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。     

正畸力作用方向对支抗种植体-骨界面应力分布的影响

目的：研究正畸力不同作用方向对种植体-骨界面应力分布的影响，以指导临床选择合适方向的正畸载荷。方法：用三维有限元方法给种植体施加150g近远中向、颊舌向及轴向载荷。对支抗种植体一骨界面进行应力分析。结果：三种方向载荷下种植体颈部，(1）Von—Mises应力值分别为：(a)近远中向——0．5330MPa；(b)颊舌向——颊侧为0．51520MPa，舌侧为0．6470MPa；(c)龈he向——颊侧为0．0702MPa，舌侧为0．0791MPa，近远中向为0．0517MPa。(2)位移值分别为：(a)近远中向——0．1630μm；(b)颊舌向——颊侧为0．2070μm，舌侧为0．1950μm；(c)龈he向——颊侧为0．0496μm，舌侧为0．0467μm，近远中向为0．0484μm。结论：在植入支抗种植体时。应根据正畸载荷力的形式．适当调整种植体的部位，尽量不要过于偏颊、舌侧，以免造成应力的过分集中，导致骨组织损伤。     

颧牙槽嵴区域骨密质厚度的锥形束CT测量分析

目的通过锥形束CT（CBCT）测量成年人与青少年的颧牙槽嵴区域骨密质厚度,评价两者的差异,为临床中微种植支抗钉在颧牙槽嵴的应用提供参考。方法采集30例患者口腔颌面部CBCT扫描数据,其中成年人、青少年各15例。分别测量颧牙槽嵴区域颊侧不同层面基准线（上颌第一磨牙近中颊尖顶所在水平线）上方13、15、17mm处骨密质厚度,并对测量数据进行统计源分析。结果成年人颧牙槽嵴区域骨密质厚度为（1．91±0．54）～（2．62±0．74）mm。在3个测量高度上,上颌第一、二磨牙间骨密质最厚,第一磨牙近颊根上方骨密质最薄。青少年颧牙槽嵴区域骨密质厚度为（1．30±0．51）～（3．08±1．01）mm。在不同测量高度上,上颌第二前磨牙与第一磨牙间骨密质最厚,最薄处则位于第二磨牙近颊根上方或第一磨牙远颊根上方。结论就骨密质厚度而言,成年人颧牙槽嵴区域微种植支抗钉的最佳植入点位于上颌第一、二磨牙间,青少年颧牙槽嵴区域微种植支抗钉的最佳植入点位于上颌第二前磨牙与第一磨牙间。成年人与青少年颧牙槽嵴区域各位点骨密质厚度均可为微种植支抗钉的稳定性提供了保障。     

动态载荷下不同骨质对天然牙-种植体联合修复应力分布的影响

目的 利用有限元方法探索下颌后牙区天然牙-种植体联合修复在不同骨质内的应力分布情况,以评定出适宜行联合修复所需的骨质类型。方法 采用三维有限元分析法,分别对骨质为Ⅰ、Ⅱ、Ⅲ、Ⅳ类颌骨类型中的天然牙-种植体联合修复体施加动态载荷,并对各界面所承受的Von Mises应力进行分析。结果 皮质骨所受最大Von Mises应力值从Ⅰ类骨到Ⅳ类骨逐渐增大,最大等效应力分别为89.229、91.860、125.840、158.420 MPa。松质骨所受最大Von Mises应力值从Ⅰ类骨到Ⅳ类骨均逐渐减小,最大等效应力分别为58.584、43.645、21.688、18.249 MPa。在同一类模型中,松质骨和皮质骨的最大Von Mises应力值均为舌颊向加载>颊舌向加载>垂直向加载。结论 骨质的类型对修复体周围骨的应力分布有重要的影响,Ⅰ、Ⅱ类骨较Ⅲ、Ⅳ类骨更适合行种植体-天然牙联合修复。     

圆柱状、根端带缝及膨胀式种植体在骨质疏松状态时生物力学比较的三维有限元分析

目的:比较圆柱状、根端带缝与膨胀式种植体在骨质疏松条件时功能状态下的生物力学效果。方法:分别建立包含柱状、根端带缝和膨胀式种植体的骨质疏松颌骨骨块三维有限元模型。对种植体轴向和颊舌向分别施加100 N和30 N的力,评估皮质骨和松质骨的最大应力和种植体-基台复合体的最大位移。结果:与圆柱状种植体相比,根端带缝种植体使皮质骨在轴向和颊舌向加载下应力峰值分别增加了3.62%和7.49%,膨胀式种植体则使其降低了11.3%和9.60%;对于在松质骨,带缝种植体使其应力峰值分别增加了37.8%和65.0%,而膨胀式种植体使其增加了107%和89.2%;轴向加载时带缝种植体和膨胀式种植体的种植体-基台复合体的最大位移分别增加了1.12%和减少了0.60%,在颊舌向加载时,最大位移分别增加了6.37%和7.04%。结论:在骨质疏松状态下,皮质骨的应力对种植体外形变化更敏感;膨胀式种植体表现出比圆柱状种植体和带缝种植体更好的应力分布和更低的应力值。     

