下颌磨牙游离缺失套筒冠修复的基牙受载分析

目的研究下颌磨牙游离缺失采用第一，第二前磨牙为基牙的套筒冠修复，义齿受载时不同基牙的位移与应力分布特点。方法采用螺旋CT扫描，自编程序和ANSYS软件建立起精确的套筒冠三维有限元模型，在其上进行不同载荷的加载，分析不同基牙的位移与应力分布趋势。结果 套筒冠义齿在受情况下不同基牙的位移差别占其总位移的9%以下，应力均匀分布于不同基牙。结论套筒冠义齿中不同位置的基牙受载时共同下沉，承担着（牙合）力。     

下颌侧切牙缺失固定桥设计基牙受力情况的实验研究

目的比较双端及单端固定桥修复下颌侧切牙缺失时基牙的受力情况。方法应用ANSYS软件,通过三维有限元法建立4种固定桥模型,分别以中切牙和尖牙、中切牙、尖牙、尖牙和第一前磨牙为基牙模拟下颌侧切牙缺失,分析基牙最大受力部位和大小。结果单端固定桥修复模型中,以中切牙作为单一基牙时,基牙根尖受力值最大;双基牙单端桥基牙根尖受力最小;双端固定桥两基牙根尖受力分布最均匀。结论下颌侧切牙缺失患者以双端固定桥修复时,基牙受力最合理;单基牙单端桥设计,中切牙受力大于尖牙,而双基牙的单端桥修复形式较单基牙理想。     

下颌固定义齿不同桥体跨度下受载的三维有限元分析

目的　分析当固定义齿桥体加长时修复体及其基牙支持组织的受力状况。方法　在建立下颌固定义齿三维有限元模型的基础上 ,将桥体的跨度分别加至原长的 2～ 4倍 ,施加相同大小的垂直向载荷 ,利用MARC软件计算并绘制各种情况下的应力分布图像。结果　当固定义齿桥体加长时 ,修复体受载后的应力分布情况不发生改变 ,但最大等效应力相应增加。当桥体跨度增加至原长的3倍时 ,最大VonMises应力为 2 11.30MPa(桥体加载 )。结论　桥体的跨度增加超过约 3个前磨牙宽度时 ,有可能会对修复体造成损害     

四种修复设计对下颌第一磨牙远中残根应力的影响

目的研究不同修复设计对下颌第一磨牙远中残根应力的影响，筛选出最佳的修复方案。方法用有限元和光弹应力分析方法，模拟6近中根拔除，远中根保留，分别采用6单冠、67联冠、56联冠、567联冠修复，比较相同载荷条件下6远中根的应力状况。结果与正常6的牙周应力相比，6远中根在6单冠修复时应力增大3倍以上，67联冠修复时应力增为两倍左右，56联冠和567联冠修复时应力均接近正常值。结论6远中残根可采用56联冠和567联冠修复。     

桩径对游离端缺失种植固定桥支架适合性影响的实验研究

目的：考察不同种植基桩桩径对游离端缺失种植固定桥支架适合性的影响，以探讨临床上有无内冠与支架适合性的关系。方法：模拟下颌一侧第二双尖牙至第三磨牙缺失，以该侧第一双尖牙为天然基牙，在缺牙区植入两个种植体，根据不同的基桩颈缘直径分为３组，用非贵金属（Ｎｉ－Ｃｒ－Ｎｂ合金）整铸法制作固定桥支架，采用三维坐标测量法比较研究其适合性。结果：不同种植基桩桩径的固定桥支架固位体中心轴的颊舌向倾斜有统计学差异（Ｐ＜０．０５），固位体的边缘变形量、浮升量、中心轴的距离差均无统计学差异（Ｐ＞０．０５）。结论：是否设计制作内冠对游离端缺失整铸种植固定桥支架的适合性有一定影响。     

两种材料套筒冠游离缺失基托下支持组织的受载位移分析

目的 研究游离缺失套筒冠活动义齿缺牙区牙槽嵴粘膜表面位移。方法 使用两种材料制作套筒冠金属部分，采用螺旋CT扫描、自编程序和ANSYS软件建立起精确的下颌骨三维有限元模型，在其上进行加载，分析缺牙区牙槽嵴粘膜表面位移情况。结果 用两种金属制作的套筒冠对于在受力情况下缺牙区牙槽嵴粘膜表面的位移无明显影响。结论 从力学的角度，使用不同金属制作套筒冠的金属部分是可行的。     

种植体长度对天然牙-种植体联合修复体应力影响的研究

目的:建立天然牙-种植体联合支持固定桥的三维有限元模型.探讨不同种植体长度对天然牙-种植体联合支持固定桥的修复体上部结构、天然牙等应力分布的影响.方法:对模型施加200N垂直向集中的力和200N颊舌向集中的力,运用CT扫描、三维有限元分析方法等手段,对比观察不同长度的种植体对天然牙及其修复体上部结构应力分布的影响.结果...     

