九种镍钛矫正弓丝相变温度的对比研究

目的 确定临床常用的9种镍钛矫正弓丝的马氏体相、奥氏体相、R相温度以及相变温度范围,为镍钛矫正弓丝的力学性能研究提供依据.方法 采用差热扫描(differential scanning calorimetry,DSC)技术,确定9种临床常用镍钛矫正弓丝(A组:Smart SE圆丝;B组:Kleen PakRTM圆丝;C组:中国镍钛牙弓丝圆丝;D组:Nitinol heat-activated圆丝;E组:Smart SE方丝;F组:Damon CuNiTi方丝;G组:L&H Titan方丝;H组:中国镍钛牙弓丝Ⅰ方丝;Ⅰ组:中国镍钛牙弓丝Ⅱ方丝;每组3根弓丝)的相变过程和相变温度.结果 A、B、D组镍钛矫正弓丝的奥氏体相结束温度(austenite finish,Af)分别为22.4℃、21.9℃、22.5℃,低于25℃,在口腔温度下不能再发生相变,没有形状记忆性能;C、H组镍钛矫正弓丝在DSC仪扫描范围内未发现相变状态.E、G、I组镍钛矫正弓丝在室温下为马氏体相和奥氏体相的混合体,Af分别为34.3℃、36.6℃、38.5℃,与口腔温度接近,具有形状记忆性能.F组镍钛矫正弓丝Af为61.5℃,远高于口腔温度,在口腔环境中也为马氏体相和奥氏体相的混合体,在口腔温度较高的情况下才能完全转变为奥氏体相,具有形状记忆功能.结论 临床常用的9种镍钛矫正弓丝的相变温度和相变过程各不相同,并非所有弓丝均具有形状记忆性能,所以应根据临床治疗目的选用不同的弓丝.

Differential scanning calorimetry analyses of phase transformations in different nickel-titanium orthodontic wires

Objective To characterize austenite,martensite and R phase temperatures as well as transition temperature ranges of the commonly used nickel-titanium(NiTi)orthodontic arch wires selected from several manufacturers.Methods Differential scanning calorimetry(DSC) method was used to study the phase transformation temperatures and the phase transition processes of 9 commonly used NiTi alloys (types:0.406 mm,0.406 mm×0.559 mm).Results The austenite finish temperatures of A,B,D NiTi wires were 22.4℃.21.9℃,22.5℃,respectively.No phase transformation was detected during oral temperature.It indicated that these types of NiTi wires did not possess shape memory property.For C and H NiTi wires,no phase transformation was detected during the scanning temperature range,suggesting that these two types of wires did not possess shape memory either.The austenite finish temperatures of E,G and I NiTi wires were 34.3℃,36.6℃,38.5℃,respectively,which were close to the oral temperature and presented as martensitic-anstenitic structures at room temperature,suggesting that the NiTi wires listed above had good shape memory effect.Although F NiTi wire also showed martensitic-austenitic structures at room temperature.its austenite finish temperature(61.5℃)was much higher than oral temperature.Conclusions The transformation phase temperatures and transformation behavior were varied among different NiTi alloys,leading to variability in shape memory effect.