title: Shaping outcomes using two Ni-Ti rotary instruments in simulated canals.
abstract: OBJECTIVE
  The aim of this study was to compare the shaping ability of Mtwo and ProTaper instruments in simulated curved root canals in resin blocks.
  
  
  METHODS
  The study was carried out using 40 simulated canals in resin blocks, all of which had the same canal diameter (0.70 mm>D>0.20 mm), length (16 mm), and angle of curvature (40 degrees). These 40 canals were divided into 2 groups of 20 specimens. Both before and after instrumentation, all the resin specimens were photographed, and all the canals examined were measured at 4 different points of reference. Using a computer image analysis program, the photographs of corresponding sections were superimposed on one another. In this way we sought to evaluate the shaping ability of these 2 systems in relation to specific portions of the root canal, also with regard to maintenance of original canal curvature. The results were analysed using Student's t-test.
  
  
  RESULTS
  Both rotary systems were found to respect the original root canal curvature, particularly in the areas most at risk of modification, namely the outer aspect of the curve in the apical third of the canal. The Mtwo instruments caused less transportation of the apex than the ProTaper instruments, but this difference was not statistically significant (P>0.05).
  
  
  CONCLUSIONS
  According to the results of this study, both these instruments respected the original canal curvature, particularly in the areas at most risk of modification, and they also showed good shaping ability in curved canals, with minimum transportation of the apex.
authors.affiliation: Unit of Endodontics, Department of Conservative Dentistry, Umberto I Policlinical, La Sapienza University Rome, Italy.
authors.forename: T
authors.initials: T
authors.lastname: Giovannone
authors.forename: G
authors.initials: G
authors.lastname: Migliau
authors.forename: R
authors.initials: R
authors.lastname: Bedini
authors.forename: M
authors.initials: M
authors.lastname: Ferrari
authors.forename: L
authors.initials: L
authors.lastname: Gallottini
mesh_terms: D019563:Mechanics; D009532:Nickel; D012390:Root Canal Therapy / Q000295:instrumentation*; D014025:Titanium
chemical_list: D009532:Nickel; D014025:Titanium