The effect of multiple autoclave cycles on the surface of rotary nickel-titanium endodontic files: An in vitro atomic force microscopy investigation

AIMS: To observe and study the effect of multiple autoclave sterilization cycles, on the surface of nickel-titanium (NiTi) files. MATERIALS AND METHODS: The file used for this study was the M(two) file (VDW) and ProTaper (Dentsply). The apical 5 mm of the files were attached to a silicon wafer and subjected to autoclave cycles under standardized conditions. They were scanned with an AFM after 1, 5, and 10 cycles. The unsterilized files were used as control, before start of the study. Three vertical topographic parameters namely maximum height (MH), root mean square (RMS) of surface roughness, and arithmetic mean roughness (AMR)were measured with the atomic force microscope (AFM). Analysis of variance along with Tukey's test was used to test the differences. RESULTS: The vertical topographic parameters were higher for both the files, right after the first cycle, when compared with the control (P < 0.01). The surface roughness increased sharply for M(two) when compared to ProTaper, though ProTaper had a rougher surface initially. CONCLUSIONS: The study confirmed that the irregularities present on the surface of the file became more prominent with multiple autoclave cycles, a fact that should be kept in mind during their reuse.