“O”型圈附着体义齿与套简冠义齿对基牙牙根应力分布的研究

目的：分析比较“O”型圈附着体覆盖义齿与套筒冠覆盖义齿的基牙牙根应力分布特点。方法：应用三维有限元应力分析方法研究了“O”型圈附着体覆盖义齿与套筒冠覆盖义齿的基牙牙根应力分布特点。结果：垂直载荷下，柱核型“O”型圈覆盖义齿基牙牙根内综合应力峰值较套筒冠覆盖义齿牙根内应力峰值下降了66.7%，应力分布更均匀，斜向载荷下，两种覆盖义齿的基牙牙根内应力峰值均较垂直载荷时高，但应力分布规律与垂直载荷类似，结论：“O”型圈覆盖义齿可以传递到基牙及粘骨膜的He力并使应力峰值降低，有利于口腔软硬组织的健康。尤其适用于需要利用残根作为基牙及其牙牙周健康欠佳的患者。     

口腔生物力学

20051817 铸模温度对牙用Ti-Zr合金铸造后力学性能影响的研究；20051818 金-瓷修复体粘弹性残余应力的有限元分析；20051819“O”型圈附着体义齿与套筒冠义齿对基牙牙根应力分布的研究；20051820 不同切端设计类型瓷贴面的三维有限元应力分析；20051821 Ⅰ类洞型设计的力学模型实验及二变量回归分析研究；20051822牙周膜动力分析的几个问题……     

SD附着体固位远中游离端可摘局部义齿三维有限元应力分析

目的：对比分析刚性及弹性附着体义齿的应力分布，为临床选用附着体提供理论参考。方法：建立下颌第二磨牙游离缺失的附着体义齿三维模型。采用有限元应力分析方法，分析2种附着体义齿基牙应力分布情况。结果：（1）在垂直载荷下，2种附着体基牙在牙槽嵴顶处均有应力集中。弹性附着体基牙牙根主应力下降26％-58％；剩余牙槽嵴应力峰值减小50％。（2）斜向载荷时，应力集中更明显，弹性附着体应力峰值仍有一定减小。结论：弹性附着体固位的可摘局部义齿，更有利于保护基牙及支持组织，保护剩余牙槽嵴。     

球帽式与套筒冠式下颌种植覆盖义齿的三维有限元分析

目的:应用三维有限元分析,比较球帽式和套筒冠式附着体对下颌种植覆盖义齿的应力分布的影响。方法:本实验应用三维有限元法分析,模拟下颌覆盖义齿在正中咬合状态下的受力情形。结果:两种模型中,骨组织界面应力主要都集中在种植体颈部周围的皮质骨中。球帽式附着体模型中牙槽嵴表面上的最大压应力峰值为-1.601Mpa,而套筒冠式附着体模型的压应力峰值为-0.296Mpa。套筒冠式附着体模型的中央种植体、侧方种植体上的应力峰值均小于球帽式附着体的种植体。结论:套筒冠式覆盖义齿较球帽式可降低种植体及剩余牙槽骨表面的应力,更有助于保存牙槽骨组织和种植体。     

垂直载荷下分割式可摘局部义齿与套筒冠义齿的有限元分析

目的研究并比较分割式可摘局部义齿与缓冲圆锥型套筒冠义齿在垂直载荷下的应力情况。方法选择上颌双侧第二前磨牙、第一磨牙缺失并伴有基牙有Ⅰ度松动的患者1名,通过螺旋CT扫描,利用Materialise Mimics、Pro/Engineer WF 2.0软件和ANSYS Workbench软件建立精确的上颌三维有限元模型,并在其上进行垂直方向加载,分析比较分割式可摘局部义齿与缓冲圆锥型套筒冠义齿缺牙区黏膜及基牙牙周膜应力情况。结果垂直载荷下,分割式可摘局部义齿缺牙区黏膜所受von Mises力值大于缓冲圆锥型套筒冠义齿缺牙区黏膜所受力值;分割式可摘局部义齿基牙牙周膜von Mises力值接近或小于缓冲圆锥型套筒冠义齿基牙牙周膜所受力值。结论在垂直载荷下,通过与缓冲圆锥型套筒冠义齿相比,分割式可摘局部义齿具有减少基牙受力,保护基牙的功能。     

