双皮层骨种植影响牙种植体稳定性的有限元固有频率研究

目的 用有限元方法研究双皮层骨种植对牙种植体初期稳定性的影响。方法 建立牙种植体和局部下颌骨块三维有限元模型,利用ABAQUS有限元软件,分析双皮层骨种植对种植体颊舌向和轴向一阶振动固有频率的影响。结果 双皮层骨种植可明显提高种植体颊舌向和轴向振动的固有频率值,且随着种植体穿颊侧皮质骨厚度的增加,固有频率值逐渐增加。结论 双皮层骨种植可明显增加种植体颊舌向和轴向的初期稳定性。     

双皮层骨种植影响牙种植体稳定性的有限元固有频率分析

目的:用有限元方法研究双皮层骨种植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,分析双皮层骨种植对种植体颊舌向、轴向一阶振动固有频率的影响。结果:在模拟的3种不同骨质类型中,双皮层骨种植均可提高种植体颊舌向、轴向振动的固有频率值,但颊舌向频率的增加有限,最高增加了13. 77%,而轴向频率值最大增加了一倍以上。结论:双皮层骨种植主要增加种植体轴向稳定性,对种植体水平向稳定性的增加有限。     

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.     

Osstell^TM换能器变幅杆方向对牙种植体扭转振动行为影响的三维有限元研究

目的：利用三维有限元分析方法,研究Osstell^TM换能器变幅杆方向对牙种植体扭转振动行为的影响。方法：采用UGS NX和ANSYS软件建立骨-种植体-换能器系统三维有限元模型,分析Osstell^TM换能器变幅杆方向对牙种植体扭转振动模态、共振频率及整个系统变形程度的影响。结果：4种骨质类型中换能器变幅杆在0°～90°不同方向影响下,扭转振动模态共振频率增加趋势较弱,而种植体、骨块的最大位移呈明显减小趋势。结论：Osstell^TM换能器变幅杆方向变化对骨-种植体-换能器系统扭转振动共振频率的影响不明显,而当换能器变幅杆垂直于牙槽嵴长轴时,扭转振动行为对骨块和种植体变形的影响较小。     

两类传感器对种植体共振频率测量值影响的三维有限元研究

研究背景：共振频率法被认为是目前相对理想的测量种植体稳定性的方法。共振频率仪的测量传感器分为L型传感器和无线式铝杆传感器两类,然而,目前种植领域尚不清楚这两类传感器所测量的种植体共振频率值有何异同。目的：采用三维有限元法研究在不同骨质类型和不同种植体长度情况下,L型传感器和铝杆传感器两种设计对种植体共振频率测量值的影响。方法：（1）建立种植体-传感器-下颌磨牙区骨块三维有限元模型（ANSYS5.6软件）。种植体尺寸：直径固定为4.0mm,长度分4个等级：8.0mm、10.0mm、12.0mm和14.0mm;传感器分为两类：L型（高度22.0mm）和铝杆型（高度11.5mm）;模拟了3种骨质类型,即D2、D3和D4骨质。（2）在本质上,种植体一阶弯曲振动模态下的固有频率与共振频率仪所测量的共振频率相同,因此本研究直接采用有限元软件计算不同参数条件下种植体-骨块复合体的一阶固有频率。结果：（1）L型传感器组种植体的频率值在3763～4464Hz之间（平均4235Hz）,而铝杆模型种植体的频率值在9192～10002Hz之间（平均9708Hz）。（2）骨质由D4变为D2时,L型传感器组种植体的频率值增加百分比在12.7～16.7%之间（平均14.9%）,铝杆传感器组的增加百分比在7.4～8.5%之间（平均7.9%）。（3）对于L型传感器组而言,长度增加其频率值逐渐增加,14.0mm与8.0mm相比,频率值平均增幅为3.2%,对于铝杆传感器而言,D3骨质模型的频率值随长度增加而增加,在D4和D2骨质条件下,频率值呈先升后降（变化幅度较小）。（4）在D3骨质情况下,L型传感器测量值和铝杆传感器测量值之间存在线性相关,具有显著性（Pearson相关系数r=0.996,P=0.004）;在D4骨质情况下,L型传感器测量值和铝杆传感器测量值之间存在负相关关系,但是没有统计意义（r=-0.846,P〉0.05）;在D2骨质情况下,两组数值存在正相关关系,但同样没有统计意义（r=0.736,P〉0.05）。结论：在相同骨质类型、相同种植体尺寸条件下,L型传感器模型的频率值远小于铝杆传感器模型的频率值;L型传感器反映骨质变化的灵敏度高于铝杆传感器;在D3骨质条件下,两种传感器均能反映出测量值随长度增加而增加这一趋势     

