目的:本研究评估了相组成,相变行为,五种热处理NiTi仪器的力学性能。
方法:ProTaperNEXT(M线,PTN),ProTaperGold(Gold-wire,PTG),一条曲线(C线,OC),EdgeTaper铂金(火线,ETP),NeoNiTi(电火花加工线,NNA),和ProTaperUniversal(常规电线,PTU,对照)与#25尖端尺寸测试(n=12/组)的循环疲劳抗性(失效循环数;NCF)和扭转抗性(断裂旋转角和断裂时的最大扭矩[极限扭转强度])。通过扫描电子显微镜检查了被测仪器的几何形状和断裂表面。使用差示扫描量热法和X射线衍射评估仪器的相变温度和相组成。数据采用单向方差分析和Tukey的事后检验进行统计分析,显著性水平设置为5%。
结果:PTG在37°C时显示出最高的NCF(P<0.05),而ETP表现出最高的骨折旋转角度,极限扭转强度,和刚度(P<0.05)。扫描电子显微镜显示了典型的疲劳条纹簇和循环疲劳断裂后的许多裂纹,而扭转断裂后,中心有一个凹陷和微孔的同心磨损模式。在差示扫描量热曲线中,热处理仪器的奥氏体精加工温度高于37°C,而PTU的温度低于37°C。PTU在25和37°C时显示出奥氏体的强峰,而ETP在25°C时显示出R相的强峰,但在X射线衍射中主要是37°C的奥氏体相。
结论:几何,合金类型,NiTi仪器的相变温度影响其机械性能。
结论:PTG显示出最高的NCF,适合明显弯曲的运河。ETP具有最高的扭转阻力,适合狭窄和收缩的运河。
OBJECTIVE: This study evaluated the phase composition, phase transformation behaviour, and mechanical properties of five heat-treated NiTi instruments.
METHODS: ProTaper NEXT (M-wire, PTN), ProTaper Gold (Gold-wire, PTG), One Curve (C-wire, OC), EdgeTaper Platinum (Fire-wire, ETP), NeoNiTi (electrical discharge machining-wire, NNA), and ProTaper Universal (conventional wire, PTU, control) with #25-tip size were tested (n = 12/group) for cyclic fatigue resistance (number of cycles to failure; NCF) and torsional resistance (angle of rotation to fracture and maximum torque at fracture [ultimate torsional strength]). The geometry and fracture surfaces of the tested instruments were examined by scanning electron microscopy. The phase transformation temperature and phase composition of the instruments were evaluated using differential scanning calorimetry and X-ray diffraction. Data were statistically analysed using one-way ANOVA and Tukey\'s post hoc test, with the significance level set at 5%.
RESULTS: PTG showed the highest NCF (P < .05) at 37°C, while ETP exhibited the highest angle of rotation to fracture, ultimate torsional strength, and stiffness (P < .05). Scanning electron microscopy demonstrated typical clusters of fatigue striations and numerous cracks after cyclic fatigue fracture, whereas there was a concentric abrasion pattern with a dimple and microvoids at the centre after torsional fracture. In differential scanning calorimetry curves, austenite-finishing temperatures of heat-treated instruments were higher than 37°C, whereas that of PTU was lower than 37°C. PTU showed strong peaks of austenite at 25 and 37°C, whereas ETP showed a strong peak of R-phase at 25°C, but mostly austenite phase at 37°C in X-ray diffraction.
CONCLUSIONS: Geometry, alloy type, and phase transformation temperatures of NiTi instruments affected their mechanical behaviour.
CONCLUSIONS: PTG showed the highest NCF, suitable for markedly curved canals. ETP had the highest torsional resistance, appropriate for narrow and constricted canals.