两种镍钛系统根管预备后发生牙根微裂的体外研究

目的：比较HyFlex CM和ProTaper Universal两种镍钛器械预备根管后，根尖区牙根微裂的发生率。方法：收集60颗完整的离体下颌切牙，使用自凝树脂和藻酸盐印模材料进行包埋，暴露根尖区3 mm。随机分成3组（n=20），对照组不进行根管预备，两个实验组分别使用HyFlex CM和ProTaper Universal镍钛器械预备根管至#40/0.06。根管预备后，在距根尖孔1 mm、2 mm、3 mm处进行水平切盘，利用立体显微镜观察并记录牙根不同横截面牙根微裂的产生情况。结果：对照组未观察到牙根裂的产生，HyFlex CM实验组牙根微裂的发生率为5%（1/20），ProTaper Universal实验组为85%（17/20），两实验组间牙根裂发生率的差异有统计学意义（P<0.01）。结论：以HyFlex CM镍钛系统进行根管预备产生根尖部牙根微裂的风险明显低于ProTaper Universal。

Comparison of the incidences of apical root cracks after canal preparation with two nickel-titanium rotary systems:an in vitro study

Objective: To compare the incidences of root cracks after canal instrumentation with HyFlex CM system and the ProTaper Universal system .Methods:Sixty mandibular incisors were mounted in resin blocks with simulated periodontal ligaments , and the apex was exposed .The control group of 20 teeth was not prepared , and the other 40 teeth were divided into 2 experimental groups ( n=20 ) .The 40 root canals of the experimental groups were instrumented using HyFlex CM and ProTaper Universal to the major apical foramen ( AF).The horizontal sections 1 mm, 2 mm, and 3 mm from the apex were observed under an optical stereomicroscope at 25 ×magnification .The presence of cracks was noted . Results:No cracks were found in the control teeth .Cracks were found in 1 of 20 ( 5%) teeth in HyFlex CM group , and 17 of 20 ( 85%) teeth in ProTaper Universal group .The difference between the two experimental groups was statistically significant (P<0.01).Conclusion: The HyFlex CM files caused fewer root cracks than the ProTaper Universal files during the root canal instrumentation .