[Comparison of shaping ability of 4 nickel-titanium rotary instruments in preparation of curved root canals].

Prupose: To compare the shaping ability of 4 nickel-titanium rotary instruments in preparation of curved root canals.

Methods: Forty extracted human maxillary first or second molars with mesiobuccal root canal curvature ranging from 20°-40° were selected. The teeth were randomly equally divided into 4 groups(n=10).