两种附着体义齿支持组织的应力比较分析

目的比较球帽附着体和栓道式附着体义齿支持组织的Von Mises等效应力分布。方法分别建立基牙牙周组织正常、吸收1/4、吸收1/3、吸收1/2的两种附着体义齿的三维有限元模型,采用垂直向加载力300N,模拟单侧后牙咬合状态,分析支持组织的Von Mises等效应力。结果基牙牙周组织不同状况下,栓道式附着体义齿的基牙和牙周膜最大Von Mises等效应力值小于球帽附着体义齿,缺牙区牙槽嵴最大Von Mises等效应力值大于球帽附着体义齿,但其分布相对较均匀。结论基牙不同牙周状况下,栓道式附着体义齿与球帽附着体义齿相比,其支持组织应力分布相对较均匀,应力集中范围小,可见栓道式附着体舌侧对抗臂的设计可以使支持组织受力更均匀,更有利于基牙健康。     

太极扣精密附着体修复类牙列缺损的临床效果观察

目的:观察太极扣精密附着体对类牙列缺损病例的临床修复效果.方法;采用太极扣精密附着体为类牙列缺损患者制作精密附着体义齿7件,观察其临床效果.结果:经过4～12个月的观察,86%以上的患者对义齿的美观性,舒适性,固位,咀嚼及发音情况表示满意.对14基牙进行检查,无扣痛、无松动,影像检查未见支持组织明显改变,其中1颗基牙牙龈边缘红肿经治疗后好转.结论:太极扣精密附着体系统具有较好的临床修复效果及应用前景.     

磁性附着体在全口覆盖义齿中的临床应用研究

目的观察磁性附着体在全口覆盖义齿中的临床修复效果。方法用Magfit磁性附着体为18例患者制作上颌或(和)下颌全口覆盖义齿共21副,在33颗基牙上安置磁性附着体。以11例常规总义齿患者作为对照。在粘固磁性附着体前后进行患者主观满意度问卷调查,采用分光光度法进行义齿咀嚼效率测试,并与对照组比较,同时观察基牙牙周状况。结果患者对磁性附着体覆盖总义齿效果满意;粘固磁体后义齿咀嚼效率显著提高,并于戴牙3~6个月后达到稳定;基牙松动情况好转。结论应用磁性附着体可显著改善全口覆盖义齿的功能,值得在临床推广应用。     

可摘义齿修复对He牙伸长的调查分析

目的：探讨可摘义齿修复体修复后对He牙伸长的原因、可能引起的并发证，并提出相应的防治措施，以引起口腔修复工作者的重视。方法：采用模型测量法对108例可摘义齿修复体对伸长牙进行测量，记录伸长的距离及伸长的颗数。结果：108例中伸长牙135颗(男90颗，女45颗)，对He牙伸长数最长3．8mm，最短1．2mm，其中96例伴有食物嵌顿，伴牙周病35例，牙体病48例，颞颌关节紊乱症26例。结论：对He牙伸长的主要原因为：塑胶牙硬度差，不耐磨，牙槽牙吸收及弯制支托在He力作用导致基牙磨损，义齿下沉而致对He牙伸长。防治措施：(1)缺少基牙者，尽可能行固定修复，或制作金属He面，防止咬He面磨损；(2)采用铸造He支托以防止支托凹磨损而使义齿下沉，阻止对He牙伸长；(3)对He力集中、游离缺失者，修复体应适当增加He支托的数目以分散He力，防止对He牙伸长。     

磁性附着体下颌全口覆盖义齿6例效果评价

磁性附着体具有操作简便 ,可自动复位 ,无需经常调节修理 ,不传递侧向力而保护基牙等优点 ,故目前已被应用于全口覆盖义齿、可摘局部义齿、种植义齿、分部义齿、颌面赝复体等各种口腔及颌面部修复体[1,2 ] 。全口义齿是磁性附着体应用的最重要领域[3 ] 。下颌全口义齿固位、稳定作用常较差 ,使用磁性附着体可显著增强义齿的固位和稳定 ,并可有效减少牙槽嵴的吸收[3 -5] 。本研究以Magnedisc80 0 (MD80 0 )和MagfitEX6 0 0 (EX6 0 0 )磁性附着体为固位装置 ,选择 6例患者制作下颌全口覆盖义齿 ,取得了良好的临床效果。1　材料和方法1.1　…     

