口腔正畸用镍钛弓丝的腐蚀性及防腐蚀

背景：口腔正畸用镍钛弓丝临床使用后期常发生弓丝力学性能降低现象,严重影响了临床治疗效果,有研究表明口腔唾液电解质环境腐蚀是影响其性能的主要因素之一。 目的：综述近年国内外关于口腔正畸用镍钛弓丝腐蚀性研究的进展。 方法：采用计算机检索中国知网数据库CNKI 1995-01/2010-10,PubMed数据库和Elsevier(ScienceDirect)数据库1975-01/2010-10与正畸用镍钛弓丝腐蚀性相关得研究。 结果与结论：在复杂的口腔环境中,温度、负载、氟离子等因素均能加速对正畸用镍钛弓丝的腐蚀,不同程度地影响正畸用镍钛弓丝的性能,降低正畸镍钛弓丝的机械性能,增大表面粗糙度进而延长了正畸治疗疗程,增加了正畸治疗成本。正畸用镍钛弓丝腐蚀所释放的镍离子降低了其生物安全性。防腐蚀处理能提高镍钛弓丝的抗腐蚀能力,主要应用表面处理技术,但目前安全有效的方法并不多,对正畸用镍钛弓丝的腐蚀和防腐蚀还有待于进一步深入研究。     

镍钛丝弹簧在口腔正畸临床的应用

镍钛丝弹簧在口腔正畸临床的应用高柠，秦葵庆，姜同学，陈爽，王道富（中国人民解放军５７００３部队门诊部口腔科）（北京有色金属研究总院）镍钛推簧与拉簧是一种用于牙齿正畸的新型弹簧，具有镍钛丝超弹性的特点，适合于正畸矫治开拓牙齿间的间隙和向不同方向牵拉牙齿…     

三棱滑切固定矫治器--结构设计与应用原理

目的开发设计一种新型的固定矫治器：三棱滑切固定矫治器，用于牙颌畸形的正畸治疗，对其结构设计和应用原理进行探讨分析。方法三棱滑切固定矫治器的结构，以三棱形弓丝和具有三角槽沟的托槽为主体，由它控制矫治牙在各个方向的移动而发挥矫治作用。结果对该矫治器的结构做出定性设计，分析探讨其调控牙齿正畸移动的方式主要为通过三棱弓丝的一个刃状边棱与托槽三角沟槽的一个边面相切，借助于弓丝本身的弹性形变力和弓丝的外加引导力而对矫治牙齿施以滑动和切入机制的矫治力。结论三棱形弓丝和与之匹配的三角槽沟托槽是这类矫治器的主要结构特征；角——槽切合锁入式结构设计在确保弓丝与槽沟完全吻合的条件下实现了弓丝入槽——出槽顺畅自由，易于临床使用和精确调控牙位的目的；“棱面相切——加力引导切入——渐进式加力”到牙齿，更加符合持续、轻力的现代口腔正畸施力原则．     

PBL教学法在口腔正畸学教学中的应用

为了提口腔专业本科生口腔正畸学的教学质量,温州医学院口腔医学院正畸教研室尝试将PBL教学法引入理论课教学中.并取得了初步的成功.本文对PBL教学法在口腔正畸学教学中的应用及所面临的问题进行了分析和探讨.     

口腔正畸生物力学的研究进展

口腔生物力学是口腔正畸学的重要基础学科之一。在传统正畸力学系统稳定运行的基础上，矫治理念仍在不断更新发展，随着各类新型矫治器不断研发、矫治技术不断提出，对不同矫治体系的生物力学效应探索是正畸领域的关注重点。口腔生物力学技术的不断优化、突破与创新也为更加真实模拟和理解矫治中的生物力学效应提供了重要途径。本文主要对近年来固定矫治、隐形矫治、矫形治疗3个矫治体系相关的生物力学研究进行综述，包括正畸新理念和正畸新技术的生物力学分析、生物力学新技术在正畸中的应用等。     

基于弓丝预应力分析的正畸有限元仿真

利用CT扫描的牙齿数据,使用逆向工程软件Mimics和CAD软件Catia,建立了具有较高精度的包含正畸托槽、牙弓、牙周膜和颌骨在内的可以进行布尔运算的实体模型;基于高等机构学的理论,将弓丝装配过程等效为托槽移动的过程,分析求得该等效过程中托槽运动的参数,利用所得参数对等效过程进行有限元仿真,以获得弓丝初始预应力及弓丝作用在每颗牙齿上的初始力和力矩;将牙齿和牙槽骨建模为刚性接触体,牙周膜为弹性体,施加分析获得的初始力系,进行接触分析,得到正畸临床状态下整个上牙颌牙周膜的应力大小和分布.通过对矫治器和牙弓、槽骨联合建模,并使用空间螺旋坐标系,本方法可以获得临床状态下的正畸矫治力和牙周组织响应,为正畸理论研究和临床实践提供指导.     

