Replace内、外连接方式种植体-基台内部的应力分析

目的 建立2种Replace实体种植体的下颌骨三维有限元模型,研究Replace内、外连接方式种植体-基台内部的应力状态.方法 测量2种种植体各部件的数据和利用螺旋CT扫描下颌骨截面形态,分别建立2种种植体的三维骨内模型,对模型采用轴向加载(200 N)、30°侧向加载(100N),分析2种种植体-基台内部的应力分布趋...     

下无牙颌覆盖义齿四颗种植体套简冠固位位置的优化设计及力学分析

目的:建立含四颗种植体的无牙下颌骨三维有限元模型并对种植体不同位置组合进行应力加载,模拟不同位置套筒冠附着体固位的下颌种植覆盖义齿受力情况,对种植体位置进行优化设计.方法:应用CATIA建模软件以及ABAQUS有限元软件建立含4颗对称分布的标准m种植体(4.1×10mm)的有限元模型.根据种植体位置不同共建立了I-VII个模型,并在模拟的义齿基托平面结构上进行垂直方向100N静态颌力加载.结果:种植体周围骨质应力分布情况显示:3-6设计有良好的应力分布情况,2-4设计和3-5设计次之,其余模型的应力分布显示出了不均衡性.结论:采用磨牙区种植的设计值得考虑,对于3-6设计而言,各个种植体周围的应力分布更为均衡合理.同时在位置设计中注意控制种植体间的距离.     

螺纹形态和螺距对种植体系统应力影响的三维有限元研究

目的研究根据标准螺纹参数设计的不同螺纹形态和螺距的9种牙种植体受载后牙槽骨及整个种植系统的应力变化,为种植体系统的优化设计及临床应用提供理论依据。方法采用Solidworks软件建立了螺纹形态分别为V形、梯形、锯齿形,螺距分别为0.7 mm、0.8 mm、1.0 mm的9种标准螺纹式种植体模型,配以基台、基台螺丝构成整套种植体系统,根据CT扫描数据重建下颌骨模型,在垂直向和与种植体长轴成15°斜向分别加载100 N力,ANSYS有限元分析软件计算比较种植体系统和周围牙槽骨的应力及位移分布状况。结果综合考虑种植体系统各部件和种植体周围牙槽骨所受应力,9种种植体中,螺纹形态为V形、螺距为0.8 mm的种植体在垂直向和斜向加载时应力较小。9种种植体各部件及周围牙槽骨最大位移量垂直向加载时为2.61μm,斜向加载时为23.78μm,9种种植体的位移差异小。结论螺纹形态为V形、螺距为0.8 mm的种植体力学性能较好。螺纹形态和螺距对种植体系统及周围牙槽骨的位移影响不大。     

无牙下颌覆盖义齿4个种植体套筒冠固位位置的优化设计和力学分析

目的:建立含4个种植体的无牙下颌骨三维有限元模型并对种植体不同位置组合进行应力加载,模拟不同位置套筒冠附着体固位的下颌种植覆盖义齿受力情况,对种植体位置进行优化设计。方法:应用CATIA建模软件以及ABAQUS有限元软件建立含4个对称分布的标准ITI种植体(4.1 mm×10 mm)的有限元模型。根据种植体位置不同共建立了Ⅰ～Ⅶ个模型,并在模拟的义齿基托平面结构上进行垂直方向100 N静态牙合力加载。结果:种植体周围骨质应力分布情况显示:3-6设计有良好的应力分布情况,2-4设计和3-5设计次之,其余模型的应力分布显示出了不均衡性。结论:采用磨牙区种植的设计值得考虑,对于3-6设计而言,各个种植体周围的应力分布更为均衡合理。同时在位置设计中注意控制种植体间的距离。     

