title: The effect of multiple autoclave cycles on the surface of rotary nickel-titanium endodontic files: An in vitro atomic force microscopy investigation.
abstract: OBJECTIVE
  To observe and study the effect of multiple autoclave sterilization cycles, on the surface of nickel-titanium (NiTi) files.
  
  
  METHODS
  The file used for this study was the Mtwo 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 Mtwo 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.
authors.affiliation: Department of Conservative Dentistry and Endodontics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad, Karnataka, India.
authors.forename: Ashish Shashikant
authors.initials: AS
authors.lastname: Nair
authors.affiliation: Department of Conservative Dentistry and Endodontics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad, Karnataka, India.
authors.forename: Mahima
authors.initials: M
authors.lastname: Tilakchand
authors.affiliation: Department of Conservative Dentistry and Endodontics, SDM College of Dental Sciences and Hospital, Sattur, Dharwad, Karnataka, India.
authors.forename: Balaram Damodar
authors.initials: BD
authors.lastname: Naik
keywords: Atomic force microscope; NiTi files; autoclave sterilization; surface roughness