fa The effect of temperature on the mechanical behavior of nickel-titanium orthodontic initial archwires ارتودنسی Orthodontics پژوهشي Research <p> <strong>Objectives:</strong>   </p><p> 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.</p><p> <strong> Materials and Methods:</strong>   </p><p> 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 55°C and 5°C, 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. </p><p> <strong>Results:</strong>   </p><p> Permanent strain was exhibited by all wires tested at 55°C. Statistically significant differences were found between almost all wires for the three considered parameters when tested at 55°C and 5°C. Loads were greater at 55°C than at 5°C. Differences were also found between traditional and heat-activated archwires, the latter of which generated longer plateaus at 55°C, shorter plateaus at 5°C, and lighter mean forces at both temperatures. The increase in average force seen with increasing diameter tended to be rather stable at both temperatures. <strong></strong></p><p> <strong>Conclusions:</strong>   </p><p> 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. </p><hr><p></p><p> <strong>Source: </strong>The Angel Orthodontists</p><p><a href="http://www.angle.org/doi/abs/10.2319/040612-287.1" target="_blank"><font color="#0000ff"> Full Text</font></a></p> NiTi archwire, Load deflection characteristics, Mechanical behavior 0 0 http://idai.ir/browse.php?a_code=A-10-32-1947&slc_lang=fa&sid=1 Luca Lombardo lulombardo@tiscali.it 10031947532846009139 10031947532846009139 Yes Department of Orthodontics, University of Ferrara, Ferrara, Italy Giorgia Toni 10031947532846009140 10031947532846009140 No Department of Orthodontics, University of Ferrara, Ferrara, Italy Filippo Stefanoni 10031947532846009141 10031947532846009141 No Department of Engineering, University of Ferrara, Ferrara, Italy Francesco Mollica 10031947532846009142 10031947532846009142 No Department of Engineering, University of Ferrara, Ferrara, Italy Maria Paola Guarneri 10031947532846009143 10031947532846009143 No Department of Orthodontics, University of Ferrara, Ferrara, Italy Giuseppe Siciliani 10031947532846009144 10031947532846009144 No Department of Orthodontics, University of Ferrara, Ferrara, Italy