title: Effect of autoclaving on the surfaces of  TiN -coated and conventional nickel-titanium rotary instruments.
abstract: OBJECTIVE
  To evaluate the effects of repeated autoclave sterilization cycles on surface topography of conventional nickel-titanium ( NiTi ) and titanium nitride ( TiN )-coated rotary instruments.
  
  
  METHODS
  A total of 60 NiTi rotary instruments, 30 ProTaper (Dentsply Maillefer) and 30 TiN -coated AlphaKite (Komet/Gebr. Brasseler), were analysed. Instruments were evaluated in the as-received condition and after 1, 5 and 10 sterilization cycles. After sterilization, the samples were observed using scanning electron microscope (SEM), and surface chemical analysis was performed on each instrument with energy dispersive X-ray spectroscopy (EDS). Moreover, the samples were analysed by atomic force microscopy (AFM), and roughness average (Ra) and the root mean square value (RMS) of the scanned surface profiles were recorded. Data were analysed by means of anova followed by Tukey's test.
  
  
  RESULTS
  Scanning electron microscope observations revealed the presence of pitting and deep milling marks in all instruments. EDS analysis confirmed that both types of instruments were composed mainly of nickel and titanium, whilst AlphaKite had additional nitride. After multiple autoclave sterilization cycles, SEM examinations revealed an increase in surface alterations, and EDS values indicated changes in chemical surface composition in all instruments. Ra and RMS values of ProTaper significantly increased after 5 (P = 0.006) and 10 cycles (P = 0.002) with respect to the as-received instruments, whilst AlphaKite showed significant differences compared with the controls after 10 cycles (P = 0.03).
  
  
  CONCLUSIONS
  Multiple autoclave sterilization cycles modified the surface topography and chemical composition of conventional and TiN -coated NiTi rotary instruments.
authors: Department of Oral and Maxillofacial Sciences, University of Napoli, Federico II, Napoli, Italy. gspagnuo@unina.it
authors: G
authors: G
authors: Spagnuolo
authors: G
authors: G
authors: Ametrano
authors: V
authors: V
authors: D'Antò
authors: C
authors: C
authors: Rengo
authors: M
authors: M
authors: Simeone
authors: F
authors: F
authors: Riccitiello
authors: M
authors: M
authors: Amato
mesh_terms: D020099:Coated Materials, Biocompatible; D003722:Dental Alloys / Q000737:chemistry*; D003799:Dental Stress Analysis; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D013052:Spectrometry, X-Ray Emission; D013227:Steam; D013242:Sterilization / Q000379:methods*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D013227:Steam; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium