Blum J Y, Cohen A, Machtou P, Micallef J P
School of Dentistry, University of Montpellier, France.
Int Endod J. 1999 Jan;32(1):24-31.
The aim of this study was to analyse the vertical forces and torque developed in the root canal system of extracted teeth during mechanical preparation using ProFile NiTi instruments.
Instrument wear and fracture is in great part due to the repeated application of forces and torque during the course of root-canal preparation but research into the direct relationship has been hampered by the lack of adequate measuring devices. Measurements of these forces and torque were made with a new force analyser device, the Endographe, that was equipped with a holder to record and generate graphs of the vertical forces and torque exerted during the preparations. These preparations was performed by endodontists or students either with a series of instruments of increasing size or with the crown-down pressureless technique.
The mean values for the endodontists of the generated vertical forces and torque varied, respectively, from 4 to 6N and from 7.105 to 12.105 Nm for the step-back technique and from 2.9 to 4.2 N and from 18.105 to 20.105 Nm for the crown-down technique. This suggested that the crown-down technique generated lower stresses (lower torque and lower vertical forces), although these findings also depend on the shape of individual canals. The students initially showed wide variations in generated forces, with significantly lower vertical force the torque values. By the end of the experimental sessions their values were similar to those of the endodontists, which indicated improvement in the efficiency of manipulation.
Further work is needed to investigate the relationship between the force and the torque data from this study and the incidence of instrument fracture with the two techniques, as the clinical implications are considerable. It must be noted, however, that the Endographe is unable to take into account the cutting efficiency of the instruments. The use of graphs provides a new approach to the analysis of mechanical preparation.
本研究旨在分析使用Profile镍钛器械进行机械预备时，离体牙根管系统中产生的垂直力和扭矩。
器械磨损和折断在很大程度上归因于根管预备过程中力和扭矩的反复施加，但由于缺乏合适的测量装置，对两者直接关系的研究受到了阻碍。使用一种新型力分析仪Endographe对这些力和扭矩进行测量，该仪器配备了一个固定器，用于记录并生成预备过程中施加的垂直力和扭矩的图表。这些预备操作由牙髓病医生或学生进行，采用一系列尺寸递增的器械或冠向下无压力技术。
对于牙髓病医生，逐步后退技术产生的垂直力和扭矩的平均值分别为4至6牛和7.1×10⁵至12.1×10⁵牛米，冠向下技术产生的垂直力和扭矩的平均值分别为2.9至4.2牛和18.1×10⁵至20.1×10⁵牛米。这表明冠向下技术产生的应力较低（较低的扭矩和较低的垂直力），尽管这些结果也取决于个体根管的形状。学生最初产生的力变化很大，垂直力和扭矩值明显较低。到实验结束时，他们的值与牙髓病医生的值相似，这表明操作效率有所提高。
由于临床意义重大，需要进一步研究本研究中的力和扭矩数据与两种技术下器械折断发生率之间的关系。然而，必须注意的是，Endographe无法考虑器械的切割效率。图表的使用为机械预备分析提供了一种新方法。