ITI种植体支持球帽附着体在无牙颌患者义齿中的应用评价

 目的 探讨球帽附着体固位下全口总义齿的临床效果。方法 随机选择22例无牙颌每个患者植入4颗国际口腔种植学会（international team for implantology,ITI）种植体,利用种植体支持球帽附着体制作全口义齿,随访近4年用X线检查和患者主观感受进行评价。结果 88枚种植体成功率达到99%,其中固位效果明显提高19例（86%,P＜0.001）,咀嚼效果明显提高12例（54%,P=0.001）,而舒适度、美观度、语音效果提高较为有限1～2例,约10%。结论 种植体支持的球帽附着体义齿临床效果好,制作简单,患者取戴方便,尤其适用于老年无牙颌患者。     

可摘义齿修复对牙伸长的调查分析

目的:探讨可摘义齿修复体修复后对(牙合)牙伸长的原因、可能引起的并发证,并提出相应的防治措施,以引起口腔修复工作者的重视。方法:采用模型测量法对108例可摘义齿修复体对伸长牙进行测量,记录伸长的距离及伸长的颗数。结果:108例中伸长牙135颗(男90颗,女45颗),对猞牙伸长数最长3.8mm,最短1.2mm。其中96例伴有食物嵌顿,伴牙周病35例,牙体病48例,颞颌关节紊乱症26例。结论:对(牙合)牙伸长的主要原因为:塑胶牙硬度差,不耐磨,牙槽牙吸收及弯制支托在猞力作用导致基牙磨损,义齿下沉而致对(牙合)牙伸长。防治措施:(1)缺少基牙者,尽可能行固定修复,或制作金属(牙合)面,防止咬猞面磨损;(2)采用铸造(牙合)支托以防止支托凹磨损而使义齿下沉,阻止对(牙合)牙伸长;(3)对(牙合)力集中、游离缺失者,修复体应适当增加猞支托的数目以分散猞力,防止对(牙合)牙伸长。     

可摘义齿修复对(牙合)牙伸长的调查分析

目的:探讨可摘义齿修复体修复后对(牙合)牙伸长的原因、可能引起的并发证,并提出相应的防治措施,以引起口腔修复工作者的重视.方法:采用模型测量法对108例可摘义齿修复体对伸长牙进行测量,记录伸长的距离及伸长的颗数.结果:108例中伸长牙135颗(男90颗,女45颗),对(牙合)牙伸长数最长3.8mm,最短1.2mm.其中96例伴有食物嵌顿,伴牙周病35例,牙体病48例,颞颌关节紊乱症26例.结论:对(牙合)牙伸长的主要原因为:塑胶牙硬度差,不耐磨,牙槽牙吸收及弯制支托在(牙合)力作用导致基牙磨损,义齿下沉而致对(牙合)牙伸长.防治措施:(1)缺少基牙者,尽可能行固定修复,或制作金属(牙合)面,防止咬(牙合)面磨损;(2)采用铸造(牙合)支托以防止支托凹磨损而使义齿下沉,阻止对(牙合)牙伸长;(3)对(牙合)力集中、游离缺失者,修复体应适当增加(牙合)支托的数目以分散(牙合)力,防止对(牙合)牙伸长.     

双翼塑料桥修复前牙64例

1991年以来，我们采用间接法制作的双翼塑料粘接桥（下简称塑料桥）修复前牙，效果满意。现报导如下。临床资料1．一股资料本组共64例。男性22例。女性42例。年龄20～43岁。修复塑料桥64付，其中义齿塑料桥32付，义齿间隙，义齿甲冠、义齿桩冠、义齿贴面等复合塑料桥28付，甲冠连续塑料桥2付，桩冠连续塑料桥2付。修复前牙120颗，上前牙106颗，下前牙14颗。2．修复方法（1）选择个别前牙缺失，间隙不低于缺牙牙冠长度1／2者为对象，按常规取模。在缺隙处嵴盖部成凹型刮除石膏1～2mm。以邻牙为基牙，延长基牙舌侧牙颈线1mm。（2）选排义齿，…     

3精密附着体修复多个磨牙游离端缺失60例

游离端可摘局部义齿常使患者感到不舒适，且戴牙数年后基牙松动拔除需更换新义齿。随着生活水平的提高，患者越来越不满足于用可摘局部义齿来恢复功能，而是期望在美观和舒适程度上能达到更高要求。近些年来，应用精密附着体修复游离端缺失牙，可在很大程度上满足患者的美观要求及咀嚼功能。笔者于2009-01至2012-01应用精密附着体治疗磨牙游离端缺失患者60例，效果良好。     

髌骨位姿异常对髌股关节接触影响的研究

目的 深入研究髌骨位姿异常对髌股关节的接触影响.方法 通过正常膝关节MRI图像数据建立了髌股关节的正常和异常接触模型,基于正交试验对不同水平的髌股关节异常接触模型进行了有限元仿真模拟.结果 1)在膝关节屈曲过程中,髌股关节接触特性(Von Mises应力、接触压力和接触面积)对髌骨的屈曲和旋转参数最为敏感;2)髌股异常...     

