激光焊,脉冲氩弧焊,电子束焊焊接钛材机械性能的比较

目的：比较激光焊、电子束焊、脉冲氩弧焊焊接钛的机械性能，寻求一种高质量的牙科焊钛方式。方法：采用Ｉｎｓｔｒｏｎ万能拉伸实验机测试焊接区的拉伸负荷、屈服负荷，计算伸长量，用扫描电子显微镜观察断口情况，用金相显微镜观察焊接区的金相变化，并测量焊接区的显微硬度。结果：激光焊钛的拉伸负荷与电子束焊、脉冲氩弧焊无明显区别；激光焊Ｔｉ－６Ａ１－４Ｖ的拉伸负荷与脉冲氩弧焊、电子束焊及原材料无明显区别。激光焊接区的显微硬度及热影响区最小，脉冲氩弧焊的显微硬度及热影响区最大。结论：激光焊接较脉冲氩弧焊及电子束焊更适用于牙科焊接钛。     

Ti-75合金在口腔修复应用的腐蚀性

为评价Ti－75合金在口腔修复应用的耐腐蚀性，用动电位极化技术测试了五种材料在人工唾液中的腐蚀性。结果显示Ti-75合金自腐蚀电位介于TA2和TC4之间，破裂电位高于CO－Cr、Ni－Cr合金；Ti－75测试面未见腐蚀，而Co－Cr、Ni－Cr合金均有全面腐蚀和点蚀；结合极化曲线整体形态分析，结论：Ti－75合金的耐蚀性与TA2、TC4相似，但优于临床现用的Co－Cr、Ni－Cr合金。     

钛的氩弧焊、激光焊和等离子弧焊的实验研究

采用氩弧焊，激光焊和离子弧焊焊接钛支架杆，与母材对照，测试其力学性能，等测试数据经统计学处理，结果显示：钛的氩弧焊，激光焊基本满足修复体焊接要求，为进一步临床应用提供实验基础。     

牙科激光焊钛机械性能的研究

目的 探讨不同条件下牙科激光焊钛的机械性能。方法 采用国产Ｎｄ－ＹＡＧ激光器在不同激光能量条件下分别焊管ＴＡ２和Ｔｉ－６Ａｌ－４Ｖ,利用Ｉｎｓｔｒｏｎ万能拉伸实验机测定其拉伸负荷,０．２％屈服负荷及伸长量,做断口扫描电镜分析,测定焊接区的维氏显微硬度。还测定了试件在人工唾注中浸蚀后焊缝的机械性能。结果 激光焊接接头的强度与材料,电压以及材料和电压的结构均有关系。灯电压为７００－７５０Ｖ时,ＴＡ２的     

激光焊接铸钛和锻钛疲劳强度的研究

目的：测试激光焊接铸造和锻造纯钛（TA2）及钛合金（TC4）疲劳强度和拉伸负荷,探讨一定条件下激光焊接后铸造和锻造钛试件的疲劳强度及临床应用的可行性。方法：将铸造和锻造纯钛及钛合金加工成一定规格的试件,进行激光焊接,焊后用疲劳试验机测得母材及焊件的疲劳强度,并进行断裂试件断口的扫描电镜分析,结果分别进行比较。结果：激光焊接铸造和锻造纯钛及钛合金试件的疲劳强度与对照组有统计学差异,激光焊接断口有气泡及断裂裂纹。结论：与母材相比,激光焊接铸造和锻造纯钛及钛合金试件的疲劳强度有统计学差异。     

