pH值对磁性固位体耐蚀性能的影响

目的　研究人工唾液的酸碱度在偏酸性的条件下,3种磁性固位体外包裹容器的耐腐蚀能力的改变。方法　将3种磁性固位体浸泡于人工唾液中,介质pH值分为5·6和7·0两组,实验温度36·5℃,时间6个月。采用恒电位法测定极化曲线实验、浸泡实验及扫描电镜方法,分析材料的耐腐蚀能力。结果　pH值下降,磁性固位体外包裹容器---不锈钢中铁离子的溶出量提高近10倍。表明在偏酸性的环境中,3种材料的腐蚀速度都加快。结论　磁性固位体的耐酸性能力相对较差,这将影响他们的使用寿命。     

H2O2对镍铬合金电化学腐蚀性能及离子析出的影响

目的:比较不同浓度H2O2对镍铬合金电化学腐蚀性能及离子析出的影响。方法:应用电化学工作站的电化学阻抗谱法和动电位极化曲线法,对不同浓度H2O2浸泡112 h后的牙科镍铬合金在人工唾液中的腐蚀行为进行比较,并用电感耦合等离子体质谱仪检测电化学腐蚀后人工唾液介质中析出的金属离子浓度。采用SPSS 13.0软件包对数据进行方差分析。结果:0%H2O2浸泡112 h后,镍铬合金在人工唾液中等效电路极化电阻Rct、腐蚀电位Ecorr、点蚀击穿电位Eb以及代表合金表面的"伪钝化"的△E(Ecorr与Eb之差)最大,而30%H2O2浸泡112 h后,镍铬合金在人工唾液中的Rct、Ecorr、Eb以及△E最小,不同浓度H2O2浸泡后镍铬合金耐腐蚀性能顺序为30%<10%<0%(P<0.05);镍铬合金在人工唾液介质中析出的金属离子Ni、Cr、Mo浓度大小顺序为0%<10%<30%(P<0.05)。结论:镍铬合金在不同浓度H2O2中浸泡112 h后,其在人工唾液中的耐腐蚀性能发生了一定变化,随着H2O2浓度的升高,越来越容易腐蚀,且人工唾液介质中析出的金属离子浓度也越来越高。     

磁性附着体铸造衔铁与成品衔铁的耐蚀性研究

目的：研究铁铬钼软磁合金的铸造衔铁与成品衔铁的抗腐蚀性能差异。方法：采用铸造工艺复制成品衔铁，对照分析金相结构，并运用电化学方法检测2种衔铁在人工唾液中的自腐蚀速度和点蚀电位。结果：铸造与成品衔铁的金相结构及其耐腐蚀性能差异明显，铸造衔铁自腐蚀电流密度为1.967μA/cm^2，点蚀电位0.264V；成品衔铁分别是2.566μA/cm^2,0.509V。结论：铸造衔铁与成品衔铁在人工口唾液中的抗腐蚀性能各有优缺点，其结构不同是差异的根本原因。     

过氧化氢对银汞合金电化学腐蚀性能的实验研究

目的研究不同浓度过氧化氢对银汞合金电化学腐蚀性能的影响。方法采用电化学工作站的开路电位、电化学阻抗谱及动电位极化曲线法对不同浓度过氧化氢（0%、3.6%、10%及30%）浸泡24h后的牙科银汞合金在人工唾液中的腐蚀行为进行比较。结果 10%和30%过氧化氢浸泡后的银汞合金在人工唾液中开路电位较快地达到了一个稳定的值,且开路电位较短时间变化范围大小顺序为0%组〈3.6%组〈10%组〈30%组;不同浓度过氧化氢浸泡后的银汞合金在人工唾液中的等效电路极化电阻大小顺序为：0%组〉3.6%组〉10%组〉30%组,与动电位极化曲线腐蚀电位（Ecorr）结果一致;而自腐蚀电流密度（Icorr）结果为：0%组〈3.6%组〈10%组〈30%组。结论随着过氧化氢浓度的升高,银汞合金在人工唾液中的耐腐蚀性能越来越差。     

