Finding appropriate nickel-titanium instruments for lingual canals in mandibular first premolars with two canals: A micro-CT study.

This study aimed to find appropriate nickel-titanium instruments for lingual canals in mandibular first premolars with two canals. Forty-two extracted mandibular first premolars with lingual canals (Vertucci type V) verified by micro-CT scanning were selected. The teeth were randomly divided into three groups, and their lingual canals were instrumented by M3, HyFlex CM and XP-endo Shaper, respectively. After instrumentation, the canal morphology was scanned again by micro-CT. The canal morphologies of pre- and post-instrumentation were reconstructed and aligned. Morphological changes of the lingual canals were evaluated. No instrument breakages occurred during the procedure of root canal instrumentation. HyFlex CM and XP-endo Shaper performed better than M3 files in preparation of lingual canals (Vertucci type V) of mandibular first premolars in terms of apical transportation and unprepared surface area.