镍铬合金在人工唾液中的电化学腐蚀行为

目的 本项研究旨在探讨镍铬合金在体外的电化学腐蚀行为。方法 实验应用极化曲线方法，将镍铬合金浸泡在人工唾液中，温度为36．5℃，pH值为7．0，测量试样的腐蚀电位和自腐蚀电流密度。应用X射线光电子能谱(X-ray photoelectron spectroscopy，XPS)，分析试样表面的元素成分变化。结果 实验结果表明，镍铬合金的点蚀电位为-390mV，钝化电位为-160mV，活性溶解区从-160mV到-270mV。它的自腐蚀电流密度为0．262μAcm^-2。极化曲线试验后，对试片表面进行XPS能谱分析，所得原子峰高图发现，随着氩离子刻蚀的由浅入深，金属元素镍(Ni)、铬(Cr)、钼(Mo)、铁(Fe)的含量逐渐增加，而非金属元素氧(O)、碳(C)的含量则逐渐减少。由于钙(Ca)为介质中的元素，其含量也呈逐渐减少。结论 镍铬合金在人工唾液中，经过电化学极化曲线试验，会发生腐蚀反应，生成腐蚀产物附着于试样表面。     

pH对银汞合金腐蚀性能的影响

为研究环境ｐＨ值改变对银汞合金腐蚀性能的影响，利用美国３６８－电化学腐蚀测试系统，对４种银汞合金在ｐＨ为６．６５和４．００的人工唾液中的自然腐蚀电位、极化电阻、极化曲线进行测试。结果表明：ｐＨ的改变对不同的合金材料产生的影响不同，４种银汞合金在ｐＨ酸移后的耐腐蚀性从强到弱依次为：高铜银汞合金（昆明产）＞高铜银汞合金（北京产）＞高铜银汞合金（美国产）≥低铜银汞合金（上海产），这与临床观察的结果是一致的。说明金属本身的耐腐蚀性不同，其表面附着膜的变化情况亦不同，故临床上选择耐腐蚀合金材料应考虑到口腔中不断变化的ｐＨ的影响。     

新型钛锆铌锡合金的耐蚀性研究

目的 评价新型钛锆铌锡合金在人工唾液中的耐蚀性,为钛锆铌锡合金的临床应用提供依据.方法 观察钛锆铌锡合金(Ti-12.5Zr-3Nb-2.5Sn)和对照纯钛(TA2)及钛铝钒合金(Ti-fAl-4V)在人工唾液中的电化学行为,比较极化曲线及极化阻力;检测钛锆铌锡合金和钛铝钒合金在人工唾液中1、2、3、5、7、15 d的离子释出情况.结果 极化曲线显示,钛铝钒合金的击穿电位(0.8 V)低于钛锆铌锡合金(＞2.5 V);钛锆铌锡合金、纯钛在钝化区的维钝电流密度(icorr)基本保持稳定,分别为3.32×10-6～3.46×10-5A/cm2和5.03×10-6～2.65×10-5A/cm2,低于钛铝钒合金(1.45×10-4～1.09×10-3 A/cm2).纯钛、钛锆铌锡合金、钛铝钒合金的极化阻力分别为371.0、252.0、60.1 kΩ·cm2.离子释出结果显示,随浸泡时间增加,两种钛合金的离子溶出量均有不同程度增加,且各时间点钛铝钒合金的离子溶出量均高于钛锆铌锡合金.结论 钛锆铌锡合金在人工唾液中具有良好的耐蚀性,可用于制作口腔修复体.     

Ti-6Al-7Nb合金铸造后抗腐蚀性能的研究

目的：研究Ti-6Al-7Nd合金在模拟口腔环境中的电化学腐蚀行为，及铸模温度对合金抗腐蚀能力的影响。方法：制作Ti-6Al-7Nd、Ti-6Al-4V、TA2三种金属铸造试件共18个，每种金属在铸模温度为室温和300℃时各铸造一组，每组试件3个。采用阳极极化技术，在37℃人工唾液中测定其稳态电位（Ecorr)，并记录其动电位极化同线。结果：在同样的铸模温度下，两种合金的Ecorr电位相近，TA2则明显负移；三种金属的Ep值相近。随着铸模温度升高，三种材料的致钝电流密度和维钝电流密度均增大，Ep正移。但其中Ti-6Al-7Nd合金的两个电流密度小于对照组。结论：Ti-6Al-7Nd合金易于钝化，其抗电化学腐蚀能力高于纯钛，与Ti-6Al-4V合金相似。铸造温度升高会降低钛材抗腐蚀能力。     

