垂直静载下颊侧短固位臂美学卡环义齿基牙及鞍基位移的激光全息计量分析比较

目的：以离体下颌骨为实验对象，分析比较四种卡环对基牙及义齿鞍基位移的影响。方法；设计4类卡环①近中He支托－颊侧短固位臂－远中邻面板固位体；②RPI卡环；③远中He支托－颊侧短固位臂－远中邻面板固位体；④锻丝三臂卡环。采用激光全息干涉计量术，分析比较4种卡环设计义齿在垂直静载下对基牙及义齿鞍基位移的影响。结果：义齿垂直加载时，近中He支托－颊侧短固位臂－远中邻面板固位对基牙及义齿鞍基的位移量大于RPI卡环，但小于锻丝卡环，基牙位移方向为近中、舌向、龈向；提示近中He支托－颊侧短固位臂－远中邻面板固位体和PRI卡环更有利于基牙健康。     

下颌游离端义齿He支托设计的有限元分析

用三维有限元的方法，对设计了三种Ｈｅ支托的下颌单侧游离端义齿，分别在人工牙上采用九种不同的加载方法，对近基牙支持组织的应力和位移进行了研究分析，并进行统计学处理。结果远中Ｈｅ支托引起基牙支持组织的应力和位移值均最大；而近中Ｈｅ支托和双支民近远中方向上，基牙牙周组织应力和位移的差异无统计学意义；无论是何种Ｈｅ支托应力和位移值均随加载点向远中移动过程中而逐渐减小。     

负荷汪颌肯氏Ⅱ类可摘义齿游离端基牙牙槽骨位移的全息干涉测量

目的：比较下颌肯氏Ⅱ类可摘局部义齿的不同卡环对基牙牙槽骨产生作用的差异。方法：在离体人下颌骨上,设计制作5种直接固位体的肯氏Ⅱ类可摘局部义齿,即RPA卡环、RPI卡环、改良RPI卡环、铸造三臂卡环、颊侧锻丝固位臂卡环,用全息干涉测量技术,比较5种固位体使基牙颊舌侧牙槽骨产生位移的情况。结果：近中He支托卡环产生的位移小于过错中He支托卡环,杆型卡环产生颊侧牙槽骨位移分布均匀,圆环形卡环引起的颊侧位移信中在根尖,结论：临床修复此类牙列缺损时应尽量使用近中He支托和杆型卡环。     

末端游离缺失可摘局部义齿He支托设计的有限元分析

本文采用二维有限元法对近、远中Ｈｅ支托设计的末端游离缺失可摘局部义齿模型进行垂直载荷条件下的应力、位移分析研究。结果表明在同一加载条件下，设计近中Ｈｅ支托时基牙牙周支持组织及基托下软组织的应力、位移值明显减小，基牙受力趋于轴向：基托下软组织的应力、位移值大于基牙牙周支持组织应力、位移值。本实验从生物力学角度论证近中Ｈｅ支托在修复末端游离缺失的优越性。     

卡环设计与基牙牙槽骨及剩余牙槽嵴吸收关系的研究

目的 研究铸造支架式可摘局部义齿卡环设计与基牙牙槽骨及剩余牙槽嵴吸收之间的关系。方法 选择牙列远中游离缺失的患者55例,基点末端基牙采用RPI型卡环13例,PRA型16例、传统三臂卡环26例,于义齿修复当时以及修复后6月和12月时,拍摄该末端基牙的定位X线根尖片,并进行数字减影分析,计算末端基牙牙槽骨及剩余牙槽嵴的骨吸收参考体积量。结果 （1）剩余牙槽嵴以及末端基牙颊舌侧牙槽嵴顶的吸收;RPA组低于RPI组和传统三臂卡环组;（2）末端基牙远中牙槽嵴顶的吸收;RPA组和RPI组低于传统三臂卡环组。结论 近中He支托设计的卡环,较远中He支托设计的卡环,有利于维护末端基牙远中牙槽骨的健康;RPA型卡环设计较RPI和传统三臂卡环设计更利于维护末端基牙颊舌侧牙槽骨以及剩余牙槽嵴的健康。     

