上颌切牙缺失两基牙双端固定桥修复的生物力学分析

目的 :研究上颌切牙缺失两基牙双端固定桥修复的应力分布。方法 :采用CT扫描获取健康成人上颌牙及其支持组织的二维图像 ,通过计算机重建技术建立三维立体图像 ,并获得了上颌切牙缺失后的两基牙双端固定桥的三维有限元数学模型 ,在相同垂直载荷和水平载荷下分析了基牙牙槽骨高度对固定桥应力分布的影响。结果 :当基牙牙槽骨无吸收时固定桥两基牙应力分布均匀 ;当基牙牙槽骨吸收 >15 %时固定桥两基牙出现应力集中。结论 :上颌切牙缺失后选择尖牙两基牙双端固定桥修复是合理的 ,但其前提是基牙牙槽骨吸收较少。     

用光弹性方法对固定桥基牙牙槽骨受力的实验研究

本文采用平面光弹性方法对下颌第一磨牙缺失的两基牙双端固定桥、半固定桥、三基牙双端固定桥、有邻牙的两基牙双端固定桥以及未修复牙的受力情况进行了实验研究,得出了固定桥基牙垂直支反力的分配比例和各类修复体基牙牙槽骨的应力条纹图。结果表明:     

下颌第二磨牙半切术后固定修复的三维有限元分析

目的探讨下颌第二磨牙半切术后不同修复方式对基牙受力的影响,为临床修复设计提供依据。方法用三维有限元分析方法,分别模拟7近中根拔除、远中根保留和远中根拔除、近中根保留后固定桥修复,同时建立了司联冠修复和司缺失单基牙固定桥修复作为对照．比较载荷状态下基牙的受力状况。结果保留7远中根、固定修复6与正常情况下受力趋势相似。应力值较大;保留7近中根、单端固定桥修复司应力明显增大且峰值出现部位由颈部转移到根尖,但较司缺失、以6为基牙的单端固定桥受力合理。结论保留下颌第二磨牙远中根较保留近中根与第一磨牙联合修复后基牙受力合理：只要选择好适应症,保留近中根也是避免下颌第二磨牙缺失的一种方法。     

单端固定桥——10年临床观察

尽管单端固定桥是一种有争议的修复方法,如果谨慎地按标准去作,还是有其适应症的。单端桥可用于修复上侧切牙,当中切牙外观很好,或中切牙是另一修复体的一部分时,预备中切牙则是不明智的。单端桥也可用于修复下颌或上颌第一或第二双尖牙。用单端固定桥改变游离端可摘义齿的设计,     

第三磨牙倾斜不同角度对下颌双端固定桥应力的影响

目的:下颌第一二磨牙缺失三基牙双端固定桥修复的条件下,分析近中倾斜不同角度的第三磨牙作为基牙后受力时修复体、牙体组织及牙周膜的应力分布情况,为临床修复提供理论依据.方法:在已建好的第一二磨牙缺失三基牙双端固定桥修复的三维有限元模型基础上,将第三磨牙近中倾斜0°、10°、20°、30°和40°,通过Ansys软件分析修复...     

上颌无牙颌修复中种植体部位和数量对应力分布的影响

目的:探讨修复无牙上颌,种植桥和附着体义齿硬性连接时,种植体部位与数量对应力分布的影响。方法:在无牙上颌模型上制作一个方便采集有限元数据的特殊义齿,螺旋CT扫描后建立3个三维有限元模型。模型1为4个种植体位于双侧中切牙和尖牙;模型2为4个种植体位于双侧侧切牙和尖牙;模型3为6个种植体,位于双侧中切牙、侧切牙和尖牙。前牙区种植体形成固定桥,与后端活动义齿采用硬性附着体连接。附着体与固定桥连接部分为阳性部件,与活动义齿相连部分为阴性部件。结果:三个模型中尖牙种植体的应力值均较大,且都集中在牙颈部,模型3<模型2<模型1,模型1约为模型3的1.85倍;在同一模型中,尖牙区种植体最大应力值在模型1约为中切牙的10倍,模型2约为侧切牙的5倍;模型3约为侧切牙的3.1倍,中切牙的6.4倍,但其侧切牙和中切牙所受最大应力分别与模型2和模型1接近。模型1阳性部件与阴性部件最大应力值均比模型2、模型3明显增大,尤其是阴性部件,约为后者的4倍。义齿腭杆的最大应力主要集中在前部附着体连接处,其次为树脂基托的连接处,腭杆水平部的转角处。结论:当附着体采用硬性连接时,前牙区选择6个种植体似乎更符合生物力学要求;建议注意附着体与金属支架连接处,腭杆与树脂基托连接处的加强。     