Vitadur α饰面瓷与GI—Ⅱ型渗透陶瓷底层的颜色匹配性研究

目的：GI－Ⅱ渗透陶瓷底层材料是以Vitadur α作为饰面瓷材料，因此二者必须具有良好的颜色匹配性。本研究的目的在于探讨不同的上瓷阶段底层瓷－饰面瓷复合体颜色的变化规律，为修复体的制作和颜色匹配奠定基础。方法：制作直径为12．5mm，厚度为0．5mm的GI－Ⅱ（IG2色）及Vita In-Ceram Alumina（A2色）底层瓷试件各21个。先烧结0．2mm的不透明牙本质瓷，然后按瓷层厚度分为0．2、0．4、0．6、0．8、1．0mm五个牙本质瓷厚度组及0．2、0．4mm两个牙釉质瓷厚度组，涂塑Vitadur α饰面瓷（A2色）并烧结。用TC－PⅡG全自动测色色差仪测定不同上瓷阶段及不同饰面瓷瓷层厚度组的颜色参数L＊、a*、b*(CIE1976L* a* b*系统），计算色相值（hab）及色饱和度值（C＊ab）。结果：不透明牙本质瓷涂塑烧结后，样本的明度值降低，色相向黄色方向偏移（P＜0．05），饱和度值变化不大（P＞0．05）；随牙本质瓷或牙釉质瓷厚度的增加，明度值和饱和度值降低，色相向红色方向偏移（P＜0．05）；在涂塑烧结0．2mm的不透明牙本质瓷及0．4mm的牙本质瓷后，以两种材料为底层的样本的色差值就达到临床可接受的色差范围。结论：底层瓷－饰面瓷复合体的颜色采瓷层厚度的影响，在临床牙体预备量容许的范围内，GI－Ⅱ渗透陶瓷底层材料和Vitadur α饰面瓷可以达到相互间颜色匹配。     

激光焊接钛及钛合金腐蚀疲劳强度的研究

目的:探讨激光焊接对钛及钛合金腐蚀疲劳强度的影响.方法:将纯钛及钛合金铸造成一定规格的试件,进行激光焊接,将焊接后的试件置于人工唾液中, 90 d后取出,测得母材及焊件的疲劳强度和抗拉强度及断裂试件断口的扫描电镜分析.结果:纯钛试件中对照组、激光焊接组和人工唾液组的疲劳强度分别为(11 489±719) 次,(4 028±124) 次, (3 200±257) 次;钛合金试件中对照组、激光焊接组和人工唾液组的疲劳强度分别为(25 126±2 037) 次,(8 422±153) 次, (7 119±242) 次.激光焊接纯钛组及钛合金组试件的疲劳强度与对照组有统计学差异,断口有气孔及裂纹;激光焊接组与人工唾液组间的疲劳强度无统计学差异,断口未见疲劳裂纹.结论:激光焊接钛试件在人工唾液中的腐蚀疲劳强度无明显降低.     

激光焊接对钛耐应力腐蚀性能影响的实验研究

目的研究激光焊接对钛耐应力腐蚀性能的影响。方法将实验组激光焊接铸钛试样焊缝区加载后浸入37℃人工唾液中,浸泡90 d。实验前、后用电子扫描电镜观察焊接试样熔区表面形貌。在万能材料实验机上作拉伸实验,测出拉伸负荷,计算抗张强度,将结果进行统计学分析。不进行应力腐蚀试验的激光焊接铸钛试样作为对照组。结果应力腐蚀试验后,激光焊接钛试件表面无变色,扫描电镜观察无腐蚀裂纹及腐蚀产物,实验组抗张强度为(657.06±54.04)MPa与对照组(609.81±37.24)MPa相比差异无显著性(P>0.05)。结论激光焊接对钛的耐应力腐蚀性能无影响。     

The study on mechanical properties of laser welds of titanium in dentistry]

