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[Clinical evaluation of two types of NiTi rotary instruments in preparation of root canals].

OBJECTIVE
To evaluate clinical effects of two types of nickel-titanium rotary instruments in preparation of molars' root canals.


METHODS
100 molars with pupal and periapical involvement were instrumented by Protaper and Hero642 files with crown-down technique. All teeth were obturated with lateral condensation method. Straightening of canal curvature was determined. The efficiency of preparation and obturation was analyzed with radiograph before, during and after operation.


RESULTS
The operating time of each NiTi group was short. The two NiTi rotary instruments could achieve continuously tapered root canal shape. The curvature of the canal reduced by -4.02 degrees +/- 2.80 degrees with Protaper and 1.72 degrees with Hero642 (P < 0.001). Five pieces of Protaper with broken, whereas no Hero642 was broken (P < 0.05).


CONCLUSIONS
Protaper, Hero642 files showed good shaping ability and improved predictability in root canal obturation. Protaper can lessen canal curvature more significantly. Hero642 files are easy to operate and not easy to separate.