Adl Alireza, Shahravan Arash, Farshad Melika, Honar Shahab
Department of Endodontics, Biomaterials Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
Endodontology Research Center, Kerman University of Medical Sciences, Kerman, Iran.
Iran Endod J. 2017 Summer;12(3):349-353. doi: 10.22037/iej.v12i3.16866.
The aim of this study was to compare the success rate and time required for bypassing the fractured segments of four different nickel-titanium (NiTi) rotary systems.
This study was conducted on the mesiobuccal canals of 60 mandibular molars with fully-formed apices. Fifteen Flex Master, K3, RaCe and Hero Shaper instruments with 0.04 taper and tip size of #30 and 25 mm in length, were obtained. These instruments were notched at a point 3 mm from the tip of the instrument and were driven into the canals using a handpiece until the instruments fractured and became lodged therein. In the next step, an endodontist tried to bypass the fractured segment using K-files. The number of bypassed samples and the time required for bypassing of each sample were recorded. The -square test was used to compare the bypassing rate among the experimental groups. One-way analysis of variance followed by Tukey's post hoc test was conducted to compare the time taken for bypassing of the fractured fragments.
One instrument in Flex Master group and two broken segments in each of the K3 and Hero groups were not bypassed. All of the samples in RaCe group were bypassed. No significant difference was found among four tested groups regarding rate of bypassing (=0.738). The time taken to bypass fragments in the Hero group was significantly more than in those of K3 (=0.047) and RaCe (=0.024).
Under the limitations of this study, design features of rotary files can influence the time needed to bypass separated fragments.
本研究的目的是比较四种不同镍钛（NiTi）旋转系统绕过骨折段的成功率和所需时间。
本研究对60颗下颌磨牙的近中颊根管进行，这些磨牙根尖已完全形成。获得了15支Flex Master、K3、RaCe和Hero Shaper器械，锥度为0.04，尖端尺寸为#30，长度为25mm。这些器械在距尖端3mm处做切口，然后用手机将其插入根管，直到器械折断并卡在其中。下一步，一名牙髓病医生试图用K锉绕过折断段。记录绕过样本的数量和每个样本绕过所需的时间。采用卡方检验比较各实验组的绕过率。进行单因素方差分析，随后进行Tukey事后检验，以比较绕过骨折碎片所需的时间。
Flex Master组有1支器械、K3组和Hero组各有2个折断段未被绕过。RaCe组的所有样本均被绕过。在四个测试组之间，绕过率没有显著差异（=0.738）。Hero组绕过碎片所需的时间显著多于K3组（=0.047）和RaCe组（=0.024）。
在本研究的局限性下，旋转锉的设计特点会影响绕过分离碎片所需的时间。
