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. All root canals were injected with the contrast medium and digital images of all canals were recorded before and after instrumentation. The computer assistant analyze image software was used to form the geometrical central line of pre-instrumented canals. Then the central line was imaged to the post-instrumented canals. The canal transportation and the decrease of curvature were measured. All the data was analyzed with SPSS11.0 software package.
Results: Difference between groups was compared using t test.When the curvature of canal > or =20 degrees ,the transportation at the beginning of the curvature and the decrease of curvature of Mtwo were significantly less than those of K3(P<0.05).When the curvature of canal <20 degrees there was no significant difference between Mtwo and K3 in the transportation and decrease of curvature(P>0.05).
Conclusions: Both Mtwo and K3 systems show good preservation of the original geometry of the root canals, the Mtwo system can better preserve original curvature of canals, when the curvature of canal is larger than 20 degrees .
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