种植体穿通下颌骨对骨界面应力分布的影响

目的：为了探讨下颌种植牙穿通下颌骨后对骨界面应力分布的影响。方法：采用三维有限元方法,通过单个穿下颌螺旋型种植体的种植,了解穿下颌种植后对骨界面应力分布的影响。结果：穿下颌种植减小了颈周密质骨内的应力,加大了根端侧穿下颌骨下缘处的应力,减小了骨界面的位移。结论：穿下颌种植,改变了骨界面的最大应力分布部位,使最大应力位于根端侧下颌骨下缘处。     

修复材料对种植体周围骨组织应力的影响

目的：研究不同上部结构材料对种植体固定修复中种植体周骨组织的应力反应特点。方法：建立种植体支持固定桥力学模型，通过三维有限元方法分别计算出采用丙烯酸树脂，釉质瓷，瓷，金合金为上部结构材料时骨组织的应力状况，结果：每况工况下，种植体颈部周围皮质骨区所受的应力都是最大的，四种材料比较时使用丙烯酸树脂对种植体颈部骨组织的应力最小，其次为釉质瓷，瓷，最大为金合金，结论：修复材料的弹性模量会影响种植体周骨组织的应力分布，弹性模量低者对种植体颈部周围骨组织有保护作用，釉质瓷可能是较为理想的修复材料。     

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.     

垂直负荷对种植体边缘骨应力分布的影响

目的　比较不同部位施加不同的垂直负荷对种植体边缘骨的应力分布的影响。方法采用电阻应变片法测试单个种植牙和 2个种植体支持的固定桥在垂直负荷时种植体边缘骨的应力。结果　负荷大小、负荷点以及二者的交互作用都可影响应力分布。单个种植牙的应力集中在种植体的颈部和根尖部 ,2个种植体支持的固定桥应力易集中在种植体近负荷点侧的根尖部、颈部 ,尤其是近负荷点的种植体。在游离端施加负荷时 ,应力与负荷大小、悬臂长度成正比。结论　减小咬合力、避免使用游离端种植义齿可以减小种植体边缘骨的应力 ,尤其是远中种植体。     

Influence of occlusal forces on stress distribution in preloaded dental implant screws

STATEMENT OF PROBLEM: Abutment and prosthetic loosening of single and multiple screw-retained, implant-supported fixed partial dentures is a concern. PURPOSE: The purpose of this study was to investigate stress distribution of preloaded dental implant screws in 3 implant-to-abutment joint systems under simulated occlusal forces. MATERIAL AND METHODS: Three abutment-to-implant joint systems were simulated by using the 3-dimensional finite element analysis method: (1) Branemark external hexagonal screw-retained abutment, (2) ITI 8-degree Morse tapered cemented abutment, and (3) ITI 8-degree Morse tapered plus internal octagonal screw-retained abutment. A thermal load and contact analysis method were used to simulate the preload resulting from the manufacturers' recommended torques in implant screw joint assemblies. The simulated preloaded implants were then loaded with 3 simulated static occlusal loads (10 N; horizontal, 35 N; vertical, 70 N; oblique) on the crown position onto the implant complex. RESULTS: Numeric and graphical results demonstrated that the stresses increased in both the abutment and prosthetic screws in the finite element models after simulated horizontal loading. However, when vertical and oblique static loads were applied, stresses decreased in the external hexagonal and internal octagonal plus 8-degree Morse tapered abutment and prosthetic screws with the exception of the prosthetic screw of ITI abutment after 70-N oblique loading. Stresses increased in the ITI 8-degree Morse tapered cemented abutment after both vertical and oblique loads. CONCLUSION: Although an increase or decrease was demonstrated for the maximum calculated stress values in preloaded screws after occlusal loads, these maximum stress values were well below the yield stress of both abutment and prosthetic screws of 2 implant systems tested. The results imply that the 3 implant-to-abutment joint systems tested may not fail under the simulated occlusal forces.     

8mm种植体骨内应力分布的三维有限元研究

目的 探讨在不同骨质条件中、达到骨整合时(40%的骨结合率),不同直径的8 mm种植体骨界面应力分布的变化规律,为短种植体的临床应用提供一定的参考和实验依据.方法 采用三维有限元方法分析6种不同直径的8 mm种植体在Ⅰ~Ⅳ类骨质条件中,受垂直和侧向力时,种植体骨界面的应力值大小及分布规律.结果 在~Ⅳ类骨质中,无论垂直或是斜向加载,应力值随着种植体直径增加,呈现减小的趋势.种植体直径3.3～5 mm时,最大应力值大小变化较为明显(曲率约为-1);种植体直径5.5～7.1mm时,变化趋于平缓(曲率接近0).另一方面,随着骨质密度降低,种植体骨界面的最大应力逐渐增大:Ⅳ类>Ⅲ类>Ⅱ类>Ⅰ类.在Ⅰ、Ⅱ类骨质中最大应力分布接近,Ⅲ、Ⅳ类骨质最大应力分布相近.结论 在临床应用短种植体时,可尽量选择较粗直径的种植体(直径3.3~5 mm),但当种植体直径足够大时(直径大于5.5 mm),再增加种植体直径对临床效果的改善不明显;实验结果显示,Ⅲ、Ⅳ类骨质时的应力值远大于Ⅰ、Ⅱ类骨质,提示在临床实践中,可以将Ⅲ、Ⅳ类的骨质通过骨挤压、骨移植等方式来提高骨密度,以保证远期成功率.     

