In vitro evaluation of 4 mechanized instruments in the retreatment of oval curved root canals: removal of filling material and resistance to cyclic fatigue.

Aims: The aim was to compare different system in removing filling material and the cyclic fatigue alteration of these instruments after retreatment of oval curved canals. Materials and methods: Sixty single-rooted teeth with oval curved canals were instrumented, filled and micro-CT scanned. The teeth were divided according to endodontic retreatment file (n=15): Reciproc (R), Reciproc Blue (RB), Pro-R (PR), ProDesign Logic RT (RT). The teeth were scanned and the volume of the filling material measured. The working time of the size-25 files during retreatment was recorded and these and fifteen new ones were submitted to the cyclic fatigue test. Data were submitted to statistical analysis (?<5%). Results: RT was faster than the other instruments and reduced the total volume of filling material more compared to RB and PR (p<0.05). More cycles to fracture were observed in the RB and RT compared to the R and PR (p<0.05). Conclusions: Based on the proposed objectives and the methodology used, TruNatomy 26.04 RT presented lower volume of remaining filling material and was faster in endodontic retreatment. RB and RT showed greater resistance to cyclic fatigue.