Song Y L, Bian Z, Fan B, Fan M W, Gutmann J L, Peng B
Department of Endodontics, School and Hospital of Stomatology, Wuhan University, Ministry of Education, Wuhan, China.
Int Endod J. 2004 Apr;37(4):265-71. doi: 10.1111/j.0143-2885.2004.00798.x.
To study and compare Great Taper (GT) hand files using a reversed balanced force technique, nickel-titanium (NiTi)flex files with a balanced force technique and stainless steel (SS) K-type files using a step-back technique.
Forty-eight extracted mandibular premolar teeth with single root canals having curvatures between 15 and 45 degrees were prepared using a modified Bramante model and randomly divided into three groups. The teeth were cross-sectioned at 2, 6 and 10 mm from the working length. Preoperative images of canals at three levels were captured at 20x magnification using a stereomicroscope. Canals in each group were, respectively, prepared to an apical size.10 GT file with 0.2 mm tip diameter, size 30 NiTiflex file and size 30 SS K-file. The GT file was used in a reversed balanced force technique, the NiTiflex file was used in a balanced force technique, and the SS K-file was used in a step-back technique. Postoperative canals were imaged under the conditions same as those for the preoperative canals. The postoperative images were superimposed over the preoperative images using software photoshop 6.0. The ability to maintain the instrument in the central axis of the canal and the deviation from the central canal axis were determined and compared by statistical analysis, along with the assessment of the amount of dentine removed.
At apical level, the centering ratio, the distance of transportation and the dentine removed in GT and NiTiflex groups were significantly less than those in SS group (P < 0.01), but no statistical differences were found between the two NiTi groups. At other levels, there were no substantial differences amongst the groups.
Compared with SS K-files, GT hand files and NiTiflex files remain better centered and produce significantly less transportation in curved canals.
使用反向平衡力技术研究和比较大锥度（GT）手动锉、使用平衡力技术的镍钛（NiTi）Flex锉以及使用逐步后退技术的不锈钢（SS）K型锉。
采用改良的布拉曼特模型制备48颗单根管、弯曲度在15至45度之间的拔除下颌前磨牙，随机分为三组。在距工作长度2、6和10毫米处对牙齿进行横截面切割。使用体视显微镜以20倍放大倍数拍摄三个水平根管的术前图像。每组根管分别预备至根尖尺寸：尖端直径为0.2毫米的10号GT锉、30号NiTiflex锉和30号SS K锉。GT锉采用反向平衡力技术，NiTiflex锉采用平衡力技术，SS K锉采用逐步后退技术。术后根管在与术前根管相同的条件下成像。使用Photoshop 6.0软件将术后图像叠加在术前图像上。通过统计分析确定并比较器械保持在根管中心轴的能力以及与根管中心轴的偏差，同时评估牙本质去除量。
在根尖水平，GT组和NiTiflex组的定心率、偏移距离和牙本质去除量均显著低于SS组（P < 0.01），但两组NiTi锉之间未发现统计学差异。在其他水平，各组之间无显著差异。
与SS K锉相比，GT手动锉和NiTiflex锉在弯曲根管中保持更好的定心效果，且产生的偏移显著更少。