Influence of bone quality on the stress distribution

Adequate bone quality and stress distribution to the bone are of decisive importance for implant success. The purpose of this in vitro study was to investigate the influence of bone quality on the stress distribution using 2 implant-bone mimicking models, simulating compact and cancellous bone quality. The resin model was made of an acrylic resin only simulating compact bone quality. The hybrid model was made of 2 kinds of materials, acrylic resin covered with a 1-mm layer of urethane to simulate cancellous bone quality. An implant was embedded in each model, and the abutment and suprastructures were connected to the implant. A strain gauge was placed perpendicular to the implant on the surface of the model and a small accelerometer was attached to the abutment. When an impact load was applied to the suprastructure, both strain and acceleration were measured. Both abutment acceleration and surface strain in the hybrid model decreased rapidly as time progressed when compared to the resin model. Abutment accelerations in the resin model were significantly lower than those in the hybrid model. In the hybrid model, the strain increased as the loading site was moved closer to the strain gauge. The influence of loading sites on strain in the resin model was greater than in the hybrid model. Therefore, the occlusal stress was distributed more widely in the hybrid model than in the resin model. This may indicate that occiusal stress in compact bone may have a tendency to concentrate in particular regions.     

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.     

Three-dimensional stress distribution around a dental implant at different stages of interface development

An anchor-type ceramic dental implant contained in a section of the mandibular molar region was modeled for finite element stress analysis. The distributions of stresses in the bone around the implant due to axial and transverse loading were calculated for different stages of normal and pathological development of the implant-bone interface. Highest stress concentrations are observed in the crestal region with transverse loading when spongy bone surrounds the implant immediately after surgery. Development of a lamina dura around the implant slightly reduces severe stress peaks, whereas ingrowth of connective tissue almost eliminates them.     

糖尿病对种植体周围骨组织的影响

一直以来,糖尿病被认为是口腔种植治疗的禁忌证,糖尿病患者也占禁忌症患者中很大一部分,因高血糖及其并发症对骨形成起反作用而导致种植失败。不仅如此,糖尿病通常和牙周病同时存在,这些糖尿病的并发症都是影响种植成功率的关键因素。和正常人相比,糖尿病患者则表现出更高的种植失败率,因此糖尿病患者口腔种植成为研究的热点。本文就糖尿病对种植周围骨组织的影响,以及临床糖尿病患者种植牙的现状作一综述。     

下颌骨典型牙位圆柱状牙种植体周围骨应力分布的三维有限元分析

目的：生理加载下不同牙位种植体周围骨应力有明显差异，采用有限方法计算，其结果是种植体设计和临床使用的重要依据，但可靠性依赖于模型和加载条件的准确性。方法：本文基于下颌骨四个典型牙位的CT数据，结合各牙位咬舍关系的测量结果，建立了三维有限元模型，并对圆柱状种植体周围骨的应力分布进行有限元分析：结果：种植体沿长轴植入时。各牙位应力分布差异较大，颊、舌侧应力分布明显不对称，应力均主要集中在种植体颈部与牙槽骨界面顶端的舌侧，且舌侧极大值为颊侧的2～3倍：结论：在种植体一骨界面上的最大应力不超过20MPa的条件下，各牙位能承受的最大袷力分别为：第二磨牙100N、第二前磨牙300N、尖牙180N、中切牙120N。第二磨牙采用牙槽骨垂直方向植入时，可承受约250N的He力.     

Influence of implant length and bicortical anchorage on implant stress distribution

Background: Short implants present superior failure rates for everybody. Purpose: The aim of this theoretic study was to assess to what extent implant length and bicortical anchorage affect the way stress is transferred to implant components, the implant proper, and the surrounding bone. Materials and Methods: Stress analysis was performed using finite element analysis. A three‐dimensional linear elastic model was generated. All implants modeled were of the same diameter (3.75 mm) but varied in length, at 6, 7, 8, 9, 10, 11, and 12 mm (Branemark System®, Nobel Biocare AB, Gothenburg, Sweden). Each implant was modeled with a titanium abutment screw and abutment, a gold cylinder and prosthetic screw, and a ceramic crown. The implants were seated in a supporting bone structure consisting of cortical and cancellous bone. An occlusal load of 100 N was applied at a 30° angle to the buccolingual plane. Results: With the selected model and bone properties, the coronal cortical anchorage was dominating, and the bone stress concentrated to that area. Conclusions: The maximum bone stress was virtually constant, independent of implant length and bicortical anchorage. The maximum implant stress, however, increased somewhat with implant length and bicortical anchorage.     

