The effect of temperature on the mechanical behavior of nickel-titanium orthodontic initial archwires

Abstract

Objectives: To investigate and compare the characteristics of commonly used types of traditional and heat-activated initial archwires at different temperatures by plotting their load/deflection graphs and quantifying three parameters describing the discharge plateau phase. Materials and Methods: Forty-eight archwires of cross-sectional diameters ranging from 0.010 inches to 0.016 inches were obtained from seven different manufacturers. A modified three-point wire-bending test was performed on three analogous samples of each type of archwire at 55uC and 5uC, simulating an inserted archwire that is subjected to cold or hot drinks during a meal. For each resulting load/deflection curve the plateau section was isolated and the mean value of each parameter for each type of wire was obtained. Results: Permanent strain was exhibited by all wires tested at 55uC. Statistically significant differences were found between almost all wires for the three considered parameters when tested at 55uC and 5uC. Loads were greater at 55uC than at 5uC. Differences were also found between traditional and heat-activated archwires, the latter of which generated longer plateaus at 55uC, shorter plateaus at 5uC, and lighter mean forces at both temperatures. The increase in average force seen with increasing diameter tended to be rather stable at both temperatures. Conclusions: All nickel-titanium wires tested showed a significant change related to temperature in terms of behavior and force for both traditional and heat-activated wires. Stress under high temperatures can induce permanent strain, whereas the residual strain detected at low temperatures can be recovered from as temperature increases. (Angle Orthod. 2013;83:298-305.)

Mechanical Performance of Nickel-titanium Archwires

“…Just a mild enhancement in mechanical properties was observed in the loading/deflection curves when compared with SE wires. This fact is in accordance with conclusions of Lombardo et al who observed lighter forces and longer plateau from HA wires 12 .…”

“…In this work (Table 3), permanent strain was irrelevant for all groups evaluated since all specimens showed a shape recovery to 99% of its original shape. Similar results were presented by Lombardo et.al even when 4-mm bending was performed at 55 °C [12] . The archwire resistance to attachment into bracket slots and intensity force delivery to teeth on unloading are mechanical factors that affect the tooth movement.…”

Stress relaxation properties of four orthodontic aligner materials: A 24-hour in vitro study

“…Super-elastic copper nickel titanium (CuNiTi) wires are even more predictable, exerting constant forces over a wide deflection range, meaning that the load remains the same even as the teeth begin to align. 9,10 Clear aligners, on the other hand, are viscoelastic, having intermediate properties between those of viscous and elastic materials. 11 This means that under loading their behavior may vary considerably over time, even when first inserted and before any tooth movement is achieved.…”

Effect of Thermocycling on Nickel Release from Orthodontic Arch Wires: an In Vitro Study

“…Atomic adsorption spectrometer analysis is an effective, dependable, and feasible method to evaluate the amount of ion released from orthodontic wires in aqueous solutions [27,33]. It has been reported that temperature changes influence the physical and chemical properties of dental materials and most orthodontic appliances [22,24,26]. Thus, the current study aimed to evaluate the effect of pH changes and thermocycling, as the two main factors that change many times during the day after each meal and drink, on the amount of Ni released from orthodontic appliances.…”

“…All these factors may lead to the release of toxic metal ions, such as Ni, from alloys [21]. Many authors have questioned the effect of temperature changes on orthodontic alloys [22][23][24]. Due to these thermal stresses, microstructural changes can take place, remarkably changing the physical properties of the dental material [24,25].…”