[Comparative study on the shaping ability of canals with 2 new nickel- titanium rotary instruments].

Purpose: To compare the shaping ability of two nickel-titanium rotary systems: Mtwo and K3.

Methods: Thirty-six mesio-buccal root canals of maxillary first molars were divided into two groups: group A(> or =20> or =) and group B(<20 degrees ),according to the angle of the canal. Then, each group was randomly divided into two subsets and prepared by Mtwo,K3, respectively.