基牙牙周损伤影响可摘局部义齿应力分布的三维有限元分析

目的 探讨三维红外扫描用于可摘局部义齿三维有限元建模的可行性,并分析基牙牙周损伤对可摘局部义齿应力分布的影响,以期为临床提供参考.方法 利用齿科非接触式红外扫描仪和Simpleware软件对下颌肯尼迪分类法Ⅱ类缺损的可摘局部义齿进行三维建模,构建正常牙槽骨组、牙槽骨吸收组和牙槽骨吸收伴牙周膜增宽组三维有限元模型.使用Abaqus有限元分析软件,研究垂直加载和颊侧45°加载条件下3组牙槽骨的应力分布.结果 垂直加载和颊侧45°加载条件下,3组模型均在义齿近中基牙和剩余牙槽嵴远中出现应力集中;牙槽骨吸收伴牙周膜增宽组近中基牙的应力最大(分别为3.57和2.50 MPa),其次为牙槽骨吸收组(分别为3.21和2.41 MPa),正常牙槽骨组最小(分别为2.63和1.79 MPa).颊侧45°加载时3组模型剩余牙槽嵴远中颊侧和远中位点上的应力值均大于垂直加载.结论 基于三维红外扫描的有限元建模方法是可摘局部义齿有限元应力分析有效的建模方式.     

老年人可摘局部义齿折裂的设计因素

目的：分析老年人可摘局部义齿折裂的设计因素，旨在提高可摘局部义齿的设计水平和质量。方法：通过对临床上216例老年人可摘局部义齿折裂病例的观察，根据王征寿分类法归纳各类义齿折裂的常见类型，分析其中的薄弱环节和设计因素。结果：一类义齿咬合低时易发牛近远中向折裂；二类义齿咬合紧时常在游离端远中发生近远中向折裂，尤以上颌结节和磨牙后垫部位多见；三类和五类义齿的舌腭侧基托常在两个缺牙区之间尤其是靠近缺牙区的部位发牛与牙弓相交叉的折裂；四类义齿常发牛人工牙脱落或腭侧基托横折；人类义齿舌腭侧基托易发生纵折，折裂线常位于人工牙与基牙交界处。以上可摘局部义齿折裂的发生部有其设计与制作上的原冈，作者对此提出了相应的对策。结论：应特别注重义齿的抗折设计，这是提高可摘局部义齿修复质量的重要环节。     

末端游离缺失可摘局部义齿牙合支托设计的有限元分析

本文采用二维有限元法对近、远中支托设计的末端游离缺失可摘局部义齿模型进行垂直载荷条件下的应力、位移分析研究．结果表明在同一加载条件下,设计近中支托时基牙牙周支持组织及基托下软组织的应力、位移值明显减小,基牙受力趋于轴向：基托下软组织的应力、位移值大于基牙牙周支持组织应力、位移值．本实验从生物力学角度论证近中支托在修复末端游离缺失的优越性。     

五种卡环设计的下颌游离端义齿支持组织的有限元分析

本文用三维有限元的方法，对设计了五种卡环的下颌单侧游离端义齿，在进行相同加载情况下，近基牙中的应力分布进行了研究．结果表明回力卡环和Ｒ、Ｐ、Ｉ卡环组无论从基牙三个方向的最大应力值，还是从基牙的最大位移和部位看，对基牙产生的损伤和扭力最小；采用远中支托三臂卡环时，基牙的应力值和位移均最大，对基牙产生的损伤也大，为临床设计下颌游离端义齿提供了力学数据     

游离端可摘局部义齿基牙牙槽骨及剩余牙槽骨改变的两年追踪观察

目的 观察游离端可摘局部义齿基牙剩余牙槽骨的改变，比较不同卡环设计类型的基牙牙槽骨及剩余牙槽骨的吸收。方法 对37例(RPI型6例、RPA型10例、Aker卡环组21例)可摘局部义齿的末端基牙牙槽骨戴用后6、12、24个月进行了定位根尖投照，采用根尖片数字减影图像处理系统，对三种卡环设计类型基牙及剩余牙槽骨的吸收情况进行了定量分析并比较。结果 37例可摘局部义齿末端基牙牙槽骨及剩余牙槽骨复查的各个时期均有不同程度的吸收，并随时间呈递增趋势。结论 在保护剩余牙槽骨方面，RPA型卡环设计优于RPI和Aker卡环；在保护末端基牙颊舌侧牙槽嵴顶健康方面，RPA型优于Aker卡环组；在保护末端基牙近、远中牙槽嵴顶，避免其吸收方面，采用近中牙争支托设计的卡环(RPA和RPI卡环)要优于远中牙争支托设计的卡环(Aker卡环)。     