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。     

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。     

牙槽骨劈开术同期牙种植的临床应用

目的　评价牙槽骨劈开技术在口腔种植中应用的临床效果。方法　对116例缺牙区牙槽嵴高度大于12 mm,颊舌向厚度在3~5 mm之间的牙列缺损患者,行牙槽嵴劈开同期植入种植体治疗。共植入ITI种植体147枚,Replace种植体52枚。根据骨劈开术后间隙及唇颊侧骨壁厚度等不同情况选择植入或不植入自体骨、人工骨粉等修复手段。术后6月种植修复,定期随诊。结果　种植区软组织愈合好,无红肿,颊舌向牙槽骨较种植前明显增宽。术后除1颗种植体失败取出外,其余种植体稳固,种植修复体能正常使用。复诊时X线检查骨吸收≤1 mm。结论　骨劈开术使牙槽骨宽度在3~5 mm的病例有了一期种植的可能,是一种简单有效的增宽牙槽骨的方法。     

牙槽突骨挤压扩张同期种植的临床观测

目的：观测牙槽突骨挤压扩张同期种植的方法处理骨宽度不足病例的近期临床效果。方法：对56名牙槽突颊舌向骨宽度不足的患者行牙槽突骨挤压扩张同期种植的方法,植入ITI种植体61颗。术后3个月行上部冠修复。在术后即刻,术后3个月,6个月,12个月行临床检查和X线检查,观测种植体临床存活率和种植体颈部边缘骨的变化。结果：使用该方法的种植体存留率为100%,经X线检查种植体颈部边缘骨水平无明显吸收。结论：运用牙槽突骨挤压扩张同期种植的方法处理牙槽突颊舌向骨宽度不足的病例,操作简单,手术创伤小,近期可以取得较理想的临床效果,远期效果有待进一步观测。     

Comparing the influence of crestal cortical bone and sinus floor cortical bone in posterior maxilla bi-cortical dental implantation: A three-dimensional finite element analysis

Abstract

Objective. This study aimed to compare the influence of alveolar ridge cortical bone and sinus floor cortical bone in sinus areabi-cortical dental implantation by means of 3D finite element analysis. Materials and methods. Three-dimensional finite element (FE) models in a posterior maxillary region with sinus membrane and the same height of alveolar ridge of 10 mm were generated according to the anatomical data of the sinus area. They were either with fixed thickness of crestal cortical bone and variable thickness of sinus floor cortical bone or vice versa. Ten models were assumed to be under immediate loading or conventional loading. The standard implant model based on the Nobel Biocare implant system was created via computer-aided design software. All materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied. Results. Von Mises stress mainly concentrated on the surface of crestal cortical bone around the implant neck. For all the models, both the axial and buccolingual resonance frequencies of conventional loading were higher than those of immediate loading; however, the difference is less than 5%. Conclusion. The results showed that bi-cortical implant in sinus area increased the stability of the implant, especially for immediately loading implantation. The thickness of both crestal cortical bone and sinus floor cortical bone influenced implant micromotion and stress distribution; however, crestal cortical bone may be more important than sinus floor cortical bone.     

Implant–Bone Interface Stress Distribution in Immediately Loaded Implants of Different Diameters: A Three-Dimensional Finite Element Analysis

