Cytotoxicity of orthodontic wire corroded in fluoride solution in vitro

OBJECTIVE: To investigate the toxicity of fluoride corrosion extracts of stainless steel (SS) and nickel-titanium (NiTi) wires on a human osteosarcoma cell line (U2OS). MATERIALS AND METHODS: The SS and NiTi wires were corroded by an electrochemical method with the application of three kinds of electrolytes: 0.2% pH 3.5 acidulated phosphate fluoride (NaF) in artificial saliva, and pH 4 and pH 6.75 artificial saliva solutions. The extracts were analyzed for nickel, chromium, and titanium ions by the atomic absorption method. The extracts were diluted with medium to different concentrations (1, 0.1, and 0.01 microL/mL). The cell survival rate was determined by the ability of test cells to cleave the tetrazolium salt to form a formazan dye. RESULTS: The results were compared using one-way analysis of variance. Differences between the treatment means were analyzed using a Student-Newman-Keuls (SNK) test and were considered significant at P < .05. The release of ionic nickel was different in different extract groups (P < .05). The SS and NiTi wires in the 0.2% pH 3.5 NaF artificial saliva group caused a dose-dependent decrease in the survival rate (P < .05). Survival rates of cells in the groups exposed to extracts of SS and NiTi wires in pH 4 and pH 6.75 artificial saliva solutions showed no statistical differences (P >.05). CONCLUSIONS: Orthodontic wires in acidulated fluoride saliva solution can cause U2OS cell toxicity.     

Comparison of Metal Ion Release from Different Bracket Archwire Combinations: An in vitro Study

Aim: The metal ion released from the orthodontic appliance may cause allergic reactions particularly nickel and chromium ions. Hence, this study was undertaken to determine the amount of nickel, chromium, copper, cobalt and iron ions released from simulated orthodontic appliance made of new archwires and brackets. Materials and methods: Sixty sets of new archwire, band material, brackets and ligature wires were prepared simulating fixed orthodontic appliance. These sets were divided into four groups of fifteen samples each. Group 1: Stainless steel rectangular archwires. Group 2: Rectangular NiTi archwires. Group 3: Rectangular copper NiTi archwires. Group 4: Rectangular elgiloy archwires. These appliances were immersed in 50 ml of artificial saliva solution and stored in polypropylene bottles in the incubator to simulate oral conditions. After 90 days the solution were tested for nickel, chromium, copper, cobalt and iron ions using atomic absorption spectrophotometer. Results: Results showed that high levels of nickel ions were released from all four groups, compared to all other ions, followed by release of iron ion levels. There is no significant difference in the levels of all metal ions released in the different groups. Conclusion: The study confirms that the use of newer brackets and newer archwires confirms the negligible release of metal ions from the orthodontic appliance. Clinical significance: The measurable amount of metals, released from orthodontic appliances in artificial saliva, was significantly below the average dietary intake and did not reach toxic concentrations. Keywords: Metal ions, Brackets, Archwires, Nickel, Iron, Copper, Cobalt, Chromium, Titanium, Molybdenum. How to cite this article: Karnam SK, Reddy AN, Manjith CM. Comparison of Metal Ion Release from Different Bracket Archwire Combinations: An in vitro Study. J Contemp Dent Pract 2012;13(3):376-381. Source of support: Nil Conflict of interest: None declared.     