牙种植体即刻负载骨界面应力分布的三维有限元分析

目的：用三维有限元法分析牙种植体即刻负载骨界面的力学特性。方法：采用CT扫描和自主开发的USIS软件建立螺纹种植体即刻负载的三维有限元下颌骨模型，用ANSYS计算垂直加载、颊舌向450及近远中向45°加载150N力时种植体骨界面的Yon Mises应力、应变值。结果：垂直加载时骨界面的Yon Mises应力集中于颈部舌侧骨皮质，应变分布均匀，以颈部骨皮质、底部颊侧骨松质及颊侧螺纹接触部位的松质骨较为集中：颊舌向加载时骨界面的Yon Mises应力也集中于颈部舌侧骨皮质，但最大值是垂直加载时的4．15倍，应变分布不均匀，主要集中于颈部舌侧骨皮质，最大值是垂直加载时的3．98倍；近远中斜向加载时骨界面的Yon Mises应力集中于颈部远中侧骨皮质，最大值是垂直加载时的3．72倍，应变集中于底部近中侧骨松质，最大值是垂直加载时的1．51倍。结论：即刻垂直加载时，种植体周围骨质应力及应变无明显集中，分布较均匀，颊舌向及近远中向加载时应力、应变明显增大，分布不均匀。     

Straumann种植体骨愈合期稳定性变化的临床动态监测

目的：应用共振频率分析仪评估Straumann种植体植入后稳定性的变化以及影响种植体稳定性的相关因素。方法：28例牙齿缺失患者共植入35枚非潜入式Straumann种植体,在术中、术后1、2、3、4、6、8、12周对种植体的稳定性进行共振频率分析（RFA）,记录分析种植体稳定性数值（ISQ）。结果：种植体稳定性ISQ值的变化趋势表现为：术后前4周出现轻微波动,4～12周略有上升,经方差分析在各时间段的ISQ值无显著差异。骨密度和种植体长度对种植体稳定性有显著影响（P〈0.05）,种植体直径、性别和颌位对种植体ISQ值无明显影响。术后12周种植体的留存率均为100%。结论：种植体稳定性与种植体长度和骨质类型关系密切。共振频率分析（RFA）评估种植体稳定性是一种可靠有效的方法。     

种植体周围骨内应力分布的三维有限元分析

目的针对不同类型的牙槽骨科学地选用种植体,提高种植体临床疗效,延长使用寿命。方法采用三维有限元分析方法,将圆柱状、螺纹状和台阶状种植体分别植入4类骨质结构中,对此12种情况进行应力分析。结果在同种骨质模型中,圆柱状种植体颈部周围骨内的应力集中最小;就同种形态种植体而言,较低的骨质密度不利于种植体的应力分布。结论圆柱状是一种最有利于降低颈部骨质吸收的形态结构。螺纹状种植体周围骨内应力最大值大于圆柱状,而螺纹自身非力学优势极大的拓展了该型种植体的使用范围,但螺纹尖端处的高应力区域和螺纹之间的低应力区域是影响其长期使用效果的潜在不利因素。台阶状种植体相对较适合骨质好的情况,其根部出现局部高应力区域,若应力处于骨生理承受范围之内,将有利于减少根部骨质疏松。     

