Clinical Study on Preparation of C-shaped Root Canals Between Hero642 Rotary Nickel-Titanium Files and Stainless K Files in Mandibular Molars

To compare the clinical effect between Hero642 rotary nickel titanium file and stainless K file in preparation of C shaped root canals in the mandibular second molar. Forty two mandibular second molars with C shaped root canal scheduled root canal treatment were divided into two groups based on the random principle. In the experimental group(n=22), C shaped root canals were prepared with Hero 642 rotary Ni Ti files in crown down technique. In the control group(n=20), C shaped root canals were prepared with K Flexofiles by hand. All teeth were obturated with lateral condensation method. The prepared time of each C shaped root canal was recorded and the incidence of EIP (endodontic interappointment pain)was observed. The effect was compared between two groups. The efficacy of preparation and obturation were analyzed by radiograph. The mean prepared time in experiment group (223 s) was significantly less than that in the control group (400 s). No instrument fracture found in both groups. Two slight apical transportations were found in each group. Two apical blockages and 3 apical ledges were found in the K Flexofile group. The incidence of EIP was not significantly different between two groups. [Conclusion]Compared with K Flexofile, the Hero642 rotary Ni Ti file can prepare the C shaped root canals effectively, easily,and safely.