Effect of sterilization on the cutting efficiency of PVD-coated nickel-titanium endodontic instruments.
OBJECTIVE
To investigate alterations in cutting efficiency when conventional and titanium nitride (TiN) coated nickel-titanium (NiTi) K-files were exposed to repeated sterilization using an autoclave.


METHODS
A total of 96 NiTi K-files (size 35) were randomly divided into two groups (A and B) of 48 instruments each. Whilst the instruments of group B were exposed to physical vapour deposition (PVD) creating a coating of a TiN layer, the files of group A were not coated. The instruments of groups A and B were randomly divided into four subgroups of 12 instruments each. A.1/B.1: Instruments were exposed to five cycles of sterilization. A.2/B.2: Instruments were exposed to 10 cycles of sterilization. A.3/B.3: Instruments were immersed in NaOCl for 30 min, rinsed in water, and exposed to five cycles of sterilization. A.C/B.C: Instruments were not sterilized (controls). The cutting efficiency of all files was determined by means of a computer-driven testing device. Special plastic samples with cylindrical canals were used and the maximum penetration depth of the files into the lumen was assessed.


RESULTS
The TiN-coated instruments of groups B.1, B.2 and B.3 showed no significant difference in comparison with the penetration depths of the controls (P> 0.05). The uncoated files of groups A.1, A.2 and A.3 displayed significantly lower maximum penetration depths (P< 0.05) when compared to the control files.


CONCLUSIONS
Repeated sterilization under autoclave or exposure to sodium hypochlorite (NaOCl) prior to sterilization did not alter the cutting efficiency of PVD-coated NiTi K-files.
Schäfer
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Department of Operative Dentistry, University of Münster, Münster, Germany. eschaef@uni-muenster.de
D000704:Analysis of Variance; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry*; D019551:Dental Disinfectants / Q000737:chemistry; D004867:Equipment Design; D006801:Humans; D007101:Immersion; D016555:Matched-Pair Analysis; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012973:Sodium Hypochlorite / Q000737:chemistry; D013242:Sterilization / Q000379:methods*; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D019551:Dental Disinfectants; D014867:Water; C040654:titanium nickelide; C041500:titanium nitride; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite