title: Chemomechanical preparation by hand instrumentation and by Mtwo engine-driven rotary files, an ex vivo study.
abstract: OBJECTIVE
  To compare the disinfecting efficacy of the sodium hypochlorite irrigation by root canal preparation with stainless steel hand files, taper 0.02 and nickel-titanium Mtwo files with taper 0.04-0.06.
  
  
  METHODS
  40 extracted human teeth were sterilized, and then inoculated with Enterococcus faecalis (ATCC 29212). After 6 day incubation time the root canals were prepared by hand with K-files (n=20) and by engine-driven Mtwo files (VDW, Munich, Germany) (n=20). Irrigation was carried out with 2.5% NaOCl in both cases. Samples were taken and determined in colony forming units (CFU) from the root canals before and after the preparation with instruments #25 and #35.
  
  
  RESULTS
  Significant reduction in bacterial count was determined after filing at both groups. The number of bacteria kept on decreasing with the extension of apical preparation diameter. There was no significant difference between the preparation sizes in the bacterial counts after hand or engine-driven instrumentation at the same apical size. Statistical analysis was carried out with Mann-Whitney test, paired t-test and independent sample t-test.
  
  
  CONCLUSIONS
  Significant reduction in CFU was achieved after the root canal preparation completed with 2.5% NaOCl irrigation, both with stainless steel hand or nickel-titanium rotary files. The root canal remained slightly infected after chemo mechanical preparation in both groups. Key words:Chemomechanical preparation, root canal disinfection, nickel-titanium, conicity, greater taper, apical size.
authors.affiliation: DMD. Clinical Consultant. Dental School, Faculty of Medicine, University of Pécs, Hungary.
authors.forename: Károly
authors.initials: K
authors.lastname: Krajczár
authors.affiliation: MD, PhD Associate Professor. Department of Medical Microbiology and Immunology, Faculty of Medicine, University of Pécs, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Tigyi
authors.affiliation: DMD. Private practice, Nagykanizsa, Hungary.
authors.forename: Viktória
authors.initials: V
authors.lastname: Papp
authors.affiliation: DMD. Assistant Professor. Dental School, Faculty of Medicine, University of Pécs, Hungary.
authors.forename: Gyula
authors.initials: G
authors.lastname: Marada
authors.affiliation: BSc, MSc, PhD. Professor. Department of Biostatistics and Health Informatics, Faculty of Health Sciences, University of Pécs, Hungary.
authors.forename: Jeges
authors.initials: J
authors.lastname: Sára
authors.affiliation: DMD, PhD. Professor. Dental School, Faculty of Medicine, University of Pécs, Hungary.
authors.forename: Vilmos
authors.initials: V
authors.lastname: Tóth