不同浓度茶多酚人工唾液溶液对牙科铸造合金腐蚀行为的影响

目的 研究镍铬合金、钴铬合金、纯钛在茶多酚人工唾液溶液中的电化学腐蚀行为.方法 将3种铸造合金分别浸泡在人工唾液以及浓度为1.25、2.50和5.00 g/L茶多酚人工唾液溶液中,采用动电位极化曲线法检测其自腐蚀电流密度(Icorr)、腐蚀电位(Ecorr)和极化电阻(Rp)等指标.结果 与人工唾液中Icorr相比、镍铬合金在1.25 g/L茶多酚人工唾液溶液中的Icorr显著增大(P < 0.01),且随着茶多酚浓度升高,Icorr逐渐减小、Rp逐渐增大.钴铬合金在4种溶液中的腐蚀速率明显不同(P < 0.01),在1.25 g/L茶多酚人工唾液溶液中的腐蚀速率显著小于在人工唾液中.纯钛在4种溶液中的腐蚀速度显著小于其他两种金属(P < 0.01).结论 有饮茶习惯的患者不宜选用镍铬合金制作修复体,而佩戴有钴铬合金或纯钛修复体的患者可适量饮茶,但无论哪类患者,都不建议饮浓茶.     

血链球菌对磁性固位体耐腐蚀性能的影响

目的:比较磁性固位体在有、无血链菌存在的人工唾液中受腐蚀后金属离子的析出情况.方法:将磁性固位体分别置于装有人工唾液的培养瓶中,随机选取10瓶,加入血链球菌悬液.其余10瓶作为对照.培养瓶置于36℃培养箱内培养,分别于3d、10d和20d时取出5ml混悬液,送实验室检测混悬液中的Fe3 、Mn2 析出的量.分析磁性固位体金属腐蚀的情况.实验数据采用SPSS10.0软件包进行单因素配对t检验.结果:在含血链球菌的人工唾液中,磁性固位体受腐蚀释放出的Fe3 、Mn2 在3d、10d、20d时的检出量显著高于对照组(P＜0.01).结论:血链菌会明显破坏磁性固位体金属的耐腐蚀性.     

氯离子浓度对牙科铬合金耐腐蚀性能的影响

目的 在人工唾液中氯离子浓度升高的条件下,用动电位极化曲线法研究镍铬合金、钴铬合金和含钛镍铬合金的耐腐蚀性能的变化。方法 测定三种铬合金在氯化钠浓度分别为0.9%、2%、3%的人工唾液中的自腐蚀电位、自腐蚀电流密度,对其进行比较分析。结果 随着氯离子浓度升高,三种铬合金的自腐蚀电流密度均增大,腐蚀速度加快。钴铬合金受氯化钠浓度的影响最小。结论 在高氯环境中,三种铬合金腐蚀性能均降低,但钴铬合金耐腐蚀能力相对较强,这将影响它们的使用寿命。     

纯钛表面TiO2、ZrO2复合涂层在人工唾液中的电化学腐蚀

目的:采用等离子喷涂技术在纯钛表面制备氧化钛/氧化锆(TiO2/ZrO2)复合涂层,比较纯钛和复合涂层在不同pH值的人工唾液中的电化学腐蚀行为.方法:通过扫描电子显微镜(SEM)观察涂层显微结构,采用动电位极化曲线法,检测纯钛和TiO2/ZrO2复合涂层在pH分别为5.5和7的人工唾液中的自腐蚀电位、自腐蚀电流密度,并比较二者的耐腐蚀性能.结果:TiO2/ZrO2复合涂层结构均匀,与纯钛基体结合紧密;pH为7.0和5.5时,钛+TiO2/ZrO2复合涂层材料的自腐蚀电位分别为-48.7mV和-78.6mV,白腐蚀电流密度值分别为2.35×10-6mA/cm2和4.26×10-6mA/cm2,而纯钛材料的自腐蚀电位分别为-10.8mV和-41.4mY,自腐蚀电流密度值分别为3.89×10-6m A/cm2和10.12×10-6 mA/cm2,提示在pH为5.5的人工唾液中,复合涂层可明显提高纯钛耐腐蚀性能.结论:TiO2/ZrO2复合涂层与纯钛基体结合良好,其在不同pH值的人工唾液中耐腐蚀性能稳定,但TiO2/ZrO2复合涂层的耐腐蚀性能优于纯钛,可对纯钛基底起一定保护作用.     