三种下颌种植固定全口义齿的初步应力比较

目的:比较同一病例3组下颌种植固定全口义齿的骨及种植体应力分布特点,为临床种植修复提供生物力学分析依据.方法:建立4个种植体3mm悬臂,6个种植体3mm悬臂,8个种植体3mm悬臂3组下颌种植固定全口义齿的三维有限元模型.在悬臂末端垂直加载100N.结果:种植全口义齿悬臂末端垂直加载时,各组种植体周围颈部骨应力集中.6个种植体组骨压应力和拉应力都最小.种植体应力主要集中在末端和中间种植体的颈部.种植修复上部支架应力主要集中在与远中末端种植体相连接处.结论:末端种植体骨应力集中,易发生松动失败;种植体颈部应力集中,易发生植入体与基桩连接失败.6个种植体支持组修复设计在该病例中较符合生物力学分布原理.     

无牙下颌固定种植义齿带末端悬臂的应力分析

目的:比较不同悬臂设计下颌种植支持全口义齿的骨及种植体应力分布特点,为临床种植修复提供生物力学分析依据。方法:建立3组下颌6个种植支持全口义齿的三维有限元模型,悬臂分别为3、6、9 mm。在悬臂末端垂直加载100 N的力。结果:种植全口义齿悬臂末端垂直加载时,末端种植体骨应力集中,易发生松动失败;末端种植体及中间种植体颈部应力集中,易发生植入体与基桩连接失败;连梁应力集中在与末端种植体连接处,此处易发生折断。悬臂长度增加骨应力、种植体应力及连梁应力明显增加。结论:悬臂越短越有利于力的均匀分布。6个种植体支持短悬臂修复设计较符合生物力学分布原理。     

应用三维有限元法对不同骨质牙种植修复体生物力学的研究

目的:分析4种骨质中两后牙同时缺失时种植体两单冠与联冠修复的最大Von-mises应力值和最大位移值,为4种骨质中两后牙缺失时最佳种植修复寻找理论依据方法:采用三维有限元分析法,建立8个含双种植体的下颌骨三维有限元模型。在第一、第二磨牙区各植入一枚种植体(直径4.0mm、长13mm光滑圆柱形及直径4.8mm、长10mm螺纹圆柱形种植体),采用垂直分散加载100N及颊舌向倾斜45°分散加载45 N,分析种植体-骨界面的最大Von-mises应力值及最大位移值结果:同种骨质中不同修复方式时,最大Von-mises应力值V_单>V_联。最大位移值D_单>D_联。结论:联冠修复方式优于两单冠修复方式。     

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。     

2种接连方式种植体的骨界面应力分析

目的建立2种包含实体种植体的下颌骨三维有限元模型,研究2种接连方式种植体（Replace和Replace Select）的骨界面应力状态。方法测量2种种植体各部件的数据和利用螺旋CT扫描下颌骨截面形态,分别建立2种种植体的三维骨内模型,对模型采用轴向加载200 N、30°侧向加载100 N载荷,分析2种种植体的骨界面的应力分布趋势。结果2种种植体骨界面应力分布特点均为从种植体颈部至根尖部逐渐减小,应力主要集中在皮质骨区和种植体颈部狭窄处的骨界面;侧向加载时骨界面的应力值均高于轴向加载。无论轴向加载还是侧向加载,ReplaceSelect种植体骨界面的应力值均高于Replace种植体。结论临床修复时应避免种植体受到过大的力,尤其是侧向力,以防出现颈部骨吸收,Replace Select种植体更应注意。     

上颌中切牙种植体全瓷基台的计算机辅助设计

目的 探索建立上颌中切牙种植体全瓷基台计算机辅助设计(CAD)软件功能模块.方法 选择1副右上中切牙缺失、已行种植的工作模型,通过三维激光扫描,直接获取愈合基台(牙合)面、种植体-基台连接底座定位突、人工牙龈内壁(牙合)1/3部分、近远中邻牙以及对(牙合)牙表面三维数据.通过空间几何变换,间接获取种植体长轴、基台-底座结合平面数据.设计最终全冠,应用定向数据偏置等功能模块对全冠进行虚拟回切,设计基台龈上部分.最后应用基于边界曲率特征的双端扫掠曲面造型等功能模块设计基台穿龈部分.结果 建立了一条上颌中切牙种植体全瓷基台CAD路线,确定了三维图形学功能函数及其组合,实现了完整的设计流程.结论 初步建立了上颌中切牙种植体全瓷基台CAD软件平台.     

