Kottoor Jojo, Velmurugan Natanasabapathy, Gopikrishna Velayutham, Krithikadatta Jogikalmat
Department of Conservative Dentistry and Endodontics, Mar Baselios Dental College, Kothamangalam, Ernakulam, Kerala, India.
Indian J Dent Res. 2013 Jan-Feb;24(1):42-7. doi: 10.4103/0970-9290.114942.
The purpose of this study was to evaluate the effect of multiple root canal usage on the surface topography and fracture of Twisted File (TF) and ProTaper (PT) rotary Ni-Ti file systems, using scanning electron microscope (SEM).
Ten sets of PT and TF instruments were used to prepare the mesial canals of mandibular first molars. TF 25, 0.06 taper and PT F1 instruments were analyzed by SEM when new and thereafter every three root canal usages. This sequence was repeated for both the TF and PT groups until 12 uses. Two images of the instrument were recorded, one of the instrument tip and the other 5 mm from the tip, both at × 100 magnification. The sequential use was continued till the instrument fractured and the number of root canal usages for the file to fracture was noted. All fracture surfaces were examined under the SEM.
Fresh TF instruments showed no surface wear when compared to PT instruments (P < 0.05). Spiral distortion scores remained the same for both the groups till the 6 th usage (P > 0.05), while at the 9 th usage TF showed a steep increase in the spiral distortion score when compared to PT (P < 0.05). PT instruments fractured at a mean root canal usage of 17.4, while TF instruments showed a mean root canal usage of 11.8. Fractographically, all the TF instruments failed due to torsion, while all the PT instruments failed because of cyclic fatigue.
PT instruments showed more resistance to fracture than TF instruments.
本研究旨在使用扫描电子显微镜（SEM）评估多根管使用对Twisted File（TF）和ProTaper（PT）旋转镍钛锉系统的表面形貌和折断情况的影响。
使用十套PT和TF器械预备下颌第一磨牙的近中根管。TF 25、0.06锥度的器械以及PT F1器械在新用时和此后每使用三次根管后通过SEM进行分析。TF组和PT组均重复此顺序直至使用12次。记录器械的两张图像，一张是器械尖端的图像，另一张是距尖端5 mm处的图像，均为×100放大倍数。继续按顺序使用直至器械折断，并记录锉折断时的根管使用次数。所有折断表面均在SEM下检查。
与PT器械相比，新的TF器械未显示表面磨损（P < 0.05）。两组的螺旋扭曲评分在第6次使用前均保持不变（P > 0.05），而在第9次使用时，与PT相比，TF的螺旋扭曲评分急剧增加（P < 0.05）。PT器械折断时的平均根管使用次数为17.4次，而TF器械的平均根管使用次数为11.8次。从断口分析来看，所有TF器械均因扭转而折断，而所有PT器械均因循环疲劳而折断。
PT器械比TF器械表现出更强的抗折断能力。