关于牙种植体的有限元研究进展

有限元法（ｆｉｎｉｔｅｅｌｅｍｅｎｔｍｅｔｈｏｄ,ＦＥＭ）自本世纪六十年代被提出以来,最初用于解决复杂的工程问题,七十年代被引入医学领域后,显示出极大的优越性。而ＦＥＭ广泛应用于口腔医学界是在八十年代,现已成为口腔生物力学研究的一个重要手段。与其他研究方法如电测法、光弹法相比,ＦＥＭ具有以下优点：能对结构、形态、载荷和材料力学性能极其复杂的构件进行应力分析;可在同一模型上对多种不同性质材料进行分析比较;模型转换较为简单等。随着ＦＥＭ在各个领域的广泛应用,其自身也不断发展。例如人最初的二维ＦＥＭ发…     

骨质量和种植体螺纹对种植稳定性影响的三维有限元分析

目的:探讨骨质量和种植体螺纹对种植体稳定性的影响。方法:建立三角型和锯齿型螺纹种植体植于4种骨类型下颌骨的三维有限元模型8个,种植体顶部中心节点加垂直和45°倾斜力200N,分析种植体的位移和界面骨的应力分布。结果:随骨弹性模量的减小,界面骨应力和种植体位移均增加;锯齿型螺纹种植体的位移都小于三角型,斜向力在4种骨和垂直力在Ⅳ类骨中锯齿型的应力小于三角型。结论:骨类型和螺纹形态都影响种植体的稳定性。骨质越好种植体越稳定,界面骨应力越小;锯齿型螺纹种植体的稳定性比三角型螺纹好。     

Effects of buccal bi-cortical anchorages on primary stability of dental implants: a numerical approach of natural frequency analysis

Summary  The purpose of this study was to investigate influences of buccal bi-cortical anchorages on natural frequency (NF) values of dental implants in different diameters utilizing the three-dimensional finite element method. Three degrees of buccal bi-cortical engagements were generated in D2 and D3 bone quality models, which were 0-mm engagement (i.e. implants just had contact with the buccal cortex), 0·5-mm (i.e. implants were penetrated into the buccal cortex by 0·5 mm) and 1·0-mm engagement, while only 0- and 0·5-mm engagement were simulated in D4 bone models. The uni-cortical engagement was set as the control. By the modal analysis, NF values of bending and axial vibration mode were computed as a function of different bi-cortical engagements. The results showed that buccal bi-cortical anchorages significantly enhanced bending and axial NF values. The increasing rates resulting from 0·5-mm engagement ranged from 10·5 to 42·3%, with a mean of 24·3%. From 0- to 0·5-mm engagement, the NF values maintained an increasing trend, and from 0·5- to 1·0-mm engagement, the values levelled off or even decreased. In 0·5- and 1·0-mm engagement models, increasing implant diameter resulted in small increases of NF values. In conclusion, buccal bi-cortical anchorages could significantly increase both bending and axial NF values of dental implants, but extra-buccal cortical bone engagement could not produce considerable incremental increases of NF values as anticipated. Increasing implant diameter could result in limited increases of NF values in case of implants being bi-cortically anchored.     

Damping factor for monitoring the bone interface at dental implants

OBJECTIVES: The aim of this study is to investigate whether the damping of osseointegrated implants, as measured quantitatively with the Osstell equipment, is related to the fractal dimension of peri-implant bone. MATERIAL AND METHODS: Fifty-five maxillary implants in function for 3 years before the present study were investigated. Two Osstell measurements were obtained for each implant with the transducer oriented first palatally and then distally. Using the half-power bandwidth method, the damping was calculated from the frequency/amplitude plot obtained from the Osstell. Damping data were then related to the fractal dimension of peri-implant bone. Fractal dimensions were calculated using a box-counting algorithm on digitally processed intra-oral radiographs of the implants. A Spearman's test was used to verify the correlation between damping and fractal dimension values. RESULTS: All the implants were clinically stable and free from symptoms. The mean ISQ was 63 for the palatal orientation and 71 for the distal orientation. The mean fractal dimension was 1.47; the mean damping value for palatal orientation was 12.3%, while that for the distal orientation was 8.2%. No significant correlation was found. CONCLUSIONS: Damping values, measured at peri-implant bone, were found not to be related to a radiographic parameter of trabecular bone pattern like the fractal dimension. The clinical implication would be that Osstell graphs displaying distinct or more rounded peaks might both indicate a stable implant as long as the associated implant stability quotients are in the range of satisfactory values proposed in the literature.     