微弧氧化前后AZ91D镁合金的耐腐蚀性能检测

目的 研究微弧氧化后AZ91D镁合金在人工唾液环境中耐腐蚀性能的改变。方法 采用微弧氧化方法对AZ91D镁合金进行表面改性,采用浸泡腐蚀及电化学腐蚀实验评价其在人工唾液中的耐腐蚀性能。结果 浸泡试验中60 d内未处理试样平均失重是微弧氧化试样的11倍;而电化学腐蚀试验中,微弧氧化处理将镁合金在人工唾液中的开路电压由-1.4511 V提高到-0.4416 V,腐蚀电流密度I0由8.4152×10-5 A/cm降低到2.0456×10-7 A/cm。结论 微弧氧化后的AZ91D镁合金在人工唾液中耐腐蚀性能显著提高,微弧氧化陶瓷层能有效的保护镁合金基体。     

氟对变形链球菌黏附前后纯钛表面腐蚀性能的影响

目的:比较氟化钠对变形链球菌黏附前、后纯钛电化学腐蚀性能的影响.方法:应用电化学工作站的电化学阻抗谱法和动电位极化曲线法,对变形链球菌黏附前、后纯钛在0g/L和1.0 g/L氟化钠人工唾液中的腐蚀行为进行比较.采用SPSS12.2软件包对数据进行统计学分析.结果:变形链球菌黏附前、后,纯钛在0g/L和1.0 g/L氟化钠人工唾液中的等效电路极化电阻Rct、腐蚀电位Ecorr、点蚀击穿电位Eb以及代表合金表面的“伪钝化”的△E(Ecorr与Eb之差)均存在显著差异(P＜0.05).结论:变形链球菌黏附后,纯钛的耐腐蚀性能降低,氟化钠也使纯钛的耐腐蚀性能降低.     

Sandwich type dental magnetic devices of Nd-Fe-B magnet and permendur

Nd-Fe-B magnets have a very high maximum energy product (BH max), which is defined as the attractive strength between a magnet and opposing magnetic materials. Permendur (Fe-49 Co-2 V) has the greatest magnetic saturation (Bs), which makes it strongly magnetized. If magnetic retainers were made with Nd-Fe-B magnets and a permendur yoke, they would be small and have strong retention. The purpose of this investigation was to develop small dental magnetic devices with Nd-Fe-B magnets and permendur yokes. The magnetic devices form sandwich-type magnetic circuits with magnetic stainless steel keepers. A 4 x 3 x 2 mm rectangular prism Nd-Fe-B magnet was used. The magnet was sandwitched between the semi-columnar yokes. To protect the magnet from corrosion, the devices were encapsulated with 304 stainless steel by silver brazing and adhesion bonding of a stainless steel tube and foil. The optimum cross-sectional area of the yoke was determined experimentally. The dimensions of the devices were phi 5 x 3.5 mm for 4 x 3 x 2 magnet. The breakaway retention for a keeper of magnetic stainless steel (Type XM 27) was 852 g on average. This breakaway retention is sufficient for dental prosthetic applications.     

Development of sealed cup yoke type dental magnetic attachment.

The purpose of this study was to develop a small cup type yoke magnetic attachment sealed from oral fluid. The magnetic device forms a closed circuit between the magnet, yokes, and keeper. A 3.2 mm phi x 1.4 mm SmCO5 magnet was put into a cup yoke of 447J1 stainless steel and covered by 447J1 stainless steel disk yoke with a 316L stainless steel ring. To protect the magnet from corrosion, the connection was sealed by laser welding. The optimum dimensions were figured out by a finite element method. The performance of the magnetic attachment was investigated. As a result, a magnet device 4.4 mm in diameter and 2.1 mm in height was developed. The breakaway retention when the keeper touched it was 341 gf on average.     

Corrosion under static and dynamic conditions of alloys used for magnetic retention in dentistry

In recent years magnetic retention has gained increasing popularity in dental practice. This investigation compared the corrosion resistance of the palladium-cobalt ferromagnetic alloy (constituent of the keeper cemented on the abutment teeth) coupled with the samarium-cobalt magnets embedded in the removable part of the denture. The behavior of three couples (cobalt-palladium, cobalt-palladium/titanium, and cobalt-palladium/palladium) has been studied. The magnets, because of their poor corrosion resistance, are encapsulated in various materials. To simulate clinical conditions, characterized by the continuous movement of the keeper with respect to the magnet, the experiments were conducted in artificial saliva under intermittent and continuous wear.     

In vitro corrosion behavior of cast iron-platinum magnetic alloys.