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目的    评价3种正畸用镍钛形状记忆合金弓丝的细胞毒性。方法    于2009年11月至2010年3月,在中国医科大学口腔医学院选择正畸临床常用的3种品牌镍钛形状记忆合金弓丝（A：Masel牌美国产热激活型镍钛牙齿矫形丝;B：Smart牌国产热激活型镍钛牙齿矫形丝;C：有研亿金牌国产镍钛丝）,制作试件各若干枚,长度0.5 cm。将其依次分为3份,一份处理后直接提取浸提液;另外两份处理后置于人工唾液中浸泡,分别于4周和8周后取出提取浸提液。选择L-929细胞系作为细胞毒性的实验对象,用倒置相差显微镜观察L-929细胞在合金丝浸提液中的生长情况,通过四甲基偶氮唑盐微量酶反应比色法（MTT 法）得出细胞在培养24 h和48 h的吸光度（OD）值以及细胞相对增殖率（RGR）,对3种品牌镍钛形状记忆合金弓丝做出细胞毒性评价。结果    在人工唾液浸泡后,3种品牌镍钛形状记忆合金弓丝的细胞毒性均随浸泡时间延长而逐渐增加（P < 0.05）;在相同的浸泡时间下,A弓丝的细胞毒性最小,C弓丝的细胞毒性最大;3种镍钛形状记忆合金弓丝细胞毒性均在正常范围之内。结论    （1）人工唾液环境增加了镍钛形状记忆合金丝的细胞毒性,并随着浸泡时间的增加细胞毒性加大。（2）不同品牌、不同浸泡时间,正畸用镍钛弓丝细胞毒性不同。     

Corrosion by galvanic coupling between amalgam and different chromium-based alloys.

OBJECTIVES: In recent years there has been an increase in the use of dental casting alloys in prosthodontic treatment. Many patients have metals or alloys, as well as amalgam fillings, in their mouth, and will have them for many years. The aim of this study was to evaluate and compare, in vitro, the galvanic corrosion behavior of chromium-cobalt alloy (Remanium GM 380) and chromium-nickel alloy (Remanium CS) when bound together or coupled with silver-based amalgam (Amalcap plus). METHODS: An electrochemical characterization of the alloys was performed by potentiostatic and potentiodynamic methods, i.e. the open circuit potential (OCP), the corrosion potential (E(CORR)), corrosion current density (i(CORR)) and corrosion resistance (R(P)). The electromotive force (EMF) of the bimetallic cells was also tested. Electroanalytical techniques were used to estimate the release of any respective element from the dental alloys under study into the artificial saliva solution. RESULTS: It was found that a bimetallic cell consisting of Remanium CS and Remanium GM 380 alloys has a very low EMF (a few mV) and is not a potential source of galvanic currents in the oral cavity. However, galvanic cells prepared from Amalcap plus and Remanium CS or Remanium GM 380 showed a much greater EMF: 104 and 109mV, respectively. This clearly indicates that in these latter cases it is possible to expect some metal ions in the saliva solution as a result of the work of galvanic currents. It was found, by adsorptive stripping voltammetry analysis, that nickel or cobalt, depending on the alloy used, appeared in the saliva solution and increased in concentration over time. SIGNIFICANCE: The results indicate that the correct design and use of dental alloys are important when determining the appropriate treatment for a specific patient.     

Comparison of ion release from new and recycled orthodontic brackets.

Bracket corrosion can occur in the oral environment. The purpose of this study was to compare the release of metal ions from new and recycled brackets in artificial saliva and buffers with different pH values over a 12-week immersion period. The brackets were divided into 2 groups: new and recycled. The recycled bracket bases were coated with adhesive and the brackets were heat treated. Nickel, chromium, iron, and manganese ions were detected by atomic absorption. The surface characteristics of the brackets were examined by energy dispersive radiographic analysis. The results were as follows: (1) Recycled brackets released more ions than did the new brackets. (2) Greater amounts of nickel, iron, and manganese ions were released in artificial saliva than in the other buffers tested. (3) Ion release from brackets in a pH 4 buffer was greater than that observed in pH 7 or pH 10 buffers. (4) The total amount of ion release increased with time. (5) After a 12-week immersion, the total ion release averaged over the period did not exceed the recommended daily intake.     