Influence of transducer orientation on Osstell stability measurements of osseointegrated implants

Background: Resonance frequency (RF) analysis is frequently used to monitor implant stability in patients. The influence of transducer orientation on RF of implants placed in jawbone has not been evaluated. Purpose: The aim of this study was to evaluate to what extent transducer orientation influences RF. The second aim was to evaluate if measurements taken with any particular orientation would best relate to marginal bone levels. Materials and Methods: Nine patients edentulous in the upper jaw received 55 implants 3 years before this study. They underwent clinical and radiographic evaluation. Using Osstell^TM (Integration Diagnostics AB, Göteborg, Sweden), four RF measurements were made for each implant. Measurements were obtained with the transducer cantilever placed buccally (B), distally (D), palatally (P), and mesially (M). Results: All implants were clinically stable. Significant differences resulted between the measurements perpendicular to the bony crest (B, P) and the parallel ones (M, D). A tendency of negative correlation was found between marginal bone levels and implant stability quotient (ISQ) measurements; however, this correlation was not statistically significant. Conclusions: In conclusion, when measuring the RF of dental implants using the Osstell, it has to be taken into account that the transducer orientation influences the measurement. It seems therefore advisable to standardize the orientation. Moreover, although there was a tendency, any statistical significant correlation between ISQ values and marginal bone levels could not be established.     

Crestal bone loss evaluation in osseotite expanded platform implants: a 5-year study

Objective: The aim of this prospective clinical study was to evaluate the survival rates at 5 years of expanded platform implants placed in the anterior zone of the maxilla and immediately restored with single crowns. Materials and methods: Implants incorporating the platform‐switching concept were placed in fresh extraction sockets in the maxillary arch, with each patient receiving a provisional restoration immediately after implant placement. After 15 days, final screwed restorations were inserted. Mesial and distal bone heights were evaluated using digital radiography on the day following implant placement and at 1, 3, 6, 9, 12, 24, 36 months and 5 years. Primary stability was measured with resonance frequency analysis (RFA) using the Osstell Mentor device. Sixty‐four implants were placed in 32 men and 32 women ranging in age between 29 and 60 (mean: 39.64 ± 5.16 years). Results: Mean mesial bone loss was 0.08 mm (SD 0.42). Mean distal bone loss was 0.14 mm (SD 0.56). Over the course of the 5 years, the mean RFA value was 72.5 ± 3.1 SD. Conclusion: The platform‐switched implants remained stable over the course of 5 years and had an overall survival rate of 97.1%. To cite this article:
Calvo‐Guirado J L, Gómez‐Moreno G, López‐Marí L, Guardia J, Negri B, Martínez‐González J M. Crestal bone loss evaluation in osseotite expanded platform implants: a 5‐year study.
Clin. Oral Impl. Res. xx , 2011; 000–000
doi: 10.1111/j.1600‐0501.2010.02130.x     

三种螺距对种植体初期稳定性影响的有限元研究

目的：利用即刻负载有限元模型,研究种植体不同螺纹螺距因素对初期稳定性的影响。方法：利用Pro／E软件、Hypermesh软件及ABAQUS有限元软件,建立四类种植体即刻负载的三维有限元模型,比较3种螺纹螺距（0．8mm、1．6mm、2．4mm）在分别垂直和水平加载时,对种植体初期稳定性的影响。结果：对不同螺纹螺距种植体来说,垂直加载和水平加载时0．8mm螺距螺纹种植体微动最小,2．4mm螺距螺纹种植体微动最大。结论：螺纹的螺距对垂直相对位移有影响,对水平相对位移影响不大。随着螺距的增加,种植体对抗垂直向载荷的抵抗力减弱。水平加载时,螺纹的螺距对颈部微动影响不明显。     

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。