de Menezes Sílvio Emanuel Acioly Conrado, Machado Batista Shirley, Brandão de Magalhães Diego Felipe, Diana Santana de Albuquerque, de Melo Monteiro Gabriela Queiroz
Dental School, University of Pernambuco FOP-UPE, Tabatinga, Camaragibe-PE, Brazil.
Iran Endod J. 2018 Winter;13(1):114-119. doi: 10.22037/iej.v13i1.18453.
The objective of this study was to evaluate whether cervical preparation with Mtwo files in a crown-down technique influences instrumentation time and the cyclic fatigue resistance of these instruments.
Two instrumentation techniques were evaluated (manufacturer and crown-down). Each group consisted of 10 kits containing four Mtwo instruments (10/0.04, 15/0.05, 20/0.06, and 25/0.06), which were used to prepare three standard simulated curved resin canals. The mean instrumentation time and the corresponding number of cycles for each instrumentation (NCI) were recorded. The instruments were rotated at a constant speed of 300 rpm in a stainless-steel canal (diameter of 1.5 mm) at a 90 angle of curvature and 5-mm radius. The center of the curvature was 5 mm from the tip of the instrument. The cyclic fatigue resistance of the files was determined by counting the number of cycles to failure (NCF). Data were analyzed by the Mann-Whitney test.
The mean instrumentation time and NCI of files 10/0.04 and 15/0.05 were significantly lower (<0.05) when the crown-down technique was used compared to the manufacturer's method for the same tip size/taper file. There was no significant difference in the mean NCF between the two techniques.
The crown-down technique did not interfere with resistance to cyclic fatigue. However, the shorter instrumentation time of files 10/0.04 and 15/0.05 could reduce the fracture risk in the case of reuse of these instruments.
本研究的目的是评估采用冠向下技术使用Mtwo锉进行根管预备是否会影响器械操作时间以及这些器械的抗循环疲劳性能。
评估了两种器械操作技术（制造商推荐方法和冠向下技术）。每组由10套工具组成，每套包含四根Mtwo器械（10/0.04、15/0.05、20/0.06和25/0.06），用于预备三根标准模拟弯曲树脂根管。记录每次器械操作的平均操作时间和相应的循环次数（NCI）。器械在直径为1.5毫米的不锈钢根管中以300转/分钟的恒定速度旋转，弯曲角度为90度，半径为5毫米。弯曲中心距离器械尖端5毫米。通过计算器械折断时的循环次数（NCF）来确定锉的抗循环疲劳性能。数据采用曼-惠特尼检验进行分析。
对于相同尖端尺寸/锥度的锉，与制造商推荐方法相比，采用冠向下技术时，10/0.04和15/0.05号锉的平均操作时间和NCI显著更低（<0.05）。两种技术之间的平均NCF无显著差异。
冠向下技术不会干扰抗循环疲劳性能。然而，10/0.04和15/0.05号锉较短的操作时间在这些器械重复使用的情况下可降低折断风险。
