Influence of Heat Treatment of Nickel-Titanium Rotary Endodontic Instruments on Apical Preparation: A Micro–Computed Tomographic Study

• Heat treatment of the nickel-titanium alloy did not influence the geometry of root canals.
• K3 and K3XF presented similar capacity to maintain a centralized preparation.
• K3 and K3XF presented reduced values of apical transportation.
• K3 and K3XF presented similar values of apical transportation.

IntroductionThe aim of this study was to make a 3-dimensional comparison of the canal transportation and changes in apical geometry using micro–computed tomographic imaging after canal preparation with K3 (SybronEndo, Orange, CA) and K3XF (SybronEndo) file systems.MethodsTwenty-eight mandibular molars were randomly divided into 2 groups according to the rotary system used in instrumentation: K3 or K3XF. The specimens were scanned by micro–computed tomographic imaging before and after instrumentation. Images before and after instrumentation from each group were compared with regard to canal volume, surface area, and structure model index (SMI) (paired t test, P < .05). After instrumentation, the canals from each group were compared regarding the changes in volume, surface area, SMI, and canal transportation in the last 4 apical mm (t test, P < .05).ResultsInstrumentation with the 2 rotary systems significantly changed the canal volume, surface area, and SMI (P < .05). There were no significant differences between instrument types concerning these parameters (P > .05). There were no significant differences between the 2 groups with regard to canal transportation in the last 4 apical mm (P > .05).ConclusionsBoth rotary systems showed adequate canal preparations with reduced values of canal transportation. Heat treatment did not influence changes in root canal geometry in the apical region.