Efficiency Of Rotary Nickel-titanium M2 Instruments, Rotary Nickel-titanium K3 Instruments Compared With Stainless Steel Hand K-file In Curved Root Canals

Objective:To research the shaping ability of M2 nickel-titanium rotary instruments, K3 nickel-titanium rotary instruments and stainless steel hand K-files during the preparation of curved root canals in extracted human molars.Methods: A total of 30 extracted MB root canals of maxillary molars were randomly divided into three groups of 10 canals. The canals were prepared by M2 instruments in group A, the canals were prepared by K3 instruments in group B, the canals were prepared by K-files in group C. Using the records of the instrument's tips location in pre- and post-instrumentation radiographs of the three groups to determine and compare the changes of root curvature and working length. The working time between the three groups is also recorded and compared.Results:The changes of root curvature after root preparation in group A and B are significant less than group C (P<0.01), but the changes of root curvature after root preparation between group A and B are no significant different (P>0.05). The changes of working length after root preparation between the three groups are no significant different (P>0.05). Group A cost the shortest root canal preparation time in the three groups, about 5 minutes; Group C cost the longest time, about 8 minutes. The root canal preparation time in the three groups is significant different (P<0.05).Conclusions:M2 nickel-titanium rotary instruments and K3 nickel-titanium rotary instruments have better effectiveness and shaping ability than stainless steel hand K-files in preparing molars curvature roots. M2 nickel-titanium rotary instruments and K3 nickel-titanium rotary instruments are the more ideal instruments than stainless steel hand K-files in preparing thin and curved roots.