Effect of irrigation on surface roughness and fatigue resistance of controlled memory wire nickel‐titanium instruments

• Published in: International endodontic journal 2017-07, Vol.50 (7), p.718-724
• Main Authors: Cai, J.‐J., Tang, X.‐N., Ge, J.‐Y.
• Format: Article
• Language: English
• Subjects: Atomic force microscopy; controlled memory wire nickel‐titanium instruments; cyclic fatigue resistance; Dental Instruments; Dentistry; Edetic acid; Edetic Acid - chemistry; Endodontics; Equipment Failure; Equipment Failure Analysis; Ethylene; Immersion; Irrigation; Lavage; Materials Testing; Microscopy, Atomic Force; Nickel; Random Allocation; Root Canal Irrigants - chemistry; Root Canal Preparation - instrumentation; Sodium; Sodium hypochlorite; Sodium Hypochlorite - chemistry; Stress, Mechanical; Surface Properties; Surface roughness; Titanium
• ISSN: 0143-2885; 1365-2591
• DOI: 10.1111/iej.12676

Aim To investigate the effect of irrigation on the surface roughness and fatigue resistance of HyFlex and M3 controlled memory (CM) wire nickel‐titanium instruments. Methodology Two new files of each brand were analysed by atomic force microscopy (AFM). Then, the instruments were dynamically immersed in either 5.25% sodium hypochlorite (NaOCl) or 17% ethylene diamine tetraacetic acid (EDTA) solution for 10 min, followed by AFM analysis. The roughness average (Ra) and root mean square (RMS) values were analysed statistically using an independent sample t‐test. Then, 36 files of each brand were randomly assigned to three groups (n = 12). Group 1 (the control group) was composed of new instruments. Groups 2 and 3 were dynamically immersed in 5.25% NaOCl and 17% EDTA solutions for 10 min, respectively. The number of rotations to failure for various groups was analysed using the one‐way analysis of variance software. Results For M3 files, the Ra and RMS values significantly increased (P  0.05) by immersing in 5.25% NaOCl and 17% EDTA solutions. Conclusions Except the HyFlex files immersed in NaOCl, the surface roughness of other files exposed to irrigants increased. However, a change in the surface tomography of CM wire instruments caused by contact with irrigants for 10 min did not trigger a decrease in cyclic fatigue resistance.