The effects of buccolingual width and position of occlusal rest seats on load transmission to the abutments for tooth-supported removable partial dentures

PURPOSE: The suitable buccolingual width and the location of occlusal rest seats for removable partial dentures have not been scientifically established. The aim of the present study was to use three-dimensional geometric analysis to evaluate the effects of buccolingual width and the location of occlusal rest seats on load transmission to the abutments for tooth-supported removable partial dentures. MATERIALS AND METHODS: A tooth-supported portion of a maxillary removable partial denture with two conventional circumferential cast clasps and an indirect retainer was analyzed. Occlusal loading of 100 N was applied to the buccal mesial cuspal incline 2.0 mm from the central fossa of the first molar or to the lingual mesial cuspal tip. Four combinations of position and width (wide, buccal shift, middle, and lingual shift) were simulated. RESULTS: For buccal loading, the wide rests and buccal-shift rests produced lower tensile forces at the indirect retainer. For lingual loading, the buccal-shift rests produced the lowest compressive force to the anterior abutment. CONCLUSION: Based on the tooth-supported removable partial dentures that were analyzed, buccal shifting of the rest seats seems to be advantageous for load transmission to the abutments.     

Visualization of stress and strain related to removable partial denture abutments.

The following conclusions are based on the conditions set forth in this investigation and apply to forces acting through a vertical direction of application only: 1. The unilateral removable partial denture produced no more stress than the bilateral removable partial denture. 2. The fully active Dalbo removable partial denture resulted in the greatest stressbreaking action. 3. The rigid Dalbo removable partial denture resulted in the least ridge displacement. 4. The rigid Dalbo removable partial denture resulted in the greatest stress concentrations in the distal abutment. 5. None of the attachments tested resulted in a distribution of the stresses along the edentulous ridge. 6. The use of two abutments (double abutments) resulted in greater stress concentrations in the distal abutment than the use of single abutments. 7. Forces in the single abutment were resisted along the long axis of the root. 8. Forces in the double abutments were resisted along the long axis of the distal abutment.     

Influence of Abutment Selection in Maxillary Kennedy Class II RPD on Elastic Stress Distribution in Oral Mucosa: An FEM Study

PURPOSE: The aim was to study the influence of abutment selection on elastic stress distribution in oral mucosa in a maxillary removable partial denture (RPD) by means of 3-dimensional finite element models. MATERIALS AND METHODS: Four RPD framework models of an equal size (by area) and underlying oral mucosa were produced for a Kennedy Class II arch. Each framework included an occlusal rest as part of a clasp assembly on one of four abutments (canine, first, and second premolars, and first molar) on the side contralateral to the edentulous ridge (tooth-supported side). Movement of the alveolar surface of the mucosa and the occlusal rest on the abutment adjacent to the ridge were fixed in a vertical direction. Movement of the rest on the tooth-supported side was restricted in all directions. Vertical or buccally oblique biting force was applied simultaneously on each of the locations representing three missing teeth. RESULTS: The frameworks with the contralateral side rest on the canine or the first premolar were less resistant to lateral forces than other framework designs, showing greater saddle displacements under the oblique force than the vertical force. The framework with the rest on the second premolar demonstrated relatively good resistance to deflection; however, both vertical saddle intrusion and the maximum equivalent stress in mucosa shown in all the models were within small ranges. CONCLUSION: The saddle movement was influenced by the abutment selection on the tooth-supported side, although resultant stress in the mucosa was insensitive to the abutment location.     

The effect of partial denture design on abutment tooth and saddle movement

A laboratory investigation designed to simulate the effect of loads applied to a free-end saddle partial denture was carried out. Abutment tooth and also saddle movement were monitored using a photogrammetric method. Loads applied to the denture saddle were transmitted through the occlusal rest and also the clasp components causing movement of both denture saddle and the abutment tooth. The direction of abutment tooth movement was towards the mesial, whether the occlusal rest was situated on the mesial or distal aspect of the tooth crown. It was also evident that the design of the clasp unit used affects the magnitude and direction of abutment tooth movement.     