正畸复合矫治弓丝力学性能的有限元分析

探讨高效能复合矫治弓丝(composite archwire,CoAW)应用于牙齿正畸中的选优研究,并对复合矫治弓丝在正畸中的临床应用,提供理论指导及选型标准.对复合矫治弓丝正畸过程的力学行为进行了有限元分析,得到了各个不同类型弓丝对LL2、LL3、LL56的作用力-位移曲线,并由此分析得出不同类型弓丝对于不同牙齿的正畸范围.     

动静组合载荷加速正畸牙移动的动力学分析

目的分析机械振动加速正畸牙移动中颌骨及牙周组织的应力分布,探讨动静组合载荷加速正畸牙移动的机理。方法采用Mimics、Solid Works、Geomagic和ANSYS Workbench软件建立包括牙齿、牙周膜、牙槽骨松质骨、牙槽骨皮质骨的有限元模型,施加侧向静态正畸力、低值高频机械振动载荷,进行动力学分析。结果牙槽骨及牙周组织的近远向正应力(Y向应力)分布可清晰区分张力、压力区,呈现周期性变化,并且其频率与加载的低值高频机械振动载荷一致;牙槽骨及牙周组织von Mises应力亦呈现周期性变化,但无法区分张力、压力区。结论在口腔正畸领域,近远向正应力为合适的力学激励表征量;侧向静态正畸力与低值高频机械振动载荷组合的动静组合载荷是一个可行的加速正畸牙移动方法。研究结果可为低值高频机械振动加速正畸移动提供指导。     

基于应力状态的细胞分子水平骨重建力生物学模型

目的建立基于应力状态的细胞分子水平骨重建力生物学模型。方法从工程角度分析骨重建过程和力学激励,吸纳力学强度设计理论思想,选取相当应力作为力学激励,基于应力状态选取合适的力学激励计算公式,提出基于应力状态的细胞分子水平骨重建力生物学模型;应用模型进行口腔临床正畸牙槽骨的模拟预测。结果张力区孔隙度降低,骨量增加;压力区孔隙度增加,骨量减少,与牙槽骨特性一致。结论基于应力状态的细胞分子水平骨重建力生物学模型考虑应力状态对骨组织失效形式的影响,体现骨重建过程是力学激励下细胞水平的自优化强度设计,有助于在细胞分子水平探讨应力状态对骨重建的影响,是骨重建理论的补充和完善,可为口腔正畸的治疗提供理论指导。     

口腔正畸临床依从性的探讨

目的了解口腔正畸临床依从性的影响因素,探讨提高口腔正畸临床依从性的方法。方法对500例接受口腔正畸治疗的患者进行分析、总结。结果口腔正畸临床依从性不但体现在如何对待矫治装置、是否按预约时间复诊、口腔卫生的保持等,还包括心理状态、个性特征及家庭和社会环境等多方面。通过健康教育、加强医患交流、心理辅导、简化治疗等措施能改善口腔正畸患者的临床依从性。结论在正畸治疗的各个阶段,对各种心理类型的患者有针对性地采用不同的对策,进行心理辅导,消除不良心态,使其在治疗过程中保持良好的依从性,可帮助正畸患者取得良好、稳定的疗效。     

Micro X-ray diffraction study of superelastic nickel-titanium orthodontic wires at different temperatures and stresses

The phase transformation behavior in three commercial nickel-titanium orthodontic wires having different transformation temperatures was studied by micro X-ray diffraction (micro-XRD). Micro-XRD spectra were obtained at three different included bending angles (135 degrees, 146 degrees and 157 degrees) and three different temperatures (25 degrees C, 37 degrees C and 60 degrees C). The regions analyzed by micro-XRD were within the separate areas of a given wire specimen that experienced only tensile or compressive strain. The intensity ratio (M002/A110) between the 002 peak for martensitic NiTi and the 110 peak for austenitic NiTi was employed as the index to the proportions of the martensite and austenite phases. The ratio of martensite to austenite increased in all three nickel-titanium wires with decreasing included bending angle (greater permanent bending deformation), and was lower within the compression area for all wires at all bending angles than within the tension area. Micro-XRD provides an effective method for quantitative evaluation of the proportions of these two phases in nickel-titanium orthodontic wires, even though considerable preferred crystallographic orientation exists because of the wire drawing process.     

