title: The evaluation of two rotary instrumentation techniques under "operator-related variables" standardized conditions.
abstract: OBJECTIVE
  We aimed here to evaluate the enlargement characteristics of two nickel-titanium rotary instrument systems that use two different preparation techniques, in simulated root canals under "operator-related variables" standardized conditions.
  
  
  METHODS
  A total of 40 simulated canals in resin blocks were divided into two groups as the Mtwo group for use with a single-length technique and the ProTaper instrument system group for use with crown down technique. To standardize the operator-related variables, all preparations were carried out with a computer controlled device that was developed and used previously as described in a published study. The pre- and post-operative digital images of the canals were superimposed and measured at 11 levels from the apical tip. The distances between the pre- and post-operative outer lines of the root canals were measured at both the inner and outer sides of the curve. The amount of removed material and the symmetry of the preparations were evaluated. Statistical analyses were performed with Mann-Whitney test.
  
  
  RESULTS
  Significantly more material was removed by Mtwo at 9 levels and by ProTaper at 2 levels (P < 0.05) while no significant difference was determined at 11 levels. The preparations made with ProTaper were more symmetrical at 4 levels while no significant difference was determined at 7 levels.
  
  
  CONCLUSIONS
  Mtwo removed significantly more material than ProTaper at different levels of the curved root canals. Mtwo and ProTaper made symmetrical preparations and maintained the original shape of the root canal at different levels under controlled operator-related variables.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Gazi University, Ankara, Turkiye.
authors.forename: Ozgur
authors.initials: O
authors.lastname: Uzun
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Gazi University, Ankara, Turkiye.
authors.forename: Ozgur
authors.initials: O
authors.lastname: Topuz
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Gazi University, Ankara, Turkiye.
authors.forename: Fatma
authors.initials: F
authors.lastname: Yalpi
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Gazi University, Ankara, Turkiye.
authors.forename: Feyza
authors.initials: F
authors.lastname: Unsal
authors.affiliation: Department of Endodontics, Center for Dental Sciences, Gulhane Military Medical Academy, Ankara, Turkiye.
authors.forename: Cumhur
authors.initials: C
authors.lastname: Aydin
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkiye.
authors.forename: Emre
authors.initials: E
authors.lastname: Bodrumlu
keywords: Mtwo; ProTaper; preparation symmetry; resin blocks; rotary instrumentation