Purpose: To establish a 3D finite element model of a mandible with dental implants for immediate loading and to analyze stress distribution in bone around implants of different diameters. Materials and Methods: Three mandible models, embedded with thread implants (ITI, Straumann, Switzerland) with diameters of 3.3, 4.1, and 4.8 mm, respectively, were developed using CT scanning and self‐developed Universal Surgical Integration System software. The von Mises stress and strain of the implant–bone interface were calculated with the ANSYS software when implants were loaded with 150 N vertical or buccolingual forces. Results: When the implants were loaded with vertical force, the von Mises stress concentrated on the mesial and distal surfaces of cortical bone around the neck of implants, with peak values of 25.0, 17.6 and 11.6 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains (5854, 4903, 4344 μ?) were located on the buccal cancellous bone around the implant bottom and threads of implants. The stress and strain were significantly lower (p < 0.05) with the increased diameter of implant. When the implants were loaded with buccolingual force, the peak von Mises stress values occurred on the buccal surface of cortical bone around the implant neck, with values of 131.1, 78.7, and 68.1 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains occurred on the buccal surface of cancellous bone adjacent to the implant neck, with peak values of 14,218, 12,706, and 11,504 μm, respectively. The stress of the 4.1‐mm diameter implants was significantly lower (p < 0.05) than those of 3.3‐mm diameter implants, but not statistically different from that of the 4.8 mm implant. Conclusions: With an increase of implant diameter, stress and strain on the implant–bone interfaces significantly decreased, especially when the diameter increased from 3.3 to 4.1 mm. It appears that dental implants of 10 mm in length for immediate loading should be at least 4.1 mm in diameter, and uniaxial loading to dental implants should be avoided or minimized.     

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。     

种植体根尖部与上颌窦底皮质骨的关系对上颌后牙区种植影响的三维有限元分析

目的    利用三维有限元分析方法评估种植体根尖部与上颌窦底皮质骨的关系对上颌后牙区种植的生物力学影响。方法    应用计算机辅助设计（computer assisted design,CAD）软件建立标准种植体及上颌后牙区三维有限元模型（M1 ~ M6）,皮质骨厚度均为1 mm,依据牙槽骨高度不同（10 ~ 14 mm）,种植体根尖部与上颌窦底皮质骨的关系如下。M1：种植体根尖部穿通上颌窦底皮质骨（窦底皮质骨的上表面与种植体根尖部位于同一平面）;M2：种植体根尖部进入窦底皮质骨厚度的一半;M3：种植体根尖部恰好接触窦底皮质骨的下表面;M4 ~ M6：种植体根尖部分别距离窦底皮质骨的下表面1、2、3 mm。采用129 N斜向加载,分别置于即刻负载与常规负载条件下,计算其应力分布、最大von Mises应力、种植体的最大位移和共振频率。结果    除M1即刻负载外,最大von Mises应力均集中于种植体颈部周围的牙槽嵴顶皮质骨表面。无论即刻负载或常规负载下,种植体根尖部进入或穿通窦底皮质骨时,牙槽嵴顶皮质骨的最大von Mises应力降低,窦底皮质骨的最大von Mises应力增加,种植体的轴向共振频率显著增加,颊舌向共振频率显著降低。即刻负载条件下,当种植体进入或穿通窦底皮质骨时,其最大位移尤其是根尖部的最大位移小于其他情况下的最大位移。常规负载条件下,种植体颈部与根尖部的最大位移几乎不受种植体根尖部位置的影响。结论    种植体根尖部与上颌窦底皮质骨的相对位置关系对种植体周围组织的应力分布、种植体的最大位移以及共振频率均有一定影响。种植体根尖部进入或穿通上颌窦底皮质骨有利于改善应力分布,减少种植体根尖部的位移,增加种植体的稳定性,尤其在即刻负载下作用显著。     

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??Objective    To evaluate the biomechanical influence of the relationship between implant tip and sinus ?oor cortical bone on posterior maxilla implantation by means of 3-dimensional??3-D??finite element??FE??analysis. Methods        Six 3-D FE models ??M1 to M6?? of standard implants and posterior maxillary region were constructed using CAD software. The thickness of both crestal cortical bone and sinus floor cortical bone were 1mm??according to different heights of the alveolar bone??the relationship between implant tip and sinus floor cortical bone was as follows. M1??the implant tip just broke through sinus cortical bone??the upper surface of sinus cortical bone and the apical surface of the implant were at the same level????M2??the implant tip broke through half the thickness of sinus ?oor cortical bone??M3??the implant tip just made contact with the lower surface of sinus ?oor cortical bone??for the remaining models??the implant tips were 1mm??2mm and 3mm apart from sinus floor??respectively. An inclined force of 129N was applied under immediate loading and conventional loading. The maximum von Mises stress??stress distribution??implant displacement and resonance frequencies were calculated using CAD software. Results    Except the M1 under immediate loading??the maximum von Mises stress of all models were concentrated on the surface of the crestal cortical bone around the implant neck. When the implant tip broke into or through sinus floor cortical bone??the maximum von Mises stress of crestal cortical bone reduced while that of sinus cortical bone increased??and the occlusional resonance frequencies of implants increased significantly while horizontal frequencies decreased??whether under immediate loading or conventional loading. Under immediate laoding??the maximum displacement of implant??especially the maximum displacement of the implant tip??was lower than the other models when the implant tip broke into or through the sinus cortical bone. However??the maximum displacements of both implant neck and tip were  hardly affected by the association between implant tip or sinus floor cortical bone under conventional loading. Conclusion    The association between implant tip and sinus floor cortical bone has effects both on stress distribution of the bone tissues around implant and on the maximum displacement and resonance frequencies of implants. Making the implant tip break into or through the sinus floor cortical bone??bi-cortical anchorage??is beneficial to improve the stress distribution and reduce the maximum displacement of implant??increasing the stability of the implant??especially under immediate loading.     