种植修复下颌磨牙游离缺失满意度的纵向研究分析

目的:纵向比较下颌磨牙游离缺失患者在未修复、活动义齿修复及种植义齿修复后的主观评价。方法:对40例戴用过活动义齿,现已完成种植义齿修复的下颌磨牙游离缺失患者,采取种植修复前自测问卷和种植修复后自测问卷形式,由患者本人填写。结果:种植义齿在咀嚼、语言、舒适性、固位等方面的满意度得分更高。结论:种植义齿是修复下颌磨牙游离缺失的最满意选择,活动义齿和未修复状态的满意度无显著意义。     

两种游离端半精密附着体可摘局部义齿的应力分析

目的:研究双侧游离缺失活动义齿使用两种不同类型的半精密附着体固位时周围支持骨的表面应力。方法:采用电阻应变测量法在人体下颌骨标本上测量以冠内栓道式及冠外垂直杆式半精密附着体固位的双侧游离缺失活动)固定联合修复体的表面应力值并做统计分析。结果:冠内附着体在基牙周围牙槽骨上产生的总体应力较大,而冠外附着体在缺牙区牙槽嵴和近缺隙侧基牙远中颈部牙槽嵴上产生的应力较大。结论:冠内附着体适用于远中基牙牙周条件良好的情况,而冠外附着体则适用于缺牙区牙槽嵴条件良好、远中基牙条件相对欠佳的情况。     

软衬材料在下颌双侧游离缺失修复中的应用研究

目的:观察软衬材料在下颌双侧游离缺失可摘局部义齿中的应用效果。方法:选择38例牙槽嵴重度吸收的下颌双侧游离缺失患者,随机分为两组。实验组在可摘局部义齿中引入软衬材料对义齿进行衬垫处理,对照组接受常规可摘局部义齿修复。检测两组义齿戴用1个月、1年及2年时的咀嚼效率,同时采用满意度问卷调查获取患者的主观评价。结果:与对照组比较,实验组义齿各个时期的咀嚼效率均获得明显改善(P<0.05),舒适程度及咀嚼功能的满意度亦高于对照组(P<0.05)。结论:软衬材料的应用可提高下颌双侧游离缺失可摘局部义齿的满意度,改善患者的咀嚼效率,取得良好的修复效果。     

A systematic review of prosthetic restoration in patients with shortened dental arches

The literature regarding the effect of prosthetic restoration in patients having distal extension edentulous space in posterior area (shortened dental arch: SDA) is reviewed in the following article. Information retrieval followed a systematic approach using PubMed. Articles in English published between 1966 and March 2011 describing the outcome of treatment with various prostheses were evaluated. From the search results of 98 articles, 21 articles met the inclusion criteria. Treatment with removable partial dentures (RPDs) improved masticatory function, patient satisfaction and oral health-related quality of life (OHRQoL). However, no significant difference was found in the outcomes between patients with RPDs and with cantilever fixed partial dentures (CFPDs). Caries developed more frequently after treatment with RPDs than CFPDs. The time to survival for CFPDs was not longer than that for RPDs, while more visits to maintain RPDs were required than for CFPDs. No significant difference was found in masticatory function, OHRQoL, and occlusal stability between patients with RPDs and those without restoration of missing molars. Consequently, treatment with RPDs for SDA seems to be less advantageous than CFPDs or no restoration for missing molars. Further research is required to validate treatment with implant-supported fixed partial dentures for SDA.     

种植体上部不同结构对下颌游离端义齿应力分布的影响

目的:观察不同上部结构的种植体支持可摘局部义齿修复下颌KennedyⅠ类牙列缺损时的应力和位移。方法:使用软件GeoStar(COSMOSM 2.85,SRAC,USA)建立4个种植体-天然牙联合可摘义齿修复下颌KennedyⅠ类牙列缺损的三维有限元模型,比较不同上部结构时种植体周围骨组织、基牙牙周膜、基托下黏膜的最大等效应力及基托下黏膜组织的位移变化。结果:有种植体支持时,单冠形式的种植体周围骨组织最大等效应力最大;缓冲型套筒冠的基牙牙周膜最大等效应力、基托下黏膜最大等效应力和位移值最大;微型太极扣种植体周围骨组织最大等效应力、基牙牙周膜最大等效应力和黏膜的最大等效应力及位移值均最小。缓冲型套筒冠种植体周围骨组织最大等效应力小于非缓冲型套筒冠,但基牙牙周膜最大等效应力、基托下黏膜最大等效应力和位移则大于非缓冲型。结论:选用种植体-天然牙联合支持修复远中游离端牙列缺损时,种植体上部结构采用微型太极扣作为附着体联接形式是最佳选择。     

Periodontal ligament influence on the stress distribution in a removable partial denture supported by implant: a finite element analysis

ABSTRACT

Objective

The non-homogenous aspect of periodontal ligament (PDL) has been examined using finite element analysis (FEA) to better simulate PDL behavior. The aim of this study was to assess, by 2-D FEA, the influence of non-homogenous PDL on the stress distribution when the free-end saddle removable partial denture (RPD) is partially supported by an osseointegrated implant.

