[Evaluation of the effects of TF and S3 nickel-titanium instruments in severely curved molar root canal preparation].

Purspose: To compare the shaping ability and dental cracks of Twisted File and S3 in severely curved molar root canal preparation.

Methods: Sixty extracted mandibular molars with mesiobuccal canals (canal curvature angles beyond 25°) were selected and divided randomly into 2 groups with 30 canals in each group. The canals were scanned by cone-beam CT(CBCT) before and after root canal preparation .