基于CBCT的下颌前牙区颌骨形态学研究

[摘要]目的：利用锥形束CT（codebeamcomputedtomography,CBCT）图像研究测量下颌前牙区的颌骨形态和宽度,为临床种植手术提供治疗依据。方法：选取2011年--2013年间50名成年受试者的CBCT检查结果,利用CBCT图像对下颌前牙区颌骨外形、唇舌侧宽度、近远中距离等进行观察和测量。结果：1．下颌前牙区颌骨形态唇侧均为凹形,最凹点位于下颌骨上中份,舌侧外形多样化,凸形比例最高。2．下颌骨前牙区颌骨唇舌侧宽度在下颌骨中1／2和下颌骨下缘较宽,在牙槽嵴顶和根尖区较窄。3．左右尖牙、侧切牙、中切牙于牙槽嵴顶的近远中距离是4．46～6．94mm,尖牙最长,侧切牙次之,中切牙最小。结论：下颌前牙缺失后,尤其是下颌侧切牙或中切牙个别缺失,如行种植修复近远中距离可能不足,易损伤邻牙;植入种植体等手术时应当注意下前牙区颌骨外形,避免因倒凹导致唇舌侧穿通;CBCT可作为下颌前牙区种植手术术前的常规影像学检查手段。     

下颌第一磨牙缺失两基牙双端固定桥修复的生物力学分析

目的：研究下颌第一磨牙缺失两基牙双端固定桥修复的应力分布。方法：采用CT扫描获取健康成人上、下颌牙及其支持组织二维图像,通过计算机重建技术获得右下颌第一磨牙缺失后的双端固定桥桥体颊舌径分别为正常时的100%、90%、66.7%和50%与右下颌双端固定桥桥体及右下颌第二磨牙颊舌径均分别为正常时的90%、66.7%和50%的7个三维有限元模型,在相同垂直载荷和斜向载荷下分析了基牙牙槽骨高度及桥体大小对固定桥应力分布的影响。结果：当双端固定桥桥体颊舌径分别为正常大小的66.7%和50%时,固定桥两基牙中的第二前磨牙在垂直向加载时均出现明显应力集中;当下颌第二磨牙牙槽骨吸收程度等于及大于35%时,下颌第二前磨牙在其垂直向加载与斜向加载时均出现明显的应力集中,下颌第二磨牙在其垂直向加载时出现明显的应力集中。结论：固定桥受载的Von Mises最大应力集中于连接体表面。对于下颌567双端固定桥,当桥体变窄,颊舌径小于正常大小的66.7%时,有可能会对基牙中的第二前磨牙造成损害。当下颌第二磨牙牙槽骨吸收程度等于及大于35%时,可能对双基牙都造成损害,并可能促使并加速牙槽骨的进一步破坏吸收。     

栓体-栓道-全冠桥体固定桥在双侧倾斜基牙修复中的应用

在下颌后牙的固定修复过程中，常见缺隙两侧基牙向缺隙侧倾斜的情况，难以取得共同就位道，不得不采取多磨切牙体组织甚至失活基牙牙髓的设计，或者采用栓体-栓道两段式固定桥修复。笔者使用栓体-栓道-全冠桥体三段式双端固定桥，既达到了磨切基牙牙体组织少，保护牙髓，又改善了两段式栓体-栓道固定桥的受力方式，取得了较好的临床应用效果。     

固定修复后倾斜基牙角度对牙周受力影响的有限元分析

目的:分析第一磨牙缺失,采用双端固定桥修复,作为基牙的下颌第二磨牙倾斜不同角度时,基牙牙周膜等支持组织的应力分布情况,为临床修复提供理论依据。方法:采用三维激光扫描与Marc软件结合的方式,分别建立下颌第一磨牙缺失、下颌第二磨牙向近中倾斜时,行双端固定桥修复后的三维有限元模型,施加载荷计算并分析牙周膜支持组织中的应力分布状况。结果:当下颌第二磨牙近中倾斜24°时,其近中牙颈部牙周膜的应力值达到0°时的2倍,同时下颌第二前磨牙牙周膜受力也呈现上升趋势。结论:固定修复时,当牙齿倾斜达到或超过24°时,应慎重作为双端固定桥的基牙。     

The cantilever fixed partial denture--a literature review.

