Abstract: Objective　To compare the shaping ability of four different Ni-Ti rotary instruments in preparing the simulated resin curved root canals. Methods    Forty simulated resin blocks with curved root canals were randomly divided into four groups（n = 10）：ProTaper Universal group，iRaCe group，Reciproc Blue group and HyFlex EDM group. Root canals were prepared by the 4 instruments. The preparation time was recorded. Images of pre- and post-instrumentation photograghs were taken by precise camera and superimposed through Adobe Photoshop CS5. The amount of resin removed from the inner and outer walls at 10 levels were measured with Image Pro Plus6.0. The data were analyzed statistically by SPSS 17.0. Results    The preparation time of iRaCe group was the shortest and the preparation efficiency was the highest  （P < 0.05）. In the apical area，iRaCe turned out to have the best centering ability；at the curved part，iRaCe and HyFlex EDM both showed a higher centering ability than ProTaper Universal and Reciproc Blue；at the straight part，iRaCe，Reciproc Blue and HyFlex EDM showed a significantly higher centering ability than ProTaper Universal（P < 0.05）. Conclusion    The four nickel-titanium instruments can maintain the original root canal well without obvious canal transportation and ledging. iRaCe，Reciproc Blue and HyFlex EDM are more outstanding than ProTaper Universal in the shaping ability of curved canals.

Key words: nickel-titanium instruments, root canal preparation, shaping ability, apical transportation

摘要： 目的    比较4种不同机用镍钛器械预备树脂模拟弯曲根管的成形能力，为临床应用提供实验依据。方法    将40个单弯树脂模拟根管随机分为4组，每组10个，分别为ProTaper Universal组、iRaCe组、Reciproc Blue组和HyFlex EDM组，采用4种不同机用镍钛器械进行根管预备，并记录各组预备时间。使用单反相机采集各组预备前后根管的形态照片，采用Adobe Photoshop CS5软件进行图像重叠，使用Image Pro Plus6.0软件测量10个观测点的根管内、外侧壁树脂去除量并计算器械的中心定位能力，采用SPSS 17.0软件对数据进行统计学分析。结果    iRaCe组预备时间最短，预备效率最高（P < 0.05）。在根尖区，iRaCe组的中心定位能力最好；在弯曲点附近，iRaCe组和HyFlex EDM组的中心定位能力较好，相对优于ProTaper Universal组和Reciproc Blue组；在弯曲点冠方，iRaCe组、Reciproc Blue组、HyFlex EDM组的中心定位能力均显著优于ProTaper Universal组（P < 0.05）。结论　4种机用镍钛器械均可较好地保持原始根管的走向，无明显的偏移及台阶等出现。与ProTaper Universal相比，iRaCe、Reciproc Blue和HyFlex EDM镍钛器械对弯曲根管表现出更加出色的成形能力，更适合用于弯曲根管的预备。

关键词: 镍钛器械, 根管预备, 成形能力, 根尖偏移