Influence of mandibular free-end partial edentulism on the force exerted on maxillary anterior teeth

PurposeThe purpose of this study was to determine the influence of mandibular free-end partial edentulism and the wearing of removable partial dentures in the partially edentulous area on the force exerted on maxillary anterior teeth.MethodsA commercially available jaw model with exchangeable teeth was used. Seven experimental conditions of mandibular free-end edentulism were set up and a distal extension removable partial denture to replace missing posterior teeth was fabricated. Strain gauges were attached to the root surface of the maxillary left central incisor, canine, first premolar and first molar, and the force exerted on them was calculated based on the calibration coefficient. An occlusal load of 49 N was applied and the forces were compared with the Kruskal–Wallis test (P < 0.05).ResultsThe force exerted on the maxillary anterior teeth increased significantly as the number of remaining teeth decreased. The force exerted on the maxillary anterior teeth decreased significantly with use of a removable partial denture.ConclusionsWhen the number of remaining teeth decreases in mandibular free-end partial edentulism, the burden on the maxillary anterior teeth increases. Our findings suggest that for patients with mandibular free-end partial edentulism, wearing a removable partial denture is effective in preserving the remaining teeth by reducing excessive stress.     

下颌游离端义齿(牙合)支托设计的有限元分析

用三维有限元的方法,对设计了三种(牙合)支托的下颌单侧游离端义齿,分别在人工牙上采用九种不同的加载方法,对近基牙支持组织的应力和位移进行了研究分析,并进行统计学处理.结果远中(牙合)支托引起基牙支持组织的应力和位移值均最大;而近中(牙合)支托和双支托在近远中方向上,基牙牙周组织应力和位移的差异无统计学意义;无论是何种(牙合)支托应力和位移值均随加载点向远中移动过程中而逐渐减小.     

不同固位形式可摘局部义齿对支持组织应力分布的研究

目的:探讨附着体义齿与常见可摘局部义齿修复单侧游离端缺失对支持组织应力分布的影响.方法:分别以磁性附着体、RPI卡环组、联合卡环组三种固位形式的可摘局部义齿修复下颌单侧游离端缺失,用三维光弹应力冻结切片技术测试义齿加载后对基牙和缺牙区牙槽骨应力分布,并与基牙不戴义齿时载荷下的应力比较.结果:磁性附着体对54|基牙和缺牙区的牙槽骨应力稍大于RPI,只占54|基牙应力的48%,且对基牙近、远中应力基本相等;联合卡环对基牙牙槽骨应力最小,对缺牙区牙槽骨应力最大.结论:磁性附着体义齿修复单侧游离端缺失能够达到RPI义齿功能效果,特别适合于对美观和舒适要求较高者,不主张使用仅靠单侧固位的联合卡环组义齿.     

Finite element contact stress analysis of the RPD abutment tooth and periodontal ligament

OBJECTIVES: The purpose of this study was to determine the influence of the occlusal rest position in removable partial dentures on the displacement of the abutment tooth and the stress distribution in the periodontal ligament (PL). METHODS: We constructed three-dimensional finite element models of the mandibular first and second premolars. A layer of the PL and a mesial or distal occlusal rest were produced on the second premolar as an abutment. A zero displacement was prescribed on the outer surface of the PL and the first premolar. In each simulation, the rest was moved 0.05 mm vertically to the apical direction, with or without restriction of horizontal movements. We simulated the contact phenomena on the abutment surfaces, and calculated the movements of the abutment and stress distributions in the PL. RESULTS: We observed a maximum distal displacement of 42 microm at the buccal cusp of the abutment and a principal compressive stress of 0.35 MPa in the PL when the abutment was vertically loaded by a distal rest that was allowed to move horizontally. However, the displacements and stresses were relatively small, and were all within the physiological limitations of the tissues. The restriction of the horizontal movement of the rests was effective in reducing the horizontal displacements of the abutment, regardless of the rest position. CONCLUSIONS: The single vertical load exerted from either the mesial or distal rest on the abutment was unlikely to cause any mechanical damage to its supporting tissues.     

The mandibular first premolar as an abutment for distal-extension removable partial dentures: a modified clasp assembly design

Sound mandibular first premolars can be used as sole abutments for bilateral distal-extension removable partial dentures, if the denture is designed to minimise the torque applied to the abutment teeth. A simplified modification of the conventional torque-releasing clasp-assembly designs is suggested for these teeth. This modification entails a mesial rest on each abutment tooth connected to the distal proximal plate via a lingual bracing arm. A circumferential clasp arm is optional for buccal retention of the removable partial denture. As with conventional designs, the metal framework is designed to permit some rotational tissueward movement of the distal extension bases, yet not compromise the retention and stability of the prosthesis.