利用ICP-MS检测再利用托槽的镍离子析出量的研究

目的：通过采用电感耦合等离子体发射光谱分析法（ICP-MS）检测不同方法去除底板粘结剂后再利用的托槽在人工唾液中析出的镍离子量,探讨这些方法对托槽镍离子析出量的影响。方法：采用全新标准方丝弓金属托槽,共20个样本,随机分为喷砂组和燃烧组,分别采取喷砂法和燃烧法去除托槽底板上粘接剂,另选同一种新托槽10个样本作为对照组。将30个样本分别浸泡在人工唾液中,采用电感耦合等离子体发射光谱分析法（ICP-MS）测定金属托槽在人工唾液浸泡4周后的镍离子析出量。结果：喷砂组和燃烧组的镍离子析出量高于对照组,差异均具有统计学意义（P〈0．05）,其中燃烧组的镍离子析出量又高于喷砂组（P〈0．05）。结论：2种去除托槽底板粘结剂的方法均会增加托槽镍离子的析出量,而燃烧法的效果又更明显。     

含氟人工唾液对金属托槽镍离子释放的影响

目的:通过检测金属托槽在含氟人工唾液中析出的镍离子量,探讨氟离子对金属托槽镍离子释放的影响.方法:采用全新标准方丝弓金属托槽,共20个样本,随机分为含氟组和无氟组.将20个样本按分组分别浸泡在不同的人工唾液中,采用电感耦合等离子体发射光谱分析法(ICP-MS)测定金属托槽在人工唾液浸泡4周后的镍离子析出量.结果:含氟组的镍离子析出量高于无氟组,差异具有统计学意义(P＜0.05).结论:氟离子的存在会增加金属托槽镍离子的析出量.     

Ion release from dental casting alloys as assessed by a continuous flow system: Nutritional and toxicological implications.

OBJECTIVES: The aims of this study were to quantify the metallic ions released by various dental alloys subjected to a continuous flow of saliva and to estimate the nutritional and toxicological implications of such a release. METHODS: Four pieces of three nickel-based, one noble, one high-noble and two copper-aluminum alloys were cast and then immersed in a continuous flow of artificial saliva for 15 days. To simulate three meals a day, casts were subjected to thrice-daily episodes, lasting 30 min each and consisting of pH decreases and salinity increases. After 15 days, the metallic ions in the artificial saliva were analyzed. Data were expressed as averaged release rate: microg/cm2/day of ion released for each alloy. The highest value of 95% Cl of each ion was adapted to a hypothetical worst scenario of a subject with 100 cm2 of exposed metal surface. The results were compared with the tolerable upper daily intake level of each ion. RESULTS: The copper-aluminum alloys released copper, aluminum, nickel, manganese and iron. The nickel-based alloys essentially released nickel and chromium, while the beryllium-containing alloy released beryllium and significantly more nickel. The noble and high-noble alloys were very resistant to corrosion. The amount of ions released remained far below the upper tolerable intake level, with the exception of nickel, released by beryllium-containing nickel-based alloy, whose levels approach 50% of this threshold. SIGNIFICANCE: The daily amount of ions released seems to be far below the tolerable upper intake levels for each ion.     

Metal release from heat-treated orthodontic archwires

Stainless steel and cobalt-chromium orthodontic archwires were subjected to an immersion corrosion test. Wires in the as-received state and wires subjected to a 1-min heat treatment at different temperatures were tested. Iron from the stainless steel and cobalt from the cobalt-chromium product were analyzed in artificial saliva after 1 week of immersion. Both products were analyzed for nickel. The results showed that the cobalt-chromium wire in the as-received state released more metals than the stainless steel. The metal release from the stainless steel wire increased rapidly when subjected to 400 degrees C or higher. For the cobalt-chromium product the increase started at about 500 degrees C. At temperatures above 500 degrees C the release of metals was 15 to 60 times higher than the lowest values. The present results should be considered in procedures involving application of heat to orthodontic wires.     