Influence of surgical technique and surface roughness on the primary stability of an implant in artificial bone with different cortical thickness: a laboratory study

Objective: The aim of this biomechanical study was to assess the interrelated effect of both surface roughness and surgical technique on the primary stability of dental implants. Material and methods: For the experiment, 160 screw‐designed implants (Biocomp^®), with either a machined or an etched surface topography, were inserted into polyurethane foam blocks (Sawbones^®). As an equivalent of trabecular bone, a density of 0.48 g/cm³ was chosen. To mimic the cortical layer, on top of these blocks short‐fibre‐filled epoxy sheets were attached with a thickness varying from 0 to 2.5 mm. The implant sites were prepared using either a press‐fit or an undersized technique. To measure the primary stability of the implant, both the insertion and the removal torques were scored. Results: Independent of the surgical technique used, both implant types showed an increased insertion and removal torque values with increasing cortical thickness, although >2 mm cortical layer no further increase in insertion torque was observed. In the models with only trabecular bone (without cortical layer) and with a 1 mm cortical layer, both implant types showed a statistically higher insertion and removal torque values for undersized compared with the press‐fit technique. In addition, etched implants showed a statistically higher insertion and removal torque mean values compared with machined implants. In the models with 2 and 2.5 mm cortical layers, with respect to the insertion torque values, no effect of either implantation technique or implant surface topography could be observed. Conclusion: The placement of etched implants in synthetic bone models using an undersized preparation technique resulted in enhanced primary implant stability. A correlation was found between the primary stability and the cortical thickness. However, at or above a cortical thickness of 2 mm, the effect of both an undersized surgical approach, as also the presence of a roughened (etched) implant surface, had no extra effect. Besides the mechanical aspects, the biological effect of undersized drilling, i.e. the bone response on the extra insertion torque forces should also be elucidated. Therefore, additional in vivo studies are needed. To cite this article:
Tabassum A, Meijer GJ, Wolke JGC, Jansen JA. Influence of surgical technique and surface roughness on the primary stability of an implant in artificial bone with different cortical thickness: a laboratory study.
Clin. Oral Impl. Res. 21 , 2010; 213–220.
doi: 10.1111/j.1600‐0501.2009.01823.x     

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.     

Initial Stability of Two Dental Implant Systems: Influence of Buccolingual Width and Probe Orientation on Resonance Frequency Measurements

Background: Although many factors seem to have an impact on the resonance frequency (RF) values of implants, there is a lack of evidence about some other parameters, which may have an influence on implant stability. Purpose: The aims of the study were to determine whether initial stability of a dental implant differs when the buccolingual width of the bone changes, to determine whether different orientations affect the RF measurements in the RF device, and to investigate two dental implants with different morphologies with regard to their initial stability. Materials and Methods: Two implant systems (Tidal Spiral Dental Implant Systems, Huntsville, AL, USA, and MIS Seven, MIS Implants Technologies Ltd., Shlomi, Israel) with diameters of 3.75 mm and 4.2 mm and with a length of 13 mm were used. Following the insertion of implants, buccolingual thinning of the models was performed in 2‐mm increments ranging between 0 and 8 mm. Results: A statistically significant decrease for implant stability quotient (ISQ) values was noticed for both diameters and both systems for all dimensional time points of the blocks (p < .05). The second system (more number of threads) resulted with higher ISQ values for both diameters than the first system (lower number of threads) (p < .001). The orientation of the probe influenced the measurements, where a standard orientation is advisable for the magnetic RF device. Conclusion: Different implant surface geometries seem to behave in different patterns in terms of initial stability. Dimensional changes in buccolingual direction seem to have an impact on the initial stability, where wider implants also presented higher ISQ values than narrow ones.