背景:旋入效应是镍钛(NiTi)旋转牙髓牙髓被拉入管的趋势,这会导致应力突然增加,导致仪器断裂,和超过顶点的过度仪器。为了减少旋入力,建议重复上下运动,以在仪器期间分配弯曲应力,尤其是在弯曲和收缩的运河中。然而,关于最佳重复次数没有共识。因此,这项研究旨在研究在工作长度上重复的上下运动如何影响扭矩/力的产生,表面缺陷,以及JIZAI和TruNatomy乐器的运河塑造能力。
方法:使用一种原始的自动根管器械来准备根管并记录扭矩/力的变化。通过使用微型计算机断层扫描进行几何匹配,选择了具有约30°弯曲度的人类下颌磨牙的中根。根据工作长度的上下运动次数将样品分为三组(1、3和6次;每个n=24),并根据仪器细分:JIZAI(#13/0.04锥度,#25/0.04锥度,和#35/0.04锥度)或TruNatomy(#17/0.02锥度,#26/0.04锥度,和#36/0.03胶带)(每个n=12)。设计,表面缺陷,相变温度,镍钛比,扭矩,力,塑造能力,和表面变形进行了评价。用Kruskal-Wallis和Dunn检验(α=0.05)分析数据。
结果:仪器具有不同的设计和相变温度。3次和6次上下运动导致与1次运动相比更小的向上力(p<0.05)。TruNatomy产生的最大扭矩明显减少,力,和表面磨损比JIZAI(p<0.05)。然而,TruNatomy显示较大的根管偏差(p<0.05)。在不同的上下运动之间未检测到成形能力的统计学差异。
结论:在JIZAI和TruNatomy的实验室条件下,在单长度仪器技术中,在工作长度上的单个上下运动增加了后续仪器在严重弯曲的运河中的拧入力。使用JIZAI时,单个上下移动会在文件上产生更多表面缺陷。TruNatomy导致仪器期间产生的压力减少,而JIZAI更好地保持了根管的曲率。
BACKGROUND: The screw-in effect is a tendency of a nickel-titanium (NiTi) rotary endodontic file to be pulled into the canal, which can result in a sudden increase in stress leading to instrument fracture, and over-instrumentation beyond the apex. To reduce screw-in force, repeated up-and-down movements are recommended to distribute flexural stress during instrumentation, especially in curved and constricted canals. However, there is no consensus on the optimal number of repetitions. Therefore, this study aimed to examine how repeated up-and-down movements at the working length affect torque/force generation, surface defects, and canal shaping ability of JIZAI and TruNatomy instruments.
METHODS: An original automated root canal instrumentation device was used to prepare canals and to record torque/force changes. The mesial roots of human mandibular molars with approximately 30˚ of canal curvature were selected through geometric matching using micro-computed tomography. The samples were divided into three groups according to the number of up-and-down movements at the working length (1, 3, and 6 times; n = 24 each) and subdivided according to the instruments: JIZAI (#13/0.04 taper, #25/0.04 taper, and #35/0.04 taper) or TruNatomy (#17/0.02 taper, #26/0.04 taper, and #36/0.03 tape) (n = 12 each). The design, surface defects, phase transformation temperatures, nickel-titanium ratios, torque, force, shaping ability, and surface deformation were evaluated. Data were analyzed with the Kruskal-Wallis and Dunn\'s tests (α = 0.05).
RESULTS: The instruments had different designs and phase transformation temperatures. The 3 and 6 up-and-down movements resulted in a smaller upward force compared to 1 movement (p < 0.05). TruNatomy generated significantly less maximum torque, force, and surface wear than JIZAI (p < 0.05). However, TruNatomy exhibited a larger canal deviation (p < 0.05). No statistical differences in shaping ability were detected between different up-and-down movements.
CONCLUSIONS: Under laboratory conditions with JIZAI and TruNatomy, a single up-and-down movement at the working length increased the screw-in force of subsequent instruments in severely curved canals in the single-length instrumentation technique. A single up-and-down movement generated more surface defects on the file when using JIZAI. TruNatomy resulted in less stress generation during instrumentation, while JIZAI better maintained the curvature of root canals.