用CAD软件辅助义齿建立力学分析模型的初步研究

目的：探讨运用CAD软件模拟制作有限元义齿模型，为简化有限元建模提供一种方法。方法：在CT扫描方法建立的下颌骨及基牙牙根的三维有限元基础模型上，用CAD软件在计算机上分别模拟套简冠及“O”型圈附着体两种覆盖义齿制作。结果：建立了“O”型圈附着体义齿与套简冠义齿的三维有限元模型。结论：运用CAD软件在计算机上直接制作有限元义齿模型，方便可行，可以为临床上修复体优化设计提供实验基础。     

自然牙根支持及种植牙支持式下颌全口覆盖义齿的三维有限元分析

目的研究自然牙根支持和种植基牙支持覆盖义齿在咀嚼过程中其周围骨皮质应力的差异，为改善种植覆盖义齿的修复效果提供依据。方法借助于ＣＴ扫描与计算机辅助设计手段，用三维有限元方法比较自然牙根支持式与种植牙支持式覆盖义齿在采用不同固位装置，不同咬合力状态下，支持组织应力分布的差异。结果①无论自然牙根支持式还是种植牙支持式覆盖义齿，在采用杆卡或按扣式附着体时，骨组织应力分布虽有不同，但这种不同与咬合力方向作用的结果相比是小的。在相同载荷下，２０°斜向加载时基牙周围骨皮质层最大应力值是垂直加载的２２～３倍。②种植基牙支持式覆盖义齿在两种不同上部结构设计，４种不同载荷条件下，基牙颈部周围骨质皮层最大应力值是自然牙支持式覆盖义齿的２５倍～４倍。结论为减少种植基牙周围骨皮质应力峰值，预防压力性骨吸收的产生，种植覆盖义齿设计时，应避免产生过大的侧方咬合力。同时，应考虑增加种植牙数目或在种植基牙上部结构中采用缓冲设计     

附着体义齿修复近中倾斜30°基牙的牙周组织应力分析

目的研究两种附着体义齿（栓道附着体义齿和套筒冠固定义齿）修复下颌第一磨牙缺失伴下颌第二磨牙近中倾斜30°的基牙的牙周组织应力分布。方法在已经建立的下颌第一磨牙缺失伴下颌第二磨牙近中倾斜30°修复前及两种附着体义齿修复后的三维有限元模型上,将200N垂直负荷和斜向负荷分别模拟加载于下颌第二磨牙,计算分析基牙牙周组织的应力情况。结果在下颌第二磨牙近中倾斜30°时,两种附着体义齿修复后倾斜基牙应力主要集中在其颈部牙槽骨或根分叉区。斜向加载下,栓道附着体义齿修复后倾斜基牙牙周组织应力小于套筒冠义齿修复。斜向加载下,下颌第二前磨牙和第二磨牙牙周组织应力远远大于垂直加载。结论在下颌第二磨牙近中倾斜30°时,栓道附着体义齿修复在改善倾斜基牙牙周组织应力方面更优于套筒冠义齿修复。斜向加载时,下颌第二前磨牙和第二磨牙牙周组织中产生较大的应力集中。     

用双套冠或磁性附着体固位的覆盖义齿制作体会

覆盖义齿是指义齿基托覆盖并支持在健康的或已做过治疗的牙根或牙冠上的一种全口义齿或可摘局部义齿。它与常规义齿的根本区别在于覆盖义齿基托下方除覆盖有粘膜外 ,还覆盖有天然牙或经过治疗的牙根。在它们上面安放附着体 ,可增加覆盖义齿的固位力 ,本文介绍了双套冠和磁性附着体的覆盖义齿制作体会。一、双套冠式附着体双套冠式附着体是借助内冠与外冠之间高度密合产生磨擦力固位的一种修复方式。内冠粘于患者口内基牙上 ,外冠通过连接体埋于义齿基托内部。1.临床要求 :完善的根管和牙周治疗后的牙齿做为双套冠式附着体的基牙。要求基牙磨…     