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.     

A 16-year study of the microgap between 272 human titanium implants and their abutments

A microgap has been described at the level of the implant-abutment connection. This microgap can be colonized by bacteria, and this fact could have relevance on the remodeling of the peri-implant crestal bone and on the long-term health of the peri-implant tissues. The authors report on 272 implants with screw- or cement-retained abutments retrieved from humans for different causes during a 16-year period. In the implants with screw-retained abutments, a 60-microm microgap was present at the level of implant-abutment connection. In some areas the titanium had sheared off from the surface and from the internal threads. The contact between the threads of the implant and those of the abutment was limited to a few areas. Bacteria were often present in the microgaps between implant and abutment and in the internal portion of the implants. In implants with cement-retained abutments, a 40-microm microgap was found at the level of the implant-abutment connection. No mechanical damage was observed at the level of the implant or of the abutment. All the internal voids were always completely filled by the cement. No bacteria were observed in the internal portion of the implants or at the level of the microgap. The differences in the size of the microgap between the two groups were statistically significant (P < .05). In conclusion, in screw-retained abutments the microgap can be a critical factor for colonization of bacteria, whereas in cement-retained abutments all the internal spaces were filled by cement. In these retrieved implants, the size of the microgap was markedly variable and much larger than that observed in vitro.     

Pilot clinical and histologic evaluations of a two-piece zirconia implant

An investigation was conducted to evaluate the clinical and histologic results of bone and soft tissue healing around a two-piece zirconia dental implant in a human model. A healthy female patient requiring tooth replacement with dental implants received a two-piece zirconia implant together with conventional titanium implants to be implemented in a prosthesis. Clinical and radiographic evaluations at 6 months revealed stable osseointegrated zirconia and titanium dental implants. Light microscopy and backscatter scanning electron microscopic analyses confirmed the biocompatibility and achievement of osseointegration, in addition to maintenance of the crestal bone level. The findings suggest that the bone-to-implant contact with a zirconia implant surface is sufficient to provide clinical and histologic evidence of osseointegration. The biopsied two-piece zirconia dental implant with platform switching demonstrated osseointegration occlusal to the implant-abutment junction, eliminating the significance of the microgap.     

Characteristics of implant-CAD/CAM abutment connections of two different internal connection systems

Titanium or zirconium computer-aided design/computer-aided manufacturing abutments are now widely used for aesthetic implant treatments; however, information regarding microscopic structural differences that may influence the biological and mechanical outcomes of different implant systems is limited. Therefore, the characteristics of different connection systems were investigated. Optical microscopic observation and scanning electron microscopy showed different characteristics of two internal systems, namely the Astra Tech and the Replace Select system, and for different materials. The scanning electron microscopic observation showed for the Astra Tech that the implant-abutment interface seemed to be completely sealed for both titanium and zirconium abutments, both horizontally and sagittally; however, the first implant-abutment contact was below the fixture top, creating a microgap, and fixtures connected with titanium abutments showed significantly larger values (23·56μm±5·44 in width, and 168·78μm±30·39 in depth, P<0·001). For Replace Select, scanning electron microscopy in the sagittal direction showed that the sealing of titanium and zirconium abutments differed. The seal between the implant-titanium and implant-zirconium abutments seemed to be complete at the butt-joint interface; however, the displacement of the abutment in relation to the fixture in the lateral direction was evident for both abutments with no statistical differences (P>0·70), creating an inverted microgap. Thus, microscopy evaluation of two commonly used internal systems connected to titanium or zirconium abutments showed that the implant-abutment interface was perfectly sealed under no-loading conditions. However, an inverted microgap was seen in both systems, which may result in bacterial accumulation as well as alteration of stress distribution at the implant-abutment interface.     