金沉积复合镍铬合金烤瓷的镍离子析出量的实验研究

目的 通过测试浸泡在人工唾液中的金沉积片复合镍铬合金片烤瓷试件的镍离子析出量,探究金沉积基底冠熔结镍铬桥体烤瓷桥是否能减少镍离子析出,降低生物安全风险.方法 将镍铬合金片与金沉积片粘接,表面烤瓷,瓷层厚度分别为0.3 mm(A组)、0.5 mm(B组)、1.0 mm(C组)和0.3 mm(D组),每组6个试件.对照组为镍铬合金片.A、B、C组和对照组浸泡在37℃酸性人工唾液中;D组浸泡在37℃酸性高氟人工唾液中.浸泡120 h后,测定浸泡液的镍离子浓度.独立样本t检验比较A～D组浸泡液镍离子浓度与对照组的差异.结果 A、B、C、D组的镍离子浓度均小于0.005 mg/L;与对照组[(0.65±0.45)mg/L]相比,差异均有统计学意义(P＜0.05).结论 金沉积基底冠熔结镍铬桥体烤瓷桥可减少镍离子析出,降低生物安全风险.     

Metal release from heat-treated orthodontic archwires

Stainless steel and cobalt-chromium orthodontic archwires were subjected to an immersion corrosion test. Wires in the as-received state and wires subjected to a 1-min heat treatment at different temperatures were tested. Iron from the stainless steel and cobalt from the cobalt-chromium product were analyzed in artificial saliva after 1 week of immersion. Both products were analyzed for nickel. The results showed that the cobalt-chromium wire in the as-received state released more metals than the stainless steel. The metal release from the stainless steel wire increased rapidly when subjected to 400°C or higher. For the colbalt-chromium product the increase started at about 500°C. At temperatures above 500°C the release of metals was 15 to 60 times higher than the lowest values. The present results should be considered in procedures involving application of heat to orthodontic wires. □ Cobalt-chromium alloy; corrosion; stainless steel     

Comparison of metal release from new and recycled bracket-archwire combinations

Most orthodontic brackets and archwires made from stainless steel or nickel (Ni)-titanium (Ti) alloys can release metal ions into the saliva. This study measures the amounts of metal released from simulated fixed orthodontic appliances. Sixty simulated fixed orthodontic appliances were manufactured in different ways and divided into four equal groups as follows: new brackets and new archwires (group 1 controls), new brackets and recycled archwires (group 2), recycled brackets and new archwires (group 3), and recycled brackets and recycled archwires (group 4). The bracket bases coated with adhesives were heated at 350 degrees C for 30 minutes. Recycled archwires were sterilized by autoclaving. Each appliance was soaked in artificial saliva of pH 7 at 37 degrees C for 45 days. At the end of this period, a sample of the artificial saliva was collected for analysis. Concentrations of Ni, chromium (Cr), iron (Fe), manganese, copper (Cu), and Ti ions were measured by atomic absorption and recorded in micrograms per liter. Analysis of variance and the Duncan multiple-range test indicated significant differences among the groups (P < .001). The study revealed the following: (1) group 4 released higher amounts of Cr, Fe, and Ti than any of the other three combinations; (2) Ni release was similar in groups 1 and 2 and in groups 2, 3, and 4; (3) the amounts of Cu, Cr, and Ti ions released from groups 3 and 4 were significantly greater than the amounts released from the other two combinations.     

Effect of chlorhexidine-containing prophylactic agent on the surface characterization and frictional resistance between orthodontic brackets and archwires: an in vitro study

Background

The purpose of this study was to assess the surface characterization and frictional resistance between stainless steel brackets and two types of orthodontic wires made of stainless steel and nickel-titanium alloys after immersion in a chlorhexidine-containing prophylactic agent.

Methods

Stainless steel orthodontic brackets with either stainless steel (SS) or heat-activated nickel-titanium (Ni-Ti) wires were immersed in a 0.2% chlorhexidine and an artificial saliva environment for 1.5 h. The frictional force was measured on a universal testing machine with a crosshead speed of 10 mm/min over a 5-mm of archwire. The surface morphology of bracket slots and surface roughness of archwires after immersion in chlorhexidine were also characterized using a scanning electron microscope (SEM) and an atomic force microscope (AFM), respectively.

