响,种植体的植入位置以及建立合理的咬合同样非常重要.

Abstract：

Objective To assess and compare the peri-implant stress distribution of three posterior implants under immediate loading with 4 different bone qualities using three dimensional (3D) finite element (FE) analysis. Methods A 3D finite element model representing three implants in a portion of mandible at the 654-| region was developed, and three implants received a crown each. Four types of bone qualities (B1,B2, B3 and B4) were designed for the model. Load of 100 N was applied on the occlusal surfaces of the crowns at a 45° angle to the vertical axis of the implants. Results Von Mises stresses in the peri-implant bone of4-| in bone quality from B1 to B4 were ( 13. 17 ± 9. 32), ( 12. 95 ± 9. 14), ( 15. 00 ± 9. 44 ), and(16.81 ±10.74) MPa, and those of 5-| were (15.51 ± 10.32), (14.73 ±8.96), (16.79 ±8.40), and(18. 34 ±8.45) MPa. Stress in bone quality B4 showed the highest value, followed by B3 bone, the loweststress were found in B1 and B2 bone. It was significantly different (P ＜0. 05). However, von Mises stresses in different quality of bone around 6-| [(42.45 ±25.71), (41.66 ±25.29), (42.70 ±23.24), (42.06 ±23.66) MPa] were close to each other, and were as twice or three times as those of 4-| and 5-| , irrespective of different bone qualities. Conclusions The stress distribution around implant under immediate loading was not only affected by different bone qualities, but also by the direction of loading, and the latter may have a greater impact when a severe load delivered.     

Biomechanical effect of abutment on stability of orthodontic mini-implant. A finite element analysis

The biomechanical influences of primary factors on titanium mini-implant, which is used as an anchorage for orthodontic tooth movement, were quantified using the three-dimensional finite element method. Six types of finite element models were designed to show various thread pitches from 0.5 to 1.5 mm. Three models were designed with abutment and three other models without abutment. A traction force of 2 N was applied to the head of the mini-implant or abutment to be at 45 degrees to the bone surface. No remarkable differences were observed in the stress distribution patterns regardless of thread pitch variance. However, the stress distribution was remarkably different between models with abutment and without abutment. The maximum stress of the model with abutment and thread pitch 0.5 mm was the least as compared with the other models. Areas of high-level stress were obviously smaller than in the models without abutment. The plots of the displacement distributions of the models with abutment also presented significant pattern differences as compared with the models without abutment. The high-level area was localized to the head of the implant and the abutment in models with abutment. Therefore, the existence of the abutment is significantly useful in decreasing the stress concentration on the bone, while the effect of thread pitch was uncertain.