title: Effect of repeated sterilization cycles on the physical properties of scaling instruments: a scanning electron microscopy study.
abstract: BACKGROUND
  Repeated sterilizations cycles cause undesirable alterations in the material properties of the instruments, such as corrosion, alterations in the hardness of the metal and the loss of the cutting sharpness of the instrument. This research examined the effect of repeated dry heat sterilization and autoclaves cycles on carbon steel (CS) and stainless steel (SS) curettes during the scaling and root planning.
  
  
  METHODS
  A total of 77 Gracey curettes were used in this study. Of these, 35 were SS and 42 were CS curettes submitted in different process: Dry heat, autoclave, inhibition of corrosion and autoclave, scaling, root planning and dry heat, scaling, root planning, inhibition of corrosion and autoclave. The inhibition of corrosion used on the carbon curettes (prior to sterilization in the autoclave) was sodium nitrite at 2%. The curettes received 10 consecutive cycles of sterilization and after that the cutting edges were examined in the electronic microscope, at 60 and 100 magnification times.
  
  
  RESULTS
  The images were evaluated by three independent examiners, who compared the photographs of each group with the control group.
  
  
  CONCLUSIONS
  The surface corrosion products and a deterioration of the edges were observed and the results showed that the SS curettes suffered little alteration with sterilization, scaling, root planning whereas the CS curettes were visibly affected by sterilization in the autoclave, but when the inhibition of corrosion was used prior to the sterilization, the oxidation was considerably reduced.
authors.affiliation: Professor, Department of Master Program in Integrated Dentistry Science, University of Cuiabá (UNIC), Cuiabá, MT, Brazil.
authors.forename: Alessandra Nogueira
authors.initials: AN
authors.lastname: Porto
authors.affiliation: Professor, Department of Master Program in Integrated Dentistry Science, University of Cuiabá (UNIC), Cuiabá, MT, Brazil.
authors.forename: Álvaro Henrique
authors.initials: ÁH
authors.lastname: Borges
authors.affiliation: Professor, Department of Master Program in Integrated Dentistry Science, University of Cuiabá (UNIC), Cuiabá, MT, Brazil.
authors.forename: Alex
authors.initials: A
authors.lastname: Semenoff-Segundo
authors.affiliation: Professor, Department of Master Program in Integrated Dentistry Science, University of Cuiabá (UNIC), Cuiabá, MT, Brazil.
authors.forename: Suzane A
authors.initials: SA
authors.lastname: Raslan
authors.affiliation: Professor, Department of Master Program in Integrated Dentistry Science, University of Cuiabá (UNIC), Cuiabá, MT, Brazil.
authors.forename: Fábio Luis Miranda
authors.initials: FL
authors.lastname: Pedro
authors.affiliation: Professor, Deparment of Dentistry, São Paulo Stadual University, São José dos Campos, São Paulo, Brazil.
authors.forename: Antônio Olavo Cardoso
authors.initials: AO
authors.lastname: Jorge
authors.affiliation: Professor, Deparment of Dentistry, São Paulo Stadual University, São José dos Campos, São Paulo, Brazil ; Professor, Deparment of Post Graduation Program in Dentistry, CEUMA University, São Luis, MA, Brazil.
authors.forename: Matheus Coelho
authors.initials: MC
authors.lastname: Bandeca
keywords: Inhibition of corrosion; root planning; scaling; sterilization