Results

There was no significant difference in the frictional resistance values between SS and Ni-Ti wires immersed in either chlorhexidine or artificial saliva. The frictional resistance values for the SS and Ni-Ti wires immersed in 0.2% chlorhexidine solution were not significantly different from that inartificial saliva. No significant difference in the average surface roughness for both wires before (as-received) and after immersion in either chlorhexidine or artificial saliva was observed.

Conclusions

One-and-half-hour immersion in 0.2% chlorhexidine mouthrinse did not have significant influence on the archwires surface roughness or the frictional resistance between stainless steel orthodontic brackets and archwires made of SS and Ni-Ti. Based on these results, chlorhexidine-containing mouthrinses may be prescribed as non-destructive prophylactic agents on materials evaluated in the present study for orthodontic patients.     

两种处理脱落金属托槽方法对镍离子析出量影响的体外研究

目的 通过检测两种方法去除底板残余粘接剂后的金属托槽在人工唾液中析出的镍离子含量,探讨其处理方法对托槽耐腐蚀性能的影响.方法 采用全新标准方丝弓金属托槽,共30个样本,随机分为3组:对照组、磨除组和喷砂组,后2组分别采取磨除法和喷砂法去除托槽底板上的粘接剂.将30个样本分别浸泡在人工唾液中,28d后采用电感耦合等离子发射光谱分析法(ICP-MS)测定浸泡液中镍离子析出量.结果 磨除组和喷砂组的镍离子析出量均高出对照组,差异均有统计学意义(P＜0.05).磨除组和喷砂组之间的镍离子析出量却没有显著性差异(P＞0.05).结论 两种去除托槽底板粘接剂的方法均会降低金属托槽的耐腐蚀性能,但两种方法的影响程度无明显差异.     

纳米非晶金刚石膜镀覆对镍铬及钴铬烤瓷合金离子析出的影响

目的：观测纳米非晶金刚石膜对镍铬及钴铬两种非贵金属烤瓷合金在人工唾液中金属离子析出的影响。方法：制备镍铬合金、钴铬合金圆片形试件各24个,镍铬及钴铬合金试件随机分成a1、b1及a2、b2各两组,a1、a2组试件表面不镀膜,b1、b2组试件表面完整镀膜膜厚60nm,将a1、a2、b1、b2每组试件平分两半,分别置于pH值为6.8和4.0的人工唾液中浸泡7天,检测各组试件的金属离子析出量。结果：a1、a2组试件在两种人工唾液中表现出其所含各种金属离子的析出,在pH=4酸性人工唾液中浸泡后的离子析出量显著高于其在pH=6.8中性人工唾液中浸泡后的离子析出量（P〈0.05）;b1、b2组试件在两种人工唾液中浸泡后,其离子析出量分别比a1、a2组试件显著降低（P〈0.01）。结论：镍铬合金、钴铬合金在中性和酸性人工唾液中表现出其所含各种金属离子的析出,在酸性人工唾液中其金属离子析出量显著增加;纳米非晶金刚石镀膜能显著降低镍铬、钴铬合金在中性和酸性人工唾液中的金属离子析出量,有良好的耐腐蚀性。     

正畸合金丝在人工唾液中腐蚀行为的电化学研究

目的：运用电化学方法研究常用正畸合金丝的耐腐蚀性能。方法：采用经典三电极体系的电化学方法,在人工唾液中检测常用正畸不锈钢弓丝、镍钛丝、β-钛丝及钴铬丝的自然腐蚀电位和腐蚀电流密度,从而研究其自身腐蚀行为。结果：在人工唾液中,4种弓丝的的自然腐蚀电位顺序为SS＞CoCr＞β-Ti＞NiTi;腐蚀电流密度顺序为NiTi＞β-Ti＞CoCr＞SS。结论：在人工唾液中,常用正畸合金丝自身均会发生电化学腐蚀,产生相应的腐蚀电流。     

Characterization and cytotoxicity of ions released from stainless steel and nickel-titanium orthodontic alloys.

