The mechanical behavior of as received and retrieved nickel titanium orthodontic archwires

Abstract

ObjectivesThe aim of this study is to investigate and compare the characteristics of as received and retrieved NiTi archwires at a constant temperature by plotting their load/deflection graphs and quantifying three parameters describing the discharge plateau phase.Materials and methodsTwo hundred four NiTi archwires, traditional and heat-activated, of various cross sections, were obtained from 5 different manufacturers. Specimens prepared from the selected wires were subjected to a three-point bending test where 92 were retrieved through an in vivo retrieval protocol (crowding group C1 and group C2), 56 went through an in vitro retrieval protocol, and 56 were as received. The in vitro retrieval protocol was performed by a gear motor connected to a stainless steel support that performed fatigue cycles to the bent wires in artificial saliva. The load/deflection graphs of as received and retrieved wires were described through three parameters and the results were analyzed with classification and regression trees (CART) and analysis of variance (ANOVA).ResultsStatistically significant differences between as received and retrieved wires were found only for the parameter plateau slope which represents the constancy of force expressed by the wire.ConclusionsThe aging of NiTi archwires influences the force constancy expressed. The behavior of the wires changes depending on the size, brand, and type of retrieval protocol. In terms of performance, the poorest is represented by all wires retrieved in vitro and in vivo group C2 (moderate to severe crowding).

Salt Heat Treatment and Passivation to Improve the Corrosion Resistance of Nitinol (Ni-Ti)

“…Nitinol (NiTi) is a metallic alloy of nickel (Ni) and titanium (Ti) in which the two elements are present in approximately equal atomic ratios. Due to the special properties of shape memory effect and superelasticity of Ni, it is widely used in various implantable materials, such as catheters, needles, staples, stents, dental wires, and orthopedic implants, and endodontic instruments [1][2][3][4][5][6]. However, NiTi alloys are more susceptible to corrosion due to ion release than stainless steel, cobalt-chromium or β-titanium.…”

Mechanical properties and clinical performance of different brands of nickel titanium archwires following intraoral use

“…Sample size calculation was performed using G*Power Version 3.1.9.2 (3). Based on the results of (2); 12 subjects per group were considered sufficient to achieve a power of a study 80 % and alpha (α) level of (5%). Sample size was increased to 13 subjects per group to compensate for a drop-out rate of 10% after 8 weeks.…”

“…However, the different commercially available superelastic NiTi wires may possess different properties depending on their manufacturing process (1). Furthermore, the mechanical properties of archwires are directly affected by oral environmental factors such as extreme pH and temperature variations, complex oral flora, and salivary enzymes (2). These factors may impact the amount of force delivered by the archwire over time.…”

A Critical Appraisal of the Use and Properties of Nickel–Titanium Dental Alloys

“…In the focused tribological literature in dental applications, friction tests with great and with small (µm) displacement were found [74], in which fretting, i.e., small oscillating displacement, experiments were more related to the clinical environment [74]. Common mechanical tests in orthodontics practice are three-point bending with a distance deflected of 2-3 mm [77,79,80] and pulling tests with a wire-bracket-ligature connection [77]. These are simplified tests that mimic the application of orthodontic archwire.…”