Orthodontics
Nausheen Eram; SM Laxmikanth; Raghunandan Chunduri; Sameena Begum; Khadeer Riyaz; Ashita Talwar
Abstract
Aim: Metallic corrosion of orthodontic appliances occurs due to potentially damaging physical and chemical agents. The major corrosion products of stainless steel are iron, chromium, and nickel. When tissues are exposed to certain concentrations of a primary irritant for certain periods, cytotoxic effects ...
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Aim: Metallic corrosion of orthodontic appliances occurs due to potentially damaging physical and chemical agents. The major corrosion products of stainless steel are iron, chromium, and nickel. When tissues are exposed to certain concentrations of a primary irritant for certain periods, cytotoxic effects may be observed. Hence, this study aimed to assess the cytotoxicity of nickel, iron, and chromium ions during fixed orthodontic treatment onto human keratinocytes (HaCaT).Methods: The metal ions nickel, chromium, and iron in concentrations of 75, 150, 300, 600, 1200, and 2400 μg/ml were prepared to assess the cytotoxicity on HaCaT cells. The control group included these metal ions at 0 μg/ml. Cytotoxicity was assessed by microculture tetrazolium (MTA) assay. The half maximal inhibitory concentration (IC50) was measured and a scanning electron microscope (SEM) was used to assess the morphological changes of the HaCaT cells. The Kruskal-Wallis test followed by the Bonferroni’s post hoc test was carried out to determine the difference in percentage inhibition within and between the groups at various concentrations.Results: Nickel showed the highest cytotoxic effects in comparison with other metal ions. Iron hexahydrate, nickel hexahydrate, and chromium hexahydrate have shown an IC50 value of 552.4 μg/ml, 364.1 μg/ml, and 641.1 μg/ml inhibition in HaCaT cells respectively. Cytotoxic effects were dose dependent on the tested materials. Comparison of percentage inhibition between groups showed a p-value of 0.372.Conclusion: The present study showed that the nickel, chromium, and iron ions induced a wide range of toxicity to human keratinocytes. The IC50 values ranged between 364.1 and 641.1. Nickel was the most toxic metal tested between the concentrations of 75 to 2400 μg/ml for HaCaT cells compared to other metal ions used in the study.
Mohammad Husain Ahangar Atashi; Saber Seyyed Goganie
Abstract
Aim: corrosion of NiTi wires in the oral cavity has been a matter of discussion in some in-vitro studies but in-vivo tests about corrosion of NiTi wires have been rarely investigated. We designed an in-vivo study to evaluate corrosion behavior of retrieved NiTi wires compared with as-received wires. Methods: ...
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Aim: corrosion of NiTi wires in the oral cavity has been a matter of discussion in some in-vitro studies but in-vivo tests about corrosion of NiTi wires have been rarely investigated. We designed an in-vivo study to evaluate corrosion behavior of retrieved NiTi wires compared with as-received wires. Methods: Considering our criteria, 15 participants demanding orthodontic treatment entered the study, two NiTi SE(G&H) wires were inserted in bracket slots and band tubes and two passively in auxiliary tubes of molars. After 2 months wires were retrieved and were evaluated regarding clinical conditions (tarnish, deformation). Then potentiodynamic test performed on distal segment of 60 retrieved wires and Rp test (polarization resistance test) for all specimens including retrieved and as-received wires. Non parametric tests were used to compare retrieved and as-received wire groups.Results: Retrieved wires showed clinically and electrochemically significant corrosion compared with as-received wires (p<0.05). All retrieved wires showed signs of tarnish which was more in lower arch. Among all retrieved wires, 5 wires showed deformation, 3 from lower arch and 2 from upper arches. One of recent two wires belonged to not-engaged group.Conclusion: Despite of adequate corrosion resistance, NiTi wires, engaged or not engaged will corrode electrochemicallyin oral enviroment and should be noticed in clinical use.
Mohsen Shirazi; E. Fakheri; Abdollah Afshar; M. Rahman
Abstract
There are few studies on the electrochemical corrosion behavior of Nitinol at various pH and temperature. Considering the pH of mouth can alter at a wide range, the present study investigated the effects of various pH and temperature of artificial saliva on the electrochemical stability of commercial ...
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There are few studies on the electrochemical corrosion behavior of Nitinol at various pH and temperature. Considering the pH of mouth can alter at a wide range, the present study investigated the effects of various pH and temperature of artificial saliva on the electrochemical stability of commercial equiatomic Ni-Ti orthodontic wire. In this manner, cyclic polarization tests were performed at different temperatures and pH. Surface conditions of wires were evaluated with Scanning-Electron Microscopy. Decreasing of pH to the acidic pHs and increasing of temperature in these pHs cause to increasing of Igor, and C.R. and decreasing of E, and Epit. The SEM micrographs indicate that the surface of sample become smoother after cyclic potentiodynamic tests. In fact, cyclic potentiodynamic tests cause to a general corrosion on the surface of sample. Corrosion behaviour of NiTi completely relies on the characteristics of its passive layer. Decreasing of pH causes to partly dissolution of the passive layer of NiTi in the acidic pHs. Influence of temperature on the corrosion behaviour of NiTi, related to the pH of solution. It appears that pitting critical temperature of NiTi in the artificial saliva is higher than 42 ̊C.