牙种植体即刻种植骨愈合过程的组织学观察

目的：了解即刻种植体的骨愈合过程，验证即刻种植的可行性。方法：在１２只犬下颌前磨牙新鲜拔牙创内立即植入纯钛牙种植体，通过组织学光镜和扫描电镜观察术后２、４、６、８、１２周种植体周围骨缺损修复过程和种植体骨结合形成情况。结果：骨缺损区内血块首先机化，而后沿牙槽窝骨壁向中心方向逐渐骨化形成新骨。小于１ｍｍ骨缺损１２周内可完全修复，种植体骨结合形成；１ｍｍ以上骨缺损则不能完全修复。结论：即刻种植体周围骨缺损的修复和骨结合形成类似于拔牙创的愈合，大于１ｍｍ的骨缺损应争取植骨。     

Experimental study of bone growth around a dental implant after Surgibone grafting

Histologic and histomorphometric results of bone growth around titanium alloy screw-type implants after Surgibone grafting in New Zealand white rabbits are presented. At 21 days, new bone was formed along the surface of the implant. At 84 days, newly formed bone replaced almost all of the trabecular bone of the graft and reached the shoulder level of the implant. There was a higher percentage of host bone area at 84 days than at any of the earlier experimental periods (P < .01). The average mineral apposition rates ranged from 1.82 to 2.35 microns/day in original bone and 2.55 to 2.80 microns/day in newly formed bone. The results suggest that Surgibone grafting in combination with dental implants can be used to increase the height of the recipient bone and therefore aid in the fixation of the implant in this animal model.     

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。     

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.     

Effect of dental implant cross-sectional design on cortical bone structure using finite element analysis

Purpose: This finite element analysis investigation evaluated the effect of different implant cross‐sectional designs on bone stress levels under different loading patterns. Materials and Methods: Finite element analysis program was used to construct four different three‐dimensional models describing 4 × 10‐mm implants in blocks of cortical and trabecular bone. A 5‐mm‐long abutment was modeled above each implant. The implant in model 1 was unthreaded, while in model 2 the implant was circularly threaded. The third implant in model 3 had the cross‐sectional shape as a 16‐sided star‐shaped design. The implant in model 4 was constructed unthreaded, with a diameter of 4.5 mm. Vertical and horizontal loads of 100 N each were applied on the top middle node of each implant assembly. All nodes at the bottom surface of the bone models were restrained. Results: By comparing models 1, 2, and 3, the lowest bone stress values under vertical and horizontal forces were observed around the unthreaded implant in model 1 (8.92 and 94.52 MPa, respectively). The highest stress value under vertical loading was shown around the threaded implant in model 2 (10.07 MPa), whereas the highest stress value under horizontal loading was observed around the star‐shaped implant in model 3 (108.40 MPa). Model 4, with a wider unthreaded design, had stress values under vertical and horizontal loading of 7.32 and 71.35 MPa, respectively. Conclusions: It was concluded that the unthreaded implant design produced the least bone stress. An increase in implant diameter could produce marked reduction in stress value in the bone around the neck of the implant.     

垂直负荷下双种植体固定桥种植体周围骨的应力研究

目的：在模型上比较在不同部位施加不同大小的垂直负荷对种植体周围骨的应力分布的影响。方法：采用电阻应变片法，测试二个种植体支持的固定桥在垂直负荷时种植体周围骨的应力。结果：负荷大小、负荷点以及二者的交互作用，都可影响应力分布。二个种植体支持的固定桥的应力，集中在种植体近负荷点侧的颈部、根尖部，尤其是近负荷点的种植体。在游离端施加负荷时，应力与负荷大小、悬臂长度成正比。结论：减小咬合力，避免使用游离端种植义齿，可减小远中种植体周围骨的应力，远中种植体可选用宽直径或长种植体。     

Influence of implant angulation with different crowns on stress distribution

The aim of this study was to perform a photoelastic analysis of stress distribution on straight and angulated implants with different crowns (screwed and cemented). Three models were made of photoelastic resin PL-2: model 1: external hexagon implant 3.75×10.00 mm at 0 degrees; model 2: external hexagon implant 3.75×10.00 mm at 17 degrees; model 3: external hexagon implant 3.75×10.00 mm at 30 degrees. Axial and oblique (45 degrees) load (100 N) was applied with a universal testing machine. The photoelastic fringes on the models were recorded with a digital camera and visualized in a graphic software for qualitative analysis. The axial loading generated the same pattern of stress distribution. The highest stresses were concentrated between medium and apical thirds. The oblique loading generated a similar pattern of stress distribution in the models with similar implant angulation; the highest stress was located on the cervical region opposite to implant angulation and on the apical third. It was concluded that the higher the implant angulation, the higher the stress value, independent of crown type. The screwed prostheses exhibited the highest stress concentration. The oblique load generated higher stress value and concentration than the axial load.