Abstract:
Objective
To evaluate the torque resistance and cutting efficiency of two different types of nickel-titanium rotary instruments under repeated sterilization cycles.
Methods
60 new ProTaper F1 and 60 new Mtwo 20# were divided into 3 groups.Each group has 20 ProTaper F1 and 20 Mtwo 20# respectively.Samples in group A were exposed to 7 consecutive sterilization cycles in a steam autoclave.Samples in group B were exposed to 14 consecutive sterilization cycles； the control group samples were not sterilized.The torque resistance and cutting efficiency of ProTaper F1 and Mtwo 20# of each group were tested.
Results
Compared with the control group， the time of fracture of instruments under repeated sterilization cycles was shortened， but there is no significant difference （P ＞0.05， ANONA test）； the cutting efficiency of ProTaper F1 and Mtwo 20# in group A were decreased by 20.34% and 15.34% respectively， while those in group B were decreased by 46.39% and 35.89% respectively.Each of these differences was statistically significant （P ＜0.05，ANONA test）.
Conclusions
Repeated sterilization in autoclave does not increase the likelihood of instrument fracture， but reduces the cutting efficiency of nickel-titanium rotary instruments.
Key words:
Sterilization,
Nickel-titanium instruments,
Torque,
Cutting efficiency
Zhi-shan LU, Lei MENG, Zhong-hao LIU. Effect of sterilization on the torque resistance and cutting efficiency of two different types of nickel-titanium rotary instruments[J]. Chinese Journal of Stomatological Research(Electronic Edition), 2011, 5(06): 589-593.