Material and Methods

Six finite element (FE) models of a partially edentulous mandible were created to represent two types of PDL (non-homogenous and homogenous) and two types of RPD (conventional RPD, supported by tooth and fibromucosa; and modified RPD, supported by tooth and implant [10.00x3.75 mm]). Two additional FE models without RPD were used as control models. The non-homogenous PDL was modeled using beam elements to simulate the crest, horizontal, oblique and apical fibers. The load (50 N) was applied in each cusp simultaneously. Regarding boundary conditions the border of alveolar ridge was fixed along the x axis. The FE software (Ansys 10.0) was used to compute the stress fields, and the von Mises stress criterion (σvM) was applied to analyze the results.

Results

The peak of σvM in non-homogenous PDL was higher than that for the homogenous condition. The benefits of implants were enhanced for the non-homogenous PDL condition, with drastic σvM reduction on the posterior half of the alveolar ridge. The implant did not reduce the stress on the support tooth for both PDL conditions.

Conclusion

The PDL modeled in the non-homogeneous form increased the benefits of the osseointegrated implant in comparison with the homogeneous condition. Using the non-homogenous PDL, the presence of osseointegrated implant did not reduce the stress on the supporting tooth.     

Effect of different materials and undercut on the removal force and stress distribution in circumferential clasps during direct retainer action in removable partial dentures

ObjectivesThis study aimed to evaluate the effect of different materials and undercut on the removal force and stress distribution in the supporting tooth and in the circumferential clasp used in removable partial prosthesis.MethodsUpper molars prepared for Akers circumferential clasp with retention and opposing arm were modeled, scanned, elaborated with CAD software and the geometries imported in FEA and analyzed. Six different materials were selected for the clasp (Polyamide, Polyoxymethylene, Polyetheretherketone - PEEK, Gold alloy, Titanium and CoCr) and 3 different undercuts (0.25, 0.50 and 0.75 mm), totaling 18 groups.ResultsThe clasps presented greater stress in their structure and potentially greater damage to the dental enamel when made with rigid materials and with more undercut; however, they presented greater ability to remain in position.SignificancePolyamide with a higher undercut is an esthetic alternative to rigid metallic clasps. It showed promising behavior because it strongly reduces the damage to the enamel, and even with an undercut of 0.75, the retention is lower than for CoCr with a 0.25 undercut, and this retention might still be sufficient. Polyoxymethylene and Polyetheretherketone (PEEK) are not suitable materials for the clasps, because the maximum stress occurring during removal with higher undercuts is higher than the material strength.     

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。     

单侧游离端义齿三种腭部连接形式的光弹应力分析

用光弹模型“冻结”法对三种不同位置腭杆的单侧游离端义齿进行侧向加载，研究缺牙区牙槽嵴、缺牙区同侧基牙和缺牙区对侧基牙的应力情况，分析连接杆传递和分散侧向力的作用。结果表明：腭连接杆的位置与侧向力的传递和分散有一定关系。前金属基托型单侧游离端义齿向缺牙区对侧基牙传递的侧向力比后腭杆型义齿传递的力小。单侧游离端义齿受侧向力时连接杆传递力的作用不明显，缺牙区牙槽嵴和同侧基牙承担主要载荷     

老年人可摘局部义齿修复对基牙的影响

目的:分析研究老年人可摘局部义齿修复后对基牙的影响,探讨其原因及预防措施。方法:对95例牙列缺失后的老年人行冷弯卡环固位式可摘局部义齿修复,记录和比较戴可摘局部义齿后基牙和非基牙的龋坏率和缺失率,用χ2检验分析其结果有无差异,并对影响基牙的原因进行分析。结果:戴用可摘局部义齿5a后,基牙的患龋率(17.38%)显著高于非基牙(7.10%);因牙折、牙周病松动及龋坏无法保留而拔除的基牙缺失率(27.01%)也显著高于非基牙(7.79%)(P<0.01)。结论:冷弯卡环固位可摘局部义齿修复后在一定程度上可增加老年人基牙的患龋率和缺失率。     

2种支架设计对基牙及相关组织受力的三维有限元分析

目的:比较使用同种材料制作的改良设计义齿和常规设计义齿对远中游离端缺损的基牙及相关组织受力的影响.方法:选择上颌单侧第一、第二磨牙缺失的55岁男性患者1例,通过螺旋CT扫描、Mimics、Geomagic Studio及ANSYS软件建模并进行有限元分析,观察基牙及相关组织的受力情况.结果:改良设计义齿基牙受力范围明显减小,牙周膜受力减小、鞍基区黏膜受力增加且更均匀,牙槽骨刺激性吸收趋势减小.结论:对于远中游离端缺损的牙列缺损患者,改良设计的可摘局部义齿具有一定的应力中断作用,能更好地保护基牙、分散()力,对缺牙区黏膜和牙槽骨具有良好的保护作用.