The NiTi superelastic alloy application to the dentistry field.

The main properties of NiTi alloys are presented, discussed and compared with respect to those of stainless steels. Special regard is given to the use of NiTi alloy as orthodontic wires and endodontic instruments. The superelastic properties of orthodontic wires and endodontic files are measured as a function of the applied stress, of the strain and of the temperature. Both biomedical devices are submitted to surface analysis to control the interface with the biological environment in which they will be immersed.     

Joining characteristics of orthodontic wires with laser welding

Laser welding 0.016 x 0.022 in. beta-Ti, Ni-Ti, and Co-Cr-Ni orthodontic wires was investigated by measuring joint tensile strength, measuring laser penetration depth, determining metallurgical phases using micro X-ray diffraction (micro-XRD), and examining microstructures with an scanning electron microscope (SEM). Welding was performed from 150 to 230 V. Mean tensile strength for Ni-Ti groups was significantly lower (p < 0.05) than for most other groups of laser-welded specimens. Although mean tensile strength for beta-Ti and Co-Cr-Ni was significantly lower than for control specimens joined by silver soldering, it was sufficient for clinical use. The beta-Ti orthodontic wire showed deeper penetration depth from laser welding than the Ni-Ti and Co-Cr-Ni orthodontic wires. Micro-XRD patterns of laser-welded beta-Ti and Ni-Ti obtained 2 mm from the boundary were similar to as-received specimens, indicating that original microstructures were maintained. When output voltages of 190 V and higher were used, most peaks from joint areas disappeared or were much weaker, perhaps because of a directional solidification effect, evidenced by SEM observation of fine striations in welded beta-Ti. Laser welding beta-Ti and Co-Cr-Ni wires may be acceptable clinically, since joints had sufficient strength and metallurgical phases in the original wires were not greatly altered.     

Degradation and fracture of Ni-Ti superelastic wire in an oral cavity.

Superelastic Ni-Ti wire is widely used in orthodontic clinics, but delayed fracture in the oral cavity has been observed. Because hydrogen embrittlement is known to cause damage to Ti alloy systems, orthodontic wires were charged with hydrogen using an electro-chemical system in saline. Tensile tests were carried out, and fracture surfaces were observed after hydrogen charging. The strength of the Co-Cr alloy and stainless steel used in orthodontic treatment, was not affected by the hydrogen charging. However, Ni-Ti wire showed significant decreases in strength. The critical stress of martensite transformation was increased with increasing hydrogen charging, and the alloy was embrittled. The fractured surface of the alloys with severe hydrogen charging exhibited dimple patterns similar to those in the alloys from patients. In view of the galvanic current in the mouth, the fracture of the Ni-Ti alloys might be attributed to the degradation of the mechanical properties due to hydrogen absorption.     

Effect of acidic fluoride solution on beta titanium alloy wire

The interaction between acidic fluoride solution and beta titanium alloy was investigated to explore the changes that occur in beta titanium alloy by fluoride-containing acetic acid solutions. For this, alloy crystal structure, tensile strength, and elements released from the alloy wires were determined using four solutions (0.05%/pH 6, 0.05%/pH 4, 0.2%/pH 6, and 0.2%/pH 4) for 1 or 3 days. The immersed wire did not form any identifiable new crystal structure compared with the as-received wire. The tensile strength of the immersed wires was significantly reduced compared to the as-received wires in the test solutions if the period of immersion increased from as-received to 3 days. The fractured area of the immersed wire was reduced compared to the as-received one. The dimple pattern at the inner part and a cup-cone morphology at the outer part of the fractured wires were similar in both as-received and immersed wires. After a 3-day immersion, the amount of the released Ti and Mo has much increased for higher NaF concentration and lower pH value. During the long-period orthodontic treatment, both patient and clinical doctor should carefully use the fluoride-containing products to minimize unexpected damage on orthodontic wires.     