OBJECTIVE: To explore the mechanical properties of laser welds of titanium under different conditions. METHODS: Home-made Nd: YAG laser welding apparatus was used to weld TA2 and Ti-6Al-4V under different laser energy. Instron universal testing machine was adopted to measure the tensile load, 0.2% yield load and absolute elongation. The fractured surface was observed under SEM, Vickers microhardness values at welding area were measured and the mechanical properties after immersion in artificial saliva were detected. RESULTS: The mechanical strength of laser welds were related with material, voltage and the combination of them. At 700V-750V, there was no significant difference between tensile load of TA2 laser welds and that of the original material. For Ti-6Al-4V, At 750V. The mechanical strength of laser welds before and after immersion in artificial saliva made no statistic difference. CONCLUSION: It is suggested that the heat-affected zone of laser welding might be small and the corrosion resistance in artificial saliva might be high. The mechanical strength of titanium laser weld might meet the clinical demands at 19-20J/P.     

Laser Welding of Cast Titanium and Dental Alloys Using Argon Shielding

PURPOSE: This study investigated the effect of argon gas shielding on the strengths of laser-welded cast Ti and Ti-6Al-7Nb and compared the results to those of two dental casting alloys. MATERIALS AND METHODS: Cast plates of Ti, Ti-6Al-7Nb, gold, and Co-Cr alloy were prepared. After polishing the surfaces to be welded, two plates were abutted and welded using Nd:YAG laser at a pulse duration of 10 ms, spot diameter of 1 mm, and voltage of 200 V. Five specimens were prepared for each metal by bilaterally welding them with three or five spots either with or without argon shielding. The failure load and percent elongation were measured at a crosshead speed of 1.0 mm/min. RESULTS: The factor of argon shielding significantly affected the failure load and elongation of the laser-welded specimens. The failure loads of argon-shielded laser-welded CP Ti and Ti-6Al-7Nb were greater compared with the failure loads of specimens welded without argon shielding for both three- and five-spot welding. Regardless of argon shielding, the failure loads of the laser-welded gold alloy were approximately half that of the control specimens. In contrast, the failure loads of the nonshielded laser-welded Co-Cr alloy were greater. The percent elongations positively correlated with the failure loads. CONCLUSIONS: The use of argon shielding is necessary for effective laser-welding of CP Ti and Ti-6Al-7Nb but not for gold and Co-Cr alloy.     

Evaluation of welded titanium joints used with cantilevered implant-supported prostheses

STATEMENT OF PROBLEM: Early failure of laser-welded titanium implant frameworks in clinical practice has prompted an investigation of the strength and durability of welded cantilevered titanium sections. PURPOSE: The purpose of this study was to determine the effect that the use of filler wire in laser welding of titanium cantilever frameworks had on the flexural strength and fatigue resistance of the welded joints. MATERIAL AND METHODS: Sixty titanium implant-supported frameworks with 12-mm cantilevers were fabricated in 4 groups (n=15), using 3 different laser welding protocols with 0, 1, and 2 weld passes with filler wire, and 1 conventional tungsten inert gas welding method. The volume of filler wire used (mean volumes 0, 1.7, 3.4, and 8.3 mm(3)) was determined by measurement of the length of wire before and after welding each joint. Ten frameworks from each group were tested for ultimate flexural strength by loading the cantilevers 10 mm from the abutment. The remaining 5 frameworks from each group were similarly tested under a simulated masticatory load of 200 N until failure, or to 1 million cycles. A 2-way analysis of variance was used to examine the flexural strengths, and log-rank statistics were applied to cyclic test data (alpha=.05). RESULTS: There were significant differences between the 4 groups for ultimate flexural strength (P<.001) and resistance to cyclic loading (P=.002). The volume of filler wire added was a significant predictor of ultimate flexural strength (P=.03), and was a borderline determinant of the number of cycles to failure at 200 N (P=.05). Each laser weld pass with filler wire roughly doubled the ultimate flexural strength and fatigue resistance of the joint relative to the previous weld. Tungsten inert gas welding with efficient argon shielding deposited the most filler wire and produced the strongest and most fatigue-resistant joints. CONCLUSION: The ultimate flexural strength and fatigue resistance of cantilevered joints in laser-welded titanium prostheses are improved by the use of filler wire. Tungsten inert gas welding with efficient argon shielding can be used in situations when a high-strength joint is required.     

