de Oliveira Abrahão Janaína, Hermont Cançado Rodrigo, de Campos França Esdras, de Arruda Santos Leandro, Damas Resende Pedro, Weidenbach Degrazia Felipe, Santos Neves Leniana
Department of Restorative Dentistry (ODR), Division of Orthodontics, Faculty of Dentistry, Federal University of Minas Gerais, Av. Pres. Antônio Carlos 6627, 31270-901, Belo Horizonte, Pampulha, MG, Brazil.
Department of Metallurgical and Materials Engineering, School of Engineering, Federal University of Minas Gerais, Belo Horizonte, Brazil.
J Orofac Orthop. 2024 Aug 27. doi: 10.1007/s00056-024-00547-w.
The aim of this study was to evaluate the extent of property changes caused by heating the distal portion of heat-activated nickel-titanium (NiTi) wires.
Forty preformed heat-activated NiTi archwires (3M Unitek, Monrovia, CA, USA) with a nominal cross-section of 0.018″ were used in this study. The archwires were divided into a control group, not submitted to heat treatment and, thus, maintaining the as-received properties, and an experimental group, in which the archwires were submitted to heat treatment for distal bending at one end. Wire segments of control and experimental groups were submitted to differential scanning calorimetry (DSC) and Vickers microhardness measurements.
The DSC results suggest local recrystallization and precipitate dissolution at the heat-treated tip, which decreases as the distance to the wire's tip increases. Vickers microhardness tests revealed significant changes for distances between 6 and 8 mm from the wire's tip. Heating the distal portion of heat-activated NiTi archwires should be performed with care since this clinical procedure may compromise the performance of these wires to a distance of 8 mm from the archwire end.
Heat treatment for distal bending in heat-activated NiTi archwires may be performed, with little impact on the areas adjacent to heat treatment. In cases presenting molars requiring significant orthodontic corrections, it should be preferred to apply other techniques to avoid archwire sliding, such as crimpable stops, or to have flame control to avoid placing a heat-treated section in the tubes of these molars.
本研究的目的是评估加热热激活镍钛（NiTi）丝的远端部分所引起的性能变化程度。
本研究使用了40根预制的热激活NiTi弓丝（3M Unitek，美国加利福尼亚州蒙罗维亚），标称横截面为0.018英寸。弓丝分为对照组，不进行热处理，因此保持其接收时的性能，以及实验组，其中弓丝在一端进行远端弯曲的热处理。对照组和实验组的丝段进行差示扫描量热法（DSC）和维氏显微硬度测量。
DSC结果表明，热处理尖端处发生局部再结晶和析出物溶解，随着与丝尖端距离的增加而降低。维氏显微硬度测试显示，在距丝尖端6至8毫米的距离处有显著变化。加热热激活NiTi弓丝的远端部分时应谨慎操作，因为这种临床操作可能会使这些丝在距弓丝末端8毫米的距离内性能受损。
热激活NiTi弓丝的远端弯曲热处理可以进行，对邻近热处理的区域影响很小。在存在需要进行重大正畸矫正的磨牙的情况下，应优先应用其他技术来避免弓丝滑动，如可卷曲阻挡器，或控制火焰以避免在这些磨牙的管中放置热处理段。
