Mojgan Kachoie; Baharak Divband; Masoumeh khatamian; Azin Nourian
Abstract
Introduction: NiTi wires which are considered the ideal alloys used during the alignment and leveling stage of comprehensive orthodontic treatment exhibit very high frictional resistance. Therefore, overcoming such resistance to sliding results in a rapid tooth movement and proper anchorage control. ...
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Introduction: NiTi wires which are considered the ideal alloys used during the alignment and leveling stage of comprehensive orthodontic treatment exhibit very high frictional resistance. Therefore, overcoming such resistance to sliding results in a rapid tooth movement and proper anchorage control. Recently, coating the wires with nanoparticles has been introduced to decrease resistance to sliding. The aim of this invitro study was to evaluate effect of ZnO nanoparticles on resistance to sliding of nickel titanium orthodontic wires. Materials and methods: 40 straight pieces of 0.016-inch NiTi wires were evaluated in two groups with and without spherical ZnO nanoparticle coating, along with 40 standard system 0.018 stainless steel brackets. ZnO nanoparticles were deposited on NiTi wires and analyzed by SEM. A universal testing machine was used to determine friction between the wires and brackets at an angle of 5°. Student’s t-test were used for data analysis. Results: The SEM results confirmed the homogeneous deposition of ZnO nanoparticles on NiTi wires. At 5º angle between the wires and brackets the means of frictional forces were 1.2475±0.13 and 1.5075±0.12 N with and without ZnO nanoparticle deposits on the wires, respectively, revealing a significant decrease of 17.24% in frictional forces in coated wires (P<0.001).Conclusion: Based on the results of this study, ZnO nanoparticle coating reduces the resistance to sliding of nickel titanium orthodontic wires.
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.
