Objective: To investigate the shaping effects of three nickel-titanium rotary instruments on preparing curved canals in posterior teeth.
Methods: 64 curved mesial canals of extracted lower molars, embedded in the Branmante models, were randomly assigned to four groups: (1) Flexofile; (2) LightSpeed; (3) ProFile; (4) Qantec SC. Apical preparation was carried out till size 30. The area of dentine removal, least remaining dentine thickness and transportation of canal center were measured.
Results: Flexofile resulted in more dentine removal and canal center transportation than LightSpeed and ProFile (P < 0.05) at the apical and mid-root levels. In the mid-root sections, Flexofile left the thinnest dental wall in the distal aspect; 87% of the canal centers in the Flexofile group were transported in a distal direction as compared with one third in other groups.
Conclusions: LightSpeed and ProFile exhibited better shaping ability than Flexofile in preparing curved canals.