The purpose of this study was to qualitatively and quantitatively characterize the substances released from orthodontic brackets and nickel-titanium wires and to comparatively assess the cytotoxicity of the ions released from these orthodontic alloys. Two full sets of stainless steel brackets of 20 brackets each (weight 2.1 g) and 2 groups of 0.018 x 0.025 Ni-Ti archwires of 10 wires each (weight 2.0 g) were immersed in 0.9% saline solution for a month. The immersion media were analyzed with inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and the ionic content was statistically analyzed with 1-way analysis of variance (ANOVA). Human periodontal ligament fibroblasts and gingival fibroblasts were exposed to various concentrations of the 2 immersion media; nickel chloride was used as a positive control for comparison purposes. The cytotoxic or cytostatic activity of the media was investigated with the MTT and the DNA synthesis assays. The results of the cytotoxicity assay were analyzed with 2-way ANOVA and the Tukey test with solution and concentration variants as discriminating variables (alpha=0.05). The results indicated no ionic release for the nickel-titanium alloy aging solution, whereas measurable nickel and traces of chromium were found in the stainless steel bracket-aging medium. Concentrations of the nickel chloride solution greater then 2 mM were found to reduce by more than 50% the viability and DNA synthesis of fibroblasts; however, neither orthodontic materials-derived media had any effect on the survival and DNA synthesis of either cells.     

Effects of chemical composition on the corrosion of dental alloys

The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.     

氟对镍钛弓丝的腐蚀性研究

目的研究氟对镍钛弓丝的腐蚀性。方法配制人工唾液和三种氟离子浓度（0．05％、0．10％、0．15％）的氟化人工唾液，选择四种镍钛弓丝，剪取末端直段，随机分为四组（0．05％组、0．10％组、0．15％和对照组），分别保存于人工唾液中。取出上述样本分别浸入相应浓度的氟化人工唾液，3min后取出。清洗后放回原人工唾液中，每天早、中、晚共三次，对照组不做浸入处理。28d后取出样本观察表面微观结构。结果氟化物导致样本的微观结构出现腐蚀表现，但不同品牌样本表现不完全相同。结论少量氟化物的存在就会加速镍钛弓丝的腐蚀，但这种加速作用还受到弓丝生产工艺的影响。     

Metal release from simulated fixed orthodontic appliances.

Most orthodontic appliances and archwires are stainless steel or nickel-titanium (NiTi) alloys that can release metal ions, with saliva as the medium. To measure metal released from the fixed orthodontic appliances currently in use, we fabricated simulated fixed orthodontic appliances that corresponded to half of the maxillary arch and soaked them in 50 mL of artificial saliva (pH 6.75 +/- 0.15, 37 degrees C) for 3 months. We used brackets, tubes, and bands made by Tomy (Tokyo, Japan). Four groups were established according to the appliance manufacturer and the type of metal in the .016 x .022-in archwires. Groups A and B were stainless steel archwires from Ormco (Glendora, Calif) and Dentaurum (Ispringen, Germany), respectively, and groups C and D were both NiTi archwires with Ormco's copper NiTi and Tomy's Bioforce sentalloy, respectively. Stainless steel archwires were heat treated in an electric furnace at 500 degrees C for 1 minute and quenched in water. We measured the amount of metal released from each group by immersion time. Our conclusions were as follows: (1) there was no increase in the amount of chromium released after 4 weeks in group A, 2 weeks in group B, 3 weeks in group C, and 8 weeks in group D; (2) there was no increase in the amount of nickel released after 2 weeks in group A, 3 days in group B, 7 days in group C, and 3 weeks in group D; and (3) there was no increase in the amount of iron released after 2 weeks in group A, 3 days in group B, and 1 day in groups C and D. In our 3-month-long investigation, we saw a decrease in metal released as immersion time increased.