The cantilever fixed partial denture (FPD) is a restoration with one or more abutments at one end and unsupported at the other end. Forces transmitted through the cantilevered pontics can cause tilting and rotational movements of the abutments. In a cross-arch unilateral cantilever FPD, the distal cantilevered unit is subjected to comparatively less force than the contralateral posterior abutment. The unilateral lack of terminal abutments causes lateral bending forces activate peripheral inhibitory feedback reactions from the periodontal and/or temporomandibular mechanoreceptors. The greatest strain in distal cantilevered FPDs is recorded mesial to the most distal retainer because most fractures occur in this location. To improve the prognosis of the FPD cantilever, the number of abutments should be increased and the number of pontics decreased. The abutment teeth need long roots and acceptable alveolar support. Prepared abutments require adequate length and parallel axial walls. An equilibrated and harmonious occlusion is necessary, as well as exemplary oral hygiene. A cantilevered FPD with adequate periodontal support can replace any tooth in the dental arch, but is especially useful as an alternative to a removable partial denture. The cantilevered FPD requires at least two abutment teeth. The only documented exception permitting a single abutment is the replacement of a maxillary lateral incisor with the canine as an abutment. An alternative to the cantilevered FPD is the osseointegrated implant. As osseointegrated implants become more popular, the need for the tooth-supported cantilevered FPD may decline, but it will remain an alternative treatment modality.     

用三维有限元方法对单端固定桥进行应力分析

目的分析磨牙游离缺失单端固定桥修复的受力情况。方法运用三维有限元应力分析法,对一侧磨牙游离缺失通过改变牙槽骨支持高度,采用不同基牙数目,不同桥体长度建立不同的单端固定桥有限元模型进行应力和位移的计算和分析。结果较高的应力集中在游离端近中的基牙上,牙槽骨高度降低会增加基牙的移位及应力集中;单纯增加基牙的数目不会导致牙周组织中应力明显相应减少;基牙数目增加会减少修复体移位及应力集中;增加桥体长度会引起义齿应力明显增加和向远中移位。结论游离缺失端行单端固定桥修复最好选择桥体为一个磨牙长度,且基牙数至少两个,以提高单端固定桥修复的成功率。     

三种不同连接方式的天然牙—游离端种植体联合支持的 固定义齿集中载荷应力分析

目的 研究三种不同连接方式的天然牙——游离端种植体联合支持的固定义齿在集中载荷下的应力值和应力分布。方法 应用三维有限元应力分析法。结果 ①固定连接式固定义齿的种植体基牙应力峰值高于天然牙;②刚性栓道式固定义齿的种植体基牙应力峰值最高;③缓冲式固定义齿的种植体基牙应力峰值最低。结论 ①固定连接式固定义齿设计可能损伤种植体基牙,需采取适当措施;②刚性栓道式固定义齿设计对种植体基牙损伤最大;③缓冲式固定义齿设计有利于保护种植体基牙。     

Biomechanics of Cantilever Fixed Partial Dentures in Shortened Dental Arch Therapy

PURPOSE: The purpose of the present study was to investigate, by means of 3-dimensional finite element analysis, aspects of the biomechanics of cantilever fixed partial dentures replacing the maxillary canine in shortened dental arch therapy. The null hypothesis was that no differences would be identified by finite element analysis in the mechanical behavior of the 2 designs of cantilever fixed partial denture under different scenarios of occlusal loading. MATERIALS AND METHODS: Single- and double-abutted cantilever fixed partial dentures were modeled and analyzed using the finite element packages PATRAN and ABAQUS. Displacement and maximum principal stresses (magnitude and location) within the fixed partial dentures, supporting structures, and the periodontal ligament/bone and abutment/retainer interfaces were examined under 20 different scenarios of axial and lateral occlusal loading. RESULTS: The results indicate that more displacement occurred in the 2 rather than the 3-unit cantilever fixed partial denture, with the greatest displacement having occurred under lateral loading. The maximum principal stresses observed in the periodontal ligament/bone interfaces were greatest buccocervically, with the highest value being observed in the 2-unit fixed partial denture under lateral loading. The highest maximum principal stresses observed in the retainer/abutment interfaces were located cervically in relation to the distal margin of the retainer of the 2-unit fixed partial denture under axial loading. CONCLUSIONS: It was concluded that in adopting a cantilever fixed partial denture approach for the replacement of a missing maxillary canine in shortened dental arch therapy, there may be merits, in terms of mechanical behavior, in selecting a double-rather than a single-abutment design. Furthermore, prostheses' displacement and functional stresses may be minimized by reducing lateral loading and avoiding pontic only loading.     