激光焊点对金瓷界面结合的影响

目的:通过激光焊点对金瓷界面结合的影响分析与临床评价,探讨激光点焊技术在固定修复中的应用价值。方法:用Herapuls激光点焊机对200例存在缺陷的冠桥行点焊修补,再行烤瓷修复。结果:200例不同材料、不同缺陷原因的问题冠桥,经分类点焊修补调整后,均取得满意的修复效果。经1a随访,无焊接点处崩瓷、断裂。结论:激光点焊对金瓷界面修复无直接影响,此技术可以解决冠桥制作中的常见问题。     

Tensile strength and corrosion resistance of brazed and laser-welded cobalt-chromium alloy joints

STATEMENT OF PROBLEM: The longevity of prosthodontic restorations is often limited due to the mechanical or corrosive failure occurring at the sites where segments of a metal framework are joined together. PURPOSE: The purpose of this study was to determine which joining method offers the best properties to cobalt-chromium alloy frameworks. Brazed and 2 types of laser-welded joints were compared for their mechanical and corrosion characteristics. MATERIAL AND METHODS: Sixty-eight cylindrical cobalt-chromium dental alloy specimens, 35 mm long and 2 mm in diameter, were cast. Sixteen specimens were selected for electrochemical measurements in an artificial saliva solution and divided into 4 groups (n=4). In the intact group, the specimens were left as cast. The specimens of the remaining 3 groups were sectioned at the center, perpendicular to the long-axis, and were subsequently rejoined by brazing (brazing group) or laser welding using an X- or I-shaped joint design (X laser and I laser groups, respectively). Another 16 specimens were selected for electrochemical measurements in a more acidic artificial saliva solution. These specimens were also divided into 4 groups (n=4) as described above. Electrochemical impedance spectroscopy and potentiodynamic polarization were used to assess corrosion potentials, breakdown potentials, corrosion current densities, total impedances at lowest frequency, and polarization charge-transfer resistances. The remaining 36 specimens were used for tensile testing. They were divided into 3 groups in which specimen pairs (n=6) were joined by brazing or laser welding to form 70-mm-long cylindrical rods. The tensile strength (MPa) was measured using a universal testing machine. Differences between groups were analyzed using 1-way analysis of variance (alpha=.05). The fracture surfaces and corrosion defects were examined with a scanning electron microscope. RESULTS: The average tensile strength of brazed joints was 792 MPa and was significantly greater (P<.05) than the tensile strength of both types of laser-welded joints (404 MPa and 405 MPa). When laser welding was used, successful joining was limited to the peripheral aspects of the weld. The welding technique did not significantly affect the joint tensile strength. Electrochemical measurements indicated that the corrosion resistance of the laser-welded joints was better than of the brazed ones, primarily due to differences in passivation ability. CONCLUSION: Laser welding provides excellent corrosion resistance to cobalt-chromium alloy joints, but strength is limited due to the shallow weld penetration. Brazed joints are less resistant to corrosion but have higher tensile strength than laser welds.     

复合弓丝在含酶人工唾液中的抗腐蚀性能研究

目的：探索激光焊接复合弓丝在含有唾液淀粉酶和胰淀粉酶人工唾液中的抗腐蚀能力,对比两种淀粉酶对弓丝抗腐蚀性能的影响及其机制。方法复合弓丝的抗腐蚀能力采用电化学极化和浸泡实验的方法评估,浸泡于含酶的人工唾液28 d后的可溶性腐蚀产物用等离子光谱仪进行检测,表面形貌采用扫描电镜、能谱仪和原子力显微镜进行分析。结果唾液淀粉酶和胰淀粉酶均能够提高复合弓丝的抗腐蚀能力;同工异构酶也会对同种合金的抗腐蚀能力产生不同的影响。结论新型金属生物材料拟应用于口腔时,淀粉酶可能对其抗腐蚀能力有影响。