周期性应力刺激对成牙骨质样细胞增殖的影响

背景：成牙骨质细胞在牙根形成、牙周病牙骨质的再生以及正畸牙根吸收的修复中起着重要的作用,其在体外培养状态下对力学信号反应特性的变化,在国内外少见报道。 目的：分析正畸牙移动张力侧及压力侧两种不同受力形式与牙骨质改建的关系。 方法：采用四点弯曲细胞力学加载仪,对体外培养的成牙骨质样细胞OCCM30分别施加2 000 με张、压应力,应用流式细胞术检测应力刺激3,6,12,24 h后OCCM30细胞周期及增殖指数的变化。 结果与结论：2 000 με张、压应力加载3,6 h后,成牙骨质样细胞OCCM30在S期的细胞百分率明显减小,细胞增殖活性降低;随着加力时间的延长,S期细胞百分率回升,加载24 h后S期细胞百分率与对照组无明显差异,细胞增殖活性恢复。张、压应力对增殖活性的影响趋势一致,相互之间差别无显著性意义。     

髌骨骨折AO张力带内固定有限元模型的建立和分析

背景：目前有关髌骨骨折内固定的生物力学研究大多集中在尸体标本上,应用现代有限元法进行分析的报道较少。 目的：建立髌骨骨折AO张力带内固定的三维有限元模型,并对所建模型进行有限元力学分析。 方法：选择1名成年女性志愿者,行下肢薄层CT扫描,将图像数据导入Mimics 10.01 软件通过Region growing提取右侧髌骨polylines,导入Geomagic studio 10.0建立髌骨几何模型。将髌骨几何模型导入PRO/E 2.0软件中,利用软件中的分割功能模拟髌骨骨折,利用软件中的扫描功能,生成两根折弯的克氏针和环形钢丝,建立三维髌骨骨折AO张力带内固定模型,导入ANSYS中建立三维有限元模型,模拟屈膝90°髌股关节作用力600 N进行有限元分析,分析其位移及变形特点。 结果与结论：AO张力带有多向加压作用,及明显对抗股四头肌向上拉应力的作用。提示有限元分析结果与生物力学结果相符,建立的髌骨骨折AO张力带内固定有限元模型有效,有助于更全面了解张力带内固定髌骨骨折的生物力学原理,为临床治疗提供借鉴。     

上颌第一磨牙弯曲牙根生物组织应力的三维有限元分析

背景：根据弯根牙牙周膜应力分布为口腔临床工作者提供正畸施力的方式和大小,以此来优化正畸力系统设计。 目的：探讨上颌第一磨牙弯曲牙根受到正畸力作用下牙根及牙周膜的应力分布情况。 方法：选用正常形态和牙根弯曲的上颌第一磨牙作为建模素材,应用CT机扫描,ANSYS Workbench 11.0 有限元分析软件建立上颌第一磨牙及其牙周膜的有限元模型,应用6种不同载荷方式对模型进行加载,分析其应力分布情况。 结果与结论：弯根牙应力集中区主要在牙颈部,其次是根尖部,牙齿在做整体移动时其牙根、牙周膜、牙槽骨应力最小。对于弯根牙的矫治需要更准确的定位以及更合理的牵引力。     

A study of the fatigue properties of small diameter wires used in intramuscular electrodes

Single and multi-strand stainless steel and cobalt-nickel alloy wires, with strand diameters from 26 to 46 microns, were fatigue tested using a modified rotating bending test to determine what factors are most important in controlling fatigue life. The relation between cyclic strain and cyclic life was determined for each material by cyclically straining test specimens at various strain ranges and recording the number of cycles to failure. The results show that (a) the fatigue curves of the 316LVM, MP35N, DBS, and Syntacoben wires are very similar and have many of the same fatigue characteristics of specimens of large cross section. (b) Multi-stranded wires have the same average fatigue life as their individual constituent strands, but the variance of that life is smaller. (c) Deformities in the wire, which are created during the manufacturing, appear to have the effect of shortening the fatigue life of these small section wires. (d) Observation of wire fracture surfaces show a relatively small crack propagation zone and a large fast fracture zone suggesting that most of the fatigue life of these small wires is in the original crack formation, which creates a large stress concentration and quickly leads to wire failure. (e) The size of the wire cross sectional area is of secondary importance compared to the amplitude of the maximum cyclic strain of the individual strands in determining fatigue life of the cable. To maximize the fatigue life of electrodes in vivo, the highest fatigue life for a given bending radius of curvature is desired. This suggests wire strands should be manufactured at the smallest diameter possible (without introducing structural flaws) to maximize service life.     

改良张力带钢丝内固定术治疗髌骨粉碎性骨折

目的：探讨改良张力带钢丝内固定治疗髌骨粉碎性骨折的疗效。方法：采用改良张力带钢丝内固定术治．一疗89例髌骨粉碎性骨折患。术后观察骨折愈合时间，X线片关节面平整程度，膝关节功能恢复情况。结果：骨折愈合时间平均为66．5d，X线片示关节面平整度良好，术后关节功能优良率达92．2％。结论：该术式手术适应证较广，操作简便，复位固定满意，疗效确切，是治疗髌骨粉碎性骨折的有效方法之一。