单端全瓷树脂粘接桥在青少年正畸后缺失切牙间隙保持中的应用1例

本文报道1例右下侧切牙缺失的正畸后青少年病例,利用右下尖牙为基牙,以单端全瓷树脂粘接桥恢复牙列完整,保持缺牙间隙并恢复功能与美观。     

Anterior rests for maxillary removable partial dentures.

Positive anterior rests were shown to be an essential element of design when considering stress distribution with a removable partial denture involving anterior teeth. Proximal plates often added stability and reduced stress accumulation in any one region. Distobuccal forces on the extension base adversely affected the primary canine abutment. Forces in the regions of the anterior base and central incisor abutment produced the most widespread transmission of stress throughout the arch. Greater stress throughout the arch was observed when forces were applied to the central incisor rather than to the right canine abutment. There is a need for established criteria of rest form and placement. Guidelines for using the natural crown as opposed to a positive rest seat in a restoration are needed. Continuing studies of other anterior rest forms should increasingly clarify this phase of treatment planning. The dentist should recognize the need for structural integrity in the anterior maxillary segment when designing removable partial dentures. A practical, defensible rationale for the routine use of maxillary anterior teeth as removable partial denture abutments must be established.     

Fixed cantilever splints on teeth with normal and reduced periodontal support

Photoelastic models were used to visualize stresses developed in teeth and supporting bone by cantilever fixed partial dentures where the most distal abutments had either crater or trough osseous defects. The effects of splinting the periodontally involved teeth to one or more additional sound teeth were studied. It was shown that for a cantilever fixed partial denture with either normal periodontal support, or a distal abutment with a moderate degree of mobility and bone loss, the following can be concluded: (1) occlusal forces on a cantilever fixed partial denture were significantly distributed to only the three teeth closest to the loaded cantilever, (2) optimum stress reduction occurred with the splinting of a periodontally compromised tooth to two periodontally sound teeth. Increasing the number of splinted abutments did not result in a proportional reduction of stress in the periodontium, and (3) no significant cross-arch sharing of occlusal loads was seen.     

下颌固定桥基牙牙槽骨单侧吸收对基牙应力分布的影响

目的:研究双端固定桥基牙牙槽骨单侧吸收对基牙应力分布的影响。方法:采用螺旋CT扫描获取健康人下颌骨、牙齿、牙周支持组织的二维图像,通过图像合成软件建立三维数字模型,并应用三维有限元分析软件生成下颌后牙三单位固定桥的三维有限元分析模型。在相同垂直和水平载荷情况下,分析基牙牙槽骨单侧吸收时固定桥各基牙的应力分布。结果:当前磨牙端基牙牙槽骨单侧吸收达25%、磨牙端基牙牙槽骨无吸收时,前磨牙端基牙开始出现应力集中;当磨牙端基牙牙槽骨单侧吸收达35%、前磨牙端基牙牙槽骨无吸收时,磨牙端基牙开始出现应力集中。结论:下颌后牙双端固定桥基牙应力分布与基牙牙槽骨吸收形式密切相关,但二者之间不是线性关系而是存在临界区,基牙牙槽骨单侧吸收的程度对基牙应力分布的影响弱于多侧吸收。     

Three-dimensional finite element stress analysis of a cantilever fixed partial denture.

A three-dimensional mathematical model was generated, representing a three-unit cantilever fixed partial denture and its supporting mandibular structures. First and second premolars were used as abutments with one posterior cantilever pontic. A 5 lb vertical load was applied to the pontic. Vertical and horizontal stresses were analyzed by means of a three-dimensional finite element stress analysis technique. The results showed that a cantilever pontic creates considerable compressive stress on the abutment nearest to the pontic and produces tensile stress on the abutment farthest from the pontic.