Cheung Lisa H M, Cheung Gary S P
Area of Endodontics, Faculty of Dentistry, University of Hong Kong, Hong Kong SAR, China.
J Endod. 2008 Oct;34(10):1233-8. doi: 10.1016/j.joen.2008.07.015. Epub 2008 Aug 23.
This study aimed to evaluate the safety and efficacy of a method of using nickel-titanium rotary instruments for preparing the C-shaped root canal system. Forty-three human mandibular second molars with a C-shaped canal configuration were prepared with a crown-down approach to an apical dimension of size 30 by using a combination of ProFile and HERO instruments. Micro-computed tomography was used to examine the canal diameter and the remaining thickness of the dentin wall along the root canal. Results showed that only isolated regions in cross section of the C-shaped canal were physically prepared by the rotary instruments. The furcal wall (concave aspect of the "C" in cross section) of all clinically identifiable canals had a similar thickness at a distance 1-7 mm from the apical constriction both before and after instrumentation. More dentin was removed from the outer (convex aspect of the "C") than the furcal aspect at the apical region, but the converse was true more coronally. All prepared canals showed a taper that matched that of the last instrument used. It was concluded that cleaning of the C-shaped canal system is incomplete with the use of rotary instruments and should be assisted by ultrasonic irrigation. Although rotary instruments seemed to be safe in such canals, further enlargement to an apical dimension greater than size 30 (0.06 taper) is not recommended.
本研究旨在评估使用镍钛旋转器械预备C形根管系统方法的安全性和有效性。采用冠向深入法，联合使用Profile和HERO器械，对43颗具有C形根管形态的人下颌第二磨牙进行预备，使其根尖尺寸达到30号。采用微计算机断层扫描技术检查根管直径以及沿根管的牙本质壁剩余厚度。结果显示，旋转器械仅对C形根管横断面的孤立区域进行了实际预备。所有临床可识别根管的根分叉壁（横断面“C”的凹面）在器械操作前后，距离根尖狭窄处1 - 7 mm的位置均具有相似的厚度。在根尖区域，从根管外侧（“C”的凸面）去除的牙本质比根分叉处更多，但在冠方则相反。所有预备后的根管均呈现出与最后使用器械相匹配的锥度。研究得出结论，使用旋转器械对C形根管系统的清理并不彻底，应辅以超声冲洗。尽管旋转器械在此类根管中似乎是安全的，但不建议将根尖尺寸进一步扩大至大于30号（0.06锥度）。