单个后牙缺失伴远端基牙倾斜的树脂黏结固定桥修复研究

目的 观察树脂黏结固定桥(RBFPD)修复下颌单个后牙缺失合并桥基牙倾斜患者的临床效果,并总结其适应证和设计特点.方法 选择2002-2003年在解放军总医院口腔科就诊的典型下颌单个后牙缺失、远端基牙近中倾斜的患者18例,所有患者基牙倾斜度不超过50°,基牙无明显松动,牙周无异常.根据基牙倾斜和模型观测结果,设计(牙合)支托和固位体的位置和形态,义齿选择普通钛合金烤瓷或钻铬合金烤瓷修复,并在修复体完成后进行5年随访.随访时进行临床检查、X线片检查并询问患者主观感受.结果 远端倾斜基牙平均倾斜33°.随访5年后,2例修复病例修复体脱落,其余义齿功能良好,牙周无明显炎症.基牙以及桥体下方牙龈无明显红肿,X线片示基牙牙周间隙无异常,患者对于修复体的外观及使用情况满意.5年期间修复体的成功率为88.9%.结论 对于伴有基牙倾斜的单个后牙缺失,采用树脂黏结固定桥进行修复的效果可靠,并具有磨牙少、基牙无需进行根管治疗等优点.     

颞骨撞击生物力学变化与骨折特点

目的 探讨颞骨撞击应力分布、应力波的传播与颞骨骨折的关系. 方法 选取捐赠的新鲜尸头12具,分别在800,1 200,1 400 kPa的驱动压力进行撞击,借助64排CT的三维立体结构图像,经计算机仿真模拟计算颞骨撞击过程生物应力的分布与传播. 结果 (1)撞击驱动压力的增加,使撞击速度、撞击加速度、撞击能量、撞击锤在颅骨颞部的位移幅度均增大.(2)在颞骨撞击瞬间,形成以撞击点为中心的Von Mises应力集中区,在颅骨-脑组织耦合处急剧衰减,随之又在颅底汇聚成应力集中区域.(3)撞击驱动压力为800 kPa时,同侧线性骨折;以1 200 kPa撞击时,同侧均出现不同程度的凹陷性骨折,1例对侧颞骨形成继发性骨折;以1 400 kPa撞击颞骨时,同侧均发生混合型骨折,对侧颞骨均形成继发性骨折,并造成颅底骨折.(4)颞骨骨折线与撞击应力集中区的分布相符合. 结论 颞骨各项撞击参数、撞击应力的分布和传递与颞骨骨折相吻合.这对颢骨撞击伤的诊断和防护有重要的临床意义.     

准静态下颞部撞击致颅脑伤的有限元模拟分析及其临床意义

目的建立准静态下颞部撞击致颅脑伤的虚拟模型，研究准静态下颞部撞击所致的应力分布以及应力波的传播，探讨颞部撞击致颅脑伤的生物力学机制。方法在Hypermesh软件中建立准静态颞部撞击伤的有限元模型，用Ls-Dyna软件对该有限元模型进行数值模拟计算，最后用Ls-Prepost软件进行后处理。结果撞击点处颞骨VonMises应力以及颅内压力随撞击速度的提高而增大；应力波在颅骨表面的传播以撞击点为圆心的径向上传播，在颅骨一脑组织耦合处急剧衰减；颅底有应力集中区域。该数值模拟的结果与生物试验结果较吻合。结论本研究对颞部撞击致颅脑损伤的诊断和防护有重要意义。     

Stress distribution inside bone after suture anchor insertion: simulation using a three-dimensional finite element method

Purpose

To define stress distribution patterns inside a bone around suture anchors inserted at different angles using a three-dimensional finite element (FE) method.

Methods

An isotropic cube model (Young’s modulus, 1,380 MPa; Poisson’s ratio, 0.3) was designed on a computer to standardize analysis conditions. A virtual Twinfix anchor was inserted into the cube at two different angles (45° and 90°) against the top surface. A traction force (100 N) was applied to the anchor at six different angles (15°, 30°, 45°, 60°, 75° and 90°) against the top surface. Elastic analysis was performed, and the distribution of the von Mises equivalent stress inside the cube was calculated. The highest value of the equivalent stress at each traction angle was compared between the 45° and 90° anchor insertion settings.

