Department of Conservative Dentistry, School of Dentistry, IHBR, Kyungpook National University, Daegu, Korea.
Department of Conservative Dentistry, School of Dentistry, Dental Research Institute, Pusan National University, Yangsan, Korea.
J Endod. 2017 Oct;43(10):1688-1691. doi: 10.1016/j.joen.2017.04.013. Epub 2017 Jul 15.
The aim of this study was to evaluate the effect of different pecking depth on the stress generated by the screw-in forces of a rotating endodontic file in simulated canals.
Twenty simulated resin blocks with a J-shaped curvature were used. Twenty OneG files (MicroMega, Besançon, France) were assigned for a screw-in test depending on the pecking depth in 2 groups (n = 10). The files were operated at 300 rpm, and the up and down speed was controlled at 1 mm/s stroke velocity and a 10-millisecond dwell time using a customized device. The distances (pecking depth) for the pecking motion were 2 mm or 4 mm for each group; "6 mm forward and 4 mm backward" and "6 mm forward and 2 mm backward" movements were applied, respectively, for the 2 pecking groups. During the operation, the positive and negative apical loads were recorded at a rate of 50 Hz using customized software attached to the device. The maximum negative apical load (screw-in force [SF]) was recorded, and the total energy during pecking motion until the file reached the working length (cumulative screw-in forces [CSFs]) was computed. The data were analyzed using an independent t test at a significance level of 95%.
No significant difference in SF was found between the 2 groups of pecking depths. However, the longer pecking depth (4-mm group) showed a significantly larger CSF compared with the shorter pecking depth group (P < .05).
The shorter pecking depth may generate lower overall stresses for the root dentin as well as the instrument.
本研究旨在评估不同啄入深度对模拟根管中旋转根管锉旋入力产生的应力的影响。
使用 20 个具有 J 形曲率的模拟树脂块。根据啄入深度将 21G 锉（MicroMega，Besançon，法国）分为 2 组（n=10）进行旋入试验。锉在 300rpm 下操作，上下速度通过定制设备以 1mm/s 行程速度和 10 毫秒停留时间控制。每组啄入运动的距离（啄入深度）分别为 2mm 或 4mm；分别应用 2 个啄入组的“6mm 前进和 4mm 后退”和“6mm 前进和 2mm 后退”运动。在操作过程中，使用定制软件以 50Hz 的速率记录正、负根尖负载。记录最大负根尖负载（旋入力[SF]），并计算啄入运动直到锉达到工作长度期间的总能量（累积旋入力[CSF]）。使用独立 t 检验在 95%的置信水平下对数据进行分析。
两组啄入深度的 SF 无显著差异。然而，较长的啄入深度（4mm 组）比较短的啄入深度组显示出明显更大的 CSF（P<0.05）。
较短的啄入深度可能会为根管牙本质和器械产生较低的整体应力。