Numerical study of effect of elastomeric stress absorbers on stress reduction in bone-dental implant interface

Objective

This paper focused on optimal stress distribution in the mandibular bone surrounding a dental implant and is devoted to the development of a modified Osteoplant^® implant type in order to minimize stress concentration in the bone-implant interface.

Material and Methods

This study investigated 0.4 mm thick layers of two elastomeric stress barriers incorporated into the dental implant using 3-D finite element analysis.

Results

Overall, this proposed implant provoked lower load transfer in bone-implant interface due to the effect of the elastomers as stress absorbers. The stress level in the bone was reduced between 28% and 42% for three load cases: 75 N, 60 N and 27 N in corono-apical, linguo-buccal and disto-mesial direction, respectively.

Conclusion

The proposed model provided an acceptable solution for load transfer reduction to the mandible. This investigation also permitted to choose how to incorporate two elastomers into the Osteoplant^® implant system.     

Influences of microgap and micromotion of implant–abutment interface on marginal bone loss around implant neck

ObjectiveTo review the influences and clinical implications of micro-gap and micro-motion of implant-abutment interface on marginal bone loss around the neck of implant.DesignLiteratures were searched based on the following Keywords: implant-abutment interface/implant-abutment connection/implant-abutment conjunction, microgap, micromotion/micromovement, microleakage, and current control methods available. The papers were then screened through titles, abstracts, and full texts.ResultsA total of 83 studies were included in the literature review. Two-piece implant systems are widely used in clinics. However, the production error and masticatory load result in the presence of microgap and micromotion between the implant and the abutment, which directly or indirectly causes microleakage and mechanical damage. Consequently, the degrees of microgap and micromotion further increase, and marginal bone absorption finally occurs. We summarize the influences of microgap and micromotion at the implant-abutment interface on marginal bone loss around the neck of the implant. We also recommend some feasible methods to reduce their effect.ConclusionsClinicians and patients should pay more attention to the mechanisms as well as the control methods of microgap and micromotion. To reduce the corresponding detriment to the implant marginal bone, suitable Morse taper or hybrid connection implants and platform switching abutments should be selected, as well as other potential methods.     

血管化腓骨重建下颌骨后用腓骨残端游离移植及牙种植的可行性研究

目的: 探讨利用残余腓骨增加下颌骨缺损腓骨重建患者垂直骨高度的临床效果。方法: 选择12例下颌骨缺损血管化腓骨重建后拟行种植牙修复的患者,利用腿部残余腓骨段进行垂直骨增量,同期或延期植入种植体并最终完成牙列修复,对术后骨吸收情况和种植体稳定性、存留率等数据采用SPSS 19.0软件包进行统计分析。结果: 术后6个月,近中骨块和远中骨块的吸收量分别为（0.94±0.18）mm和（0.89±0.15）mm;术后12个月,吸收量分别为（1.16±0.21）mm和（1.07±0.17）mm。种植体植入6个月和12个月后,ISQ值分别为（67.25±6.43）和（71.08±4.89）;边缘骨吸收量在植入术后6个月和12个月分别为（0.65±0.12）mm和（0.76±0.18）mm。术后1年种植体存留率为87.1%。结论: 非血管化腓骨具有可靠的抗吸收能力,在下颌骨缺损重建术后垂直骨高度不足的情况下,可为种植体植入提供充足骨量,并维持长期稳定性和存留率。     

Influence of the size of the microgap on crestal bone levels in non-submerged dental implants: a radiographic study in the canine mandible

