THE EFFECT OF SODIUM HYPOCHLORITE ON CYCLIC FATIGUE RESISTANCE OF TWO DIFFERENT ROTARY NI-TI INSTRUMENTS IN CURVED ROOT CANALS

*Samaa Amin Abdelrahman, Medhat Taha El-Faramawy and Sara Hossam

ABSTRACT

Aim: The objective of this research is to assess the impact of utilising sodium hypochlorite irrigant on the cyclic fatigue resistance of two distinct rotary files maintaining a constant radius while subjected to two canal curvatures of 60 and 45 degrees. Material and methods: total of 64 files with #25 with 6% aper were selected and divided into two groups (n=32) according to file type: Group I (W3-pro) (F1), Group II (Revo-s) (F2), Each group was further divided into 2 subgroups according to irrigation (n=16); Subgroup A (saline irrigation) and Subgroup B (sodium hypochlorite). Each file was immersed in the selected irrigant for 5 minutes. A specific stainless-steel block with an artificial canal of 45° curvature and 5 mm concave-tempered steel radius. All instruments of the groups were rotated until fracture occurred. Each file was tested for cyclic fatigue till fracture and the sample was prepared for SEM examination to detect mode of fracture. Results: At both curvatures 60 degrees and 45 degrees, group I was significantly higher than group II. While in 45 degrees, group I (no fracture) was significantly higher than group II. In B 60 degrees, group I was significantly higher than group II. While B 45 degrees, group I (no fracture) was significantly higher than group I. Group IA 60 degrees of curvature and Group IB 60 degrees of curvature were significantly the highest, while Group IA and IB 45 degrees of curvature revealed no fracture up to 10 minutes of rotation. Group IA 45 degrees of curvature was significantly the highest, while Group IB 60 degrees of curvature was significantly the lowest. Conclusion: The cyclic fatigue resistance of CM wire is greater than that of conventional wire. Fatigue resistance is inversely proportional to curvature severity. Irrigation in NaOCl does not affect cyclic fatigue resistance.

Keywords: CM wire, cyclic fatigue resistance, NiTi files, static model and NaOCl irrigation.