Influence of sodium hypochlorite and chlorexidine on the dynamic cyclic fatigue resistance of XP-Endo Finisher instruments

Aim: This study evaluated the cyclic fatigue resistance of XP-Endo Finisher (XPF), associated with two different irrigation solutions: sodium hypochlorite 6% (NaOCl) or chlorhexidine digluconate gel 2% (CHX) in a dynamic model. The null hypothesis tested was that there was no statistically significant difference. Methodology: 30 new files were divided into three groups (n=10) based on the irrigation solution used. Group 1: XPF using CHX as an irrigation solution; Group 2: XPF using NaOCl as an irrigation solution; Group 3 (control group): XPF using lubricating oil (LO). The artificial canal was manufactured measuring 1.5 mm wide, 20 mm long, and 3.5 mm deep with a straight cervical segment measuring 14.29 mm. A curved apical segment 4.71 mm with 3 mm radius and 90° of curvature and an ending with straight apical portion measuring 1 mm long. Resistance to cyclic fatigue was determined by recording time to fracture, and the file surface was examined under scanning electron microscopy. Results: Data were tabulated and subjected to statistical analysis of variance. Student-Newman-Keuls test for multiple comparisons, with a significance level of 5%. The average time took for file fracture was 306.7 seconds for 2% chlorhexidine and 67,6 for 6% sodium hypochlorite. 2% CHX was significantly different from the NaOCl and LO groups (P< .001). Conclusions: XPF presented the best results of fracture time and the number of cycles to fracture when used along with 2% chlorhexidine in canals with severe apical curvature, and there was no statistical difference in fragment size.