Assessing the fatigue resistance of NiTi instruments: A DSC-based approach to understanding temperature effects

IF 7.1 1区医学 Q1 DENTISTRY, ORAL SURGERY & MEDICINE

International endodontic journal Pub Date : 2025-05-23 DOI:10.1111/iej.14257

Emmanuel J. N. L. Silva, Jorge N. R. Martins, Murilo Priori Alcalde, Marco A. Versiani

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引用次数: 0

Abstract

Aim

This study aims to demonstrate that phase transformation analysis, assessed via differential scanning calorimetry (DSC), offers a more comprehensive understanding of NiTi instruments' mechanical behaviour than traditional fixed-temperature fatigue testing by evaluating phase transformation temperatures and their impact on cyclic fatigue strength of ProTaper Universal and ProTaper Gold at 20 and 35°C.

Methodology

Fifty ProTaper Universal F2 (n = 25) and ProTaper Gold F2 (n = 25) NiTi instruments were compared for geometric design (blade length, helical spirals, spiral density, spiral geometry, tip design and surface quality) and metallurgical properties including elemental analysis (energy-dispersive X-ray spectroscopy) and phase transformation temperatures. Then, cyclic fatigue strength was tested at room (20 ± 1°C) and body (35 ± 1°C) temperatures using a standardized artificial canal and cyclic fatigue resistance test. Time to fracture (in seconds) was recorded, and data were statistically analysed using the independent Student's t-test for intergroup analysis and the paired Student's t-test for intragroup analysis (α = 5%).

Results

Both instruments had a 17 mm blade with 10 spirals (0.59 spirals/mm), similar geometry and NiTi wires with near-equiatomic nickel-titanium ratios, differing only in metal alloy colour. DSC analysis showed distinct phase transformation temperatures, with ProTaper Universal exhibiting an R-phase start (Rs) at 16.2°C and finish (Rf) at −12.7°C, while ProTaper Gold had an Rs at 44.0°C and Rf at 28.6°C, though both transitions occurred gradually. Fracture time was significantly longer at 20°C than at 35°C for both instruments (p < 0.05), with ProTaper Gold showing a greater reduction (58%) but maintaining superior cyclic fatigue strength at both temperatures (p < 0.05).

Conclusion

The cyclic fatigue strength of NiTi instruments depends on temperature, highlighting the limits of assessing performance at a single predefined temperature. DSC offers key insights into phase transformation, enabling a better interpretation of mechanical properties beyond mechanical testing alone. Integrating metallurgical characterization with cyclic fatigue analysis improves the evaluation of NiTi instruments, ensuring a more accurate understanding of their mechanical performance.

Abstract Image

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评估NiTi仪器的抗疲劳性：一种基于dsc的方法来理解温度效应。

目的：本研究旨在通过差示扫描量热法（DSC）评估相变分析，通过评估相变温度及其在20°C和35°C下对ProTaper Universal和ProTaper Gold的循环疲劳强度的影响，可以比传统的固定温度疲劳测试更全面地了解NiTi仪器的机械行为。方法：比较50台ProTaper Universal F2 （n = 25）和ProTaper Gold F2 (n = 25) NiTi仪器的几何设计（叶片长度、螺旋、螺旋密度、螺旋几何、尖端设计和表面质量）和冶金性能（包括元素分析（能量色散x射线光谱）和相变温度）。然后，采用标准化人工管进行室内（20±1°C）和身体（35±1°C）温度下的循环疲劳强度测试和循环疲劳抗力测试。记录骨折时间（以秒为单位），组间分析采用独立的Student’st检验，组内分析采用配对的Student’st检验（α = 5%）。结果：两种仪器的刀片均为17 mm，有10个螺旋（0.59螺旋/mm），几何形状相似，镍钛丝的镍钛比接近等原子，仅金属合金颜色不同。DSC分析显示了不同的相变温度，ProTaper Universal在16.2°C时表现为r相开始（Rs），在-12.7°C时表现为r相结束（Rf），而ProTaper Gold在44.0°C时表现为r相，在28.6°C时表现为Rf，尽管这两种相变都是逐渐发生的。两种仪器在20°C时的断裂时间明显长于35°C时的断裂时间(p结论：NiTi仪器的循环疲劳强度取决于温度，突出了在单一预定义温度下评估性能的局限性。DSC提供了相变的关键见解，能够更好地解释机械性能，而不仅仅是机械测试。将冶金特性与循环疲劳分析相结合可以提高对NiTi仪器的评估，确保更准确地了解其机械性能。

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来源期刊

International endodontic journal 医学-牙科与口腔外科

CiteScore

10.20

自引率

28.00%

发文量

195

审稿时长

4-8 weeks

期刊介绍： The International Endodontic Journal is published monthly and strives to publish original articles of the highest quality to disseminate scientific and clinical knowledge; all manuscripts are subjected to peer review. Original scientific articles are published in the areas of biomedical science, applied materials science, bioengineering, epidemiology and social science relevant to endodontic disease and its management, and to the restoration of root-treated teeth. In addition, review articles, reports of clinical cases, book reviews, summaries and abstracts of scientific meetings and news items are accepted. The International Endodontic Journal is essential reading for general dental practitioners, specialist endodontists, research, scientists and dental teachers.