Bahia Maria Guiomar Azevedo, Melo Marta C C, Buono Vicente Tadeu Lopes
Department of Restorative Dentistry, Faculty of Dentistry, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 May;101(5):675-80. doi: 10.1016/j.tripleo.2005.04.019. Epub 2005 Sep 30.
The aim of this study was to assess the influence of cyclic deformation up to one half and three quarters of the fatigue life of NiTi rotary endodontic instruments on their behavior in torsion.
Thirty sets of 0.04 and 0.06 ProFile instruments in sizes #20, #25, and #30 were randomly divided into 3 groups: 1 contained 10 sets of new files, torsion tested to failure, while the other 2 groups, with 10 sets each, were first submitted to fatigue tests of up to one half and three fourths of their fatigue life, respectively, in geometrical conditions similar to those of the clinical practice and then torsion tested for rupture.
Statistical analysis of the values obtained for the torque to failure and maximum angular deflection, using the Student t test at the 95% confidence level, showed that the cyclic deformation of instruments of up to one half and three fourths of their fatigue life gives rise to a significant reduction in these parameters.
The simulated clinical use of ProFile instruments for shaping curved canals adversely affects their torsional properties.
本研究旨在评估循环变形达镍钛旋转根管器械疲劳寿命的二分之一和四分之三时，对其扭转性能的影响。
将30套尺寸为#20、#25和#30的0.04和0.06规格的Profile器械随机分为3组：1组包含10套新器械，进行扭转测试直至断裂，而另外2组每组10套，首先在与临床实践相似的几何条件下分别进行达其疲劳寿命二分之一和四分之三的疲劳测试，然后进行扭转测试直至断裂。
使用95%置信水平的学生t检验对获得的断裂扭矩和最大角挠度值进行统计分析，结果表明，器械循环变形达其疲劳寿命的二分之一和四分之三时，这些参数会显著降低。
模拟临床使用Profile器械对弯曲根管进行塑形会对其扭转性能产生不利影响。