BACKGROUND: Accumulating evidence suggests that alveolar crestal bone resorption occurs as a result of the microgap that is present between the implant-abutment interface in dental implants. The objective of this longitudinal radiographic study was to determine whether the size of the interface or the microgap between the implant and abutment influences the amount of crestal bone loss in unloaded non-submerged implants. METHODS: Sixty titanium implants having sandblasted with large grit, acid-etched (SLA) endosseous surfaces were placed in edentulous mandibular areas of 5 American fox hounds. Implant groups A, B, and C had a microgap between the implant-abutment connection of <10 microm, 50 microm, or 100 microm, respectively, as did groups D, E, and F, respectively. Abutments were either welded (1 -piece) in groups A, B, and C or non-welded (2-piece screwed) in D, E, and F. All abutment interfaces were placed 1 mm above the alveolar crest. Radiographic assessment was undertaken to evaluate peri-implant crestal bone levels at baseline and at 1, 2, and 3 months after implant placement whereupon all animals were sacrificed. RESULTS: The size of the microgap at the abutment/implant interface had no significant effect upon crestal bone loss. At 1 month, most implants developed crestal bone loss compared with baseline levels. However, during this early healing period, the non-welded group (D, E, and F) showed significantly greater crestal bone loss from baseline to one month (P <0.04) and 2 months (P < 0.02) compared with the welded group (A, B, and C). No significant differences were observed between these 2 groups at 3 months (P > 0.70). CONCLUSIONS: Crestal bone loss was an early manifestation of wound healing occurring after 1 month of implant placement. However, the size of the microgap at the implant-abutment interface had no significant effect upon crestal bone resorption. Thus, 2-piece non-welded implants showed significantly greater crestal bone loss compared with 1-piece welded implants after 1 and 2 months suggesting that the stability of the implant/abutment interface may have an important early role to play in determining crestal bone levels. At 3 months, this influence followed a similar trend but was not observed to be statistically significant. This finding implies that implant configurations incorporating interfaces will be associated with biological changes regardless of interface size and that mobility between components may have an early influence on wound healing around the implant.     

连续动态加载下单种植体周围骨组织应力的三维有限元分析

目的:探讨一个咀嚼周期内连续动态加载对单种植体周围骨组织最大Von Mises应力分布的影响。方法:在同一牙种植体全瓷冠修复的三维有限元模型上模拟一个咀嚼周期0.875 s的连续动态载荷,应用ANSYS软件考察骨组织的最大VonMises应力并与假设的瞬间动态加载结果相比较。结果:一个周期动态加载0.151～0.260 s与0.261～0.300 s时种植体周围骨组织的最大Von Mises应力值比瞬间动态颊斜向舌加载与舌斜向颊加载时增加;卸载后0.574 s时种植体周围骨组织的最大Von Mises应力值在一个周期动态连续加载模式比瞬间动态舌斜向颊加载模式增加。结论:一个周期动态载荷中,力的连续加载使种植体周围骨组织的最大Von Mises应力值增加;在一个咀嚼周期末,最大Von Mises应力累积作用比较明显。     

上部结构材料对无牙下颌种植固定修复影响的三维有限元分析

目的通过三维有限元方法探讨上部结构材料对无牙下颌种植固定修复生物力学的影响,为无牙颌修复治疗提供参考。方法构建无牙下颌种植固定修复三维有限元模型,用6种牙科材料(纯钛、钴铬合金、金合金、氧化锆、聚醚醚酮及碳纤维增强聚醚醚酮)分别对种植上部结构进行赋值,得到6种模型,模拟斜向加载,对种植体、周围骨组织及上部结构进行应力分析。结果无论采用何种材料,斜向加载下模型应力均集中于后牙区种植体远中颊侧颈部及周围骨皮质,骨松质受力远小于骨皮质。6种模型种植体及骨皮质的应力由小到大分别为氧化锆、钴铬合金、纯钛、金合金、碳纤维增强聚醚醚酮、聚醚醚酮。聚醚醚酮模型磨牙区种植体及骨皮质von Mises应力最大值分别为44.96和29.13 MPa;氧化锆模型磨牙区种植体及骨皮质的von Mises应力最大值分别为21.29和17.79 MPa。与聚醚醚酮模型相比,氧化锆和金属模型种植体及周围骨皮质的应力值更小,且应力分布更均匀。结论无牙下颌种植固定修复中使用氧化锆和金属等非聚合物材料制作上部结构,更有利于种植体及周围骨组织的应力分散。