OBJECTIVE: The objective of this study was to investigate the corrosion resistance of cast Fe-Pt alloys of varying compositions for use as attachment keepers and to make a comparison with the corrosion resistance of magnetic stainless steel. METHODS: The corrosion behavior of cast Fe-Pt alloy keepers (Fe-40 at%Pt, Fe-38 at%Pt, Fe-37 at%Pt and Fe-36 at%Pt) was evaluated by means of an immersion test and an anodic polarization test. The solutions used were a 1.0% lactic acid aqueous solution (pH=2.3) (10 ml) and 0.9% NaCl solution (pH=7.3) (10 ml). As a control, the corrosion resistance of a magnetic stainless steel keeper (SUS 447J1: HICOREX) was also measured. RESULTS: Chromium and platinum ions were not detected in either the 1.0% lactic acid or 0.9% NaCl solutions. The only released ions detected were the Fe ions in the 1.0% lactic acid solution. The amounts of Fe ions released from the Fe-40 at%Pt and Fe-38 at%Pt alloys were significantly (p<0.05) lower than from the Fe-37at%Pt, Fe-36 at%Pt and SUS 447J1 alloys. In the anodic polarization test, the potentials at the beginning of passivation for the four Fe-Pt alloys were higher than for the SUS 447J1 alloy in both solutions. SIGNIFICANCE: The Fe-Pt alloys, especially the alloys with higher Pt percentages (Fe-40 and 38 at%Pt), indicated a high corrosion resistance compared to the magnetic stainless steel keeper. A reduction in the Pt percentage may decrease the corrosion resistance in the oral environment.     

Corrosion resistance of the Pt-Fe-Nb magnets for dental-casting

Magnetic attachments have been used in clinical dental practice, but there is some difficulties associated with removable bridges. One possible solution is to make whole bridges of Pt-Fe magnet alloys and its abutment out of magnetic stainless steel by casting. In terms of castability and magnetic properties, the promising composition of the Pt-Fe-Nb magnet alloy is Pt-30.0 mass% Fe-0.6 mass% Nb and Pt-30.0 mass% Fe-0.5 mass% Nb-0.03 mass% Si. In the present study, the corrosion resistance of these alloys was investigated based on the elusion test, electrochemical behavior and surface characterization by EPMA analysis. The released elements from the Pt-Fe-Nb magnets were mainly Fe ions in quantities similar to that of stainless steel for biomedical use, and the Pt-Fe-Nb magnet alloy, the Pt-Fe-Nb-Si magnet alloy and platinum resembled each other in electrochemical behavior. The present findings suggest, that the Pt-Fe-Nb magnet alloy provides excellent corrosion resistance and has important clinical dental applications.     

人工唾液中氯化钠浓度对钴铬、镍铬、含钛镍铬合金腐蚀行为的影响

目的：在人工唾液中氯化钠浓度升高的条件下,用电化学阻抗谱研究3种牙科常用合金（钴铬、镍铬、含钛镍铬合金）腐蚀行为的变化。方法：测定在人工唾液中氯化钠浓度分别为0.9%、2%、3%的条件下,3种合金的电化学阻抗谱,将各体系中合金界面电容和电荷转移电阻拟合,分析其腐蚀机制和耐腐蚀性能的变化。结果：随着氯化钠浓度升高,3种合金的界面电荷转移电阻（Rt值）都分别减小,界面电容（Qdl）增大,腐蚀反应过程加剧,抗蚀能力降低。但钴铬合金的Rt值是最大的。结论：在高氯环境中,3种合金腐蚀反应加快,抗腐蚀能力均降低,但钴铬合金抗腐蚀能力相对较强,这将影响它们的使用寿命。     

不同pH值与氟离子浓度对口腔常用金属修复材料电化学腐蚀的影响

目的 研究不同pH值与不同浓度氟离子(F-)对HBIC种植体和常用的四种冠修复金属材料在人工唾液中电化学腐蚀的影响.方法 将5种口腔常用金属,金合金(Au)、镍铬合金(NiCr)、钴铬合金(CoCr)、铸造纯钛(Ti)、HBIC种植钛材(H-Ti)分别置于不同pH值与含和不含F-的人工唾液中,采用动电位极化曲线法测得其自腐蚀电位和自腐蚀电流密度,分析材料的耐腐蚀性.结果 金合金、钴铬合金、镍铬合金的腐蚀电流密度随着H+的浓度增加而变大,差异有统计学意义(P<0.05),铸造纯钛及种植钛材在酸性含氟人工唾液中的腐蚀电流密度和自腐蚀电位变化明显,差异有统计学意义(P<0.05),F-对金合金的耐腐蚀性影响不明显.结论 pH的改变以及含氟环境会加剧种植体及其常用上部冠修复材料的电化学腐蚀性,金合金与纯钛的耐腐蚀性能较强.