不同基牙牙周状况下双侧游离缺损冠外附着体义齿的三维有限元分析

目的：探讨不同基牙牙周状况下,下颌后牙双侧游离缺损冠外附着体义齿支持组织的应力分布情况。方法：建赢下颌双侧67游离缺损冠外附着体义齿修复时基牙牙周健康和基牙牙周吸收的三维有限元模型,分析垂直载荷下基牙牙周状况不同时,基牙牙周组织及缺牙区牙槽嵴的VonMises应力分布。结果：与牙周健康的模型相比,当第二双尖牙牙周吸收1／3时,远中基牙牙周膜和牙槽骨的最大应力值均增加了两倍多;当第一和第二双尖牙牙周均吸收l／3时,远中基牙牙周膜和牙槽骨的最大应力值是基牙健康时的四到五倍。随着牙周吸收的基牙数目的增加,缺牙区牙嵴的最大应力值增加了47％。增加基牙数目可显著降低远中基牙的牙周组织和缺牙区牙嵴的应力,使义齿支持组织的应力分布更为均匀。结论：冠外附着体义齿修复下颌双侧后牙游离缺损时,若两侧只有第二双尖牙牙周吸收1／3时,修复设计时可考虑增加基牙数目,若第一和第二双尖牙牙周均有吸收则不建议再选作附着体义齿基牙。     

不同牙根长度对双套冠覆盖义齿基牙受力的影响

目的 分析下颌双套冠覆盖义齿牙槽骨吸收程度不同对其应力分布的影响。方法 用三维有凶法,分析牙根长度不同时基牙的应务分布。结果 随着牙根周围牙槽骨高度下降,基牙根周骨内最大压应力值增加,应力集中范围增大,但在牙槽骨吸收至根尖１／３的范围内,应力值小于正常情况下牙周膜可耐受的最大压应力值。结论 下颌根周牙有吸收至根尖１／３的尖牙,在行截冠术和完善的牙体治疗后,如能保持合理的冠根比,即可用做覆盖义齿的基     

Effect of magnetic attachment with stress breaker on lateral stress to abutment tooth under overdenture

Recently, a newly developed magnetic attachment with stress breaker was used in retentive components in overdentures. Excessive lateral stress has a more harmful effect on natural teeth than axial stress, and the magnetic attachment with stress breaker is expected to reduce lateral forces on abutment teeth and protect it teeth from excessive stress. However, the properties of this retainer have not yet been determined experimentally. This study compares the lateral forces on abutment teeth for three retainers under loading on the denture base in a model study. A mandibular simulation model is constructed to measure lateral stress. Three types of retentive devices are attached to the canine root. These devices include the conventional root coping, the conventional magnetic attachment and the new magnetic attachment with stress breaker. For each retentive device, load is generated on the occlusal table of the model overdenture, and the lateral stress on the canine root and the displacement of the overdenture measured. The magnetic attachment with stress breaker does not displace the denture and exhibits lower lateral stress in the canine root than conventional root coping and magnetic attachments.     

下颌改良杆卡式种植覆盖义齿的应力分布——垂直载荷与斜向载荷的比较

采用三维各向异性有限元法分析全下颌改良杆卡式种植覆盖义齿垂直载荷与斜向载荷下的应力分面。结果显示,种植体的最大应力出现在种植体骨外段的近、远中面;种植体界面骨组织的最大应力位于种植体颈部周围的骨皮质界面;斜向载荷下种植体及其骨组织界面的应力值高于垂直载荷时,且垂直载荷下种植体骨界面的应力分布更均匀;近远中向斜向加载时种植体及其骨组织界面的最大应力值高于舌颊向加载时。     

冲击载荷下骨外段种植基桩不同高度对下颌覆盖总义齿应力分布的影响

目的 分析骨外段种植基桩高度不同对下颌种植覆盖总义齿应力分布的影响。方法 应用ＣＴ扫描法建立下颌种植覆盖总义齿三维有限元模型,分析冲击载荷下骨外段种植基桩高度不同对下颌种植覆盖总义齿应力分布的影响。结果 随种植基桩高度的降低,种植体内部及种植体软硬组织界面应力分布更为均匀。结论 在保证义齿固位稳定的前提下,在一定范围内降低种植体骨外段基桩高度有利于保护种植体及其周围软硬组织健康。     

下颌桩核基牙式全口覆盖义齿基牙牙本质的应力分析

目的：研究下颌桩核基牙式全口覆盖义齿基牙牙本质的应力分布状况，为临床工作提供实验依据和理论基础。方法：应用三维有限元应力分析法研究下颌桩核基牙式全口覆盖义齿基牙牙本质的应力分布特点，计算其应力值并与自然基牙作对比分析。结果：在相同载荷条件下，两种形式基牙在牙本质根尖部均出现应力集中现象。桩的存在可改变应力的范围和大小，使颈部拉应力范围变小、数值增大，根尖部的应力集中现象稍有减小。结论：桩核式基牙核的制作形态及门然基牙的制备形态符合He力的轴向传导方式。桩除固位作用外还有力的传导、应力中断及缓冲作用。桩核可以改变基牙牙本质原有的应力传导方式，使颈部牙本质折裂的可能性增大。     