Results

Stress concentration was most evident around proximal anchor threads, particularly on the traction side. Interestingly, stress gradually declined with an increase in traction angle only for the 90° insertion setting. At 15° and 90° traction angles, the equivalent stress was lower for the 45° insertion setting than for the 90° insertion setting. In contrast, the 90° insertion setting exhibited lower equivalent stress than the 45° insertion setting at 30°, 45° and 60° traction angles.

Conclusions

Insertion of an anchor at 90° might reduce the stress concentration around the proximal anchor threads on the traction side and provide lower equivalent stress in the middle range of traction angles (30°–60°) than insertion at 45°. This could avoid early postoperative anchor failure.     

The effect of stress on proton relaxation times (T1 and T2) of rat liver

T1 of the liver has been shown to lengthen after sham operation or partial hepatectomy, reaching a maximum about 24 hours after surgery. Surgical stress, which includes tissue injury and repair, has been suggested as the source of the change. We subjected rats to three types of stress that do not include tissue damage and repair to determine the role of stress alone in the length of T1 of the liver. Prolonged swimming, ACTH injection, or fasting did not affect T1 times. Tissue damage and/or repair appear to have a major role in determining T1 in the liver.     

Contact pressures at grafted cartilage lesions in the knee

The use of tissue-engineered cellular constructs is currently under clinical evaluation for the surgical treatment of articular cartilage lesions in the knee. The primary failure mode in such cartilage repair techniques is related to fixation. In addition, the repair tissue is believed to be very fragile in the post-operative period, and unable to support the intra-articular loads. We have developed a laboratory testing protocol in order to quantify the contact pressure distribution that develops on fibrin glue grafts applied to full-thickness cartilage lesions. The contact pressure distribution has been mapped on the contact surface of specimens subject to compression, in three configurations (intact, defect and grafted), at increasing load levels. All the maps show stress concentrations at the rim of the defect and a more uniform stress distribution around the rim after defect grafting. At a contact load of 180 N, the peak contact pressure measured on cartilage is 2.5 MPa. In presence of the graft, the peak pressures on the cartilage area surrounding the defect are reduced by 16%, on average. In contrast, both the mean contact pressure on the graft and the grafts contact area increase. The graft was found to carry around 80% of the total applied contact load, at all load levels tested. Fibrin glue was chosen as a grafting material in our study because it shows material properties very representative of currently-implanted cellular constructs. Thus, the results of this study have quantified aspects of recipient graft sites that may assist in optimising such grafting procedures from a biomechanical point of view.     

Computer modeling of airbag-induced ocular injury in pilots wearing night vision goggles

BACKGROUND: Airbags have saved lives in automobile crashes for many years and are now planned for use in helicopters. The purpose of this study was to investigate the potential for ocular injuries to helicopter pilots wearing night vision goggles when the airbag is deployed. METHODS: A nonlinear finite element model of the human eye was created. Ocular structures such as the fatty tissue, extraocular muscles, and bony orbit were included. The model was imported into Madymo (Mathematical Dynamical Models) and used to determine the worst-case position of a helicopter pilot wearing night vision goggles. This was evaluated as the greatest Von Mises stress in the eye when the airbag was deployed. RESULTS: The worst-case position was achieved by minimizing the distance between the eyes and goggles, having the occupant look directly into the airbag, and making initial contact with the airbag halfway through its full deployment. Simulations with the goggles both remaining fastened to and breaking away from the aviator helmet were performed. Finally, placing a protective lens in front of the eyes was found to reduce the stress to the eye but increase the force experienced by the surrounding orbital bones. CONCLUSION: The finite element model of the eye proved effective for evaluating the experimental parameters.     

正畸治疗在前牙美容修复中的临床应用

目的评估正畸在前牙美容修复治疗中的临床作用,并探讨其治疗方法和修复特点。方法对34例前牙缺损缺失需行美容修复的患者,先进行正畸治疗,为前牙美容修复创造条件或降低其修复难度后,再用义齿进行修复。结果34例患者对修复体的功能、形态和美观方面牙合均感到满意;随访1~6年,修复体稳固,基牙无松动,牙周组织健康;前牙覆牙合覆盖关系稳定。结论正畸固定矫治技术在前牙美容修复治疗中,可以降低修复难度,扩大治疗的范围,达到更加完善的口腔功能及美观的要求。