Division of Endodontology, Department of Preventive Dentistry, Periodontology and Cariology, University of Zürich, Zürich, Switzerland.
Int Endod J. 2012 Feb;45(2):169-76. doi: 10.1111/j.1365-2591.2011.01967.x. Epub 2011 Oct 12.
To compare the apical fit in two dimensions of the first K-file versus the first Lightspeed LSX instrument binding at working length after an initial crown-down preparation.
Twenty maxillary molars with fully developed roots and four separate root canals were selected. Canals were pre-flared with ProFile.04 taper instruments to three quarters of estimated working length. Working length was electronically determined using a size 06 K-file. Progressively larger K-files were inserted passively to working length. The first binding K-file was termed initial apical file (IAF). Then, the first binding LSX initial apical lightspeed-instrument (IAL) was determined. Teeth were scanned with and without instruments in place using micro-computed tomography. Cross-sections of the apical part of the root canals were analysed as follows: the largest and smallest diameters of the root canal and the diameter of the instrument were calculated and related to each other. Statistics were performed using Kruskal-Wallis test and Wilcoxon test. The alpha-type error was set at 0.05.
Initial apical file sizes ranged from 8 to 30 and were lowest in second mesiobuccal and highest in palatal canals. IAL sizes ranged from size 20 to 40. The apical large canal diameter was assessed more accurately by the LSX instruments (P < 0.0001). However, the smallest available LSX instrument (i.e. size 20) did not reach working length in 39 of 80 canals.
Instruments with a flat widened tip were found to determine apical cross-sectional diameter better than round, tapered instruments.
比较在初始冠向下预备后至工作长度时，第一根 K 锉和第一根 Lightspeed LSX 锉在二维方向上的根尖适配。
选择 20 颗上颌磨牙，这些磨牙具有完全发育的根和 4 个独立的根管。使用 ProFile.04 锥度器械预扩根管至工作长度的四分之三。使用 6 号 K 锉确定工作长度，并用电子方法测量。然后用渐大的 K 锉被动插入至工作长度。第一根有适配的 K 锉称为初始根尖锉（IAF）。然后，确定第一根有适配的 LSX 初始根尖光高速器械（IAL）。用微计算机断层扫描（micro-computed tomography）在有和没有器械的情况下扫描牙齿。对根尖部分的根管进行横截面分析，计算根管的最大和最小直径以及器械的直径，并相互比较。使用 Kruskal-Wallis 检验和 Wilcoxon 检验进行统计学分析。设定 alpha 型错误为 0.05。
IAF 的尺寸范围为 8 至 30，在第二近中颊侧根管中最小，在腭侧根管中最大。IAL 的尺寸范围为 20 至 40。LSX 器械更准确地评估根尖大根管直径（P < 0.0001）。然而，在 80 个根管中，有 39 个根管的最小可用 LSX 器械（即 20 号）未达到工作长度。
与圆形、锥形器械相比，具有平宽尖端的器械在确定根尖横截面直径方面表现更好。
