THE SUPERELASTIC PROPERTY EVALUTION OF NITI ORTHODONTIC WIRE THROUGH THREE POINT BENDING TEST USING SIMULATED ORAL CONDITION MODEL

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HAJFATHALIAN M.; NILI AHMADABADI MAHMOUD; HABIBI PARSA M.; SHAH HOSSEINI T.; GHADIRIAN H.; HOSSEINZADEH NIK T.

Title

THE SUPERELASTIC PROPERTY EVALUTION OF NITI ORTHODONTIC WIRE THROUGH THREE POINT BENDING TEST USING SIMULATED ORAL CONDITION MODEL

Author(s)

Keywords

NICKEL TITANIUM (NITINOL)Q3

ORTHODONTIC ARCHWIREQ3

SUPERELASTICITYQ3

THREE POINT BENDING TESTQ3

Abstract

Equi-atomic Nickel-Titanium (NiTi or Nitinol) has the ability to return to a former shape when subjected to an appropriate thermo-mechanical regime. Pseudoelastic and shape memory effects are some of the behaviors presented by these alloys. The unique properties concerning these alloys have encouraged many investigators to look for applications of NiTi for biomedical applications. One of the most successful applications of Nitinol is ORTHODONTIC ARCHWIRE. The best features of these wires are super-elasticity, the phenomena that causes easy engagement (loading conditions). Superelastic nitinol wires deliver clinically desired light continuous force during deactivation (unloading conditions), enabling effective tooth movement with minimal damage for periodontal tissues. SUPERELASTICITY is characterized by a load-deflection plot with a horizontal region [plateau] during unloading, implying that a constant force may be exerted over that particular range of tooth movement. It is known that the NiTi alloy wire undergoes a phase transformation from an austenitic to a martensitic phase as the load increases during the loading process. Metallurgical studies have attributed these characteristics to a reversible phase transformation from the body centered cubic structure to the monoclinic structure of nickel-titanium when the stress reaches a certain level during deformation.The increasing amount of energy stored inside the NiTi wire during this process is consumed during the unloading process as the transformation is reversed, and the martensite structure reverts to austenite. SUPERELASTICITY is only exhibited by wires showing high endothermic energy in the reverse transformation from the martensitic phase to the parent phase and with low Load/deflection ratios. These wires show nearly constant forces in the unloading process, a desirable physiological property for orthodontic tooth movement. NiTi archwires have gained acceptable by orthodontists as initial alignment wires. Most of the information about the behavior of orthodontic wires is based on mechanical laboratory THREE POINT BENDING TESTs to study load-deflection characteristics. A three-point bending test allowed load-deflection curves offer reproducibility. Variations in model design have been shown to affect load- deflection plots. The load deflection performance of NiTi wires depends on the design of the test model. Modified THREE POINT BENDING TEST which simulates wire force on the teeth in the oral conditions has more correct results than ordinary THREE POINT BENDING TEST. The purpose of this study is to investigate the load-deflection characteristics of superelastic nickel titanium wires with a new model design trough modified bending tests. In this research a new three point bending fixture was invented and designed to determine the superelastic property in clinical conditions, and the wire samples were held in the fixture similar to oral cavity. By means of this instrument the THREE POINT BENDING TEST simulates wire force on the teeth in the oral configuration. The lower section of fixture is a rail fabricated from steel, a special movable base with a curved canal assembled over the rail. The upper section designed to simulate the teeth arrangement and curvature: A stainless steel disk (316L, Ø80 mm, h10 mm) selected; and twelve rods (316L, Ø 5 mm, h10 mm) welded to the points representing center of teeth on the disk. The center points of teeth were located on the medium upper standard arc. Distance between the center points of teeth (interbracket distance) was similar to Wilkinson model.To achieve deflections 1, 2 and 4 mm, teeth 5,3 (right) and 2 (left) were selected respectively and rods in these points were movable. A fillet face machined on the rod surface parallel to the standard arc. Brackets fixed on the flat face of rod by superglue and orthodontic wire attached to fixed appliance. The superelastic behavior has been investigated through load-deflection tests. By rotating steel disk, different locations of teeth with different wire curvature were selected for loading. Commercial arch wires (Force I-American Orthodontics, Ø0.016 in) were loaded to 1, 3, 4 mm deflections. Each bending test was carried out three times. The results show that the constant force for commercial NiTi archwire (Force I) used in this study is more than 150 grams and minimum deflection required for superelastic property is more than 0.7 millimeters. In deflections lower than 0.7 millimeters, these archwires did not show plateau at unloading sequence, because martensitic transformation have not performed at low deflections. In these conditions (lower tooth deflections) the superelastic property is not available.

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APA: Copy

HAJFATHALIAN, M., NILI AHMADABADI, MAHMOUD, HABIBI PARSA, M., SHAH HOSSEINI, T., GHADIRIAN, H., & HOSSEINZADEH NIK, T.. (2008). THE SUPERELASTIC PROPERTY EVALUTION OF NITI ORTHODONTIC WIRE THROUGH THREE POINT BENDING TEST USING SIMULATED ORAL CONDITION MODEL. JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TEHRAN), 42(5 (115)), 631-637. SID. https://sid.ir/paper/14307/en

Vancouver: Copy

HAJFATHALIAN M., NILI AHMADABADI MAHMOUD, HABIBI PARSA M., SHAH HOSSEINI T., GHADIRIAN H., HOSSEINZADEH NIK T.. THE SUPERELASTIC PROPERTY EVALUTION OF NITI ORTHODONTIC WIRE THROUGH THREE POINT BENDING TEST USING SIMULATED ORAL CONDITION MODEL. JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TEHRAN)[Internet]. 2008;42(5 (115)):631-637. Available from: https://sid.ir/paper/14307/en

IEEE: Copy

M. HAJFATHALIAN, MAHMOUD NILI AHMADABADI, M. HABIBI PARSA, T. SHAH HOSSEINI, H. GHADIRIAN, and T. HOSSEINZADEH NIK, “THE SUPERELASTIC PROPERTY EVALUTION OF NITI ORTHODONTIC WIRE THROUGH THREE POINT BENDING TEST USING SIMULATED ORAL CONDITION MODEL,” JOURNAL OF FACULTY OF ENGINEERING (UNIVERSITY OF TEHRAN), vol. 42, no. 5 (115), pp. 631–637, 2008, [Online]. Available: https://sid.ir/paper/14307/en

Scientific Information Database

ISSN: 2588-4824

Journal Paper

THE SUPERELASTIC PROPERTY EVALUTION OF NITI ORTHODONTIC WIRE THROUGH THREE POINT BENDING TEST USING SIMULATED ORAL CONDITION MODEL