Effect of reinforcement on overdenture strain

Because the abutment becomes the fulcrum, and the denture base over the coping is usually thin, the overdenture is susceptible to fracture. We hypothesized that rational reinforcement can reduce strain and prevent deformation and fracture of the overdenture. We investigated the effect of reinforcement on overdenture strain around the copings and at a midline. A mandibular edentulous model with a 2-mm-thick artificial mucosa and abutment teeth installed bilaterally in the canine position was produced. The coping had a dome-shaped upper surface with a height of 6 mm. On the lingual polished surface, strain gauges were attached at the canine position and at the midline. A vertical load of 49 N was applied on the occlusal surface. Among several kinds of reinforcements, the cast metal reinforcement that covers both the midline and the coping top significantly reduced the strain on the overdenture. It is suggested that this simple reinforcement is effective in preventing deformation and fracture of the overdenture.     

Influence of overdenture abutment tooth contour on the periodontium: a preliminary report

The effect of overdenture abutment tooth contour on plaque retention and periodontal health was evaluated in four patients over a 1-year period. Each patient had mandibular canines with similar periodontal support; however, one abutment was dome shaped while the other had 2 mm of natural peripheral root contour coronal to the ginvival margin. Eight parameters of periodontal health were measured, and no significant differences between different contours were observed after 1 year. Furthermore, irrespective of overdenture abutment contour, no deterioration in periodontal status occurred. Two subjects had significant wear of the overdenture abutments after 1 year. Further evaluation of more subjects over a longer period of time is indicated.     

Influence of abutment height on strain in a mandibular overdenture

The purpose of this study was to investigate the influence of coping heights on the strain around the abutment teeth and at the middle part of mandibular overdentures, using strain gauges. A mandibular edentulous model with a silicone artificial mucosa of thickness 2 mm was made. Two artificial roots were embedded on both sides in the canine position. The coping had a dome-shaped upper surface at a height of 0, 2, 4 and 6 mm. On the lingual polished surface of the overdenture, three strain gauges were attached in the left canine position at the vertical level corresponding to the top of the 6, 4 and 2 mm copings and two strain gauges were attached in the middle section (upper and lower). A vertical loading of 49 N was applied on the occlusal surface of first premolar, first molar and second molar. When loading on the first premolar adjacent to an abutment, the largest tensile strain was observed on the overdenture surface close to the top of each coping, independent of coping heights. When loading on the first premolar on the opposite side, the tensile strains around the coping were remarkably smaller. In the middle part of the overdenture, the compressive strains became larger by reducing the coping height or loading on distal point. The largest tensile strain was observed on the overdenture surface close to the top of copings, independent of coping heights.     

Stress distributions in maxillary bone surrounding overdenture implants with different overdenture attachments

In this study, effects of different overdenture attachments on the stress distributions in the maxillary bone surrounding the overdenture implants are studied. Four different types of attachment are considered. They are rigid Dalbo Stud, movable Dalbo Stress Broken, movable Dalro, and movable O-ring attachments. Three-dimensional finite element analysis was conducted with commercial package to obtain the stress distributions in the maxillary bone. Varying the attachment types and angle of inclination of load, the stress distributions in the portions of compact bone and trabecular bone were monitored separately. The analysis was conducted by assuming two different boundary conditions at the interface between cap and overdenture abutment in order to evaluate influence of interface boundary condition on stress distribution in the maxillary bone. They were perfect bonding condition and contact with friction at the interfaces. However, it is preferable to assume perfect bond condition at the interface for rigid type attachment systems and contact with friction at the interface for movable type attachment systems. From the numerical results, it was found that the load transfer mechanism of the implant system is altered significantly by the types of the overdenture attachment and also special care must be taken to assign proper boundary conditions at the interface for the analysis. The movable type Dalro attachment generated the highest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for contact with friction. The rigid type Dalbo Stud attachment generated the smallest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for perfect bonding condition.